There’s been a lot of information floating around theses days about the “correct” tire pressure for best fuel efficiency.
http://car…ssure.html
Some recommend the “recommended” pressure listed on the car (30 psi for my car), and some recommend the “maximum” pressure listed on the tire (44 psi for my tires).
I realize that if the pressure is too low the tires will suffer, and if it’s too high, handling (and safety) will suffer.
After reading a lot of blogs and other info on this, I’ve about decided that the correct answer is somewhere in between (somewhere around 36 psi for me).
Want to weigh in on this?
Use the recommnded pressure in the book, r on the door post or glove box. The number on the tire is the tire manufacturer’s maximum safe inflation pressure for that tire. It will give you an uncomfortable ride. The only use for it is if the tire were used on a trailer carrying a lot of weight or if you entered a fuel economy contest to get maximum mileage.
I agree with Doc. While there can be significant losses in fuel economy (not to mention safety) from significant underinflation, all the numbers I’ve seen say there’s next to nothing to be gained from significant over inflation, and the handling and ride can be messed up. The number on the sidewall is an absolute maximum, it’s the number on the car sticker that should be followed. Make sure you check first thing in the morning, before any driving. Would a couple of extra psi over the sticker numbers hurt? Probably not, but won’t make much difference in the mpgs.
The tire pressure that the manufacturer recommends is optimized to keep an even patch of the tire in contact with the road surface. When you over-inflate a tire what tends to happen is that the shoulders of the tire lift upward slightly away from the road surface and the pressure gets focused on the center of the tire. This decreases grip with the road and causes the tire to wear unevenly (center wears faster than sides) However, this is best illustrated when the tire is underinflated because you will see excessive tire wear shift to the outside of the tread as wear decrease on the inside of the tread.
Now some people will argue that you can manipulate tire pressures and they scoff at possible safety issues but slight changes can induce drastic changes in handling depending on the vehicle. For instance 2psi is enough to change the handling characteristics of many cars in aggressive maneuvers. It is possible to safely add pressure to a tire but it dependent on the vehicle in question. Luxury cars tend to use a more conservative pressure and compromise a bit and can usually get away with adding 2psi with no ill effects. I would go so far as to say that you can get away with 2psi on most cars if you make sure to add it evenly to all 4 tires. However, drastic changes such as running maximum pressure(a very bad idea) or adding 6psi+ to the tires is not a wise idea and starts to manipulate how the tire meets with the road.
Engineers must take into account vehicle weight, tire size, steering geometry, and body-roll when they recommend a pressure. Every car has different requirments and inflation pressure is more than comparing similar tire sizes. If you want to crank tire pressure up I’d go no further than 33psi and call it a day.
Having tires a LITTLE over inflated will be fine. But DRASTICALLY over inflating can cause drastic decreases in your vehicles stability. Who ever says to put the MAX pressure instead of using the manufacturers recommended tire pressure in my opinion is CRIMINAL. Someones going to get in an accident and someones going to get killed following that advise.
Higher pressure will increase mileage. However if you start with the car manufacturer’s recommended value there is not much more to gain.
The car manufacturer test the tyres on your car under a number of different conditions and test for safety under emergency conditions before recommending tyre pressure.
The pressure on the side of the tyre has not been tested with your car or any car. It is only a measure of the amount of pressure that particular tyre can be safely run at, assuming that the pressure is safe for the car.
The only real use of that number on the side of the tyre is to tell you that if it is less than the car manufacturer calls for, you can't safely use those tyres on your car.
None of the above proves that it would be unsafe to use the 85-90% of the max on the tyre. It only proves that it has not been tested. I prefer to have my tyres (and the other guy's as well) inflated to a pressure that has been tested and found safe for handling under emergency conditions that I hope I never have.
References:
This is sponsored by a tyre manufacturer Bridgstone - Firestone and instructs the reader to check the owner’s manual for the correct tyre pressure.
Here is another from the Goodyear site.
Check Your Air Pressure
Keep your tires properly inflated and you could improve gas mileage by more than $1.50 every time you fill your tank. The recommended tire pressure for your vehicle is located on a sticker inside your driver-side door or noted in your owner’s manual.
You might also try the US Department of transportation.
http://www.nhtsa.gov/cars/problems/E...intenances.htm
They say:
You can find the correct tire pressure for your tow vehicle in the owner?s manual or on the tire information placard.
Yes, I agree that 35-36 psi will improve mileage slightly and not hurt anything other than the ride quality. THAT’S the manufacturer’s main concern. As far as drastically altering the handling characteristics of your car, not going to happen…
Your comment about the “recommended” pressure being mostly for the best “ride quality” is what I’ve suspected, being that it’s from the car manufacturer. I don’t know any test results (I doubt that there are any), but I suspect that a slight increase (up to 6 psi) from the recommended pressure would improve gas millage slightly and have negligible affect on safety.