staggered setup, strange diameter?

[dkl]

Since you have been running the wrong tires for a while, it could cause extra wear on your t-case. It would be wise to do a scan to see if your t-case fluid needs changing. Note that you won't get an idiot light to tell you that you need this service...only way to know is with a scanner.

[jgold47]

I must have been on crack when I looked last night. it is a 255/50....

the difference just must be the tread wear.

Now I need to find matching rears!

[dkl]

It may not be a treadwear issue. Different tire brands/models can varied greatly in dimensions, even with same stated size. I was running different tire brands between front/back on my staggered setup and the car would always throw an error code of "clutch gearbox-ECU: reduction torque intervention because of too high tire size tolerance". I was only able to correct it after matching up all tires from the same manufacturer and model.