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First of all, I am either inexperienced or very lucky because I have never had a flat bike tire in my life. Now comes the question.

I have a basic "Specialized Sirrus 2013" hybrid bike which has run 2500 kilometers (over 1500 miles) in various conditions. The tires are "Specialized Nimbus 700x28c". Today I accidentally noticed that the rear tire is indeed damaged:

Tire damage

I have no idea how long it has been like this or what is the cause (maybe a very sharp rock?). The cut/scrape is about 1 millimeter wide, 6-7 millimeter long and 3-4 millimeter deep (0.04x0.25x0.15 inches). It is clean of substantial debris but stays open like that when normally inflated at 115 Psi.

What actions should I take? The tire is not flat and I am able to ride normally but should I be concerned?

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Impossible to tell for sure, but it does not appear to be a serious cut. Unless you're in a situation where you must avoid a flat if at all possible, I wouldn't worry about it. –  Daniel R Hicks Jul 22 at 22:07

4 Answers 4

It does not look to me like the cords are damaged, which means the tire will still have its strength to hold the air pressure of the tube.

You have three easy options. Personally I would take the last:

  1. Ignore it. It will probably last until the tire has no tread left. The cut itself will bulge a little, so this will be the point of failure of the tire. The bump may cause the tire to make noise of vibration as you ride- If you notice this the tire has little life left, or may quietly wear down till with the rest of the tire.

  2. Put a sleeve in. Get a piece of tough material like canvas (the side wall of an old MTB tire is great), insert it under the cut. This will provide a stronger area around the cut and prevent the weakness causing further problems and extend the life a little more as it will reduce the size of the bulge caused by the cut. Its a technique used as a temporary repair for tires to get you home, and works for tires with significant cuts (I have seen it used successfully on a MTB ride for a tire with a 2-3cm full thickness cut.) As we all know, there is nothing more permanent than a temporary fix that works.

  3. Replace the tire. A shredded tire on the road is really a pain. Unlike a puncture, which is generally repairable, the only fix is a new tire - do you carry a spare tire? Although I always carry a tube and repair kit, I only carry a spare tire for very long rides (and usually just one in our group will carry a spare). If I have a spare tire in good nick, why would I leave a dodgy tire on the bike?

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If the cut were to open up and he got a blowout it should still be possible to "boot" the tire (usually a relatively new dollar bill, folded twice, works well for this). But of course that would require some skill the OP likely does not have. –  Daniel R Hicks Jul 22 at 22:09
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2 is only temporary. It will shift and rub thru a tube. –  Blam Jul 22 at 23:05

Pull the tire. Don't just clear it of substantial debris - clear it of all debris. If there is something in there it will work though the cords. If you are into the cord then still do not give up as that is a decent tire. From the inside if you can see damage to the cord then time to get a new tire.

While you have it off pull the front and rotate. Front tire takes less abuse and less weight. If I have the rear tire off, it is more worn than the front, and run same tires front and rear then I rotate. Another opinion is to put the best tire in front. SheldonTireRotation

For me I get a new tire and save that as an emergency spare.

Don't do an insert - that is just what you do to get home. It will shift and wear out a tube in no time at all.

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Pulling the tyre and checking for debris is excellent advice. Gouges like that can harbour lots of little bits of glass and grit that will cause a puncture in time. But I've run tyres with plenty of similar cuts, at high pressure, until they're completely bald. Nothing to worry about, especially as it's on the back (a front blowout, OTOH, can be extremely unpleasant). –  headeronly Jul 22 at 23:35
    
Since the OP is inexperienced, it's probably worth explaining tyre rotation. Rather than buying tyres as a pair, it's cheaper to buy a single new tyre, and put it on your front wheel (where you really need the fresh rubber for cornering grip). Replace the worn-out rear with the old front - it will be plenty good enough (as @Blam mentions, front tyres wear much slower than rears). Keep the old rear for an emergency spare. –  headeronly Jul 22 at 23:38
    
@headeronly But I don't agree with putting the fresh tire in the front. I always put the most worn tire in the front. If I don't think it is safe then I throw it away. You have different opinion - cool. Not saying your opinion is wrong. –  Blam Jul 23 at 1:08
    
That's cool - both ways make sense to me. Fresh rubber on the back is better for accelerating grip and puncture resistance. I was just trying to discourage putting a clapped-out flat-spotted tyre on the front, cos that won't corner well at all. –  headeronly Jul 23 at 1:34
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You put the new tire on the front. sheldonbrown.com/tire-rotation.html –  Batman Jul 23 at 3:26

You don't need to be too worried about it.

From my own preference in the past, if the tire plies are not exposed, tires with mere surface damages can still last a very long time. Rubber is sturdier than what most people think. I ride a CX on MTB trails and get tires scuffed all the time.

Especially if you are not doing anything intense (I assume because you ride a hybrid), this should not be a serious safety issue.

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It looks to me from the condition of the tread like you'll be replacing the tire pretty soon in any event. It might be possible to limp along like this a while longer, using a liner or such (I've used a dollar bill in a pinch for that), but what can happen is eventually the tube will poke through the tire and when that happens it wears quickly or pinches and "pop" you'll have a flat tire. I had that happen to my mt bike's tire when I was trying to get a few more miles out of a worn tire, but not a problem b/c I only use that mt bike on dirt trails, going slow up steep up hills, and always go very slow downhill. So it was at most an inconvenience. But if you were say to be riding on a paved road at 40 mph and the tire popped, well, then it might be more than an inconvenience. Buy a replacement tire.

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