# Bent valve stem (Presta)...



## FishrCutB8 (Aug 2, 2004)

So the top of my valve stem is bent a little. I have no idea how it happened. I can still get air into the tire. My question is, should I:

1) Attempt to straighten the valve

2) Just put on a new inner tube

3) Just keep pumping, and don't worry about it.


Also, is this a common occurence? What causes it and how can I avoid it?


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## Coolhand (Jul 28, 2002)

FishrCutB8 said:


> So the top of my valve stem is bent a little. I have no idea how it happened. I can still get air into the tire. My question is, should I:
> 
> 1) Attempt to straighten the valve
> 
> ...


On mine, if they are mildly bent, I continue to use them. I have moved this to the wrenching forum, so that the other (better) wrenches can weigh in. A quick digital photo might help with the determination though.


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## Spoke Wrench (Aug 20, 2001)

FishrCutB8 said:


> So the top of my valve stem is bent a little. I have no idea how it happened. I can still get air into the tire.


I have two answers to your question. My straight answer is that as long as I can continue to get air into the tube I continue use it so I suppose that would be choice #3. Unless you are using valve extenders (ugh) for some deep section rims, you'll probably never have a problem.

My smart alac answer would be to drill out your rims and switch to schrader valve tubes.


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## The Walrus (Apr 2, 2000)

Are you talking about the plunger that one unscrews, or the actual stem? As long as you can inflate, I say don't mess with it. I've had plungers that got tweaked, but as long as they screwed/unscrewed and the tube held air, I didn't sweat it. I've gotten a bit antsy about the stems themselves lately--I've flatted 4 out of my last 6 rides, and 2 of those 4 times, I've sheared off the stem while using my frame pump, even while taking care not to let the pump rock back-and-forth.


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## bikeboy389 (May 4, 2004)

The Walrus said:


> Are you talking about the plunger that one unscrews, or the actual stem? As long as you can inflate, I say don't mess with it. I've had plungers that got tweaked, but as long as they screwed/unscrewed and the tube held air, I didn't sweat it. I've gotten a bit antsy about the stems themselves lately--I've flatted 4 out of my last 6 rides, and 2 of those 4 times, I've sheared off the stem while using my frame pump, even while taking care not to let the pump rock back-and-forth.


I agree. If it's just the threaded center stem, and it still works, I say go with it. If it's the outer (typically brass) part, be very careful of it. It's probably not dangerous, but it's a lot likelier to shear off, and if it happens on a ride (or when you're repairing a flat) and you don't have a whole new tube with you you're stranded.


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## qwertzy (May 25, 2005)

*maybe a pump problem?*

I have a friend who has the same problem cronicly. I think it's due to a dodgy frame pump as mentioned. My mate even has the stem bit actually fall off and the tube still held air so I think while the stem is still there it's ok, but I'd look at your frame pump. Is it letting enough room for the valve inside the pump seal? I have a frame pump that I have no problem with. Maybe you could ask to try one in the store if you replace it?


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## The Walrus (Apr 2, 2000)

I've never had issues with the pump (Blackburn FP-1) at any other times. It just occurred to me that both of the sheared stems came from the back wheel of one bike, a wheel which, when I got it, had had spokes that were so loose that they flopped; I had gone around the wheel, tightening the spokes and checking the trueness before any of this started, but I'm wondering if the rim could have sustained enough damage to actually stress the stem while I'm riding.


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## Squint (Jan 22, 2004)

The Walrus said:


> I've never had issues with the pump (Blackburn FP-1) at any other times. It just occurred to me that both of the sheared stems came from the back wheel of one bike, a wheel which, when I got it, had had spokes that were so loose that they flopped; I had gone around the wheel, tightening the spokes and checking the trueness before any of this started, but I'm wondering if the rim could have sustained enough damage to actually stress the stem while I'm riding.


I had this problem, almost always with the rear wheel and after mountainous riding with only one type of rim (Matrix Aurora). I switched rims and had no more problems. This wasn't a problem in the flat Midwest and only started after I moved to CO.


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## qwertzy (May 25, 2005)

*wheel out of true*

i wouldnt have thought that the rim trueness would affect the valve stem, because the wonky rim would be exerting pressure on the whole tube not just the valve, but I guess you never know?


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## Dinosaur (Jan 29, 2004)

*Probably technique with floor pump..*

The valve stems are easy to bend. It might be because of the technique you are using with your floor pump. The tendency is to yank off the valve from your pump from the presta valve so you don't loose a lot of air from your tire. Constantly yanking (no pun intended) in this manner can result in bending the valve stem. You can try to straighten the stem with a pair of plyers, but this can cause the stem to break. If the tube still holds air you can just keep on using the tube until the stem breaks and have a spare one ready to mount just in case (I buy my tubes in bulk of ten when they go on sale). The stem might break tomorrow, or it might never break, hard to say. If you are really concerned about it, replace the tube. 

I also have a hard time getting over 70 pounds or so with a frame pump as I snap off valve stems very easily. I use long stem valves as I have two bikes and one requires long stem valves. The long stem valves are prone to break. I just switched to co2.

Or you could switch to a Silca brass chuck head on your floor pump, (if you can find an old one that is not plastic).The way the new floor pump valve heads are constucted (dual valved) make them more difficult to use. Or find a pump that just has a presta valve head (like a Silca)...

Or just use more finesse when unclipping your pump valve. That rush of air you hear is usually air left over in your pump, not air from your tube. Or just pump a couple of pounds over your inflation point to compensate and still be careful when unclipping.


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