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Old 03-10-08, 08:40 PM   #1
Bacciagalupe
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Constant Tire Blow-Outs

Over the years I've used quite a few tires, of various shapes & sizes: 20" folding bikes, 700c hybrids and road bikes. Half Schrader, half Presta.

Last year I picked up a used 80s 700c road bike. For some reason, the tires on the road bike blows out fairly frequently. The front has blown twice, the rear once. On one occasion it's destroyed the sidewall.

My standard procedure is: put a little air into the tube, seat one side of the tire, insert tire, seat the other side, inflate a little bit, pat down the tire to make sure it's in place, slowly inflate and watch for bulges.

Now, while I can accept the possibility that I'm putting the tire on incorrectly, it strikes me as a little unlikely as I've successfully put tires onto bikes for a few years in a row, including on my other 700c bikes.

Anything I can or should check? Any aspect of the tire which might contribute to this? I've only put 2000 miles on the bike and this is the 3rd blowout. Very frustrating....
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Old 03-10-08, 08:48 PM   #2
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Rim strip!
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Old 03-10-08, 09:14 PM   #3
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Go over to the C&V forum, we are experts at using old wheels over there.

By blow out do mean a big pop? If so, then the only cause can be in improperly seated tire. Older rims (although, I would have guessed only even older 27" rims) did not used to have a hook on the extreme edge of the lip. The hook is a little inward bulge that keeps the wire from slipping over the edge and blowing out. Unhooked rims just cannot hold very high pressures; something like 65psi.

If you actually wrecked a rim, I question the integrity of the rim to begin with. Brake wear does eventually weaken the rim, and I suspect that you started with rims that were at the end of their lives anyway.

I am all for cobbling together old parts, but it sounds like you need to examine those rims carefully to see what you are dealing with.

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Old 03-10-08, 09:19 PM   #4
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Check the rim to see if it's got a sharp edge on the inside of the lip. On the older rims the bead retaining lip is rounded and it relies a lot more on the tire bead being a tighter than the more usual modern fit. The new ones use the extra grip of the sharper edged lip to provide the same thing.

If I'm right about the rim then your only option is to find a brand and model of tire that fits with a tighter fit. In otherwords you should not be able to work it on without using levers and the "right" tire will require a lot of attention to keeping the bead down in the hollow on the opposite side and all around and even then it'll snap home from the last levering with a nice sharp BANG!
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Old 03-10-08, 09:22 PM   #5
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Any possibility you are using the wrong size tire on the rim?
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Old 03-10-08, 09:39 PM   #6
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Rim strip!
...and a set of Conti Gatorskins!
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Old 03-10-08, 09:41 PM   #7
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Steel rims?
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Old 03-10-08, 09:50 PM   #8
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Here's my 2 cents . First , check that both rims are perfectly round. If you have a flat spot on a rim (from hitting a pothole) the tire ,even if it is properly inflated, could blow off the rim at that spot. Check the inside sides of the rims and make sure that the rim strip or rim tape is properly covering all of the spoke nipples or rim holes. Interior problems like those just mentioned usually cause cuts on the inside of the tube. Perhaps, as listed, you may have the wrong kind of tire that is not sitting on the inside of the rim properly. Check to ensure that the tube is correct for the tire and rim.
Blow outs could be from hitting a pothole , at full inflation, a flattened rim, or even leaving the bike outside in the hot sun. Hope something works out for you.
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Old 03-10-08, 10:07 PM   #9
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80's? 700C? are you sure?
http://sheldonbrown.com/tire-sizing.html
If in doubt, take it to your LBS.
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Old 03-10-08, 11:53 PM   #10
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Thanks for the responses. Very helpful indeed....

The blow-outs are pops. The tube bulges, pushes past the rim, and bang.

The rims have the older style / rounded hook for the tire bead. The 700c tires usually go on much easier than with most of my other bikes -- I barely needed the tire lever for the tires I just put on last week. It doesn't look like the rims are actually damaged, and at least with the front wheel, the rim tape covers all the spokes.

Edit: The rims are Araya 700c's.

I think I'm going with BCRider and jgedwa on this. Kind of sucks since I just bought some very nice, and not particularly cheap, 23c's that are too narrow for my cross bike. This bike also has a rather long list of little things that need to be fixed. ~gaah~ Ah well, at least the latest blowout didn't destroy the sidwall.

Tires don't spoil after a year or so, do they?

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Old 03-11-08, 12:26 AM   #11
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Put them in a big garbage bag and try to get out most of the air and then seal the bag with a twist tie or tape or whatever. Then keep them in the coolest and darkest place you can. Keeping the air and most importantly the sun off them and as cool as you can will let you store them for a couple of years anyway.

If you have a garage do not assume that it is a cool place. It can get stinking hot in there in the summer and that's very hard on any rubber material. Ages it FAST.

The fact that you could put the bead on without tools or very little bar use tells me that you have the very issue I wrote about. I ran into the same thing trying to use some very nice kevlar bead tires on some old rims. Blew out two tubes before I looked at the problem a little closer. And yes, I was able to put the bead on without tools at all with a little massaging to keep the rest of the bead in the center hollow.

On the other had one time before I new what I was doing with this whole bike deal I actually was able to pry a 700c tire onto a 27 inch rim. Hooked or round bead? You sure don't need to worry about it when you've got THAT sort of tight fit. I had to cut the tire off and then Dremel the bead wire with a cutoff disc to get the darn thing off!
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Old 03-11-08, 06:26 AM   #12
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Quote:
Originally Posted by Bacciagalupe View Post
My standard procedure is: put a little air into the tube, seat one side of the tire, insert tire, seat the other side, inflate a little bit, pat down the tire to make sure it's in place, slowly inflate and watch for bulges.
If it's like my Araya rims, a key step after mounting the other side of the tire is to make sure that a bit of tube is not caught under the bead. I do this by pinching the sidewalls together as I inspect my way around the wheel, making sure that I can see the rim strip on both sides of the pinched section.

FWIW, I very rarely use tools to mount tires so I don't see what being able to do that has to do with tire problems.
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Old 03-11-08, 06:27 AM   #13
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Rim strip!
A+++++++
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Old 03-11-08, 07:04 AM   #14
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Sometimes it helps to air the tire up, let the air out and air it up again. I hope that it allows the tire to fall where it is supposed to fall. Also helps to air it way over limit the first time and then let it down to normal. To be sure the bead seats.

I have special problems using kevlar beads on unhooked/barely hooked rims. I know it can't stretch; but it sure seems to. I have much better luck with wire beads on such rims.

jim
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