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I noticed some strange damage on my rear tire, where there appear to be diagonally cuts going around the entire wheel. I have no idea what might have caused this damage. I first saw it a few months ago, but didn't think anything of it because I had just replaced my tires with these relatively fancy Panaracer kevlar tires so I figured they should hold up for at least a year.

Anyway, just a few days ago I felt my rear tire bumping and when I looked at it, I could see the tube is starting to bulge out slightly through the cracks in the tire sidewall. The front tire is completely fine, but it's starting to look like I have to replace the back tire.

So my questions are, has anybody else dealt with this issue before? Any ideas what might have caused this damage? Am I indeed correct that the tire needs to be replaced?

The first picture has the most severe scarring, the second picture shows how it extends around the entire wheel.

tire scarring

more damage

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Since replacing the tires, how many miles have you put on this bike, and on what sort of terrain? A year is not a ridiculous amount of time for a tire to wear out, depending on what you're doing with it. –  jaustin Jul 10 '11 at 22:46
    
Comparatively little and comparatively light. I have probably ridden about 600ish miles, and all paved streets. The thing that perplexes me the most is not whether the tire would wear out, but the unusual location and symmetry of the wear. Having the tire rubber wear out would not surprise me, but I didn't expect to have whole-tire damage along the sidewall in such a regular pattern. It seems to imply either a manufacturing defect or some very strange, regular abrasion. I can think of nothing I had done that would cause such damage, so I'm just fishing for other ideas. –  Daral Jul 11 '11 at 1:04
    
The periodic nature of the cuts is weird. I can't imagine any external cause for it. You're not putting too much pressure in the tube and overstressing the tyre, are you? Brakes or something on the bike (pannier mounts?) aren't rubbing on it? –  Ian Howson Jul 11 '11 at 1:47
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FTR, this tire is either a Panaracer Pasela, or Pasela TG. In it's narrowest form, a 700x23c they recommend a 100psi maximum. If this is as it appears, a 26 x 1.25 or 1.5, that pressure recommendation drops to 60 psi. Could possibly be a 700x38c which would be a max pressure of 90 psi. –  zenbike Jul 11 '11 at 12:03
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The consistent and regular pattern on the sidewll is caused by the threads of the cloth base of the tire breaking. This happens when the rubber coating over the cloth becomes brittle due to age and dry rot. Your climate, or the age of the tire, possibly exacerbated by the pressure you're running in the tire, causes this kind of damage. It's no one's fault, but I'd recommend using black sidewalls, as natural rubber used in the tan sidewall doesn't last as well. It's common, and a well known issue in any bike shop. –  zenbike Jul 11 '11 at 12:07

3 Answers 3

up vote 2 down vote accepted

Looks to me like the tire's been run flat. If not that then I'd say the tire's defective -- that the factory left out a layer of cord or some such.

What pressure have you been running (and how much do you weigh)?

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I guess I should mention that I deflated the tire after I noticed the issue, so that it why it might appear to be running flat. Under normal conditions I would keep it pretty well pumped up. I would guess I pressurize it to somewhere around 75ish PSI, but I didn't use a gauged pump so I just got it up to the point of sufficient firmness. My body weight is around 140 lbs (64 kg). –  Daral Jul 11 '11 at 6:24
    
You're pretty light, and those tires usually aren't rated for more than 60-65 lbs, when new. You really don't need to run really high pressures for your body weight. –  zenbike Jul 11 '11 at 7:06
    
@Daniel, that damage is not from a run flat situation. That would look more like a single circular line around the whole circumference of the tire sidewall. In addition, it would look more "chewed" than cut, on that line. –  zenbike Jul 11 '11 at 8:29
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Just FYI anybody else runs across this, it turns out I had the tire accidentally underpressured (30-40 PSI). I ended up replacing them, and hope to avoid the issue in the future by staying around 60 PSI. –  Daral Nov 20 '11 at 1:16
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30-40 PSI is still more than enough pressure for a rider of your weight. The pressure printed on the tire is a maximum pressure, not a minimum. But I'm glad you chose to unaccept my answer, and go with the answer with 0 votes. –  zenbike Nov 22 '11 at 10:32

First of all, you're right about replacing the tire--if you have any cracks in the sidewall and/or a bulging tube, a tire MUST be replaced. Judging by those pictures, I would replace the tire immediately.

Depending on the tire, and what you're doing with it, a year may or may not be an unreasonable length of time for a tire to wear out. Others with more experience will probably have something to say on that.

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A year is not an unreasonable length of time to wear out the tread on a tire, but the tread on the tire looks to be only lightly worn. A tire shouldn't experience sidewall failure like this in a year, unless it's abused somehow. –  Daniel R Hicks Jul 11 '11 at 16:00
    
Or unless it sat on a LBS wall for a few years before purchase... –  zenbike Jul 11 '11 at 18:47

Yes, you are right that the tire must be replaced.

No, the tires are not defective. This type of cross hatching is caused by age and weather deterioration. It appears like diagonal cuts because the weave of the cloth start breaking threads, and they are woven diagonally.

The tire is either at least 3-5 years old, or has been stored in a climate which speeds dry rotting. In this case the tire appears much older than that.

It is generally seen most obviously on tires which have tan side walls, as this one does. The tires with black side walls do the same thing, but it isn't as visible or as quick to happen.

A tire has a shelf life of 3-4 years, even if not ridden. I realize you said that you'd replaced them about a year ago. That could be climate affecting tire life, or it could be that they were old stock on the LBS shelf for some time before you bought them. If you see crosshatching, or your tire feels papery and dry, rather than like rubber on the side wall, replace them. A blowout at speed is a dangerous thing, and a year of use is an acceptable lifetime.

FTR, this tire is either a Panaracer Pasela, or Pasela TG. In it's narrowest form, a 700x23c they recommend a 100psi maximum. If this is as it appears, a 26 x 1.25 or 1.5, that pressure recommendation drops to 60 psi. Could possibly be a 700x38c which would be a max pressure of 90 psi.

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If the tire were too old generally you'd see some checking of the sidewall rubber, which I can't discern in those photos. –  Daniel R Hicks Jul 11 '11 at 11:45
    
The periodic cuts are what side wall checking becomes when left ...um.. unchecked. ;-) Side wall checking is caused by the breaking of threads in the woven cloth that is the base of the tire. It weakens the cloth in that area, and allows a tear to begin. It looks like lines in the side wall when just beginning, but will eventually look like this. The extreme nature of the checking in this instance is what tells me the age is more than just a touch past the shelf life of the tire. –  zenbike Jul 11 '11 at 11:50
    
On old tires you will often see checking (due to the rubber getting hard) without any sign of the sidewall breakdown in the pictures. It may be that the tires are too old, but my experience (I have a lot of experience with old stuff) wouldn't lead me to suspect that age is the primary problem. –  Daniel R Hicks Jul 11 '11 at 15:49
    
Where is your experience from? You have strong opinions, which sometimes run completely contrary to accepted wisdom from every experienced mechanic and bike guru I've ever met. I've spent 15 years in bike shops, and I see these issues every day. I am not trying to say I know everything there is to know, but I know a lot, and I can recognize a damaged tire and its cause pretty easily on sight. What is your history, and your experience? If you can give me a reason for your certainty, maybe it will annoy me less when you say things I know are wrong. –  zenbike Jul 11 '11 at 18:35
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The kind of damage caused by riding on depressurized tires, at your body weight, would mean you were running between 20-30 psi on a 90psi tire. The psi printed on the tire is a max pressure. Running 10-20% less is acceptable especially for a light guy like you. Changing your behavior to prevent a problem is good. In this case, avoid gumwall tires, buy recent stock, and consider a new set every 2 years normal. I'll post some good tire options for you when I get back to the shop. –  zenbike Jul 12 '11 at 4:46

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