Recommended Tire Pressure Question. (archive)

If the pressure recommendations on the sticker is for the 235/60-16 stock tires, it won't necessarily be the same with 18" tires, as the volume of the tires may be different. Remember that it's the amount of air that counts, not the pressure, so it will differ among tires with different volumes.

*** I do not agree. Pressure is pressure, and it is the pressure that counts, and that has nothing to do with volume. Of course the volume will be different, because the tires are of different sizes. But 33 psi puts the same force on the sidewalls of either tire.

BMW is recommending 33 psi, and while it is okay to go up a little, 5 additional pounds is a lot.

Also, low-profile tires don't react the same way as "conventional" tires when pressure is increased. Conventional tires tend to bulge out on the middle if the pressure is too high, but low-profile tires tend to expand sideways, in effect keeping the tire flat.

Big-T

*** Why would a 235/60-16 tend to bulge out any more in the center than a 235/50-18?

Have you ever run drag radials? Do you know what happens to the tread pattern on the ground, and your traction if you over-inflate? The tread becomes rounded, and the tread pattern does not make full contact on the outer edges. My position is that his tires will do the same thing at 5 pounds over.

Seems like closer to the factory recommended tire pressures as per the sticker in the door jam would be better.

38 psi for the front is too much IMHO!

Won't the tires wear more in the centers, as the tires will not be flat across the tread area?

DHG

ANYONE HAVE AN OPINION ON TIRE PRESSURE?
DRIVER'S DOOR SAYS 33 FRNT AND 41 REAR.
I just went with 38 and 41, it feels a little stiff but I like it and seems to handle better.
I have 18 in. Michelin Pilot All Weather XGT Z4
99 740il

*** Here he is saying what BMW is recommending for the 18" wheels (stock). I still believe that
38 cold for the front is to high, but it is not my car. Time will tell if he spots prenature center tire wear. And because of the different rim widths and tire sizing, he cannot rotate.

DHG

Follow Ups:

Here's what happens at low pressures (stock) guysimpson 23:00 6/18/2001 (1)
- Re: Here's what happens at low pressures (stock) Ascot Green 750 00:32 6/20/2001 (0)

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