Understanding tyres and tyre pressures


Registered User

I want to get a better understanding of the spec of my wheels/tyres and how that relates to tyre pressures. I've attached a photo of my placard, but have some specific questions.

I have 225/40 R18 wheels (Sport suspension), I can see those listed on the placard, but what do the letters after that refer to? E.g. "92Y XL" or "92V XL M+S"?

I assume the rows in each section refer to the load/weight of the vehicle? E.g 3 persons/1 bag, or 5 person/3 bags. Etc. But what does the book icon with the "i" on it indicate?

At the bottom, there are two lines reading "T 125/70 R16" and "T 125/70 R18" with another recommended pressure setting? What is this referring to?

Given that normally there are 2/3 of us in the car, with little/medium luggage, I assume I should be aiming for the top row of the placard? E.g. Front 36psi, back 33psi.

Any help with these questions really appreciated.




A6 C6 4F 2010 LeMans Avant
91 and 92,93 ... is the load index per tyre. Letter after that number is the speed index for the tyre.

Have a look here:


Also, check your handbook for the explanation in regards to those extra loads with the book and "i" mark or M+S.

I never looked at these stickers as my wheels were not listed, on the cars I owned. Will check current car, tho.

You need to make sure you have correct tyre pressure according to the season also


Staff member
VCDS Map User
"T 125/70 R16" and "T 125/70 R18" are the dimensions of the tyre on a spacesaver spare. So if you have one of these they need to have 61 PSI in them.
I should read the manual regarding tyre pressures as to what the "i" means . Possibly slightly lower tyre pressures for a smoother ride at the expense of mpg.
M+S is mud and snow so essentially a tyre designed for winter conditions.