I know that you should follow the tag stamped inside the car for OE tire sizes, but what about aftermarket wheel and tire sizes. Should I follow whats on the car or whats on the tire? I've always wondered, usually go somewhere in between if its a huge difference.

 

That is a great question!

I start with the vehicles specs, never the tires.

My reasoning is that the max psi# by the tire manufacturers does not take into consideration that all vehicles do not have the exact same weight loads and are not always the ideal 50/50 weight ratio.

I can then increase the rear a bit for extra passengers, heavy cargo or when pulling a trailer (if I ever find a used OEM hitch)

I'm sure that after my post there will be a really smart engineer that will give you a much more complicated and more precise explanation!

 

I have been meaning to ask the same question for awhile now.

I put on a set of 22'' deluxe rims on my Cayenne and don't know what the tire pressure should be. The TPMS is set for the 21'' wheels and generally measures the tire pressure to be ~38.

How do we know what the ideal pressure should be?

 

Since I'm new to Cayenne I've been wondering about tire pressure also. I have 20" sport techno replica with 275 width Yokohama Parada spec x. The Porsche recommended pressure seems to be working well.

 

Iv also been wondering the same thing i have rinspeed 23" wheels with 315/25 tires

 

I fill the front with 38 psi and rear with 42 psi (as indicated by inside stamp)
this is on 20-inch cayenne sport techno wheels
Average outside temp (38oC)

 

I was just looking at my Dads 2008 cayenne and the rear psi stamped in the door was 49 psi but the manual states 43 psi? The max loaded psi for the tire is 50 psi. Which should I go with and does anybody else door stamp show 49 psi too?

 

Tires are 18 inch

 

Here is a Simple way to get the proper pressure for any tire, wheel,load.

Drive your Cayenne (or any car for that matter). Anytime you stop touch the tires in 3 spots. You want to feel the inner and outer edges and the middle.

If the inner strip is warmer than the outer edges then you have too much pressure. If the outer strips are warmer than the center you do not have enough pressure.

If one side is warmer than the other, your alighnment is off.

The best part of this is you can adjust your pressure on they fly for road trips, loads, passengers etc. Every Cayenne will be slightly different due to mods, etc.

You many be amazed at how low the pressure needs to be on big rubber to where them flat.

I have gotten 60K out of MTRs and other tires by setting them this way.

Simply, easy, no special tools needed.