Hi - New member here, and also new to wheel changes...

I have a newly acquired 2011 A5, Premium Plus with the stock 18" 10-spoke wheels and all-season 245-40-18 tires. Thinking of changing to a "better-looking" 19" wheel (from Hartmann), and adding 255-35-19 summer tires. I don't want to adversely affect the performance/handling engineered into the car, but wondering whether the changes (overall diameter and offsets) will matter? Overall diamter calculated as wheel + sidewalls*2...

Current diameter = 653.2mm (25.71 inches)
New diameter = 661.1 (26.02 inches)

Will the ~1/3 inch difference large enough to mean the odometer, tpms, and other systems are off? Need to be recalibrated?

Also the Hartmanns have an ET-25. Anyone know how that compares to the stock setup (unknown)?, and the effect of this relative to the current position of wheels.

Info and insights appreciated...

 

Hi OnYourLeft and welcome to the forum!
The .3'' difference is considered negligible as will barely have any effect on the speedometer and odometer. A recalibration would not even be necessary.

The offset could be problematic if it is a ET *negative* 25 because that would shove the tire into the fender lip. If you meant the offset is a standard 25 or positive 25 that fitment should be perfect. It might come towards the lip more than stock but not enough to run into it or cause problems.

 

Good to know. Thanks Miles. Yes, offset on new wheels I'm thinking of have an offset of positive 25.

 

I run 18" rims with 245x40 snow tires (from TireRack) in the Winter and my OEM 19" Sport pkg 255x35 in the summer. No issues. Of course the 255x35 are lower sidewall height but as Miles cites it's a negligible speedo difference as the respective overall profiles are close.