Author Topic: Stem leaks  (Read 2410 times)

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Offline TwoWheeledExplorer

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Stem leaks
« on: August 13, 2012, 03:06:17 pm »
Ever since I put puncture resistant Schwalbe tires on my Bianchi Volpe, I have had an inordinate number of flats...from the other end. I have had to replace 5 tubes, 2 front, 3 rear because of the valve stem shearing off at the juncture with the tube. >:( The shop even put one of them in, and today it was flat again. Tubes from Kenda, Giant and WTB, so different manufacturers. Any thoughts, ideas, suggestions?

Thanks!
Ride safe,
Hans
St. Brendan's Two-Wheeled Explorer
www.twowheeledexplorer.org
Dedicated to the adventure of missionary exploration...to the ends of the earth.

Offline John Grossbohlin

Re: Stem leaks
« Reply #1 on: August 13, 2012, 07:05:25 pm »
What kind of pump are you using.... one with a hose or one without a hose?  In my experience those without a hose put stress on the stem while pumping which eventually results in the stem breaking loose from the tube. I ran into that very problem with presta tubes on last year's trip with a short frame pump... I have NEVER had it happen with my floor pump at home and I didn't have the problem with the Schrader values on the mountain bike I used on a 3,142 mile trip.

As such, a Lezyne Micro Floor Drive HP, a frame pump with a hose, was acquired for future trips.... It has a hose which will allow for daily "top offs" of tire pressure and for repairs without stressing the stem.  Most of our bikes will continue to have more traditional frame pumps for on-the-road repair purposes. However, for daily top offs and repairs on the road the Lezyne will be the primary pump and at home the floor pump will be the primary pump.

BTW, this problem isn't something new... I recall back some 35+ years ago the LBS was very careful to show people how to use frame pumps with presta values to prevent breaking the stem. In those days Zefal and Silca frame pumps were common. Regarding technique, in addition to holding the tire and pump together while pumping the removal technique was to hit the pump away from the stem instead of twisting/pulling to remove it from the value. We never had problems... On the other hand, with the newer relatively low volume short pumps, which require about a 1,000 strokes to attain pressure, the problem is far worse.

Offline rcrampton

Re: Stem leaks
« Reply #2 on: August 13, 2012, 07:29:17 pm »
I had those kind of flats off and on with presta vales. My best guess is that I was stressing the stem/tube interface when I was pumping them up.

I drilled out my rims with a step bit so I could use schrader valves. I like being able to hit my tires with a quick burst from a service station, the tubes have been easier for me to find on semi-remote tours and I have never had these kinds of flats.

People use presta valves all the time without problems but I didn't play well with them. Not sure which you're using. A CO2 cartridge or pump with a hose on it may help.

Online DaveB

Re: Stem leaks
« Reply #3 on: August 14, 2012, 06:51:59 pm »
The first thing to do is check the condition of the rim's valve hole.  If ithas a burr or rough edge or the rim tape has slipped, that might very well be your problem.  What rim tape are you using? Velox or one of those nearly useless plastic strips?  Replace anything that's not Velox.

Finally, you can reinforce and protect the valve base by cutting a 1"x1/2" strip from a damaged tube, punch a small hole in the center and slip it over the valve stem of the new tube.

Offline indyfabz

Re: Stem leaks
« Reply #4 on: August 15, 2012, 06:50:15 am »
Tubes from Kenda, Giant and WTB, so different manufacturers.

To quote a line from a Porgy & Bess tune, "It ain't necessarily so." Different brands, but they could all be made by the same manufacturer.

Offline bogiesan

Re: Stem leaks
« Reply #5 on: August 15, 2012, 07:41:15 am »
Ever since I put puncture resistant Schwalbe tires on my Bianchi Volpe, I have had an inordinate number of flats...from the other end. I have had to replace 5 tubes, 2 front, 3 rear because of the valve stem shearing off at the juncture with the tube. >:( The shop even put one of them in, and today it was flat again. Tubes from Kenda, Giant and WTB, so different manufacturers. Any thoughts, ideas, suggestions?
Thanks!
Ride safe,
Hans

The tube is slipping inside the tire casing. Change only the rear tire for a couple hundred miles and see if the problem goes away.
You don't say if you're using Prestas. Lots of folks refuse to use the stem nut but this is one of its main functions, to keep the stem stable.
I disagree with the advice to reinforce the stem joint with a piece of an old tube. This can create quite a bulge that will cause other issues.. However, since I'm convinced the tube is sliding around inside the tire casing this might actually help prevent that.
I play go. I use Macintosh. Of course I ride a recumbent

Online DaveB

Re: Stem leaks
« Reply #6 on: August 15, 2012, 12:12:00 pm »
I disagree with the advice to reinforce the stem joint with a piece of an old tube. This can create quite a bulge that will cause other issues..
Cut to a suitable size, the reinforcing patch caused no bulges and no other problems.  I've done it on numerous tubes and tires with no downside at all.

Offline bogiesan

Re: Stem leaks
« Reply #7 on: August 18, 2012, 04:26:39 pm »
Well, yes,, properly done, should work. Not everyone around here can do stuff like that without instruction or coaching.
I play go. I use Macintosh. Of course I ride a recumbent

Offline TwoWheeledExplorer

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Re: Stem leaks
« Reply #8 on: August 19, 2012, 08:24:30 pm »
Yes, they are Presta stems, and yes, I do use the stem nut usually, but the Giant tubes have smooth stem casing; not nut. Not all of the failures have been with the Giant tubes, but it is possible the nut was loose on the ones that were other brands. I will try some of these suggestions and let you know what works or doesn't.

BTW, I only Schraeder stems on my work (patrol) bike. The compressor in the park shop has the standard auto-style chuck on it, so it's easier to use than Presta adaptors or a floor pump.

Ride safe,
Hans
St. Brendan's Two-Wheeled Explorer
www.twowheeledexplorer.org
Dedicated to the adventure of missionary exploration...to the ends of the earth.

Offline newfydog

Re: Stem leaks
« Reply #9 on: September 26, 2012, 12:06:56 pm »
I have had MTB tire/rim combinations where this problem was horrible.  What happens is the the tire bead slips on the rim during hard braking, rotating the tube and stressing the valve base.

I find they hold up better without the stem nut, allowing some tilting instead of shearing off.

I have cured it to some degree by sanding the rim to give it more grip on the tire, but the best answer seems to be find a tighter rim/tire pair where they don't slip and rotate.