I have a pair of Challenge Parigi-Robaix clinchers with only about 500 miles on them. The other day I swapped one onto a different rim for a special event, and tonight when I went to remount it back onto its original rim, I noticed this:



There is a noticeable groove about 4" long between the tread and the gumwall, which seems to expose the casing. I'm not sure if this is normal and just a cosmetic issue (I know these tires are thin thin thin, with fragile casings and basically a painted on gumwall), or if this is a sure sign of impending failure. The groove happens to fall right on a fold line; when I deflate the tire that groove is where the tire folds onto itself.

Thanks in advance.

When my tires look like this I put them on my wife's bike. She hasn't crashed yet. So you're fine.

In other words, I wouldn't ride them like that. But that's because I like to trust my bike.

if you are going on long rides,,take them off. Just short rides not far from the house,,keep them on

I would not ride any further from home on those than I was willing to walk to get back.

Okay, so what's the actual risk? Sudden blowout from the casing giving way?

I've been riding colle-a-main tubulars for 45+ years. This is fairly common, and not in itself any indication of impending failure. But keep a watch on it because if you see the actual tread curl away near the edges you want to deal with it. (peel back loose tread, apply a thin coat of rubber cement and allow to dry completely, then press together. Get it right the first time, because when prepared like this the rubber cement acts like a contact cement.

BTW- if you ride in all weather conditions, you want to put in the miles. Between rain and UV the coating on the wall can break down quickly, so the clock is ticking and you want to wear them out before they age out on you.

It does look to me like the sidewalls are essentially just a paper-thin gum coating on top of the casing. The rubber tread section is thicker. As you can see it's not really peeling back, it's pretty much intact. It's more like there's just separation between the rubber and the gum sidewall. I'll try some rubber cement and keep an eye out, but it does make me nervous.

Yes. I had some Specialized "Turbo" tires that separated in that manner. I managed to get within a couple blocks of home before the casing failed.

Interesting. I wonder if in my case it's a matter of tread separating from the casing, which might mean the casing is fine, or if the casing itself is failing, causing the separation. This sucks, it's an expensive tire with only 500 miles on it. Geesh. I guess it's no better time for those Grand Bois Serfs that I've been wanting to try...

Don't sweat it. Look again, the cord structure looks fine in the photo.

And I'm sure it is, otherwise there would be a wide area or a wiggle and the partly separated cord distorted the inflated tire. Odds arr that what you're seeing is abrasion damage to the edge while the tire was folded. This has always been a concern with good tubulars, which is why experienced riders know how to fold them so only the tread is out. I take this one step farther and wrap my folded spare tightly in Saran wrap before tucking it into my seat bag.

If you're going to ride lightweight gum coated colle-a-main tires, you have to get used to some of the minor issues. Otherwise you'll be tossing expensive tires long before you've gotten the value out of them.

Pretty damn minimal chance of the tread separating further. End of story, no casing failure in the offing. Worry when the tyre changes shape.

O_O

I'd say that's pretty freakish.

Don't forget the long walk home. I had to walk 15 miles through the woods once because some nut put a hugh spike in the trail. Ripped the side of my tire beyond repair.