I was looking for new tires and have settled on General UXP's, our local canadian tire had them on sale but the only size i could get was a 205/50 17 as opposed to the stock 205/45 17. So I was feeling pretty good about that, knowing that the sidewalls were going to be about 4% bigger, no problem I thought. I decided to check at one of the local Tire shops to see if there was anything else available plus the guy I know that works there is pretty knowledgeable when it comes to tires. So with respect for the bigger size tire he says that the tire shops are only allowed to put on a tire that is within 3% of the stock tire. He says that anything bigger effects the traction control, antilock, and anti-skid functions because the computer is programmed to work with a specific tire size. I've read a lot in these forums about people changing tire sizes and wheel sizes but I've never heard anyone talk about the effect it might have the computerized functions. Any comments on this?

 

All of the functions work by comparing relative speeds of the various tires, not absolute speeds, so as long as you're replacing all of the tires with larger tires (or at least both fronts or both rears), you won't have any problem with the computerized functions. I'm pretty sure that the various stock tires available on the MINI span a range greater than 3%.

If anything, going with taller tires will mitigate some of the speedometer "optimism" that plagues most MINIs.