I have a set of 225/45/15 RA-1s mounted on a 7" wheel for my MC with SS+ and healthy camber via camber plates. I have done about 10 autox events and 3 autox schools on these tires. I didn't shave them. The tires have been great, although I did notice that even with 2 degrees of neg camber, the MINI manages to abuse the outside shoulder of the tire quite a bit more than the rest of the surface. Some of this is due to the narrow-ish wheel.

Over the last couple of months, I started seeing a weird wear pattern on the outside shoulder of all 4 tires. The outside section of the tread seems to be ribbed, perfectly spaced 1 inch wide bumps running around the tire. These ribs have been slowly becoming more pronounced to the point that the outside quarter of the tire tread looks knuckled. The high points of the knuckles seem to be coinciding with where the tread blocks used to be when I first got the tires. The wear on the rest of the tire is normal, down to the last 2/32nds and no knuckling or anything. As the knuckling has gotten worse, I have noticed a drop-off in performance - probably up to .5 seconds on a 45 second course.

Has anyone experienced something similar on their RA-1s? Normally, I wouldn't care much given the amazing amount of abuse the tires have taken over the last 2 years. But everyone I talked to and everything I have read says that the RA-1s last and last and grip and grip until they cord. There is no mention of the outside edges starting to knuckle.

 

Sort of get a mental picture of what your talking about - but a *real* picture would be better... it sort of sound like you might have them under inflated and they are still rolling over the edge - have you chalked them and see if/how far they are rolling over ?

 

RA-1s do that. I think every worn down RA-1 I've seen, on MINIs, Miatas, etc, looked like that. Don't worry about it. IMHO. Someone will be along shortly to say the complete opposite. :D

 

Tire pressures could be a possibility but I doubt it. I run around 35-40psi up front, and the still roll over somewhat. I think the wheel width might have something to do with that. The sidewalls are a bit pinched.

Someone over at GRM's message boards refered to this type of wear as scalloping. His thought is that it has something to do with toe - like too much toe in, which should be a non-issue on my car since I am running very healthy (too healthy on one side) toe out.

 

Really? I am assuming there is some performance drop-off associated with this? I don't feel like the tires grip through the turn as well as they used to since the scalloping thing came around.

These Minis and Miatas you have seen scalloping their RA-1s - did they have mild alignments or negative camber and toe out?

 

If it's what I'm picturing, I've seen similar wear on all kinds of treaded R tires. I think what happens is the edges of the tread blocks are less supported and more prone to tearing the rubber off whereas the center of the tread block is nicely supported and doesn't wear as bad. For what it's worth, I am just about finished with my 225/45/15 ra-1's, but mine were shaved and run mostly on 8" wide wheels- the outside tread block never showed any funny wear such as that.

 

Common and nothing to worry about...