I'm getting ready for a track event and was changing out my normal Kumho street tires for my track tires. When I removed the right rear Kumho, this is what I found. See attached pictures. These tires are 12 months old and have only 5000 miles on them, although that includes 3 DE events. In 2 of those DE, I shared the car with my son so it got double abuse those times. Is this a tire defect? A mounting defect? Using them too hard?

Clarify tire use - It was just recently that I bought track tires. These Kumhos have been on the car for 12 months and were used for the DE events.

 

Looks like a tumor

Seriously, I've seen that before from curbing a tire. Can't really tell from the pics if there are any marks on the tire.

In any case, looks like it should be replaced asap.

 

holy crap that looks bizarre. i had at one point spun at the track and ended up on gravel. some gravel stuck in between the tire sidewall and the rim which caused it to deform a bit but nothing as exaggerated as that. deflated the tire, removed gravel, reinflate, and tire came back all normal. yours look more like tire defect?

 

The tire radial belt is damaged and near total failure. It must be replaced.
Probably due to pothole, or some stationary object impact, IMO.

 

I agree with Mike^^. When you dismount the tire you will see a "pinch" mark on the inside of the tire.

 

Yep, most likely hit something that de-laminated the interior plies of the tire. Air getting into the tire is making the bulge grow. We see it all the time on the inside. It may have happened weeks or even months ago.

Replace it.

 

Your life is valuable.

Recycle the tire!

 

Got it - replace tire. So I guess I'll replace both rears - there wasn't a lot of life left in them anyway. Kind of surprising for Kumhos with only 5000 miles, even though some of them were pretty hard.

 

I see two areas of delamination. I may be possable that there was some tire mounting damage that finally gave away. When you have the tires unmounted I'd talke a look inside.

One other possability is that the tires were run in two different directions (not always on the same side of the car) which can cause ply seperation as well.

 

i have those tires on my VW....they cant even get my car traction so i have no idea how your 911 is holding up with them . anyway i have a small bubble in my rear tire too....stupid backroads leading to my house have some rough bumpy pavement are to blame. get some pilot sports or pirellis

 

i have same problem, i just noticed it today.

 

your tire is pregnant. put it in a warm garage and after 9mos you'll have 4-8 powerwheels tires

 

Looks like a pothole was the culpret. I live in an area where pot holes grow pretty large. I've had this happen with different brands of tires with varying degrees of damage. Time for a new tire.

 

Time for 2 new rear tires.