Bicilover

I was traveling slow just finished going up a hill on my steel framed Masi Single speed when I went right over the handlebars so fast I didn't know what happened.

Upon inspection the Presta valve on the front wheel had snapped above the nut that secures it to the rim and a spoke either side was snapped at the nipple with the nipples left floating inside the rims

The air went down so fast I didn't not know what hit me or have any chance to control it.

Has anyone experienced a Presta valve break (completely shear off) above the nut before ?

Is their any use of having the nut anyway?

The tube was a Lifeline tube from Chain Reaction

I was a a bit shook up because if I was travelling in traffic or at speed it could have been a lot worse , been cycling for over 40 years and never experienced this before

njkayaker

???

The value shouldn't spontaneously break that way. I don't see how it would break spokes either.

I could see it breaking if the stem was pushed laterally (sideways).

Maybe, something got caught and broke everything.

=====================

You don't need the nut. (I don't use the nut.)

If the tire is flat, without the nut, you might need to push the stem out to attach a pump. Put a finger on the outside of the tire opposite the stem and push the tire into the rim.

You don't need the little plastic cap either (that's mostly to keep the stem from poking a hole in the tube when it's being shipped).

Troul 

where was the cap?

Berg417448

My suspicion would be that something you didn't notice got stuck in the spokes and broke the spokes and snapped off the presta valve.

HTupolev

Two spokes and a valve stem next to each other all snapping sounds like probably a physical obstruction got caught in the spokes. If something like a stick gets into the spokes it can be carried up and jam against things like fender stays and fork blades.

Iride01

My wheels are picking up little sticks and twigs on the train and tossing them at my son's bike following behind. It's not unreasonable at all that something got caught you didn't see and then it was gone.

I've pulled a presta valve out of the tube before with an air chuck that didn't release.

I use the nut. It keeps me from shoving the stem into the other side of the tube when putting the air chuck on them. But if you don't like them, you don't have to use them. Many don't. Matters not to me what you do for you.

vane171

If you went over the handlebars, then something must have got caught in the wheel and did the damage. By themselves, I mean spokes or the valve breaking, whatever and in what order they broke, it wouldn't have thrown you like that. Maybe check closely if the fork has some marks on it, scratches or a dent. You might have got a bolt caught in the spokes which got carried up to the fork where it jammed, then fell off and you just didn't notice it on ground.

I snapped off Presta valve last year when I was pumping up bike rear wheel with one of those hand held short pumps. I know that the wheel should be free to move, not have the bike leaning against wall when you use such pump but it broke anyway, maybe was fatigued from some previous abuse. It wasn't my bike.

BTW no 'pro' has valve nuts, that's as pedestrian as it gets

drlogik 

It also may have been one spoke broke, got tangled with the valve and other spoke as it passed through the fork crown and snapped the other two at once and stopped the wheel and you went overboard. You're lucky you didn't break any bones. If it's an older bike, take the tires and straps off and inspect all of the nipples. See if the spokes have adhered to each other where they intersect also. Count yourself lucky.

Barry2 

Take a look at the back side of the forks just below the rim of the wheel.
Whatever it was got brought up and stuffed in there by the rotation of the wheel.

Barry

wolfchild

It would of never happened if you used a Schrader valve with custom made aluminium cap.

Troul 

you're not supposed to go over the posted speed limit, wearing ear buds, & not ringing your bell constantly.

pdlamb

I'm with the consensus opinion, you were the victim of a Killer Stick.

I've experienced a front tire blowout around 20 mph, maybe faster, coming down a hill. Luckily I was able to control the bike, but that's irrelevant here. While unpleasant, it didn't stop the bike or throw me over the bars. Stopping the wheel suddenly can throw you. A stick that gets caught between the wheel and fork can be responsible for that sudden stop -- and it can break a couple spokes and your valve stem in the process.

Charliekeet

Agreed, though when I can get them, I prefer a Presta to Schrader adapter with a Ti cap for better stick-breaking tensile strength!

Chuckles1

The only spoke I've ever broken was going slow on a rough jeep trail. A stick flipped up, went between spokes, and when it reached the seat stays, blammo! Glad it was on the rear, as if it were on the front, I'd have gone ass-over-tea-kettle, as my brother called it when recounting a childhood biking incident recently.

63rickert

Given the broken spokes the stick hypothesis sounds likely. There is however another common way of breaking off a valve stem. The tire and tube start moving on the rim. Only happens when tire pressure is very low. Happens to those who lube the tube and tire with talc for easier tire mounting. Could happen with a slow leak. Depends a lot on how tight the tire fits. Never happens with a tire inflated hard.

Here’s the part with the nut. If there is no nut the valve stem gets cocked sideways. Hopefully you see that. Then you deflate and realign. And try to remember to keep your tires well inflated. With a nut on there the tube is just as stressed but there is nothing to see. The nut keeps the valve pointed straight. The break comes as a complete surprise.

Stuff happens. I ran over a strip of scrap metal, it wedged between chainring and chain, broke the chain, scarred two chainring teeth. A friend kicked up a stone that hit the frame (steel) so hard the tube dented. Doubt that either of us will ever repeat those incidents. You could ride a lifetime and never have a problem. But it happens.

Bicilover

I like this theory

I was thinking I was hearing a little rattle the past few days (thought it was coming from my saddle bag), this could have been the broken nipple floating inside the rim

It has Weinmann dp18 medium depth v rims with stainless spokes and high flange track hubs

Have had the bike for 10 years and the wheels have been bombproof up until now, never had to true them once.


"It also may have been one spoke broke, got tangled with the valve and other spoke as it passed through the fork crown and snapped the other two at once and stopped the wheel and you went overboard. You're lucky you didn't break any bones. If it's an older bike, take the tires and straps off and inspect all of the nipples. See if the spokes have adhered to each other where they intersect also. Count yourself lucky.

Phil_gretz

Were you riding with the Italians?

redcon1

That's what I was thinking. Look for the remains of an alloy Silca frame pump nearby.

Happy Feet

It's heartbreaking when that happens. Your dreams deflate as fast as the tire.

AllWeatherJeff

Breaking Away reference:

rsbob 

A random attack by the mutant spoke monkeys. Look for the remains of a Cuisenarted banana peel. (No Alice, presta valves and spokes don’t spontaneously combust)

Glad to hear you weren’t hurt.

zandoval 

RATS... Hope you are OK... Going over the bars in traffic is bad!

Many times I have had loose retainer nuts on my presta valves. Is the valve stem hole worn? Is it possible the valve snapped from wear movement from the rim?

Anyway, here's another thing on my Pre Flight Check List.

Make sure the presta valve nuts are tight and not worn. Thanks.

Bicilover

Thanks for your comment

The nut on the presta valve is tight and the rest of the valve is still there below it, the valve hole is not worn , the valve snapped above the nut ,