Tire pressure myths, facts, observations, and improvements (canned post)
Note: I posted this in another thread, but I realized it makes more sense to just post it here and link to it when it's needed in other threads. I plan to edit this as time goes on and I refine it.
Tire Air Pressure Myths and Facts A canned post by theholycow Originally posted at https://www.gassavers.org/showthread.php?t=7712 Please include the link if you post/distribute this elsewhere. Edit: Some decent numbers can be found at https://www.metrompg.com/posts/tire-p...resistance.htm Increased tire pressure is a cure-all for problems, and generally an improvement even when there are not problems. I have been driving with greatly increased tire pressure for hundreds of thousands of miles, and have not suffered ANY consequences, though other drivers with other vehicles could. I have only benefitted from it. There are limits, though. You should never significantly exceed the tire's maximum pressure rating, which is stamped on the side of the tire (often next to its maximum load rating, which requires the maximum pressure). If you add pressure and find that your handling has suffered or your ride is terribly harsh, you should reduce pressure until that issue is gone. Those things are very important limits. If you exceed them, you could possibly cause a tire failure (though I doubt it); however, real consequences may include center wear, possible liability in an accident, and sketchy handling that could cause an accident. Within those limits, you can find the following advantages: - Decreased rolling resistance which means increased gas mileage - Better handling due to reduced sideways curling of the tire under the lateral load of a hard curve - Better handling due to quicker response from less tire flex - Better wear, unless you normally wear tires perfectly evenly and always get more than their treadwear warranty out of them If that's all so great, why do car manufacturers not recommend the full pressure of the tire? It's because they recommend the lowest pressure that their legal department approves based on industry-standard load-inflation charts. For any amount of load on a tire, there's a minimum safe inflation which provides the softest ride. To sell cars, they want the ride as soft and compliant as possible when you test-drive it. More pressure isn't bad, it's just not traditional to try to sell a car that way. Modern automotive tubeless radial tires are NOT subject to the same types of failure as the bicycle tires you remember popping as a child. They won't blow off the rim (unless you use way, way more than their maximum rated pressure). They won't pop when you hit a bump. They won't explode in your face. They almost always fail from underinflation (which causes overheating) or a break in the sidewall caused by an impact (which is less likely to happen if you have more pressure preventing the bump from squeezing the sidewall against the rim). https://www.tirerack.com/tires/tirete...e.jsp?techid=1 has a section cautioning against overinflation which includes this: Quote:
https://www.officer.com/article/artic...on=19&id=27281 Here's selected pieces: Quote:
I had a 1997 Pontiac Grand Am SE V6 with P205/55R16 tires. I bought some Bridgestone "Turanza T" tires, which lasted about 70,000 miles (that was less than 3 years for me) before the sidewalls were cracked and the tread was worn at the corners. I ran them at the pressure printed on the car's door post, which may have been 30 or 35 psi. I replaced them with the same, but inflated the new ones to the tire's maximum pressure, 44psi. Handling went from soft and sloppy to responsive and decent. Ride did not suffer. They wore perfectly evenly and had 80,000 miles on them when I sold the car -- and they were still good for more miles. On my 2002 GMC Sierra 1500, I keep my tires inflated to their full 80 psi rating. Sometimes I run the rear tires a little lower, because the handling gets sketchy with the bed empty and the road surface slick. Other than that, I get long, even wear and decent handling. 6/18/2008: New data makes me question my tire width theories, but supports higher inflation pressure. A post by user slogfilet with a very interesting link shows that higher inflation does NOT reduce contact patch. I can't say for sure that the new data is correct, or even analyzed correctly, nor can I say if it's wrong. I hope to do some of my own testing. It would also suggest that the theories about how increased inflation helps FE may be wrong, but that only affects the explanation behind the observations; hard data from users on this forum shows that increased inflation helps FE, and that hard data is undeniable. |
Here's some additional Tirerack articles and what they have to say. Tirerack barely addresses overinflation, but continually cautions against underinflation.
Air Pressure vs. Wet Performance Quote:
Quote:
Quote:
Quote:
Edit 2008-11-02: Found this large compilation of articles stressing the importance of never running underinflated for the trucking industry: https://www.retread.org/Inflation |
Wow I have been running my car tires at 32 Psi for years! but on my mountain bike I have them up to 44 to 50psi because the bike is faster!
Why have I not thought of this before! I will change my car tires this month as mines have perished, I will totally inflate them to the maximum levels on the side walls, thanks man. |
Just be cautious until you're sure the car still handles well with the tires at that pressure. Since you're going to be buying new tires, take a look at the other tire thread I posted the same day about tire width.
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The single most significant change to my mileage (so far) has been pumping the pressure up past the manufacturer's suggestion. The fact is that my tires are so cheap that the savings in gasoline far outweigh the six months to a year that I lose in tread life.
That said, I wouldn't recommend this if you're rolling on $200 Pirellis. B |
I suppose every car and driver is different, but increased pressure has always increased tread life for me.
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Is it true that race cars and touring cars run high Psi in there tires?
Does this apply to trucks and buses? |
Well, in the first post in this thread I did quote a bit about autocross racers using higher pressure. Additionally, NASCAR teams (and I'm sure those in other motorsports too) are constantly adjusting their pressure to adjust traction, though I don't know exactly what pressure range they use.
It applies to trucks and buses (and RVs and trailers) so much that load-inflation charts for those tires are much easier to find, and many include text explaining that for higher speed all the pressures must be adjusted up. I don't know if tire rolling resistance is as big a factor for trucks and buses, so I don't know if the FE improvement will be noticable. I do know that the wear advantages are just as useful, at least in my experience with trucks up to 15,000 pounds. |
I put my tire pressure up to 44Psi at the front and 40 at the back and the car felt stiffer but my goodness it can roll now! I can tell its faster which sounds stupid I know, the manual recommended 32Psi all round but I realised after reading THC first post that this was just legal cover, not what is best.
The steering feels a lighter but not dangerous, I would say it feels more direct on the road. This is a great tip and I wish I knew about it years ago, thanks ever so much man! |
:D Glad to hear of your good results!
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