I too have seen this before. When I saw this it was on a 315/17 that
I was using on a 9.5" wheel. I called Mike Taylor, operations manager for
CUT, they are the importer for Kumho. He advised me that it was due to the
fact that the tread and the side wall are two separate pieces of rubber.
They are put together sometime during the mold process, we did not get into
the tire construction seminar. He said it was nothing to worry about. I have
never seen this on my own tires except for the 315s on the 9.5" wheels. I
have ran my vette with 275s on 9.5" no problem, and we ran our Mazda MX6
with 225s on 6.5" wheels no problem. The 315s that did show the crease
around the edge never failed, I ran them to the cords.
I did see last weekend a set of new 245/17s that had a crease around
the edge. This was only on one tire, and did not fail during the event. It
looked like a cosmetic defect in the mold. I think part of what keeps race
tires inexpensive, compared to high performance street tires, is that they
don't have to spend a lot of time worrying about cosmetics.
I just had a brand new set of 275/17s delivered today, they all look
perfect, no crease. However if you do look close at the side wall, it
appears as part of the rubber is darker, like where the side is blended with
the top. I am not a tire tech, but it seems reasonable to me that the tires
are made of more than one piece.
I have never seen or heard of one of there tires coming apart. I
would check to see if the cars that are encountering this, do not have any
bolts or any other sharp objects rubbing. If you have specific questions I
would ask someone who know, Kumho or cut. Before you call them I would wait
a week, as most of the people in the know are at the runoffs.
Jason Isley
jisley@cell1.com
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