rylhwk

Last week i was riding on the gravel roads about 4 miles from home and got a flat (no spare). While waiting for the wife and kids to pick me up i took the tire and tube apart. I noticed the hole/tear in the tube was at the base of the valve. What causes this and i'm guessing it's the weak point of the tube? Anything i can do to prevent this in the future? Thank you all and have a HAPPY and SAFE JULY 4!!!

Jiggle

I would check the edge of the valve hole in the rim and chamfer if it looks sharp. I'd also check the rim strip. If you were riding over bumpy terrain, the vibration could have caused the valve stem to bounce and rub against the edge of the valve hole. If it looks like that happened, you can put a buffer of electrical tape or use the stem nut to secure it from moving.

cale

A tear at the base of the valve is typically caused by the inner tube moving inside the tire relative to the hole. If you are running inner tubes with Schrader valves, you need to run the tire with more air to keep the tube valve centered under the hole. If you're using Presta valve-equipped tubes, you need to be careful to run adequate air pressure, a rim that supports Presta valve use, and a locking nut on the valve to help keep it seated.

rekmeyata

In addition to all the above good info, today's tubes no longer use a thick either steel or rubber reinforcement around the valve stem which is the reason for the rise of mini pumps with a hose. If you pumped up the tire before the ride it is possible that you put too much stress on the valve and then after a period of time with air pressure adding to the weak area it simply let go.

By the way I never use the presta valve lock nut that is suppose to hold the stem in the correct location on the rim, but if you have really deep rims then you may need to use it but not because the valve will move but so that you don't have to struggle to get the valve into the hole to add air when it's flat or real low on air.

cale

Haha, leaving off this part that is obviously specified with the tube (tube, nut, and cap) is as old as the hills. The valve nut and cap were not thought to be "essential" enough to warrant the extra "weight". And so started the trend of leaving lock nuts and caps off racing bikes. It was the same sort of ridiculous nonsense that led to decades of 39/53 chainrings (great for racers but the rest of us?) and a complete disregard for helmet safety within the peloton (at least until they were forced to wear their helmets).

Edited to add: there is ample evidence that mini pumps do little damage to valves that are secured with lock rings. If the bike can't withstand the social pressure to forgo using a lock ring, you could carry one in your saddle bag. Haha

Bill Kapaun

When the tube was initially installed, one might not have made sure the valve was properly seated before applying full pressure.
Probably more likely on narrow rims.

ramzilla

I've had so many blow outs from this same type of failure around the stem I've given up. I only install thorn - proof tubes now. They're thick enough to survive actual use. The only drawback is if you're a weight weenie. Thorn proof tubes are heavy.

rylhwk

Thanks for all the info! I do use the presta system and was using the nut. I think the tube was probably about a year old and seen all kinds of weather and roads. Guess i should be lucky that the tube was that old and doesn't happen very often. Think ill take off the new tube and check everything over real good before i put it back on. Thanks again!

rekmeyata

Nonsense in racing vs everyday people? You mean the same nonsense that Carbon Fiber bikes are now all the rage when everyday people really don't need them? you mean that kind of nonsense?

Funny think about valve stems is when someone fixes a flat and replaces the tube they rarely put on the locking nut until AFTER the tire is at full pressure, this is when the damage is caused, and because the damage is on the upswing due to the grommets on the inside of the tube's valve stem are now gone to save 1/2 a cent a tube, pump manufactures are beginning to see the benefit of a hose on the pump. Of course even a hose on a pump could be pulled and stress the stem, but the likelihood is less.

But there are other reasons for not using the nut and weight isn't one of them, so instead of me typing endlessly just read this: Use a lock nut on a presta valve? - Bicycles Stack Exchange

cale

Exactly, except carbon fiber is a huge benefit if you are crazy enough to buy it. I'd gladly give up my carbon fiber bike if it meant more people would take up the sport.

Not in my experience nir have I ever heard of this theory. You may be right but then that makes me extremely lucky as far as flats are concerned.

The last comment is simply a testament to your massive ego. Good luck with that.

mstateglfr 

Wat?

I figured minipumps with a hose exist for those who find it more convenient. I figured that like everything in cycling, there are multiple ways to skin a cat.
co2 pump
frame pump
minipump
minipump with hose
minipump that transformer styled expands to have foot holds

etc etc etc

rekmeyata

YEEEESSSSSSS, my MASSIVE EGO must be fed...err except for one thing, please explain that my last comment which follows this sentence is somehow a reflection of my MASSIVE EGO.

But there are other reasons for not using the nut and weight isn't one of them, so instead of me typing endlessly just read this: Use a lock nut on a presta valve? - Bicycles Stack Exchange

cale

It feels like you're talking down to me.

dabac

IME, valve stem breaking free from the tube is down to the tire sliding on the rim, dragging the tube with it until the valve stem separates from the tube.
Again, IME, usually caused by low tire pressure. MTBers are more prone to seeing this than road riders. Folding tires are more prone to this than steel bead.
A couple of times I've coated the bead area of a folder with liquisole to increase friction.
Never needed it myself, but I've heard people using tubular glue to secure one side of the tire to the rim in extreme cases.

Poor pumping technique is often presented as a cause too.
Seems possible, but I've never busted a valve stem through pumping, and I can't say I've ever thought about how to inflate "gently".
Maybe I got lucky in my "natural" technique?

IME, stem nut or not doesn't seem to have much/if any influence.
Whether allowed to take a lean first, or held rigidly upright, if the tire creeps, the stem will tear.

Short valve in deep rim, a stem nut will make inflating easier though.

Presta valve in Schrader drilled rim, or Presta in Presta-drilled rim doesn't appear to do much either. I've run Presta-in-Schrader for decades without any issues reliably traceable to valve/rim mismatch.
Only thing "special" I do is that I use self-adhesive rim tapes, and cut my own valve holes. Don't use adapters, don't thread a valve nut on first.
Until they broke and fell off, I did use adapters on the hubside face of the rim.
You'd be AMAZED how quickly water seeps into the rim if you have Presta-in-Schrader and ride through a deep puddle or two.

rekmeyata

It depends if I'm taller than you.