jadatis

To my opinion the tire Failure in the Ford/Firestone -Afaire where courced by the to high given maximum load of the offroad-looking tires wich where allowed lesser deflection the a normal car tire because of profile blocks covering the sidewal, wich stiffens those sidewalls.

What you do is asuming all car users ar Dummies , and are the blame of the blowing tires and the accidents wich courced more then 100 death people.

The calculation of the advice pressure was wrong too but because American calculation stopped at 26 psi the pressure still would have been OK if the tires where not given to high maximum load.

But now about TS car.
After 2000 ( when the Ford Firestone affaire was, coincidence?) the European Car makers swiched over to another system of pressure advice on the stickers.

Before 2000 they used for normal use a by the car-maker determined axle load for 3 persons and a little load in the car. Maximum loaded they used the GAWR's to fill in the formula to calculate the needed pressure , and in the 1990's rear pressure needed for the maximum load of tire or even maximum pressure of tire.
Advice presssure was given for maximum technical car speed.

After 2000 normal use advice pressure was for GAWR's and sayd to be for 4 persons and load , so what before 2000 was for maximum loaded.
Heavy duty was for when towing rear again maxload or maximum pressure of tire, to cover possible and most likely to happen overloading on rear.

The maximum load of a tire is given ( up to V speedcode) for 160km/99m/h.
and a normal car tire in American system needs 35 psi/2.4 bar to carry that maximum load savely. For higher speed this maxloadpressure/ referencef-pressure needs to be highened up with a system depending on speedcode of tire. Also for alighnment ( often rear done wheels like this on the axle /-\) the maxloadpressure has to be highenen up with a system for all tires the same.

But this all confusing story means that if you dont drive faster then 99m/h and only have 2 persons and a little load in car, wich is 99% of the use, probalby for you too, you can do savely with much lower pressure.
then comfort and Gripp are much better and still save for the tires, wich is the goal of the calculations of the tire-and car-makers.

I can calculate that lowest pressure if you give me the loads on the axles and the specifications of tires.

Greatings from a pigheaded Dutch self declared tire-pressure specialist.

iconoclast

not me... i didn't write the legislation... it's basically for litigation reasons and mitigating liability more than safety... the very same reason we have thinner all-weather mats with warnings all over them. (thanks toyota!)

i would love a sun visor without a warning label and so i have to buy one from EU market dealer, i want mirrors without a "objects in mirror..." warning so i have to buy the EU versions, i want child seats without labels slapped all over them so i have to purchase the EU version etc etc etc.

mothease

I have a 2014 Q7 TDI Premium Plus. It came with Perilli Scorpion Zero tires. Door jam states 44 front, 49 rear. Dealer keeps putting in 36psi and told me too 44/49 is maximum. I went to tire dealer to ask and they said put in around 40psi. Another dealer said to put in 36psi and when I'm fully loaded to put in 44/49. These tires were extremely noisy and finally after 6 months and 8,900 miles dealer/audi replaced them with Michelin Latitude's. My what a difference: A lot quieter and much better ride (this car now floats which I like). I just went to Michelin's site and their recommendation is 44psi front/49psi rear). So guess I'll up my pressure. I really don't know who to believe.

uberwgn

For me, I'll use the Owner's Manual information that was provided with the vehicle. See post #3 in this thread.

Welcome aboard, Moth !!

minsicomm

Let me tell you my tale of woe:

I just begrudgingly replaced a set of nearly bald Pirelli Scorpion Verdes on my Q7 after one year and about 20k miles. All because I followed the door jamb sticker instead of looking in the owners manual. This is good for Pirelli because I had always had good experiences with their products, and I was ready to swear them off. But since its my mistake, I rescind all curses and voodoo hexes I wished upon them.

So, anyway, in 3 full years of owning it (starting my 4th), I've had 3 sets of tires. A very expensive, and unanticipated mistake. I'm not an aggressive driver, and had always gotten at least 40k out of tires, usually more, regardless of type of vehicle. So this was a nasty shock.

This new set (Nitto NT421Q) I have them all set at 35, and its made a big difference. I might raise the PSI slightly to 36 or 37 to see if I can make it just a bit more fuel efficient, and a little less grippy. The ride is just a touch too soft and sticky for my tastes. But I think I'll get more than 20k out of them.

I read this thread, and someone mentioned that the labels changed 10 year ago. Except I was driving a 1996 before this, and plan on keeping this q7 a good 12-15 years as well. My takeaway is that we should always reference the owners manual from now on instead of relying on habit, or what our dads taught us 25 years ago.