I'd say coincidence. Long time tubie user here, just switched to clinchers this year after 20 years of tubies.
Only flat I had last year on my tubulars was a vittoria corsa with about 300km on it, same thing, some sort of failure/leak and the valve stem.

Vittorias use mostly latex innertubes for their highest quality tubulars. Those latex innertubes are fast while they last and pretty annoying when they get a sidewall failure or blowout, sometimes at a random spot but a lot of times near the junction they have to make for the valve stem. I would not use them unless you were sponsored by Vittoria and getting free replacements out the wazoo.

My last 3 tubes developed leaks at the base of the stem. Vittoria cx, kenda volare, tufo s3 lite.

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Is the valve core loose?

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One thing to watch out for when mounting tubulars--when to put the tire on, you start from the vale stem, and stretch it as you go, so you can get the tire on the rim. If you are not careful, you will pull it to one side too much, and pinch the valve stem in the rim. I had a tire all mounted up and then noticed the valve stem was leaning to one side--and it was leaking.

Hate to bump an old thread but I've been having this problem with several tires (different manufacturers) for the last two years or so. Mystery flats that were leaking air at the base of the valve stem. No apparent cause and usually after at least several hundred kilometers of use. This is happening too many times to be simple coincidence and with every manufacturer I've bought - Vittoria, Continental, Tufo, Schwalbe, etc.

Could airing the tires with the force required to mount and dismount the pump head strain the tube enough to weaken it where the valve stem is? That's the only thing I could think of that might be the cause. I've always installed my tires with valve stems first, so I know that isn't an issue. I've strongly considered switching to clinchers but that would only reduce replacement costs not eliminate the problem. Very frustrated.

the answer is switching to clinchers (or a tubular) with a threaded valve latex tube, so that you can seat the nut against the rim and prevent any valve leakage or seam or pressing to inflate issues, which is their only drawback IMO.

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Check the valve hole inside the rim to check for any sharp edges which might be causing the issue.
Rub it smooth with some sandpaper if needed.
If you're using valve extenders, check that isn't where the leak is occurring.

If all else fails, chuck some sealant in.

Had the same issue with the Vittorias, probably went through about 4 tires. Took one apart - quality constructed and robust design at the valve base. There was just a hole tear that opened up the latex tube. Very strange.

Have had good luck with the Tufo, just bought a couple of sets of the high carbon tires (25mm) from Wiggle $50 each. Also got a set of 28mm from Ebay. Nice tires.

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Tufo tires have very high rolling resistance.

I used tubies for years even in Hawaii switch to clinchers 5 years ago best move I have ever made. Stop leak is worth a try, sometimes works, after putting in rotate and shake the wheel. Raced Hawaii with thumper never found the reason for the thump...lol

Either I'm doing something wrong or tubulars are just vulnerable to this problem. In the past it never happened. During those halcyon days, rims were shallow and no one was using extenders. I recall most of my tires had threaded valve stems...could be the indirect causative factor with modern deep section rims through the inability to 'lock' the valve stem in place during inflation. There's a lot of movement both vertically and laterally when inserting/removing a floor pump head, inducing wear and tear after many inflations. It's unavoidable.

This is an issue that NEEDS to be addressed by manufacturers. Either they should provide reinforcement to susceptible areas of their tubulars or the aftermarket should start producing threaded extenders. Myself and those people who posted here cannot be the only people who have fallen victim to this kind of failure. I'm not being hyperbolic. Most of these ruptures resulted in sudden loss of pressure; it could lead to a serious situation at speed. Fortunately, I wasn't riding very fast in any of these incidents.

I use valve extenders. If you know of any with threads on them I would love to get some.

It's not only Vittoria. Not sure, but I believe I've lost more tires from Continental to this problem. In truth no manufacturer is immune. It's the nature of the beast with modern deep aero rims, I'm sure of it.

Good to know, might check them out. Maybe they are more resilient in that area of the tube. Wish I had a list of tubulars with that kind of specifically designed construction. At wit's end...

I've tried sealant once unsuccessfully. This is usually a substantial rupture and a tire will deflate completely within a couple of seconds. Under water there's so much air released it's a constant stream of bubbles. I doubt any sealant would work, not permanently anyhow.

The problem has occurred with different wheelsets and there wasn't anything sharp on the surface around the valve hole on any wheel I could find. Something is causing strain over time in that area, which weakens the tube leading to eventual failure. The only thing I envision is the valve stem moving around during inflation. I inflate before each ride so it's frequent.

Why was it the best move you ever made? I understand the cost of replacing tubulars is very high and definitely not for everyone (trying to convince myself of this). The upside is the ease of changing a flat on the road. No tools required, just peel off the bad tire and put the spare on, inflate and you're good to go. You don't even need to glue the spare. Contrast that with super tight-fitting clinchers that require a LOT more effort to remove and remount with a spare tube...I'd much rather deal with tubulars on the road when I'm tired from riding.

Silca sells these. It also sells little aero stem fairing thingies which spread out the force of the nut when tightened down on the threaded extension

Thanks for the heads up! Never heard of these before. I'll definitely look into getting at least one pair to try on my main wheelset. Awesome.

Never had any of that mentioned probs with either continental,specialized, or veloflex tubies.
On all of em I used conti extenders (Just about less than .5“ to stick out) plus wrap some tape where the extender meets the valve hole to sit kinda tight and keeps from rattling.

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-shoki

Just to update my situation with these accursed valve problems, I've experienced THREE additional failures since I last posted. Two were Vittoria Rubinos of the most recent variety and yesterday a Continental Gatorskin underwent the same failure. I had two other Gatorskins fail the same way in the past several years, and was sort of expecting this tire not to last. It turned out to be good for only a couple of weeks, essentially still new.

I remain at a complete loss to explain why this happens to me so often. It is a far more frequent problem than actual punctures. Nothing seems to help prevent it. Certainly not sealant or any method of mounting the tire. It is giving me excellent reasons to abandon tubulars, which I love for their ride qualities and tool-less ease of roadside replacement.

If anyone has a possible theory to a likely cause or prevention not already mentioned, please post your thoughts.

Honest question: If your tubulars aren't glued more securely than that is there any chance they migrate while riding and cut into the base of the valve?

I usually struggle to remove a tubular (unless using a heat gun, anyway) and have destroyed more than one in the process. My understanding is that a very strong bond is necessary both to prevent rolling the tire off the rim (in cyclocross, anyway) and to enjoy the lowest possible rolling resistence.

x2. I've never considered it *that* easy to replace a tubular on the road. If it's considered easier than fixing a clincher flat, then something is off.

And a non-preglued spare might be good to get you home, but I absolutely wouldn't consider it a long-term replacement.

Very good question and one which I actually asked myself right before I posted. If I'm not applying sufficient glue then why does the valve appear to be perfectly aligned with the valve hole in my rims? The tire stays securely on even during steep cornering and I'm close to 220lbs. Also, I normally inflate between 125-140 PSI making the tire very tight on the rim. If the tire is creeping it's very slight. Unless, it occurs only during the ride and moves back to its initial position when stationary, in which case it wouldn't be evident upon inspection. Is that what you mean?

I thought of every possible cause and even purchased a new pump that requires little effort to insert the valve into the pump head. I originally thought that was the cause because my old pump required a lot of force. If I'm not using sufficient glue then the remedy would be to simply use more. I can always try that. Unfortunately, seeing how snow is in the forecast next week I might not find out if this was the problem before next spring.

Spare tires are only used to get home when I have a flat. I never use them for anything else.

When you get a flat tubular tire, you cut across the tire with a razor blade, all the way through to the rim.

Then stick your finger inside and peel it off like a snake.

Semi-prone's mention of peeling off the bad tire "no tools required" made me think his tire wasn't glued securely. I don't know if that could lead to stem damage.

What's your weight, usual tubular size and pressure ?
Glue method ? Pre-stretch for how long before mounting and glueing ?
What kind of roads (surface) do you have ?
Do you automatically put sealant in your tubs ?

FWIW the only tubs I experienced with leaks at the base of the stem are Vittorias. They use very thin latex tubes in their tubulars, half the weight of pink latex tubes for clinchers. So I see a weak point right there. I steered away from Vittoria a few years ago, and haven't had the problem again. I occasionnally have a slow leak coming from the valve stem, I associate with hitting some pothole or big crack, etc on my rides. Only then I try the latex method with Effeto Mariposa Latex (20-25 ml is fine), and usually the tub is good to go for another 1000-2000 km.
Oh! And I am done with cheap tubs. They all fail within days. I only use Veloflex Sevice Course 25 mm now, or Continental Competition 25 mm. On the training wheels, Conti Sprinters are the best trainers. They last forever.
I just bought Conti Podium TT 22 mm for the TT bike to try next summerThey're stretching now. Will install and glue in 3-4 months.


LOuis :-)

What tools does one require to remove a tubular? I remove them by hand as does everyone I know. Yes, it can be difficult especially on the road. At least I don't need multiple tire levers with super tight fitting modern clinchers that require a lot of strength to remove and reinstall. There's a reason why I have my clincher wheels collecting dust. I'll be forced to use them instead if I cannot find a solution to this problem. As it is right now, the cost of frequent tubular replacement far exceeds the advantages. Not worth it.

Regarding security, my tires never rolled off their rims in 30+ years. Something has changed with tubular construction because this problem never occurred decades ago. I had punctures for sure, but no problems associated with internal damage. I didn't even know this was possible until it started happening to me. The main ostensible difference was in the past my rims were aluminium and now they're carbon.