Air pressure in tires

I have a 2007 Chevy Impala. The tire manufacturer lists 44 lbs as the limit on my tires; the Chevy dealership insists that the air pressure should be around 32 lbs.

At 7500 miles, one tire’s tread was worn significantly; the other 3 tires were fine. The dealership said it was because that tire was underinflated; however, the tires always had around 40 lbs in them. They did replace that tire under warranty, but insisted on keeping the pressure in the lower range.

Now I’m finding out that my gas mileage isn’t as good; I had much better results when I had more air in the tires. I know from listening to your show that I would get better gas mileage.

My question is: at what air pressure should I keep my tires at - what the dealership says or what the tire people say? And why are they not in agreement? I just sold my other Impala with 98,000 miles on it and I got better mileage!

Thanks for your help and keep up the good work. I used to listen to you all day on Sirius Satellite radio but now I have XM and your show is not aired. Please get with XM so I can listen to you again. And I have your 2008 desk calendar in my office and everyone was surprised that I liked Car Talk! But they flock around my desk to see what the question for the day is!

In this case the dealership is correct. They are repeating the manufacturer’s recommendation which is always “correcter.” Keep your tires at around 32 psi, just as it says to do on that label on the car’s doorframe. By contrast, the tire manufacturer’s label is merely the maximum load limit. It is not a recommendation at all.

This is a common question. The 44 pounds is MAXIMUM pressure, not good in most cases. The 32 is the recommended pressure for your model of car, looking at a number of issues, including handling safety. A few pounds over, like 35, are not dangerous, but 44 would be really harsh. Stick to car recommendations, not maximum pressure ratings.

The low gas mileage is probably not related to tires that were at least car manufacturer ratings. There is another problem.

Agree, the car manufacturer’s rating is the way to go. Drivers who compete in economy runs really inflate their cars to the maximum or more! That reduces rolling resistance and gives better mileage. However, it is un comfortable, the tires will wear in the middle, and it is hard on the suspension.

Since you are trying to do the best for your car as well as your comfort, the dealer is right.

Bad alignment can also prematurely wear out your tires. Hope they dealer checked the alignment after mounting the new tires.

Tyre manufacture says 44 lbs is the max for their tyres. Chevy (not just the dealer) says a tyre that size should be inflated to 32. There is NO conflict with those instructions. The Tyre manufacturer has no idea what car those tyres are going to be used on and what the needs of that car are.

So why does the Tyre manufacturer say 44 MAX, because if the car manufacturer were to say it needed to be inflated to 50 PSI, you would know that those tyres were not safe on that car.

It normally is OK to pump the tyres to two or three psi over the recommended amount because they may loose a little and all else being equal it is much safer being a little over than a little under.

I’m going to echo what the others have said here, but use some different words. The tire manufacturer lists 44 psi as the MAXIMUM SAFE PRESSURE, not the RECOMMENDED pressure. The vehicle manufacturer listed the RECOMMENDED pressure. I would generally consider the vehicle manufacturer’s as the minimum pressure, but don’t go too far above that. Since most people check their tire pressure when they change the oil, about every three months, and a tire generally loses about 1 psi per month, I’d fill to 35 psi. This is what I actually do and I get good even wear out of my tires, and they last a long time.

As for one tire wearing out, here is where your dealer is loosing credibility with me. If all tires were at 40 psi, then all would have worn out faster in the middle. When only one tire is worn out, I’d look at the alignment. If that tire wore on both outer edges, then I’d look into a suspension problem. You could have a very dangerous defect at that corner of the car that could cause you to lose control and be in an accident. The dealer had better look very close at all the components on that corner of the car and fix any defects or your heirs could end up owning this dealership. If the service manager doesn’t take you seriously, talk with the general manager or the owner directly. They have the most to lose, next to you that is.

As for fuel economy, going above 30 psi doesn’t add a noticeable amount to your gas mileage, but going below can reduce it significantly.

The recommended pressure is on your door post and in the owner’s manual. That is the pressure you should inflate your tires to.

XM Radio: The public radio station is in WNYC. You need to find out if and when the program is on.