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Old 03-12-10, 01:34 PM   #1
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Tire cracks - time to replace?

I've got a set of Conti GP4000 with some cracking on the sidewalls. I can't see the tubes underneath, but some of them are more than hairline. There is no cracking or splitting on the tread, which is really still in great shape.

I ask the question more for the curiosity of it. I'm going to change the tires anyway. I'm just wondering, as a general matter, if that cracking means the end of the line for tires so I know if it happens again.
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Old 03-12-10, 01:44 PM   #2
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No.
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Old 03-12-10, 01:47 PM   #3
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What is the age of the tires?
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Old 03-12-10, 01:52 PM   #4
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What is the age of the tires?
I don't know, they came with the bike. Judging by the overall condition, aside from the cracks, not very old. They still have a lot of the knobbies on them from the manufacturing process.
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Old 03-12-10, 01:59 PM   #5
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+1 No. Check out Sheldon Brown's site about tire. http://sheldonbrown.com/tires.html Go to the bottom of the page under "Tire Wear-When should you replace your tires?".
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Old 03-12-10, 03:59 PM   #6
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... Judging by the overall condition, aside from the cracks, not very old. They still have a lot of the knobbies on them from the manufacturing process.
Judging from your description of age/condition ^ , I would think these cracks are likely the consequence of poor manufacture and/improper curing. I would be very leery of it, and I would NOT recommend that anyone ride on them for that reason.
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Old 03-12-10, 04:40 PM   #7
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I'll take a couple of photos this afternoon and post them. It's a good lesson for me, thanks for the replies!
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Old 03-12-10, 06:27 PM   #8
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It's a safety thing. Imagine being unhealthy for any length of time.
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Old 03-13-10, 10:23 AM   #9
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The only purpose that sidewall rubber has is to offer some protection to the cloth that makes up the actual tire casing. There are some tires (I'm thinking specifically of tubular track tires) that have no rubber at all on the sidewalls. In a pinch, I've ridden a recently-purchased bike 10 miles home on tires that have no sidewall rubber at all. If there is a crack or two in the sidewalls, you'll be fine. It doesn't affect the structural integrity of the tire at all.
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Old 03-15-10, 07:33 AM   #10
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The only purpose that sidewall rubber has is to offer some protection to the cloth that makes up the actual tire casing. There are some tires (I'm thinking specifically of tubular track tires) that have no rubber at all on the sidewalls. In a pinch, I've ridden a recently-purchased bike 10 miles home on tires that have no sidewall rubber at all. If there is a crack or two in the sidewalls, you'll be fine. It doesn't affect the structural integrity of the tire at all.
+1.

I don't know how many times someone has told me a bike is going to need new tires, because they're flat and cracked and dirty and terrible looking, but after I pump them up there is nothing wrong with them. If the tube holds air, it's fine. If the tire holds the pressure of the tube, with no visible gashes or bulges or whatever, it's fine. If you're not sure, pump them up to full pressure and wait a week or two, then inspect them again. If you still can't find any problems, relax. The tire is probably fine.

Would I go on a month-long cross-country tour with 30 year old tires? No, of course not. But if I'll be staying within a hundred miles of home, I wouldn't worry about it.

Can I really be sure? No, of course not. Tires can fail, for various reasons, and you can never be 100% sure it won't. A brand new tire can turn out to be defective, and blow off the rim or something after ten miles or less; or a rock or something can hit a hidden weak spot and cause catastrophic damage to a tire of any age. But cracks in the rubber don't mean much, if anything.
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Old 03-15-10, 07:41 AM   #11
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Cracks on a car tire are a huge problem. The edges of the crack rub on each other and cause a lot of heat and will cause the tire to fail monstrously at speed.

Bike tires do not share this problem because of the lower weights and the speeds.

Good rubber grips well. Thick rubber will (marginally) resist flats better. New rubber looks good. Other than that, ride the thing if it is not bulging out anywhere.

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Old 03-15-10, 07:42 AM   #12
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wish I would have read this thread before throwing a pair of crackers in the garbage bin...

I fished them out but they seem kinked and mis shapen so no use at all now I guess?
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Old 03-15-10, 07:54 AM   #13
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I fished them out but they seem kinked and mis shapen so no use at all now I guess?
Kinked and misshapen doesn't mean much. Gashes, slashes, holes, tears, and that kind of thing, are significant, though. There's no harm in trying them out if you can't find any real problems. Mount them on a rim, complete with rim strip and inner tube, and inflate. If you can mount the tire and inflate to full pressure and nothing alarming happens, it's probably fine. Look it over carefully before you go for a long ride.

Bottom line, of course, is: don't ride it if if you don't feel safe on it. But if you can't find any problems, don't worry about it.
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Old 03-15-10, 08:06 AM   #14
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After reading this, I am now going to leave the original tires on my 73 Raleigh Sports. They have a few cracks, nothing severe and hold air. It should be fine for tooling around town.
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Old 03-15-10, 09:03 AM   #15
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some people wait until they hear the threads popping and the tube bulging through ... hahaha happened to me. never again!
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Old 03-15-10, 04:10 PM   #16
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Live dangerously, do what you want. If you'd put them on your wife's/son's/daughter's bike before the big race, go ahead.

If not, well.....The MS Paint your mishaps on SS/Fixie forum is waiting for your contribution.
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Old 03-15-10, 04:26 PM   #17
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I don't know, I guess it's a personal choice after all... but me personally, would rather pay $30 and get a decent pair of new tires, than thinking of the possibility of walking the bike back on the middle of a 20-30 mile ride...
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Old 03-15-10, 04:30 PM   #18
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The rubber on really old tires seems to get hard. In my mind, this would cause a lack of adhesion to the road surface on sharp corners. They kind of sproing off crap in the road. I changed the old tires on my bikes.
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Old 03-15-10, 05:11 PM   #19
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Completely forgetting about the tire cracks (yes, I fight bouts of stupidity sometimes, on-set by the flock of small children in my house), I rode these tires about 25 miles over a pretty good course and they performed well. In fact, fully inflated, I couldn't even see the cracking, which is why I forgot about it. I'm still going to replace them, just because I want to more than anything else. I don't want a 20 mile walk, or a face plant or something else.
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Old 03-15-10, 05:24 PM   #20
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c'mon, where's your sense of adventure?

got dental coverage?

an ortho on call?



Some tubes will last 20 years, and when they go, you slow down and change them.
Some tires will last 20 years, and when they go, it's a crap shoot on avoiding mayhem.
I'd prefer to see a few more of your builds before you wipe out, eh?
BTW, identical RB-1 to yours is for sale here, $500.
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Old 03-15-10, 05:33 PM   #21
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That Alpina Pro MTB I picked up, I took out for a short ride on the very original tires...about 1000yards from home I thought the wheel went out of true...turns out the wheel is fine, but the sidewall of the tire let go and the tube started bulging. I got off and walked, and the tube inside blew off like a firecracker. Scared me a bit....

I rode the Paramount, the RB-1 has wheels off to be trued themselves while I work on the paint a bit. That Paramount was a nice, nice ride.
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Old 03-15-10, 05:43 PM   #22
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I don't know, I guess it's a personal choice after all... but me personally, would rather pay $30 and get a decent pair of new tires, than thinking of the possibility of walking the bike back on the middle of a 20-30 mile ride...
+1
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Old 03-15-10, 06:16 PM   #23
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I have to humbly disagree with Sheldon Brown. Old dry rotted tires that have hard cracking sidewalls need to be replaced. I have had a lot of tires just explode when the tire sidewall failed and the tube burst through.

The weird thing is, age does not seem to matter as much as the environment the tire was stored in and how much it was used. A tire that never gets rode will become harder faster than one that gets some use. I have seen badly dry rotted and ruined tires on nice bikes from the mid 1990s that didn't get ridden much and I have seen tires from the early 1980s that I would still trust. Maybe is has somewhat to do with the initial quality of the tires or maybe older tires were made better.
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