Tire Pressure - All Season Tires

[3Zero]

I recently picked up a 2005 A4 USP fitted with P6 'All Season' tires. From what I can tell, the car was originally equipped with summer tires. Tire placard recommends 41 PSI. A4 owners manual suggests increasing tire pressure by 3 PSI for "All Season" tires implying a recommended tire pressure of 44 PSI (still under max rating for the tire).

Do you agree that 44 PSI is correct? Opinions?

I contacted Pirelli. They offered no insight. Dealer had tires inflated to 35 PSI ... !

Tire size is 235 40 18 - stock for this model.

Thanks in advance!

[Doc@tirerack]

Our numbers indicate Audi recommends 39 PSI for the 235/40-18 size .... We normally add 2 PSI for every 10 degrees of "expected" temperature drop for that week/month.

[3Zero]

The real question here is whether I ought to follow the manufacturer's recommendation to run M+S tires at 3PSI greater than summer tires (same size). Something to do with sidewall stiffness ... The info is buried 2/3 the way thru the owners manual. Am i the only one who noticed this ...?

[Doc@tirerack]

Sure, if you anticipate a temperature drop coming. That small PSI change may "stiffen" the sidewall slightly, but not enough to create uneven tread wear.

[3Zero]

Thanks for your time, Doc.

Not to be-labor the point but if I am reading the manual correctly it means that if I were to come into your shop with Conti Pro Contacts properly inflated at 41PSI (door placard - this is the 3.0) and swap to the same size Pirelli P6 'All Season M+S', we would set the tire pressure to 44PSI. The pressure would be set higher just because the P6 is M+S.

This is aside from any correction for outdoor temperatures.

The question is whether or not this is recommended practice.

[Doc@tirerack]

Adjusting the PSI just for a switch to M+S is a new one on me. The tire size is the tire size regardless of compound and will carry the same load at the same PSI. OE tires were the Conti Sport Contact 2's (XL) on Ultra Sport, the Pro Contacts are all season as well. At our little install bay, we just inflate to placard specs. Maybe the guys that wrote the manual were anticipating the temp drop ?

[1.8cab]

Our numbers indicate Audi recommends 39 PSI for the 235/40-18 size .... We normally add 2 PSI for every 10 degrees of "expected" temperature drop for that week/month.

I have 235/40-18s on a B6 A4 cabriolet. The door placard says 32psi front and 35psi rear for 17" wheels. There is no recommendation for 18" wheels. Should I stick with the recommendation for 17" wheels or go with 39psi?

[MacDaddy]

it looks like changing the pressure for the season and changing it for handling are getting treated like one and the same.


colder weather will drop your cold tire pressure, and warmer weather will increase it. thats why you should regularly check tire pressure, also air will very slowly leak out of any tire.

so anyway, weather aside, it seems audi is suggesting that if you use all season tires, try adding 3psi so the car will handle like it does with summer tires. what i would do if inflate your all seasons to the recommended pressure in the door jam, try them out for a few days then try adding 3psi like audi suggests. then use whatever pressure you like better.

[3Zero]

Thanks for all the feedback. I did a little more research and here's what I concluded: door jam pressure is insufficient for these tires.

I ran a little test. With TP at 40-41 PSI (per spec) I drove the car at highway speeds for 20-30 minutes, then pulled off at a rest stop. I then got out and felt the temperature of the tread at different points from inner to outer sidewalls with my hand. Call it the 'manual pyrometer' test. Lo and behold, the tread was noticeably warmer at the edges when compared to the center - which was cool. I concluded that the tire was underinflated and have since bumped the TP up to 44PSI. I have not re-tried the manual pyrometer test.

Sure, ride is on the stiff side (sport suspension) but, I suppose, at least all of the tread is in contact with the road.