Recently had my 970.2 GTS at the dealer for two rear tire replacements (nail punctures) and also to refinish the front passenger side wheel.

When they mounted the front passenger side they also put on a brand new tire. Is it standard practice not to remount the tire that was already on the wheel? It wasn't no where near bald with the tread measuring 7/32. I know tires should be replaced in sets so I was really just looking to get a new set for the rears and run the fronts as they were since they still had good life in them.

And how problematic is it to run one new tire at 10/32 and the driver side at 7/32? Or is the difference/impact negligible?

 

That’s crazy! I’ve never heard of a reputable tire shop (let alone a Porsche dealership) that would endorse running tires with different amounts of wear. As an example, my winter tires are near new but have a 2016 date code. During my intermediate service, my P-car dealership noted that replacements are indicated as Porsche considers tires older than 5 years as outdated. I don’t believe they would sign off on “mismatched” tread wear. I’d push hard for them to make this right.

 

It’s hard to imagine that a 1% difference in rolling diameter is significant for these cars. The front tires will have a different effective rolling diameter than the rear due to the powertrain weight on the front which will cause the sidewalls to deflect essentially reducing the rolling diameter. Throw in compression from bumps on one wheel to confuse the matter. I think the early experience with all wheel drive that wasn’t designed robust enough and burned out clutches in the transfer cases has distorted the thinking on this. I would agree if you drive at autobahn speeds on smooth roads the difference might be important. On US crap roads and lower speed limits this difference is not likely important.