Meyecul

Thank you. So I had it right. I originally mentioned mine have been running 32 to 33 max. Book says 32 for both front and rear under normal load (bottom line for the 21s)

Cracker Dave

Clearly something is at odds, I've attached a photo of the tyre pressure information from my car, label on European cars to the rear of the drivers door. Tyres are 285/45 R20, normal pressures 38 psi, comfort setting 33 psi. The handbook states that when using comfort setting increased tyre wear may occur. With most of the problems of tyre wear being on US cars, I think all US cars are running in comfort setting.

srbsq7

Is this down to UK not using runflats though?

Cracker Dave

Good point, but are your tyres wearing unevenly and do all US spec cars come with run flats, if they do then it really must come down to different suspension settings?

Meyecul

The OEM 21s in the US are not runflats, they are summer high performance. I have the air suspension and drive in either Auto or Dynamic, never comfort and needed new ones at 940O miles (okay I could have driven a bit longer on them but fronts were so worn down on the edges). I think it was the "perfect storm".... OEM conti sportcontact 5 is soft rubber, on a heavy SUV and waiting until my first service (10k) to rotate (should have rotated at 4k and even then, I think would have been lucky to get 20k out of the OEM Conti tires). I am hopeful that switching to the highly rated Conti DWS all season will work out better. So far, so good and much prefer having an all season tire vs summer.

gsobol

Comfort (for tires) is not referencing your drive mode settings. It's referring to tire manufacture designation of a tire stiffness feel. When inflated to 32psi tires will be softer, giving you a feeling of more comfort, at 38psi they will be harder therefore more harsh on bumps (less comfort).

I found that most car manufacturers list standard recommended psi a little low, which causes feathering of the tires. For most of my past SUVs recommended psi was 32psi. Over the years I have noticed significant feathering when driving at that psi settings, feathering was reduced or almost gone when operating at 35psi. That's what I plan to use on Q7 (R20 runflats).

Meyecul

Oh, I see. Thank you. Hmm. Yeah.. perhaps trying 34-35 would be more optimal. My dealer sets them at 33 so just a tick above the recommended psi

gsobol

There is also one more factor. When do you check your tire pressure? If the tires were left in the sun for a few hours, pressure will be few psi higher - not really "cold" tire pressure, opposite at night. If you measure the pressure and it seems high and you lower it to 32psi, you might have deflated the tire below optimal level.

The term "cold tire pressure" is kind of misleading. Basically it refers to tire pressure before you start driving in particular conditions (summer, winter, elevation, etc.), but other factors play a roll too - such as the sun and shade. Generally I would check the tire pressure once a month in a morning (when it's cloudy outside) and try to stick with adjusted pressure for a month (barring unforeseen circumstances).

JT4

Stopped by my dealer on Saturday to pick up some touch up paint I had ordered. While there I spoke to my SA and requested that they check the alignment.

I have to give my dealer credit, without an appointment they put it on the rack and happy to say the alignment was in spec. Based on what I read in this thread I figured I'd better have it checked. And it doesn't hurt to have it on record in case I run into an issue down the road with premature tire wear..

detlefvi

Had mine realigned and recalibrated yesterday. It was out of alignment, especially the rear suspension contributing to the front tire feathering.