Author Topic: This One Simple Trick Will Increase Gas Mileage by 15%!!  (Read 26671 times)

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #50 on: June 18, 2015, 07:40:12 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.

And again, the max SUGGESTED pressure is likely in the 36-38PSI range (there will be a "suggested range" of ~32-38PSI on the door jam) and THIS is what Ford suggests as a Max.  The 44 or 46PSI is not a "suggested" max, it's a "DO NOT UNDER ANY CIRCUMSTANCES GO OVER THIS LEVEL" max.

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #51 on: June 18, 2015, 09:28:17 AM »
Interesting. So you think that Ford knows better about the behavior of all of the tires that could conceivably be put on a Ford than the manufacturer of any given tire knows about its product?

Posthumane

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #52 on: June 18, 2015, 09:45:34 AM »
There are a number of variables that go into deciding what pressure to put on the door jamb. Door jamb labels are based on the stock tire make/model/size and take into account things like noise/vibration/harshness (NVH) which results from higher inflation pressures, as well as tire wear based on common load patters. If you routinely load the vehicle to max or run a slightly narrower than stock tire, higher inflation pressures are a must.

Basically, inflation pressure is a trade off of several factors. Higher pressures result in less compliance which generally results in lower rolling resistance, to a point. A certain amount of compliance is necessary though since having the entire wheel move vertically as a result of minute surface undulations results in higher rolling resistance. A high pressure generally won't result in a reduction in wet traction unless you get to the point where contact patch starts to be significantly reduced. In fact, hydroplaning resistance is directly proportional to tire pressure in smooth tires (i.e. not designed specifically with water channels). However, with less sidewall compliance, going past the traction limit will result in a much more sudden loss of grip with less warning compared to tires with lower pressure, which for many drivers may result in poorer performance at the limit.

The paint on the tire trick probably won't tell you much about predicted tire wear across the tread. It only shows gross differences where there is or isn't pavement contact. The entire tread area should still be touching the ground with increased pressure (if it isn't, then you're waaay over inflated) but there will be a pressure gradient across the tread - the centre will have slightly higher ground pressure than the sides. Your paint will still wear off fairly evenly on the tread.

Btw, an under inflated tire is much more likely to cause a blowout than an over inflated one. Several causes of blowouts include overheating of the tires from too much sidewall flex, the tire bead rolling off the rim during cornering, and the tire bottoming out on the rim when hitting something like a pothole.

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #53 on: June 18, 2015, 10:05:35 AM »
Interesting. So you think that Ford knows better about the behavior of all of the tires that could conceivably be put on a Ford than the manufacturer of any given tire knows about its product?

I don't think either one of them would suggest inflating to or more than the stated maximum, so it really doesn't matter now, does it?

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #54 on: June 18, 2015, 10:38:31 AM »
My understanding of bike tire pressure is that higher doesn't equal better.  You want to aim for about 15% deflection of the tire when the rider's weight goes on it.  (You can find charts online for given tires and rider weight).  Higher tire pressures than that actually make you slower because the bike tire wastes more energy bumping up and down along uneven road surfaces.  Your tire is also your suspension on your bike, very high pressures will be painful on your hands and hard on your rims.

music lover

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #55 on: June 18, 2015, 10:57:58 AM »
Interesting. So you think that Ford knows better about the behavior of all of the tires that could conceivably be put on a Ford than the manufacturer of any given tire knows about its product?

Yes.  All the tire manufacturers are in agreement...use the pressure recommended by the maker of the vehicle. The information is readily available to anyone who bothered to look it up instead of guessing:

Firestone states this on their website:

"The first place to look for the correct air pressure for your specific tires is your vehicle owner’s manual. Correct air pressure should also be listed on the tire placard attached to the vehicle door edge, doorpost, glove box door or fuel door."

Bridgestone:

"Look on the driver’s side door jamb or your owner’s manual to find the recommended cold tire PSI for your front and rear tires.  If you cannot find it, you should consult your vehicle dealer, manufacturer, or a qualified tire professional."

Goodyear:

"To find the proper air pressure for your tires, look in your vehicle's owner's manual, on the sticker on the driver's side doorjamb, or in the glove box."

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #56 on: June 18, 2015, 11:04:12 AM »
Posthumane thank you for you thoughtful and obviously educated thoughts.    So I should just skip the paint test and it wouldn't tell me more than a visual inspection regarding the bell shaped pressure gradient differential you describe.

On a related note --- I bought this vehicle from a good friend.   The tires were all oddly worn and he said that the vehicle had always done that due to it being all wheel drive. 

He stated he always rotated front to back.   I questioned this with my tire supplier and he stated that the X pattern was recommended for all wheel drive vehicles using radial tires.   So that is what I have done and I have noted no difference in tire wear.

Tire wear is important to me as tires in this size vehicle (well any really) are expensive. 

Here is a quote from over at one of the hypermiler sites "Higher air pressure tires run cooler. This is the main reason for less wear. Less friction less wear,"   I fell pretty confident that is true.    So by maxing out my inflation (and not an ounce over mind you)  I should be saving on both gas and tires.  Sweeeeet!

I'm comfortable with the supposed bumpier ride attributed to higher pressured tires.   It appears I do most of my driving on very smooth roads. 

Anyone reading this please check your tires to be sure you are above minimum inflation as that can cause overheating in summer weather like we're having. 

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #57 on: June 18, 2015, 11:10:52 AM »
Interesting. So you think that Ford knows better about the behavior of all of the tires that could conceivably be put on a Ford than the manufacturer of any given tire knows about its product?

Yes.  All the tire manufacturers are in agreement...use the pressure recommended by the maker of the vehicle. The information is readily available to anyone who bothered to look it up instead of guessing:

Firestone states this on their website:

"The first place to look for the correct air pressure for your specific tires is your vehicle owner’s manual. Correct air pressure should also be listed on the tire placard attached to the vehicle door edge, doorpost, glove box door or fuel door."

Bridgestone:

"Look on the driver’s side door jamb or your owner’s manual to find the recommended cold tire PSI for your front and rear tires.  If you cannot find it, you should consult your vehicle dealer, manufacturer, or a qualified tire professional."

Goodyear:

"To find the proper air pressure for your tires, look in your vehicle's owner's manual, on the sticker on the driver's side doorjamb, or in the glove box."

One suspects that is a recommendation with the focus on comfort and not fuel economy or tire life.   Mustachians tend to not follow the herd and be less concerned with comfort and more concerned with economy.   One would guess that companies such as GM are not very good at predicting risk or budgeting given their poor record of financial management.    So yeah,  I didn't even go to their sites and focused my research on sites with people actually hyperinflating tires with years of experience.    You could check out eccomoder.com

music lover

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #58 on: June 18, 2015, 11:22:47 AM »
On a related note --- I bought this vehicle from a good friend.   The tires were all oddly worn and he said that the vehicle had always done that due to it being all wheel drive. 

He stated he always rotated front to back.   I questioned this with my tire supplier and he stated that the X pattern was recommended for all wheel drive vehicles using radial tires.   So that is what I have done and I have noted no difference in tire wear.

AWD does nothing to make tires wear unevenly. Perhaps you should talk to a mechanic instead of a friend.

The X pattern for rotation is fine, unless you have directional tires. Directional tires should only be switched from to rear and would be turning the "wrong" way if put on the other side of the vehicle.
« Last Edit: June 18, 2015, 11:30:58 AM by music lover »

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #59 on: June 18, 2015, 11:25:18 AM »
One suspects that is a recommendation with the focus on comfort and not fuel economy or tire life.   Mustachians tend to not follow the herd and be less concerned with comfort and more concerned with economy.   One would guess that companies such as GM are not very good at predicting risk or budgeting given their poor record of financial management.    So yeah,  I didn't even go to their sites and focused my research on sites with people actually hyperinflating tires with years of experience.    You could check out eccomoder.com

Seriously?  Car companies fall all over themselves for a fraction of a MPG, and you think they're sandbagging for a little ride comfort?  You want to disregard the engineers who do this stuff for a living and listen to Joe Schmo on the internet, fine, but don't tell us it's anything resembling a good idea. 

music lover

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #60 on: June 18, 2015, 11:29:30 AM »
One suspects that is a recommendation with the focus on comfort and not fuel economy or tire life.   Mustachians tend to not follow the herd and be less concerned with comfort and more concerned with economy.   One would guess that companies such as GM are not very good at predicting risk or budgeting given their poor record of financial management.    So yeah,  I didn't even go to their sites and focused my research on sites with people actually hyperinflating tires with years of experience.    You could check out eccomoder.com

No thanks. I'm sure the technicians at the auto manufacturers know what they're talking about, and also the tire manufacturers who state the very same thing.

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #61 on: June 18, 2015, 11:32:27 AM »
Interesting. So you think that Ford knows better about the behavior of all of the tires that could conceivably be put on a Ford than the manufacturer of any given tire knows about its product?

I don't think either one of them would suggest inflating to or more than the stated maximum, so it really doesn't matter now, does it?
I think any of them would be perfectly fine with inflating to the stated maximum. Presumably that's why it exists. As far as I know nobody in this thread is advocating inflating above the stated maximum (even though doing so is likely pretty safe).

Posthumane

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #62 on: June 18, 2015, 11:56:41 AM »
My understanding of bike tire pressure is that higher doesn't equal better.  You want to aim for about 15% deflection of the tire when the rider's weight goes on it.  (You can find charts online for given tires and rider weight).  Higher tire pressures than that actually make you slower because the bike tire wastes more energy bumping up and down along uneven road surfaces.  Your tire is also your suspension on your bike, very high pressures will be painful on your hands and hard on your rims.
This is correct. With bike tires you can calculate what the optimum inflation pressure is based on the size of the tire and the load on it (rear bike tire generally carries more load than front). This is doable with bike tires since they are generally soft and have a round tread section. With car tires it becomes a little more complicated since the construction of the tire (with steel belts and chords in the carcass) cause it to hold a roughly rectangular shape with widely varying pressures.

On a related note --- I bought this vehicle from a good friend.   The tires were all oddly worn and he said that the vehicle had always done that due to it being all wheel drive. 

He stated he always rotated front to back.   I questioned this with my tire supplier and he stated that the X pattern was recommended for all wheel drive vehicles using radial tires.   So that is what I have done and I have noted no difference in tire wear.

AWD does nothing to make tires wear unevenly. Perhaps you should talk to a mechanic instead of a friend.

The X pattern for rotation is fine, unless you have directional tires. Directional tires should only be switched from to rear and would be turning the "wrong" way if put on the other side of the vehicle.
Agree with music lover - if you have odd tire wear it is not generally* a result of AWD, and you may have some alignment issues. Misalignment could also cause increased fuel consumption due to tire scrubbing. I rotate my tires front to rear on an AWD vehicle and have no odd wear problems.

Skip the paint test unless you are going to autocross/race and want to see how far the tire folds over. If you want to measure the ground pressure across the tire the best way is probably with a sensitive IR thermometer, but those are usually not cheap and you are probably better off monitoring the tread depth for any discrepancies.  Higher pressures do make a tire run slightly cooler due to less flex, just be aware that this is offset by a reduced contact patch area if you go too high in pressure which will wear faster.


* I say generally as there are some exceptions - some higher performance AWD cars used a viscous coupling limited slip centre differential, and used a slightly different final drive in the rear compared to the front to "load up" the limited slip unit and provide a slightly rearward power bias. This caused increased tire wear.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #63 on: June 18, 2015, 12:13:07 PM »
On a related note --- I bought this vehicle from a good friend.   The tires were all oddly worn and he said that the vehicle had always done that due to it being all wheel drive. 

He stated he always rotated front to back.   I questioned this with my tire supplier and he stated that the X pattern was recommended for all wheel drive vehicles using radial tires.   So that is what I have done and I have noted no difference in tire wear.

AWD does nothing to make tires wear unevenly. Perhaps you should talk to a mechanic instead of a friend.

The X pattern for rotation is fine, unless you have directional tires. Directional tires should only be switched from to rear and would be turning the "wrong" way if put on the other side of the vehicle.

Well I didn't have to talk with anyone to observe the wear patterns.  So yeah,  apparently on my vehicle AWD did in fact result in uneven wear when rotating front to back.  Conversely the X pattern has shown even wear.     So in fact AWD on my vehicle does make tires wear unevenly. 

I'll would let you know how my personal experience with maximum psi works out but I'm planning on selling or parking the beast pretty soon and will likely never reach the usable end of my tire life.   

But I can tell you that everyone I've read (and I've read a lot since posting this thread) that has actually run their tires at or above max psi reported that their tires lasted longer and that they wore dead even.   People who stuck near the 32 psi level experienced more wear on the outer edges of the tires,  more overall wear and lower gas mileage. 

Hey I'm not promoting anything dangerous here folks --- just suggesting to inflate to at or near the max PSI which is well within the safety margin of the tire manufactures.  Use your door or the tire.  Whichever you like.

And yes --- driving a car is much more dangerous than most people think it is  ---

So,

Drive as few miles as needed (there is a direct correlation to number of miles driven and fatalities)
Always wear shoulder and waist belts appropriately adjusted
Always drive alert
Never drive impaired
Never text or phone call while driving
Avoid driving distractions such as eating or listening to radios
Drive defensively
Drive below the posted maximum speed limit (I'll bet more than a few of us break this daily??)
Avoid driving during busy times and at night
Allow a safe distance (1 car length per 10 mph, and almost no one does this)

Remember that driving in the rain is the cause of more accidents than driving in the snow.  (its been raining like an MF here all week!)   Slick roads are very dangerous and I think most people don't know that or forget that.

Yes ----safety first
 




GuitarStv

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #64 on: June 18, 2015, 12:21:07 PM »
Driving in rain doesn't cause accidents.  Driving in rain requires more attention.  Mistakes made by vehicle operators still cause all the accidents.

music lover

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #65 on: June 18, 2015, 12:57:43 PM »
Well I didn't have to talk with anyone to observe the wear patterns.  So yeah,  apparently on my vehicle AWD did in fact result in uneven wear when rotating front to back.  Conversely the X pattern has shown even wear.     So in fact AWD on my vehicle does make tires wear unevenly.

Are you "that guy" who never admits that he might be wrong??

If the tires on your car are wearing unevenly, then there is a problem either with your car or your driving. AWD that is working correctly does NOT cause uneven tire wear. Tens of millions of people with AWD vehicles have never experienced uneven tired wear.

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #66 on: June 18, 2015, 01:03:23 PM »
On a related note --- I bought this vehicle from a good friend.   The tires were all oddly worn and he said that the vehicle had always done that due to it being all wheel drive. 

He stated he always rotated front to back.   I questioned this with my tire supplier and he stated that the X pattern was recommended for all wheel drive vehicles using radial tires.   So that is what I have done and I have noted no difference in tire wear.

AWD does nothing to make tires wear unevenly. Perhaps you should talk to a mechanic instead of a friend.

The X pattern for rotation is fine, unless you have directional tires. Directional tires should only be switched from to rear and would be turning the "wrong" way if put on the other side of the vehicle.

Well I didn't have to talk with anyone to observe the wear patterns.  So yeah,  apparently on my vehicle AWD did in fact result in uneven wear when rotating front to back.  Conversely the X pattern has shown even wear.     So in fact AWD on my vehicle does make tires wear unevenly. 

I'll would let you know how my personal experience with maximum psi works out but I'm planning on selling or parking the beast pretty soon and will likely never reach the usable end of my tire life.   

But I can tell you that everyone I've read (and I've read a lot since posting this thread) that has actually run their tires at or above max psi reported that their tires lasted longer and that they wore dead even.   People who stuck near the 32 psi level experienced more wear on the outer edges of the tires,  more overall wear and lower gas mileage. 

Hey I'm not promoting anything dangerous here folks --- just suggesting to inflate to at or near the max PSI which is well within the safety margin of the tire manufactures.  Use your door or the tire.  Whichever you like.

And yes --- driving a car is much more dangerous than most people think it is  ---

So,

Drive as few miles as needed (there is a direct correlation to number of miles driven and fatalities)
Always wear shoulder and waist belts appropriately adjusted
Always drive alert
Never drive impaired
Never text or phone call while driving
Avoid driving distractions such as eating or listening to radios
Drive defensively
Drive below the posted maximum speed limit (I'll bet more than a few of us break this daily??)Avoid driving during busy times and at night
Allow a safe distance (1 car length per 10 mph, and almost no one does this)

Remember that driving in the rain is the cause of more accidents than driving in the snow.  (its been raining like an MF here all week!)   Slick roads are very dangerous and I think most people don't know that or forget that.

Yes ----safety first
 

Driving UNDER the posted speed limit on a road where most/all other drivers are exceeding it by 5-10mph is MUCH more dangerous than moving with the speed of traffic. 

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #67 on: June 18, 2015, 01:07:53 PM »

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #68 on: June 18, 2015, 01:16:31 PM »
Grantmeaname --- That was awesome. 

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #69 on: June 18, 2015, 01:20:18 PM »
On a related note --- I bought this vehicle from a good friend.   The tires were all oddly worn and he said that the vehicle had always done that due to it being all wheel drive. 

He stated he always rotated front to back.   I questioned this with my tire supplier and he stated that the X pattern was recommended for all wheel drive vehicles using radial tires.   So that is what I have done and I have noted no difference in tire wear.

AWD does nothing to make tires wear unevenly. Perhaps you should talk to a mechanic instead of a friend.

The X pattern for rotation is fine, unless you have directional tires. Directional tires should only be switched from to rear and would be turning the "wrong" way if put on the other side of the vehicle.

Well I didn't have to talk with anyone to observe the wear patterns.  So yeah,  apparently on my vehicle AWD did in fact result in uneven wear when rotating front to back.  Conversely the X pattern has shown even wear.     So in fact AWD on my vehicle does make tires wear unevenly. 

I'll would let you know how my personal experience with maximum psi works out but I'm planning on selling or parking the beast pretty soon and will likely never reach the usable end of my tire life.   

But I can tell you that everyone I've read (and I've read a lot since posting this thread) that has actually run their tires at or above max psi reported that their tires lasted longer and that they wore dead even.   People who stuck near the 32 psi level experienced more wear on the outer edges of the tires,  more overall wear and lower gas mileage. 

Hey I'm not promoting anything dangerous here folks --- just suggesting to inflate to at or near the max PSI which is well within the safety margin of the tire manufactures.  Use your door or the tire.  Whichever you like.

And yes --- driving a car is much more dangerous than most people think it is  ---

So,

Drive as few miles as needed (there is a direct correlation to number of miles driven and fatalities)
Always wear shoulder and waist belts appropriately adjusted
Always drive alert
Never drive impaired
Never text or phone call while driving
Avoid driving distractions such as eating or listening to radios
Drive defensively
Drive below the posted maximum speed limit (I'll bet more than a few of us break this daily??)Avoid driving during busy times and at night
Allow a safe distance (1 car length per 10 mph, and almost no one does this)

Remember that driving in the rain is the cause of more accidents than driving in the snow.  (its been raining like an MF here all week!)   Slick roads are very dangerous and I think most people don't know that or forget that.

Yes ----safety first
 

Driving UNDER the posted speed limit on a road where most/all other drivers are exceeding it by 5-10mph is MUCH more dangerous than moving with the speed of traffic.

I thought our whole discussion here was on the over or under maximum question ---  Now we're encouraging going 12- 25% over if that is what all the cool kids are doing?  ;)

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #70 on: June 18, 2015, 01:28:01 PM »
Grantmeaname --- That was awesome.
It's from xkcd, one of the cleverest webcomics around. Well worth a read if you're not familiar.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #71 on: June 18, 2015, 01:32:12 PM »
Looks pretty cool.  I just saved to the favs.   Will check it tomorrow and let you know what I think.  I kinda thought it was a Tim Urban thing initially.

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #72 on: June 18, 2015, 01:59:13 PM »
Seriously?  Citation needed?  Do you people have anything between your ears?  What's safer, 10 cars moving in the same direction at 70mph, or 9 cars moving at 70 trying to dodge 1 going 54? 

And no, politically-driven speed limits have nothing to do with engineering-derived PSA limits on tires.  Exceeding one does not have anything to do with exceeding the other. 

Seriously, you guys are fucking with me, right?  There's no way you're this dumb.

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #73 on: June 18, 2015, 03:01:14 PM »
Seriously?  Citation needed?  Do you people have anything between your ears?  What's safer, 10 cars moving in the same direction at 70mph, or 9 cars moving at 70 trying to dodge 1 going 54?
I'm dumb for questioning the 'fact' you pulled out of your ass?

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #74 on: June 18, 2015, 03:12:56 PM »
Seriously?  Citation needed?  Do you people have anything between your ears?  What's safer, 10 cars moving in the same direction at 70mph, or 9 cars moving at 70 trying to dodge 1 going 54?
I'm dumb for questioning the 'fact' you pulled out of your ass?

Roll eyes.  Here's a pretty well cited article I pulled up in 30s on Google.

http://www.ooida.com/IssuesActions/Issues/speed_limiters/documents/Speed-Limiter.pdf

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #75 on: June 18, 2015, 03:17:47 PM »
That's a press release and it's about something different than your assertion.

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #76 on: June 18, 2015, 03:20:34 PM »
That's a press release and it's about something different than your assertion.

Wat?

It's an article for a trade publication that includes several links to studies.

It's titled

"Differential speed limits make roads less safe
Studies show that a higher variance of vehicle speeds in traffic flow increases the risk of an
accident
"

Which is exactly what I said. 

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #77 on: June 18, 2015, 03:36:00 PM »
You literally just googled a press release from a group of people with a significant financial incentive to drive faster, and it suggests that if they drive faster the roads will get safer. Shocking, no? I would question whether the press release fairly represents the entire literature. Moreover, most of the studies summarized in the biased press release deal specifically with truck-car collisions which means they may be poorly applicable to general circumstances involving two passenger vehicles. I'll also note that of the citations and arguments in the biased press release, the vast majority either boil down to "state X is doing it so your state should too", "it would make our members happy so you should do it", or "here's a change that was made consistent with what we want and no discussion of the results".

Finally, there's a major, obvious methodological flaw in both of the studies that even relate somewhat closely to your assertion. Both studies deal directly with only the one effect of increasing minimum speeds that is potentially favorable - fewer 'interactions' between the general traffic flow and any given slow vehicle. Neither addresses that vehicles moving slowly decrease the average speed of other vehicles and thus all traffic, an effect that could reduce or eliminate the supposed gain from decreasing the interactions. In fact, it's not hard to believe that that effect could be extremely significant. As even your biased press release notes, a 65-70mph increase here in Ohio was enough to increase accident fatalities by a sixth.

Bring a real study next time.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #78 on: June 18, 2015, 04:06:51 PM »
Holy shite grantmeaname your on your freaking game today!

You could throw in something about the dangers of driving at higher speeds is exponentially more dangerous as you increase speeds.   Most people don't understand that concept and even seasoned drivers perceive very little risk difference between driving at 55 and 75. 

My point was to stick to or below the "maximum" speed limit as many posters here asserted that inflating my tires 4% above maximum was akin to walking into a lions cage with a steak around my neck.  ( I have since acquiesced to just max to appease them)      While the fast driving is an exponentially more dangerous behavior,  mild over inflation at worst is only linearly more dangerous and in many cases safer due to better cornering and minimizing tire overheating potential.

The simple math is that a person who drives slightly below the speed limit will maintaining slightly elevated tire pressure is safer for themselves and other drivers than a person with standard inflation that drives slightly over the speed limit.   

People tend to become confused with the exponential vs. linear comparisons.   

Bottom line slight speeding very dangerous ---- maximum inflation minimum if any increased risk and possibly safer.     

Chris22

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #79 on: June 18, 2015, 04:38:15 PM »
Bottom line slight speeding very dangerous ---- maximum inflation minimum if any increased risk and possibly safer.   


No.  Holy christ no.  Statistically no one follows the speed limit, so that is very dangerous? 

How about this:  speed limits are set (indirectly) by poiliticians.  Tire pressure maximums are set by engineers.  Which ones are more likely to be correct? 

For fuck's sake.

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #80 on: June 18, 2015, 05:00:49 PM »
Well, driving is a very dangerous activity (depending on your definition of very dangerous), so by extension driving over the speed limit is very dangerous. Speed limits are somewhat arbitrary - in some places they are very conservative, in others they are not. Tire pressure specifications for vehicles have a lot of safety factor built into them, as every engineer would know.

Bob, I think this thread has run its useful course, and one of the takeaways that one can glean is that although this is a forum dedicated to critical thinking on financial matters rather than following common rhetoric, that attitude does not necessarily extend beyond financial matters. I suggest posting to automotive/engineering forums on topics like these to get more rounded/researched opinions.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #81 on: June 18, 2015, 05:31:02 PM »
Agreed,  thanks everyone.   Drove home below speed limit, with tires inflated to max psi and saved 15%/on gas.   Easier than. GEICO!

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #82 on: June 19, 2015, 10:39:38 AM »

Bottom line slight speeding very dangerous ---- maximum inflation minimum if any increased risk and possibly safer.   


No.  Holy christ no.  Statistically no one follows the speed limit, so that is very dangerous? 

How about this:  speed limits are set (indirectly) by poiliticians.  Tire pressure maximums are set by engineers.  Which ones are more likely to be correct? 

For fuck's sake.

Any engineer will confirm that speeding is more dangerous than overinflated tires and it's not even close.


RWD

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #83 on: June 19, 2015, 11:58:06 AM »

Bottom line slight speeding very dangerous ---- maximum inflation minimum if any increased risk and possibly safer.   


No.  Holy christ no.  Statistically no one follows the speed limit, so that is very dangerous? 

How about this:  speed limits are set (indirectly) by poiliticians.  Tire pressure maximums are set by engineers.  Which ones are more likely to be correct? 

For fuck's sake.

Any engineer will confirm that speeding is more dangerous than overinflated tires and it's not even close.

Really?
http://priceonomics.com/is-every-speed-limit-too-low/

Guses

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #84 on: June 22, 2015, 02:23:11 PM »
I ride on my bike tires inflated to 75 PSI instead of their rated 65.

My car tires are inflated to 51 PSI which is the tires' rated pressure.

Over inflating a tire by 5% it's rated pressure will not suddenly induce catastrophic failure. In fact, here is a quotation from a engineer that worked at a tire company (quote from Pop. Mech.):

"Myth: A tire is in danger of bursting if pressure exceeds the "max press" number on the sidewall.

The truth: The "max press" number has nothing to do with a tire's burst pressure. The "max press" and "max load" numbers indicate the pressure at which the tire will carry the maximum amount of weight. A new, quality tire will not pop at an even multiple of the "max press." I'm sworn to secrecy about the exact burst pressure, but I wouldn't hesitate to double the "max press" of any new passenger-vehicle tire on a new wheel. But hitting a big pothole at super-high pressures may cause a failure."

Digital Dogma

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #85 on: June 22, 2015, 02:40:43 PM »
Id be extremely cautious about overinflating your tires, it will reduce your friction which not only means better MPG, but much worse traction. Emergency braking will get worse, and you could potentially cause a crash because you want a higher mpg.

Having been in a car crash at 45mph, it isnt worth it, Ill find a safer way to save.

Guses

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #86 on: June 22, 2015, 02:52:23 PM »
Id be extremely cautious about overinflating your tires, it will reduce your friction which not only means better MPG, but much worse traction. Emergency braking will get worse, and you could potentially cause a crash because you want a higher mpg.

Having been in a car crash at 45mph, it isnt worth it, Ill find a safer way to save.

The best way to avoid car crashes is not to drive.

Since you are obviously still driving, you have accepted the inherent risks involved. The question at this point is if the risk are increased proportionally with the pressure of the tires(I am guessing the answer is "no")?

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #87 on: June 22, 2015, 03:40:30 PM »
You got in that collision due entirely to the car's stopping distance?

scottish

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #88 on: June 22, 2015, 04:06:21 PM »
My last set of tires wore out in the center of the tread.    The garage I was going to consistently over-inflated them by 7 PSI.   One case does not prove anything, so I'm interested to see how Bob's experiment works over a year or two.    Do you live in the snow belt Bob?   And if so, will you reduce pressure in winter?

For the record, my gas mileage seemed to be better and my traction seemed to be worse.      I now inflate my tires according to the sticker on the door pillar.   (This is what the engineers that designed the vehicle specified, after all.)

GuitarStv

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #89 on: June 22, 2015, 04:48:29 PM »
My last set of tires wore out in the center of the tread.    The garage I was going to consistently over-inflated them by 7 PSI.   One case does not prove anything, so I'm interested to see how Bob's experiment works over a year or two.    Do you live in the snow belt Bob?   And if so, will you reduce pressure in winter?

For the record, my gas mileage seemed to be better and my traction seemed to be worse.      I now inflate my tires according to the sticker on the door pillar.   (This is what the engineers that designed the vehicle specified, after all.)



That appears to be what usually happens.

Making Cookies

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #90 on: June 22, 2015, 07:04:10 PM »
We increased our fuel economy back in the recession by beginning to car pool 100% of the time and staying closer to home. I run my tire pressures about 3-4 PSI over the car's recommended pressures - and well under the tire's max pressure.

By carpooling (it took several years to get jobs near each other but my wife had a vision crisis so we needed to do that in case she got to a point again where she couldn't drive). We went from ~30K miles pe year to something more like 15K.

RetiredAt63

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #91 on: June 28, 2015, 07:25:22 AM »
You guys are talking mile per hour, right?  From 55 to 75 is a huge increase!  For me that is going from 88 kph (well below highway limits, they are 100 kph here, well 80 or 90 on secondary routes) to 120 kph. I cruise at about 100 and only get to 120 when I have to pass someone fast (or merge into heavy fast traffic, which is no fun).

I see a huge difference in mileage as my routes shift from 80 to 100, and the rare times when I am cruising at 115 (basically the "keep up with the right hand lane traffic" situation when the other lanes were so busy that I didn't want to push people into them just so they could get past me).

Having just re-inflated the tires on a lawn trailer and a wheel-barrow, I have experienced first-hand the difference between a badly inflated tire (8 psi for max 25psi) versus proper (24 for max 25). Obviously the difference between 20 and 25 would be less, but it would still be there.

Holy shite grantmeaname your on your freaking game today!

You could throw in something about the dangers of driving at higher speeds is exponentially more dangerous as you increase speeds.   Most people don't understand that concept and even seasoned drivers perceive very little risk difference between driving at 55 and 75. 

forummm

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #92 on: August 17, 2015, 02:42:27 PM »
Looks like Bob hasn't died in a fiery tire explosion accident....yet..

I gave mine a +2PSI boost today over the mfg rating when I filled them up. They were a bit low. Curious to see if I notice an effect.

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #93 on: August 17, 2015, 10:07:30 PM »
Other than the effect that you're DEAD?

Seppia

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This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #94 on: August 17, 2015, 11:17:55 PM »
Just read the whole thread, it's surreal.
How a bunch of educated, numbers driven people could advocate over inflating tires above the recommendations of car manufacturers just to save a few pennies, all while ridiculing the only seemingly (to me) sane person that basically states "hey guys if some engineers recommend a range maybe we should stick to it" really escapes me.
The most facepalm-inducing remarks are the "people have over inflated and everything is fine!" 
Well, that proves how safe today's technology is, not that it's a smart thing to do.
I am a diver and no-deco tables have a built in margin of safety. Will you die is you stretch that margin? Most probably not, but the odds are higher of something bad happening.
Over inflating also causes longer braking distance and lower grip, which again seem like very bad things to give up in exchange for a few pennies.
I found particularly disturbing the comment "well what makes driving dangerous is the amount".
Duh. So if I only do a small amount of it I can do it less safely? Because we do recognize that longer braking distance and lower grip are bad right?

To paraphrase the above comment but with a somewhat less life damaging potential recommendation, what really saves money on your gas expenses is the amount of miles you drive.
Drive less but inflate the tires as you should.
If it were only your life I would say go for it, but you share the road with others.
If the recommended range is 34-36 be content with 36 and suck up the extra 15 cents you will pay per month, you can afford them.

Bob W

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #95 on: August 18, 2015, 07:49:30 AM »
Just read the whole thread, it's surreal.
How a bunch of educated, numbers driven people could advocate over inflating tires above the recommendations of car manufacturers just to save a few pennies, all while ridiculing the only seemingly (to me) sane person that basically states "hey guys if some engineers recommend a range maybe we should stick to it" really escapes me.
The most facepalm-inducing remarks are the "people have over inflated and everything is fine!" 
Well, that proves how safe today's technology is, not that it's a smart thing to do.
I am a diver and no-deco tables have a built in margin of safety. Will you die is you stretch that margin? Most probably not, but the odds are higher of something bad happening.
Over inflating also causes longer braking distance and lower grip, which again seem like very bad things to give up in exchange for a few pennies.
I found particularly disturbing the comment "well what makes driving dangerous is the amount".
Duh. So if I only do a small amount of it I can do it less safely? Because we do recognize that longer braking distance and lower grip are bad right?

To paraphrase the above comment but with a somewhat less life damaging potential recommendation, what really saves money on your gas expenses is the amount of miles you drive.
Drive less but inflate the tires as you should.
If it were only your life I would say go for it, but you share the road with others.
If the recommended range is 34-36 be content with 36 and suck up the extra 15 cents you will pay per month, you can afford them.
I'm still alive,  hyperinflated and saving money.   It's not like I'm risking my life scuba diving or motorcycle riding.   It is more like $400 per year saved for me.    It is more of a comfort issue than safety for me as I always drive slow and rarely slam o n the brakes.    The better cornering with over inflated tires actually adds safety to my driving.   

Seppia

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #96 on: August 18, 2015, 08:01:29 AM »
I see your points and I am sure you are a very safe driver, but I hope there's no negating you are somehow trading safety for money.
You could save $400 driving less :)
Everything we do includes risk (like my scuba diving), and the solution is not to stay home and do nothing all day, but I am not sure I would skip my safety second regulator from my diving equipment because "the main one likely will never fail, plus I have done hundreds of dives and I am still alive, and it saved me $400, and I dive safer than most people do".

Or at the very least I would avoid making fun of those who say it would be better to maybe stick to the recommendations of those who built the damn piece of equipment you are using

grantmeaname

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #97 on: August 18, 2015, 11:48:06 AM »
You're acting like all decisions that add risk are equally risky. Inflating your tires to the tire manufacturer's recommended cold maximum and diving without a second regulator are similarly risky activities. The fact is we all accept some level of risk at all times by our actions, so such extreme language isn't really a productive way to look at it. I walked down the street today without wearing kneepads, a helmet, gloves, or a condom... The fact that there are some precautions I don't take doesn't make me a reckless maniac, it means that I have weighed the advantages and disadvantages of all the options and settled on one that provides a reasonable mix. 44 psi on tires rated for 44 psi is just another such example.

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #98 on: August 18, 2015, 01:29:07 PM »
GM based its initial recommendation for my Volt's tires on the 35psi used for the Cruze, because the platform was the same. The additional 900# added by the battery and other novel powertrain components somehow totally escaped their consideration throughout the design and testing phases.

Early Volt drivers found that the recommended pressure produced a high rate of classic underinflation symptoms, including cracked and pitted sidewalls, edge wear, and frequent blowouts. Not surprisingly, increasing the pressure to 40-45 psi evened out the treadwear and reduced catastrophic events. Empirical testing by one pair of owners indicates that 49psi on the more heavily loaded front and 45 on the slightly lighter rear actually produces the most even treadwear.

GM, in response, increased the recommended pressure by about 2psi. Why so little? Community consensus is that they're unwilling to admit to having been so wrong. Look at the recent recalls, and tell me OEMs are never wrong.

Just food for thought. I'm not advocating exceeding the tire's limits, but I don't think anyone here is.

music lover

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Re: This One Simple Trick Will Increase Gas Mileage by 15%!!
« Reply #99 on: August 18, 2015, 02:11:35 PM »
Just read the whole thread, it's surreal.
How a bunch of educated, numbers driven people could advocate over inflating tires above the recommendations of car manufacturers just to save a few pennies, all while ridiculing the only seemingly (to me) sane person that basically states "hey guys if some engineers recommend a range maybe we should stick to it" really escapes me.
The most facepalm-inducing remarks are the "people have over inflated and everything is fine!" 
Well, that proves how safe today's technology is, not that it's a smart thing to do.
I am a diver and no-deco tables have a built in margin of safety. Will you die is you stretch that margin? Most probably not, but the odds are higher of something bad happening.
Over inflating also causes longer braking distance and lower grip, which again seem like very bad things to give up in exchange for a few pennies.
I found particularly disturbing the comment "well what makes driving dangerous is the amount".
Duh. So if I only do a small amount of it I can do it less safely? Because we do recognize that longer braking distance and lower grip are bad right?

To paraphrase the above comment but with a somewhat less life damaging potential recommendation, what really saves money on your gas expenses is the amount of miles you drive.
Drive less but inflate the tires as you should.
If it were only your life I would say go for it, but you share the road with others.
If the recommended range is 34-36 be content with 36 and suck up the extra 15 cents you will pay per month, you can afford them.
I'm still alive,  hyperinflated and saving money.   It's not like I'm risking my life scuba diving or motorcycle riding.   It is more like $400 per year saved for me.    It is more of a comfort issue than safety for me as I always drive slow and rarely slam o n the brakes.    The better cornering with over inflated tires actually adds safety to my driving.

How can you possibly determine that there is "better" cornering with overinflating tires if you "always drive slow"? To get better traction, one must first approach the limit of traction to find the difference between recommended pressure and overinflation.

Your 15% mileage gains don't add up either:

http://www.popularmechanics.com/cars/a940/4199963/