Preface: This forum is a shitty place to ask about towing. "What you can get away with a few times" and "What you can do safely and reliably" are two different things.
So if pedal power can transport hundreds of pounds of cargo why couldn't my car that has the power of 110 horses be capable of transporting thousands of pounds? My car is a 2011 hyundai accent hatchback, with good driving habits I can get 40 mpg. For $200 I can score a 4x8 trailer off of facebook classifieds and in theory turns my car into a pickup truck.
Short answer: Because you're doing 3-5mph (maybe 7mph on the flats) when loaded with a heavy trailer, and aren't likely to kill or injure anyone but yourself if the load overwhelms his bike. A bike doesn't have the brakes, weight, or traction to really handle that on any sort of slopes, and isn't subject to insurance (though if you injure or kill someone else, you sure as hell are subject to lawsuits).
So if I wanted to get serious and haul tons of weight with my car what modifications are needed, is 110 HP capable of such a task? I know the first step is to get a heavy duty tow hitch, then maybe upgrade the brakes and what about the suspension? I'm just theorycrafting as of right now, I know with normal light use these items would not be necessary but I would like to know what the boundaries are with this.
If you want to haul "tons of weight," the first step is to sell your car and buy a truck suited to doing so. A F150 class vehicle will tow a few tons, depending on configuration. I wouldn't tow past about 75% of rated capacity as a general rule of thumb.
Long answer: The problem isn't just the power, brakes, and suspension - it's the weight. If you're towing with a rear hitch, you cannot safely tow more than 50-60% of vehicle weight. The weight on the hitch back there, even with suspension upgrades, unloads the front axle - and you use that to steer and brake.
The weight on the hitch is called the tongue weight - and it's vitally important to trailer stability. You want 10-15% of the trailer weight as tongue weight (meaning the trailer is heavier in the front than the rear). If this isn't done, the trailer is going to sway around, swing, wag the car, and generally be an unsafe nightmare to tow at any speed. And your car's wight is correlated to safe tongue weight. If you don't have a heavy enough to vehicle, a heavy tongue will unload your front axle enough to cause you problems with traction for steering.
If you look at how to tow heavy (10k+ lbs), almost everyone is using a 5th wheel hitch in a pickup. The difference here is that the tongue weight is
in front of the rear axle - so instead of pressing down behind the rear axle and lifting the front, it's pushing down in front of the rear axle and pushing the front down as well. This means you don't suffer the loss of traction you would with a rear hitch. Everyone towing heavy is using a 5th wheel in a pickup, for a damned good set of reasons.
In addition, your vehicle has a tow rating. Exceeding that is very much at your own risk, because if you do cause damage with that configuration, your insurance company is likely to tell you that you didn't obey your vehicle limits, and they're not going to cover you.
...depending on the trailer you may also want to get a brake controller.
Most lightweight trailers you can tow behind a car either don't have brakes or have hydraulic surge brakes (which are annoying as hell, but get the job done). I don't know of anyone who has a brake controller for electronic brakes in their car - trailers with electronic brakes generally are used to tow heavy things, which a car can't tow.
I wouldn't attempt to tow *too* far beyond the rated amount, the brakes will not be too much of an issue because a heavy duty trailer should have its own brakes, suspension will also depend on the trailer (trailer weight and tongue weight a.k.a. the down force on the hitch are different) and the load placement on the trailer.
I wouldn't attempt to tow at the rated amount unless it were something like clear, dry conditions in Iowa or Kansas. The tow rating is an upper limit, not a recommended amount. Towing at the tow rating of a vehicle with any sort of terrain or in less-than-perfect conditions is a bad idea.
What's 'possible' and what's 'safe' are different things -- if you're towing 2000lbs on a car that's rated for towing 1000lbs (or not rated to tow at all) and you get into an accident, you're looking at a really bad day.
Yup. :( Not going to quote the whole story, but that type of thing scares the shit out of me. I'm planning to (within the next year or two) buy a 5th wheel trailer for long road trips with the family, and despite having a pretty damned good tow vehicle, I don't intend to tow regularly beyond about 75% of rated capacity. Yeah, that limits my trailer size, but I want to have a good excess margin of stability and braking. Better that than losing control of the tow vehicle and trailer and injuring or killing myself, my family, and possibly other people.
Just because you can move it on flat ground does not mean you can tow it safely over the road.
Well this is enough to stop me from exploring this further. It sounded good on paper. Take a cheap gas efficient car and beef it up so it could have tow limits like a big truck. But since this puts me in the unknown territory or a area that has not been tested thoroughly I don't want to take the risk. I'll just stick to the limits of my car, thanks!
Really glad to hear that. Your car doesn't have a 5th wheel hitch option. If you manage to work one up, I'd love to see the photos, but then you run into the problems that your frame isn't designed for that kind of load.
Keep your gross weight per axle within the limits on your door, or you're a test pilot. And that's not good.
I wouldn't let one anecdote scare you. This person was using a large towing rig and towing down a steep mountain pass. Not stated but probably the case was that he wasn't using the best judgement on speed. Hauling across a flat town short distances using properly sized towing equipment for your vehicle can be very safe to do. I have a ball hitch on my Honda Civic that I can pull a small trailer behind. It can more than safely haul an appliance or some sheets of plywood across town and save me a $50 delivery fee every single time. In the fifteen years I've had my 'rig', I've more than saved the cost of the hitch, wiring and trailer by a factor of ten or more. I also wouldn't even dream of hauling something down a steep mountain pass with it.
Your Civic probably has either no tow rating or a 1000lb tow rating. It's a small economy car, so I'll be nice and give you 1000 lbs. A cheap Harbor Freight trailer weighs around 300-400 lbs, so you can tow ~500 lbs without exceeding the tow rating.
That's very different from "a couple tons" as the OP wants to tow, which I will, again, strongly assert you cannot do safely with an economy car.
And you note that you wouldn't tow it down a mountain. Good. :)
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Seriously. If you have a small car, 1000 lbs is a good limit. And if your car has a tow rating, don't exceed about 75% of it unless you know damned well what you're doing.
If you want to tow heavy (3000-4000 lbs or more), get a truck.