mrbill

I have a 2001 Passat Variant which came with 195/65-15 steel wheels, which I've recently upgraded to 205/55-16. I'm posting here because this is the same change as in the A4 Sport Package.

Does Audi recommend a tire pressure increase for this plus-one wheel?

meem

i've always understood that you're supposed to keep the tire pressure the same regardless of the tire profile. some folks seem to like to run a few psi more on lower profile tires, but i've never heard their rationale.

mrbill

Tirerack says to keep the same pressure. Ronal and some other wheel maker say to increase pressure.

ryoung

... The load capacity of a tire is proportional to the amount of air in it. You can increase the load capacity by either installing a larger tire (on the same diameter rim) or increasing air pressure.

In your case, installing a larger tire on a larger rim reduces the internal volume of the tire by 8% (by my calculations, please double-check). So if you're currently running 30 psi, for a starting point you should raise the pressure to 32 psi (30 x 1.08).

The caveat: This only works reasonably well with two tires that have the same construction. If your changing from Pirelli to Bridgestone, for example, things get murky.

Randy

Kirk

... I've tried various combinations from 32 to 37 between front and rear. Right now I'm at 33f/34r. This reduces some understear. The A4 quattro will have different balance of traction than your front drive Passat if you are trying to play with under/overstear. I would say that 32psi all around is a good place to start. Remember too, that these are cold pressures. It is ok to add air to warm tires, but do not remove air from warm tires. I usually add more air than I want at the gas station at night and then let air out to my desired level in the morning after the car has sat all night.

As a side, you might want to check www.vwvortex.com in the Passat forum, I'm sure you will get some good advise from Passat drivers.

Kirk