Author Topic: This One Simple Trick Will Increase Gas Mileage by 15%!!  (Read 26848 times)

Bob W

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This One Simple Trick Will Increase Gas Mileage by 15%!!
« on: June 15, 2015, 10:12:00 AM »
Yeah,  I know,  funny huh?

So I checked my tires on the 1999 Mercury Mountaineer.  Damn 32 lbs!   Max inflate rated at 44 lbs.   I filled those babies up to 46 lbs.

Took daughter home to her moms house which is about 45 miles at 32 lbs and MPG 18.5 (I have a digital tracker)   Filled up the air.   Return trip 21.4 MPG.

That is a 15% increase in MPG!  Our annual car gas bill for 2 cars runs about $2,400 (yeah, I know I'm researching higher MPG cars)   So this little trick will save us $400 per year if we do nothing different. 

So yeah,   check your tires and don't be shy about going a tad over the max inflate.    By the way,  hypermilers increase their Prius mileage to 65 mpg simply by overinflating a tad.  Bike riders take note as well --- you could be peddling with 15% less effort. 


YMMV!

forummm

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #1 on: June 15, 2015, 10:35:07 AM »
Filling your tires is great. But you may also have gone uphill on the way there and downhill on the way back. Or driven more efficiently on the way back. The research says any increase should be a few percent or less. Not 15%.

For example:
https://www.fueleconomy.gov/feg/maintain.jsp
http://www.popularmechanics.com/cars/a940/4199963/

music lover

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #2 on: June 15, 2015, 10:51:34 AM »
The maximum inflation rate only tells you the maximum safe pressure for the tire. The recommended pressure is determined by the manufacturer for optimum performance, and that is what you should follow:

http://blog.tirerack.com/blog/docs-advice-on-tires/what-is-the-best-tire-pressure-for-my-new-tires

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #3 on: June 15, 2015, 10:52:51 AM »
You filled your SUV tires to 46lbs?  I bet that thing rides like a buckboard.  And given that it's just a Ford Explorer in a fancy dress, and Ford Explorers are notoriously sensitive to tire failure, I'd say that's a pretty stupid thing to do.

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #4 on: June 15, 2015, 12:26:41 PM »
Doesn't over inflation cause a higher likelihood of popping the tire? Also doesn't it decrease the tread unevenly causing you to replace tires earlier? May be a wash in the long run.

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #5 on: June 15, 2015, 12:38:34 PM »
Don't over inflate your tires as that can lead to premature tire failure such as tread separation.  Traveling at higher speeds over extended periods of time will cause the tire to heat up and increase the PSI even more, which will likely cause a blow out.  It's not fun when a tire blows at 70 mph and it can cause a lot of damage to your car.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #6 on: June 15, 2015, 12:39:33 PM »
You filled your SUV tires to 46lbs?  I bet that thing rides like a buckboard.  And given that it's just a Ford Explorer in a fancy dress, and Ford Explorers are notoriously sensitive to tire failure, I'd say that's a pretty stupid thing to do.

No noticeable difference in ride quality.   

The tires are riding even across contact with the road.   I suppose tire failure is a possibility but I have read a lot of the hypermiler posts on this.   It appears their consensus is that at max inflation or slightly above is oky doky.

Higher inflation pressures usually provide an improvement in steering response and cornering stability while diminishing braking response.  So that is a trade off.   I use my brakes minimally and usually cost up to stop signs and lights.  (I corner and steer way more than brake)

So yeah,  I'll run this little experiment a bit longer.

For those not interested in maxing their MPGs still be sure to check your tires for pressure.   Even a few pounds low can diminish MPG and lead to excess tire wear and possible overheating. 

FrugalSpendthrift

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #7 on: June 15, 2015, 12:57:01 PM »
Doesn't over inflation cause a higher likelihood of popping the tire? Also doesn't it decrease the tread unevenly causing you to replace tires earlier? May be a wash in the long run.
I guess they could be more likely to puncture, because they will ride a little stiffer making it tough to absorb potholes.  Over inflated tires are more likely to wear the center prematurely.  They are also more likely to hydroplane in water.

It's all a trade off.  Tires that don't have good traction are good for mpg, because they reduce rolling resistance.  My old subaru came with what I though were terrible tires, until I discovered the tires won awards for low rolling resistance.  They weren't the best for cornering or braking, but they are good for their fleet MPG rating.

Xlar

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #8 on: June 15, 2015, 01:21:00 PM »
You filled your SUV tires to 46lbs?  I bet that thing rides like a buckboard.  And given that it's just a Ford Explorer in a fancy dress, and Ford Explorers are notoriously sensitive to tire failure, I'd say that's a pretty stupid thing to do.

No noticeable difference in ride quality.   

The tires are riding even across contact with the road.   I suppose tire failure is a possibility but I have read a lot of the hypermiler posts on this.   It appears their consensus is that at max inflation or slightly above is oky doky.

Higher inflation pressures usually provide an improvement in steering response and cornering stability while diminishing braking response.  So that is a trade off.   I use my brakes minimally and usually cost up to stop signs and lights.  (I corner and steer way more than brake)

So yeah,  I'll run this little experiment a bit longer.

For those not interested in maxing their MPGs still be sure to check your tires for pressure.   Even a few pounds low can diminish MPG and lead to excess tire wear and possible overheating.

Over inflating your tires is definitely dangerous. If by 44 psi max you mean that is the specification in the door jam and you're still under the tire's max rating that is one thing but if you mean that you are over the tire's max rating that is dangerous.

BobW, you have a ton of posts and you're definitely respected within the community so I'd ask you to be very careful when making recommendations that could endanger other readers if they put the recommendation into practice.

I'm also not sure why you put this under the Antimustachian Wall of Shame and Comedy.

Ashyukun

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #9 on: June 15, 2015, 01:24:28 PM »
Yeah,  I know,  funny huh?

So I checked my tires on the 1999 Mercury Mountaineer.  Damn 32 lbs!   Max inflate rated at 44 lbs.   I filled those babies up to 46 lbs.

Took daughter home to her moms house which is about 45 miles at 32 lbs and MPG 18.5 (I have a digital tracker)   Filled up the air.   Return trip 21.4 MPG.

That is a 15% increase in MPG!  Our annual car gas bill for 2 cars runs about $2,400 (yeah, I know I'm researching higher MPG cars)   So this little trick will save us $400 per year if we do nothing different. 

So yeah,   check your tires and don't be shy about going a tad over the max inflate.    By the way,  hypermilers increase their Prius mileage to 65 mpg simply by overinflating a tad.  Bike riders take note as well --- you could be peddling with 15% less effort. 


YMMV!

I'm definitely with the others in that inflating the tires to the max rated pressure is courting disaster. If you're not inflating them after driving a LOT in 100-degree weather you're running the risk of them failing when they heat up while driving. That said- inflating them a bit more than the recommended pressure isn't likely to cause a failure, but likely will wear the tires oddly.

On bikes, I'd caution against over-inflating the tires even more strongly- a blowout on a bike is far more likely to hurt you a LOT more than a blowout in a car. However, there is a NOTICEABLE difference in riding when you have the tires properly inflated vs under-inflated, so do keep an eye on the pressure and keep it topped off, it makes the ride a LOT easier.

MgoSam

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #10 on: June 15, 2015, 01:39:54 PM »
Why is this in the anti-mustachian section? Shouldn't this be in the "Share your Badassity!"

Rollin

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #11 on: June 15, 2015, 02:07:25 PM »
It has always been my practice to inflate to recommended tire pressures when I am not hauling a heavy load of people or cargo.  So, when I am loaded up I pressure up.  The maximum load rating for a tire is based on the higher pressure.  In other words you should increase the tire pressure as your load is increased.  How can having higher pressure (to the load rating) with a light load of people or cargo cause a blowout problem other than some premature wear down the center?

For those that suggest the tire getting hotter under higher pressure, therefore increasing the chances of a blowout, I'm not sure you have this correct.  Now, if the tires are underinflated you can have significant issues with heat causing blowouts.  Remember all the Explorer tire blowouts with Firestone years ago?  Much of that was underinflation, increased heat, coupled with significant steering movement at high speeds (avoiding an obstacle for example).

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #12 on: June 15, 2015, 02:14:11 PM »
It has always been my practice to inflate to recommended tire pressures when I am not hauling a heavy load of people or cargo.  So, when I am loaded up I pressure up.  The maximum load rating for a tire is based on the higher pressure.   In other words you should increase the tire pressure as your load is increased.  How can having higher pressure (to the load rating) with a light load of people or cargo cause a blowout problem other than some premature wear down the center?

For those that suggest the tire getting hotter under higher pressure, therefore increasing the chances of a blowout, I'm not sure you have this correct.  Now, if the tires are underinflated you can have significant issues with heat causing blowouts.  Remember all the Explorer tire blowouts with Firestone years ago?  Much of that was underinflation, increased heat, coupled with significant steering movement at high speeds (avoiding an obstacle for example).

No.  Tires offer a suggested range, and an absolute maximum pressure.  Usually the suggested range is something like "32-36 PSI" and the max is something like 44 PSI.  I would recommend you inflate to the 36 in this scenario, not the 44.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #13 on: June 15, 2015, 05:21:29 PM »
It has always been my practice to inflate to recommended tire pressures when I am not hauling a heavy load of people or cargo.  So, when I am loaded up I pressure up.  The maximum load rating for a tire is based on the higher pressure.  In other words you should increase the tire pressure as your load is increased.  How can having higher pressure (to the load rating) with a light load of people or cargo cause a blowout problem other than some premature wear down the center?

For those that suggest the tire getting hotter under higher pressure, therefore increasing the chances of a blowout, I'm not sure you have this correct.  Now, if the tires are underinflated you can have significant issues with heat causing blowouts.  Remember all the Explorer tire blowouts with Firestone years ago?  Much of that was underinflation, increased heat, coupled with significant steering movement at high speeds (avoiding an obstacle for example).
yep,  I figured this post would bring out the naysayer parrots.   I might sugeest researching the hypermiler tire guys who are experts on this hack.   For the record slight over inflation does not cause uneven wear,  improves cornering,  makes for a stiffer ride,  decreases braking efficiency,  improves traction, decreases braking efficiency and improves mileage significantly.   The hot tire comes from under inflation and the max inflation number already includes anticipation of tire heat up.   You should check your tire inflation when cold.   Of course I could be wrong.

milesdividendmd

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #14 on: June 15, 2015, 06:07:51 PM »
Bob W, I like it!

But then I'm the type of guy who alters his oven to reach 850 F in order to cook a proper pizza.

Keep us posted either way.

forummm

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #15 on: June 15, 2015, 06:51:38 PM »
It has always been my practice to inflate to recommended tire pressures when I am not hauling a heavy load of people or cargo.  So, when I am loaded up I pressure up.  The maximum load rating for a tire is based on the higher pressure.  In other words you should increase the tire pressure as your load is increased.  How can having higher pressure (to the load rating) with a light load of people or cargo cause a blowout problem other than some premature wear down the center?

For those that suggest the tire getting hotter under higher pressure, therefore increasing the chances of a blowout, I'm not sure you have this correct.  Now, if the tires are underinflated you can have significant issues with heat causing blowouts.  Remember all the Explorer tire blowouts with Firestone years ago?  Much of that was underinflation, increased heat, coupled with significant steering movement at high speeds (avoiding an obstacle for example).
yep,  I figured this post would bring out the naysayer parrots.   

« Last Edit: June 15, 2015, 06:53:35 PM by forummm »

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #16 on: June 15, 2015, 07:03:22 PM »
That was awesome forummmmm!   

TRBeck

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #17 on: June 15, 2015, 07:32:21 PM »

But then I'm the type of guy who alters his oven to reach 850 F in order to cook a proper pizza.


Need more info, please. Instructable or something?

Rollin

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #18 on: June 15, 2015, 08:07:24 PM »
It has always been my practice to inflate to recommended tire pressures when I am not hauling a heavy load of people or cargo.  So, when I am loaded up I pressure up.  The maximum load rating for a tire is based on the higher pressure.  In other words you should increase the tire pressure as your load is increased.  How can having higher pressure (to the load rating) with a light load of people or cargo cause a blowout problem other than some premature wear down the center?

For those that suggest the tire getting hotter under higher pressure, therefore increasing the chances of a blowout, I'm not sure you have this correct.  Now, if the tires are underinflated you can have significant issues with heat causing blowouts.  Remember all the Explorer tire blowouts with Firestone years ago?  Much of that was underinflation, increased heat, coupled with significant steering movement at high speeds (avoiding an obstacle for example).
yep,  I figured this post would bring out the naysayer parrots.   I might sugeest researching the hypermiler tire guys who are experts on this hack.   For the record slight over inflation does not cause uneven wear,  improves cornering,  makes for a stiffer ride,  decreases braking efficiency,  improves traction, decreases braking efficiency and improves mileage significantly.   The hot tire comes from under inflation and the max inflation number already includes anticipation of tire heat up.   You should check your tire inflation when cold.   Of course I could be wrong.

Yes, as it seems like a lot of misinformation and if you read through they kinda say different things (contradictory).

From USDOT - Understanding Tire Pressure and Load Limits

Tire inflation pressure is the level of air in the tire that provides it with load-carrying capacity and affects the overall performance of the vehicle. The tire inflation pressure is a number that indicates the amount of air pressure– measured in pounds per square inch (psi)–a tire requires to be properly inflated. (You will also find this number on the vehicle information placard expressed in kilopascals (kPa), which is the metric measure used internationally.)

Manufacturers of passenger vehicles and light trucks determine this number based on the vehicle's design load limit, that is, the greatest amount of weight a vehicle can safely carry and the vehicle's tire size.The proper tire pressure for your vehicle is referred to as the "recommended cold inflation pressure." (As you will read below, it is difficult to obtain the recommended tire pressure if your tires are not cold.)

Because tires are designed to be used on more than one type of vehicle, tire manufacturers list the "maximum permissible inflation pressure" on the tire sidewall. This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions.


Or just look at some of the tables in the link below and see how load capacity increases with tire pressure, so if I add 7 passengers to my van I add probably 900-1200 extra pounds and should increase my pressure to accommodate that - up to the maximum of course.  Believe me when I say i can feel the difference when I am at the lower recommended inflation pressure of 32 psi and have my van full of buddies and their camping gear and mountain bikes, and when I'm up near the high end of the inflation max.


http://toyotires.com/sites/default/files/page-files/LoadInflation_Table_P-LT_102913.pdf

milesdividendmd

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #19 on: June 15, 2015, 09:38:44 PM »


But then I'm the type of guy who alters his oven to reach 850 F in order to cook a proper pizza.


Need more info, please. Instructable or something?

This captures the essence of the pursuit.

http://www.varasanos.com/pizzarecipe.htm

Or if you want the specifics of my personal quest I wrote a post about it on my eponymous blog entitled "penny wise and pound foolish."

RWD

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #20 on: June 15, 2015, 09:51:56 PM »
You filled your SUV tires to 46lbs?  I bet that thing rides like a buckboard.  And given that it's just a Ford Explorer in a fancy dress, and Ford Explorers are notoriously sensitive to tire failure, I'd say that's a pretty stupid thing to do.

The tires are riding even across contact with the road.

To verify an even contact patch you'll need to measure tread depth at three points (inside, middle, outside) after putting on some significant mileage. Definitely something to keep an eye on.

Xlar

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #21 on: June 16, 2015, 07:11:38 AM »
It has always been my practice to inflate to recommended tire pressures when I am not hauling a heavy load of people or cargo.  So, when I am loaded up I pressure up.  The maximum load rating for a tire is based on the higher pressure.  In other words you should increase the tire pressure as your load is increased.  How can having higher pressure (to the load rating) with a light load of people or cargo cause a blowout problem other than some premature wear down the center?

For those that suggest the tire getting hotter under higher pressure, therefore increasing the chances of a blowout, I'm not sure you have this correct.  Now, if the tires are underinflated you can have significant issues with heat causing blowouts.  Remember all the Explorer tire blowouts with Firestone years ago?  Much of that was underinflation, increased heat, coupled with significant steering movement at high speeds (avoiding an obstacle for example).
yep,  I figured this post would bring out the naysayer parrots.   I might sugeest researching the hypermiler tire guys who are experts on this hack.   For the record slight over inflation does not cause uneven wear,  improves cornering,  makes for a stiffer ride,  decreases braking efficiency,  improves traction, decreases braking efficiency and improves mileage significantly.   The hot tire comes from under inflation and the max inflation number already includes anticipation of tire heat up.   You should check your tire inflation when cold.   Of course I could be wrong.

Yes, as it seems like a lot of misinformation and if you read through they kinda say different things (contradictory).

From USDOT - Understanding Tire Pressure and Load Limits

Tire inflation pressure is the level of air in the tire that provides it with load-carrying capacity and affects the overall performance of the vehicle. The tire inflation pressure is a number that indicates the amount of air pressure– measured in pounds per square inch (psi)–a tire requires to be properly inflated. (You will also find this number on the vehicle information placard expressed in kilopascals (kPa), which is the metric measure used internationally.)

Manufacturers of passenger vehicles and light trucks determine this number based on the vehicle's design load limit, that is, the greatest amount of weight a vehicle can safely carry and the vehicle's tire size.The proper tire pressure for your vehicle is referred to as the "recommended cold inflation pressure." (As you will read below, it is difficult to obtain the recommended tire pressure if your tires are not cold.)

Because tires are designed to be used on more than one type of vehicle, tire manufacturers list the "maximum permissible inflation pressure" on the tire sidewall. This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions.


Or just look at some of the tables in the link below and see how load capacity increases with tire pressure, so if I add 7 passengers to my van I add probably 900-1200 extra pounds and should increase my pressure to accommodate that - up to the maximum of course.  Believe me when I say i can feel the difference when I am at the lower recommended inflation pressure of 32 psi and have my van full of buddies and their camping gear and mountain bikes, and when I'm up near the high end of the inflation max.


http://toyotires.com/sites/default/files/page-files/LoadInflation_Table_P-LT_102913.pdf

I agree that you need to increase the pressure in the tire when you add more load. I even would agree that increasing the pressure would improve fuel economy and all the rest of it. The bit that I disagree about and that is dangerous is inflating the tire over the maximum tire pressure listed on the tire. The manufacture chose that pressure to be the maximum because, from their testing, it was the maximum safe pressure that the tire could be filled before failing...

I don't see how there could be any disagreement that this is dangerous. Now if Bob W had said that he inflated up to the maximum tire pressure then I would be totally okay with that and agree that it would improve fuel economy while reducing braking performance.

Also, as a note, all tire pressures should be measured when the tire is cold (not after driving on your tires). So Bob W is correct in saying that the listed maximum pressure takes into account that the tire will heat up during regular driving.

forummm

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #22 on: June 16, 2015, 07:17:35 AM »


But then I'm the type of guy who alters his oven to reach 850 F in order to cook a proper pizza.


Need more info, please. Instructable or something?

This captures the essence of the pursuit.

http://www.varasanos.com/pizzarecipe.htm

Or if you want the specifics of my personal quest I wrote a post about it on my eponymous blog entitled "penny wise and pound foolish."

I've met Varasano a couple times. He even offered me pizza during the middle of a 10k I was running as I passed by his restaurant (I declined). True story. They have Rubik's cubes at some of the tables.

TheGrimSqueaker

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #23 on: June 16, 2015, 07:59:51 AM »
I recently bought tires for the Squeakmobile (Scion). To maximize my benefit, and because the factory tires had turned out to be such crap that they wore out long before their estimated mileage, I decided to get some more expensive tires that came with a mileage warranty. If the tires fail or wear out before the warranty period expires, the manufacturer will either replace the tire, or amortize the cost of the remaining mileage and give that to me as a credit toward the replacement tire. This worked out to a better cost per actual mile than if I did a like-for-like replacement.

Does over-inflating the tires affect the warranty coverage? I like the idea of extra mileage, but do have to go over potholes and rough terrain sometimes (while camping or hiking). It makes sense for me to consider other costs.

Rollin

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #24 on: June 16, 2015, 08:20:24 AM »
I agree that you need to increase the pressure in the tire when you add more load. I even would agree that increasing the pressure would improve fuel economy and all the rest of it. The bit that I disagree about and that is dangerous is inflating the tire over the maximum tire pressure listed on the tire. The manufacture chose that pressure to be the maximum because, from their testing, it was the maximum safe pressure that the tire could be filled before failing...

I don't see how there could be any disagreement that this is dangerous. Now if Bob W had said that he inflated up to the maximum tire pressure then I would be totally okay with that and agree that it would improve fuel economy while reducing braking performance.

Also, as a note, all tire pressures should be measured when the tire is cold (not after driving on your tires). So Bob W is correct in saying that the listed maximum pressure takes into account that the tire will heat up during regular driving.

Correct, correct!  Everything that I have read says DO NOT inflate about the maximum.  I think there was some confusion in earlier posts when they used the term "over-inflate" when they actually meant to write "inflate above the recommended psi" - not the max psi.

Mr. Green

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #25 on: June 16, 2015, 09:20:50 AM »
No on here has asked the question why slightly over-inflating those tires would increase gas mileage. It is most certainly because you have created a more "rounded" contact surface. Less surface contact equals less friction to cause rolling resistance. I would simply caution you that less surface contact also equals poorer handling.

Xlar

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #26 on: June 16, 2015, 09:24:08 AM »
I agree that you need to increase the pressure in the tire when you add more load. I even would agree that increasing the pressure would improve fuel economy and all the rest of it. The bit that I disagree about and that is dangerous is inflating the tire over the maximum tire pressure listed on the tire. The manufacture chose that pressure to be the maximum because, from their testing, it was the maximum safe pressure that the tire could be filled before failing...

I don't see how there could be any disagreement that this is dangerous. Now if Bob W had said that he inflated up to the maximum tire pressure then I would be totally okay with that and agree that it would improve fuel economy while reducing braking performance.

Also, as a note, all tire pressures should be measured when the tire is cold (not after driving on your tires). So Bob W is correct in saying that the listed maximum pressure takes into account that the tire will heat up during regular driving.

Correct, correct!  Everything that I have read says DO NOT inflate about the maximum.  I think there was some confusion in earlier posts when they used the term "over-inflate" when they actually meant to write "inflate above the recommended psi" - not the max psi.

Glad we're on the same page :)

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #27 on: June 16, 2015, 09:46:20 AM »
So after much consideration of everyone's input I am backing off from 46 to 44 lbs.   That should hopefully end the debate on the over(hyper) inflation question.   My braking distance will remain relatively high,  my cornering will remain improved,  my mpg will be substantially increased,  my ride somewhat rougher (I have not noticed this at all) and I should be within safety specs.   Regarding the tires wearing more in the middle, this is old school pre radial talk.

I don't think there is a perfect inflation number for all the variables and I may be on the high side.  But my vehicle does weigh 4,000 pounds.  Since I will be buying a high MPG car in the not too distant future this will be my temporary behavior for this vehicle.   

From my understanding of it, hysteresis plays the biggest role in tire fatigue. This seems to be demonstrated by the fact that tires which have been run at low pressure for extended periods of time are prone to cord failure and tread separation. So reducing sidewall hysteresis by means of increased pressure would appear like a good way to reduce the occurrence of fatigue failure.

It would also suggest that a tire inflated towards the higher end of its Max inflation stamp will last longer than one inflated below the suggested rates.   

It is a very interesting discussion over at eccomodder.com regarding this topic.  Considering a tire may make 30 million rotations in its useable life, that is a lot of freaking rotations!

Appreciate everyone's cautioning about safety --- safety first!   I am taking that into consideration. 

I am saving my pennies and looking towards a 5-10K fuel efficient vehicle and retiring the gas hog to back up,  camping and snow duty.   It is a great SUV but at 300K it is time to consider options. 


r3dt4rget

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #28 on: June 16, 2015, 09:52:01 AM »
No on here has asked the question why slightly over-inflating those tires would increase gas mileage. It is most certainly because you have created a more "rounded" contact surface. Less surface contact equals less friction to cause rolling resistance. I would simply caution you that less surface contact also equals poorer handling.
That's not correct. Modern tire's are designed with metal ribs that force a tire to hold it's shape within reasonable pressure ranges. So the shape of the tire between 30 PSI and 50 PSI is not really changed when it's under the weight of the vehicle. It is a myth that higher pressure = more tire wear. This myth originates from pre-radial tire design, when indeed tires would be shaped like donuts.

It's more efficient because less energy is lost. Have you ever tried to ride a bike with a flat tire? A lot of energy is wasted trying to get force to the ground through a flat tire.

I have a lot of personal experience with this subject. On my last set of tires I ran them at about 50 PSI. Max rating was 44 PSI. Tread warranty on those tires was 80,000 miles. With regular balancing, alignments, and checking the pressure, I made them last the full warranty period before replacement. In my own data I discovered a 7% increase in fuel economy going from 30 PSI to 40 PSI.

What people have to realize is that the "Max Pressure" is not the true maximum pressure. There is a large safety margin put in place by the manufacturer. Risk management departments would never allow a manufacturer to state the actual maximum performance of a product. If you visit hypermiler forums you will encounter people who inflate their tires to 50, even 65 PSI without a single issue, despite the max ratings being 44 or 51 PSI. The tires can handle much more than their stated maximum, especially when these tires are for light commuter cars not driving under extreme circumstances.

Also realize that the tire pressure information for your car is calculated for maximum ride comfort, not efficiency or performance. A car with tires inflated to 30 PSI will ride more comfortably than an identical car with tires inflated to 45 PSI, without costing the car maker any money in suspension design. The reality is that a car will handle, stop, accelerate, and get better economy at higher tire pressures while sacrificing some ride and noise comfort.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #29 on: June 16, 2015, 09:54:46 AM »
No on here has asked the question why slightly over-inflating those tires would increase gas mileage. It is most certainly because you have created a more "rounded" contact surface. Less surface contact equals less friction to cause rolling resistance. I would simply caution you that less surface contact also equals poorer handling.

Yeah,  it doesn't actually work like that with radials.   A slight over inflation does not cause a rounding from side to side. (a hump in the middle of the tread)  The rolling resistance is diminished as the tire is rounder and there is less contact from front to back on the tire.  The tire does not hump in the middle of the tread as has been suggested.   (to test your tires for even wear simply use a paint roller and paint the tire tread.  Let dry and then drive for a bit.   You will be able to see the wear patterns pretty quickly)

As far as handling,  autocrossers (those who play parking lot swerve and steer time trial contests) overinflate as a rule.   The over inflation improves cornering significantly.    Over inflation does effect braking distance by increasing it.   

milesdividendmd

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #30 on: June 16, 2015, 09:59:19 AM »



But then I'm the type of guy who alters his oven to reach 850 F in order to cook a proper pizza.


Need more info, please. Instructable or something?

This captures the essence of the pursuit.

http://www.varasanos.com/pizzarecipe.htm

Or if you want the specifics of my personal quest I wrote a post about it on my eponymous blog entitled "penny wise and pound foolish."

I've met Varasano a couple times. He even offered me pizza during the middle of a 10k I was running as I passed by his restaurant (I declined). True story. They have Rubik's cubes at some of the tables.

You must be an atlantite.

How's the pie?!

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #31 on: June 16, 2015, 10:03:24 AM »
No on here has asked the question why slightly over-inflating those tires would increase gas mileage. It is most certainly because you have created a more "rounded" contact surface. Less surface contact equals less friction to cause rolling resistance. I would simply caution you that less surface contact also equals poorer handling.
That's not correct. Modern tire's are designed with metal ribs that force a tire to hold it's shape within reasonable pressure ranges. So the shape of the tire between 30 PSI and 50 PSI is not really changed when it's under the weight of the vehicle. It is a myth that higher pressure = more tire wear. This myth originates from pre-radial tire design, when indeed tires would be shaped like donuts.

It's more efficient because less energy is lost. Have you ever tried to ride a bike with a flat tire? A lot of energy is wasted trying to get force to the ground through a flat tire.

I have a lot of personal experience with this subject. On my last set of tires I ran them at about 50 PSI. Max rating was 44 PSI. Tread warranty on those tires was 80,000 miles. With regular balancing, alignments, and checking the pressure, I made them last the full warranty period before replacement. In my own data I discovered a 7% increase in fuel economy going from 30 PSI to 40 PSI.

What people have to realize is that the "Max Pressure" is not the true maximum pressure. There is a large safety margin put in place by the manufacturer. Risk management departments would never allow a manufacturer to state the actual maximum performance of a product. If you visit hypermiler forums you will encounter people who inflate their tires to 50, even 65 PSI without a single issue, despite the max ratings being 44 or 51 PSI. The tires can handle much more than their stated maximum, especially when these tires are for light commuter cars not driving under extreme circumstances.

Also realize that the tire pressure information for your car is calculated for maximum ride comfort, not efficiency or performance. A car with tires inflated to 30 PSI will ride more comfortably than an identical car with tires inflated to 45 PSI, without costing the car maker any money in suspension design. The reality is that a car will handle, stop, accelerate, and get better economy at higher tire pressures while sacrificing some ride and noise comfort.

Yes,  glad to see you did an 80K test.   You are spot on with the exception of the "stop" part.  Everything I've read from hypermilers and autocrossers suggests that stopping is diminished.   

Thanks for you input!!!

Rollin

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #32 on: June 16, 2015, 10:14:50 AM »
No on here has asked the question why slightly over-inflating those tires would increase gas mileage. It is most certainly because you have created a more "rounded" contact surface. Less surface contact equals less friction to cause rolling resistance. I would simply caution you that less surface contact also equals poorer handling.
That's not correct. Modern tire's are designed with metal ribs that force a tire to hold it's shape within reasonable pressure ranges. So the shape of the tire between 30 PSI and 50 PSI is not really changed when it's under the weight of the vehicle. It is a myth that higher pressure = more tire wear. This myth originates from pre-radial tire design, when indeed tires would be shaped like donuts.

It's more efficient because less energy is lost. Have you ever tried to ride a bike with a flat tire? A lot of energy is wasted trying to get force to the ground through a flat tire.

I have a lot of personal experience with this subject. On my last set of tires I ran them at about 50 PSI. Max rating was 44 PSI. Tread warranty on those tires was 80,000 miles. With regular balancing, alignments, and checking the pressure, I made them last the full warranty period before replacement. In my own data I discovered a 7% increase in fuel economy going from 30 PSI to 40 PSI.

What people have to realize is that the "Max Pressure" is not the true maximum pressure. There is a large safety margin put in place by the manufacturer. Risk management departments would never allow a manufacturer to state the actual maximum performance of a product. If you visit hypermiler forums you will encounter people who inflate their tires to 50, even 65 PSI without a single issue, despite the max ratings being 44 or 51 PSI. The tires can handle much more than their stated maximum, especially when these tires are for light commuter cars not driving under extreme circumstances.

Also realize that the tire pressure information for your car is calculated for maximum ride comfort, not efficiency or performance. A car with tires inflated to 30 PSI will ride more comfortably than an identical car with tires inflated to 45 PSI, without costing the car maker any money in suspension design. The reality is that a car will handle, stop, accelerate, and get better economy at higher tire pressures while sacrificing some ride and noise comfort.

...and you are still alive to type this out!?  My gawd, you live on the edge :)
« Last Edit: June 16, 2015, 10:17:19 AM by Rollin »

Posthumane

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #33 on: June 16, 2015, 10:38:49 AM »
I would like to point out that the max inflation pressure on a tire sidewall has a fair amount of safety margin built into it. Tires are often inflated above the rated max inflation pressure in order to seat the bead on the rim when it is being installed. Modern car tires in good shape won't catastrophically fail from over inflation until about 120 psi. That being said, when one does go it is indeed very spectacular and dangerous. I'm sure you can find a mechanic training video on youtube which shows a tire being shot 100 m in the air as it explodes, and taking out the dummy standing over it.

There are optimal pressure calculators for bicycle tires which will specify the inflation pressure for minimal rolling resistance given the tire size and load place on it. Going either above or below that will increase resistance. For me with a slightly loaded bike the optimal inflation pressure is around 90 psi on 700c-28 tires. Some tire brands will let me reach that pressure, some won't (my current ones have a max rating of 85 psi so that's what I run them at).

For autocrossing tires are typically inflated to get optimal cornering grip, not lowest rolling resistance. At low pressures the tire will roll over onto the sidewall slightly under hard cornering, reducing contact patch and grip. This can be checked by putting white shoe polish or on your sidewalls and running a course, then adjusting the pressure and repeating. A more accurate way is to measure tire temperatures at various points on the tire with an IR thermometer. However, pressures for optimal rolling resistance tend to be much higher than for optimal cornering.

Although radial tires don't really balloon as much as old bias ply ones did, they don't hold their shape perfectly and you may still find slightly increased wear in the centre of the tread compared to the sides. Conversely, under inflated tires will wear more on the edges of the tread. It's up to you to determine if this tradeoff is worth the decreased fuel consumption.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #34 on: June 16, 2015, 01:42:34 PM »
Yeah,  I'm doing the paint the tire trick to assure myself of the wear pattern.  I'll report back on the outcome. 

JAYSLOL

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #35 on: June 16, 2015, 07:35:04 PM »
I run my work truck and my car tires slightly over-inflated, but only by 2-4 lbs.  I think its good to keep in mind is that tire size makes a difference.  On a small car (example my tercel) the standard rims can use anywhere from 155 - 185 wide tires (although at one point i had an un-mustachian set of much wider fancy alloy rims and low profile tires on it, face palm).   The 185s take 10+% off the fuel economy and cost more to buy compared to the 155s.  I've found it has been better having a small car and running narrower tires only slightly over inflated to still get full life out of a very inexpensive set of rubber rather than having a large vehicle that requires large tires and over inflating the shit out of them to get back some of the mileage

forummm

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #36 on: June 16, 2015, 07:56:11 PM »



But then I'm the type of guy who alters his oven to reach 850 F in order to cook a proper pizza.


Need more info, please. Instructable or something?

This captures the essence of the pursuit.

http://www.varasanos.com/pizzarecipe.htm

Or if you want the specifics of my personal quest I wrote a post about it on my eponymous blog entitled "penny wise and pound foolish."

I've met Varasano a couple times. He even offered me pizza during the middle of a 10k I was running as I passed by his restaurant (I declined). True story. They have Rubik's cubes at some of the tables.

You must be an atlantite.

How's the pie?!

It's been a few years since I've been over there, but I remember it being very good.

GetItRight

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #37 on: June 17, 2015, 10:50:29 AM »
Enjoy the reduction in traction and accelerated tire wear, and beware blowouts. Ideal tire pressure depends on the tire, wheel, vehicle weight, and weight distribution. Increase tire pressure if loaded heavy. By running the tire pressure you mentioned in the original post you are creating a safety hazard for yourself and others on the road, and depending on how much more quickly you wear out your tires maybe not even saving money.

gimp

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #38 on: June 17, 2015, 11:02:21 AM »
Bob, I respect you, but this is some seriously stupid fucking shit. Come on. You've inflated tires beyond their maximum inflate rating, which is itself far beyond what your vehicle's manufacturer recommends.

They don't recommend this so that you burn more gas. They recommend this for safety, tire longevity, and oh yeah, have I mentioned safety? Tire blowouts, reduced traction, uneven tire wear (see: tire blowouts) all sorts of dumb shit happens when you do this.

Any mechanic out there will tell you that what you are doing is dangerous as well as stupid.

Congratulations on maybe saving $400 a year. Tires are expensive and treating them this way will result in you paying for new tires. The less you spend on your tires, by the way, the more likely they are to fail from being abused like this.

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #39 on: June 17, 2015, 12:45:53 PM »
Bob, I respect you, but this is some seriously stupid fucking shit. Come on. You've inflated tires beyond their maximum inflate rating, which is itself far beyond what your vehicle's manufacturer recommends.
I take it you didn't read the whole thread?

Running the tires at sidewall maximum pressure seems perfectly safe - I've done it for years with no problems, as have whole communities of people online. Even 2 psi above sidewall maximum is probably fine, given that the sidewall maximum 44psi in the morning increases significantly as the tire heats up - but he backed down to the 44psi recommended by the tire manufacturer as soon as it was suggested in the thread.

frugalnacho

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #40 on: June 17, 2015, 01:07:32 PM »
Why is this in the anti-mustachian section? Shouldn't this be in the "Share your Badassity!"

Or an ad on the weather channel?  One weird trick to increase gas mileage by 15%!

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #41 on: June 17, 2015, 01:32:13 PM »
Why is this in the anti-mustachian section? Shouldn't this be in the "Share your Badassity!"

Or an ad on the weather channel?  One weird trick to increase gas mileage by 15%!

No idea?  I thought I started the thread in either GD or SYB?  Perhaps a moderator attempt at humor?

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #42 on: June 17, 2015, 01:45:15 PM »
Bob, I respect you, but this is some seriously stupid fucking shit. Come on. You've inflated tires beyond their maximum inflate rating, which is itself far beyond what your vehicle's manufacturer recommends.
I take it you didn't read the whole thread?

Running the tires at sidewall maximum pressure seems perfectly safe - I've done it for years with no problems, as have whole communities of people online. Even 2 psi above sidewall maximum is probably fine, given that the sidewall maximum 44psi in the morning increases significantly as the tire heats up - but he backed down to the 44psi recommended by the tire manufacturer as soon as it was suggested in the thread.

Well I have backed it down to 44 for now.  (doubt most people read 100 comment long threads in entirety.)

A couple of additional comments for those starting at the bottom of the thread. ---- Most of the comments saying it is o.k. to run em high seem to be well researched/reasoned and to have actually done this on a regular basis.   Many of the "you're gonna die at 45 psi" folks appear to be shooting from the hip.    The reality is that there are pluses and minuses and risks on both ends of the equation.   And I do really appreciate the "don't do nuthin stupid" input.   

I have a propensity to do stupid things on a pretty regular basis, so it is nice when someone mentions that I may be entering that territory.  (yeah, I did the math and this isn't the stupid thing territory)

That and most failed to notice that I am driving a 4,000 lb SUV that goes close to 5,000 lbs when I'm full up with people.   That in itself fits the definition of heavy load which is what the max inflation number is designed for. 

Been too rainy here (like nonstop) to do the paint test for even wear.  I'll be sure to update this thread once that test is done, even if it is off the screen by then.

Gone Fishing

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #43 on: June 17, 2015, 02:01:28 PM »
Enjoying the thread! Looking foward to seeing the results of the paint test.  I have routinely inflated my tires up to the manufacturer's limit for better milage.  I never done any real milage testing, but my tires have never worn abnormally either.  I do notice a little more vibration at 70+MPH, but a mustachian/hypermiler shouldn't really be driving over 70 anyway.

Slowing down on the hwy gives me the best milage, 55 is around 15% better than 70, but can irritate other drivers and cause a hazard if too much slower than the flow of traffic. 

MoneyCat

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #44 on: June 17, 2015, 05:30:06 PM »
Got to say I love the title of this thread.  Somebody has been reading Buzzfeed! :-P

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #45 on: June 17, 2015, 08:41:50 PM »
Enjoying the thread! Looking foward to seeing the results of the paint test.  I have routinely inflated my tires up to the manufacturer's limit for better milage.  I never done any real milage testing, but my tires have never worn abnormally either.  I do notice a little more vibration at 70+MPH, but a mustachian/hypermiler shouldn't really be driving over 70 anyway.

Slowing down on the hwy gives me the best milage, 55 is around 15% better than 70, but can irritate other drivers and cause a hazard if too much slower than the flow of traffic.
since my vehicle is a gas hog and has a fuel economy read out I like to drive 55 while I do the time vs mpg equation in my head.   Drives my wife freaking crazy.       

This_Is_My_Username

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« Reply #46 on: June 18, 2015, 06:24:37 AM »
i also use very high psi (~45), and the only down side is that the traction is very poor cornering in the wet.

I have had a few short moments where the car loses traction and drifts sidewards.  A reminder to drive slower : )

otherwise, its all good, there are big savings to be had : )

Bob W

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Re: .
« Reply #47 on: June 18, 2015, 06:45:44 AM »
i also use very high psi (~45), and the only down side is that the traction is very poor cornering in the wet.

I have had a few short moments where the car loses traction and drifts sidewards.  A reminder to drive slower : )

otherwise, its all good, there are big savings to be had : )
yeah since I generally follow hypermiler methods I do sometimes corner a little hard to avoid braking.   I'll have to watch that.  It would seem that a stiffer tire may be more prone to slippage on wet pavement,  although according to auto crossers it significantly improves cornering on dry.    Driving slow with high awareness is always a good policy. 

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #48 on: June 18, 2015, 07:01:57 AM »
Also if the tires are to inflated, if you hit a bad pothole the tire could blowout.  You would then be out a tire.
personal experience or a reference source?  I'm kinda doubting manufacturers would approve inflation rates that lead to blow outs but as always I could be wrong.

music lover

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #49 on: June 18, 2015, 07:09:05 AM »
That and most failed to notice that I am driving a 4,000 lb SUV that goes close to 5,000 lbs when I'm full up with people.   That in itself fits the definition of heavy load which is what the max inflation number is designed for.

The people that designed and built your vehicle know exactly what it weighs and have done extensive testing to determine the optimum pressure. They also know that people will often carry passengers in the vehicle. The fact that you chose the number on the tire and not what the manufacturer of your vehicle recommends indicates that you made an uneducated choice.