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Old 10-20-09, 09:13 AM   #1
DPN
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Tubular Tire Mystery

I have a pair of new Vittoria Corsa Evo CX tubulars mounted and ridden about 200 miles.

I know that latex tubes leak down pretty fast, but the back tire is leaking down way faster than the front tire. I can tell a difference after 20 miles or so...

I took the rear wheel off and submerged the entire wheel and tire assembly, but couldn't determine where the small bubble stream was REALLY coming from.

I dismounted the tire, and when submerged I see a bubble stream coming out where the stem exits the base tape. The hole could be anywhere! I can't see ANY bubbles coming out of the tread.

I can repair tubulars, but I don't know where to start peeling back the base tape...

Sounds like a candidate for Tire Alert? Or am I missing something? The tire is practically new...
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Old 10-20-09, 09:37 AM   #2
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Sounds like manufacturer defect. I'd call about having that tire replaced.
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Old 10-20-09, 10:34 PM   #3
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The old method of finding the leak in a tubular...or more accurately, to determine where to peel and cut is to inflate the tire and then clamp sections of the tire (once removed from the wheel) between two pairs of small blocks of wood. Submerge the section between the two clamped area to see if you get any bubbles. If no bubbles then remove one set of blocks/clamps and relocated them to the other side of the remaining blocks/clamps to establish another section to submerge. Keep leapfrogging the block/clamp units until you figure out approximately what section of the tire/tube the bubbles are coming from. Mark the tire, peel back the base tape, and cut the thread within the area marked. Pull the tube thru the opened area and find the exact hole...then patch restuff, resew, reglue the base tape, reglue the tire.

This is an utter pain in the arse. If the tires you are running are $40 or less you might want to consider just replacing them with new ones as the effort to find the hole and do a correct patch job outweighs the time/labor energy in my opinion. If you are getting flats often then $40/tire or even $20/tire can really hit home and one should probably evaluate a couple of things such as:
A) Where on the road they ride (riding to the far side of the road typically has more debris such as glass that can cause a flat).
B) It may be more economical for time and labor to switch to clinchers.

-j
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Old 10-21-09, 06:25 AM   #4
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Quote:
Originally Posted by DPN View Post

I took the rear wheel off and submerged the entire wheel and tire assembly, but couldn't determine where the small bubble stream was REALLY coming from.

I dismounted the tire, and when submerged I see a bubble stream coming out where the stem exits the base tape. The hole could be anywhere! I can't see ANY bubbles coming out of the tread.
Any reason to think the hole ISN'T near the valve? Pretty common for little tears there.
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Old 10-21-09, 07:30 AM   #5
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I have a pair of Evo CX that started out needed inflation every day - like yours, and now they won't hold air at all. I think that they are both leaking at the base of the valve, as I can twist the valve somewhat - although they won't pull out, so they're seated somehow, but leaking at the seat? I haven't pulled back the tape to look at this arrangement, though. I'm saving these for my next project, and I haven't decided whether to tackle this at home or ship 'em off to TireAlert myself.

If you open yours up at the valve I'd be interested to know what this area looks like.
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Old 10-21-09, 08:18 AM   #6
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Thanks for the suggestions...

Yeah, I know...tubulars can be a pain in the a**, but I bought a set of 50mm deep carbon tubular wheels for use every now and then. My first "real" bike, a 1973 Raleigh Competition MK II, had tubulars and I always said one day I'd use them again. Usually I ride Eatson clinchers...

I did have a few cans of Vittoria Pit Stop, so I figured I had nothing to lose by trying that, although the success rate seems to be around 20%...however, I stuck the can on the valve, pushed, and the stuff flowed in and partially inflated the tire (butane, I think). I started slowly spinning the wheel, added more pressure with my floor pump, and left it overnight.

Believe it or not, it is holding air better than it ever has, so I have to put myself in the Vittoria Pit Stop fan club. If it was a leak at the valve it seems to have fixed it. The real test will be when I take off the tire to re-glue it. If it still holds then I'm good...

Bob Barker, if I ever DO remove the base tape around the valve I'll post some pics, but MAYBE I'm okay for a bit.

Thanks again...

DPN
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Old 10-21-09, 02:21 PM   #7
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I agree with trying some Pit Stop, but you also could just open up the valve area, get some pressure into it, and see if you can find the airstream. Also look really hard for debris. Some punctures are caused by tiny bits of wire that came off of a disintegrating car or truck tire.

Still, those tires may be costly enough to make sense going to Tire Alert.
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Old 10-21-09, 02:32 PM   #8
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The PitStop is what I was going to suggest. Another thing to try in cases like these is the Stan's liquid latex. It has worked the same for me than the Vittoria PitStop and it is much cheaper. The only issue with it now is that it seems there are 2 versions of the tires: one that you can take the valve off and the other you can't.
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Old 10-21-09, 04:40 PM   #9
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I have valve extenders so my tires have removable valve cores.

I have some Stan's on order. Reading various forums seems to indicate that Stan's MAY be a bit more effective than Pit Stop, but so far it's still holding!

If the leak comes back I'll take off the base tape, satisfy my curiosty about where the leak actually was, and send it off to Tire Alert!
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Old 10-21-09, 05:23 PM   #10
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I was once out on a solo training ride, way, way out in the country. I got a flat in my tubular tire so put on my (only) spare tire. I rode a few hundred yards and the spare started leaking down too. I had at least 30 miles to get home and no patch-kit. I really, really was not looking forward to stopping and pumping up my tire every 200 yards for 30+ miles. I had $0.75 of change with me but no other resources or tools for getting the tire patched. I made my way several miles to a small country quicky-mart store and weighted my options. I used the change I had to buy a can of root-beer, the most sticky liquid available at the store. I used my mouth to fill the slow leaker tire with root-beer and then pumped it up crossing my fingers. At best, I was hoping that the root-beer "patch" would slow the leak down enough to let me ride several miles at a time, meaning I might only need to pump up my tire a dozen times instead of a hundred. The damm thing held pressure all the way home without needing to be re-filled and still had high pressure in in several days later. I wouldnt necessarily recommend proactivly filling your tires with root-beer, but it was great for getting out of a sticky situation!
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Old 10-21-09, 05:30 PM   #11
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^^^ great story!
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Old 10-28-09, 09:05 AM   #12
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Just a follow up...

A week after using the Vittoria Pit Stop the latex tube is holding air better than it ever has. It STILL has pressure from last week! Before the thing would have been flat after 24 hours.

I also bought some Stan's to try on the front wheel...

No root beer needed, yet!
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Old 10-28-09, 12:33 PM   #13
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Latex has permeability that is the root cause for the "leakage". The reason the tires now magically hold air is that he tiny holes in the latex are now closed with he Pit Stop which has distributed itself over the internal surface of the tube.
I think one of the reasons for using Latex is for weight reduction. The Pit Stop off sets that feature and provides butyl rubber like characteristics.

GreyJay: You could say the sticky situation migrated from outside the tire to inside.
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