Valve Stem Snapped Off Mid-Ride

[ImmortalBach]

As my rear tire went off a rock ledge I heard my tire lose pressure, thinking it was a flat. The valve stem sheared off right at the rim. One thing to note is the rear valve stem had the Bosch wheel rim magnet attached and I’m wondering if that factored into this happening. The valve stem was only four months old. Perhaps I overtightened the valve nut? I’m trying to figure this out so it doesn’t happen again.

 

[RustyIron]

With the magnet in place, I wouldn't suspect lateral stress. Maybe overtightening? I tend to make mine really tight to avoid leakage. Or maybe it was a junky valve stem? I buy cheap Chinese ones by the dozen. The moral of the story is for big rides, have a spare in your bag.

 

[Semmelrocc]

Seeing the "bruises" on your rim I would also suggest overtightening.
But hey, on a positive note: your tyre is perfectly aligned with where your valve used to be.

 

[Weeksy]

Had it once in 20 years... no idea why, but yeah happened once.

 

[ImmortalBach]

With the magnet in place, I wouldn't suspect lateral stress. Maybe overtightening? I tend to make mine really tight to avoid leakage. Or maybe it was a junky valve stem? I buy cheap Chinese ones by the dozen. The moral of the story is for big rides, have a spare in your bag.

It was a cushcore brand valve, so it wasn’t a cheapy

 

[Rod B.]

As my rear tire went off a rock ledge I heard my tire lose pressure, thinking it was a flat. The valve stem sheared off right at the rim. One thing to note is the rear valve stem had the Bosch wheel rim magnet attached and I’m wondering if that factored into this happening. The valve stem was only four months old. Perhaps I overtightened the valve nut? I’m trying to figure this out so it doesn’t

ImmortalBach,
Your tires and rims have a lot of rock scuffing. The Bosch wheel rim magnet has a large surface area. It is subject to rock strikes and can cause additional stress/leverage on the valve stem. Shit happens ya know. With time and use, a lot of stuff has likely been kicked up into your rear wheel and it's likely struck the Bosch wheel rim magnet/valve stem pretty hard. The valve stem has likely taken multiple hits over a period of time. Your last hit dropping down the ledge was one hit too many.

It's possible you may have overtightened the valve stem. To shear off the valve stem would require a significant amount of tightening on the valve stem nut in order to overstress and shear off the valve stem. It's possible, but not likely. Only you know how hard your tightened the nut. A rock strike is the more likely culprit based upon your rim and tire scuffing.

I also ride rocky terrain and my wheels take a lot of rock strike abuse. To avoid valve stem issues, I try to keep my valve stems as short as possible, i.e. just tall enough so that I can get an air pump on the valve stem. I realize you need to use a longer valve stem due to the Bosch wheel magnet system.

I do not care much for the cheap soft aluminum valve stems which come OEM on many rims. If you are currently using soft aluminum valve stems which have a conical rubber gasket molded onto the end, I would replace them with heavy duty valve valve stems. I've done this and have been very happy with long term use. I especially prefer the type which has a two piece valve stem, i.e. the rubber gasket is separate from the valve stem itself. Two piece valve stems tend to be more robust in strength and build quality.

Here are several examples of what I'm talking about:

Muc-Off Valve Stem

Velo Valve Stem - Sold on Amazon

One last note. I like valve stems which allow me to insert a hex wrench into the valve stem head to hold it in place while I tighten the valve stem nut. This prevents the valve stem and rubber gasket from twisting/turning and possibly damaging my rim tape as I tighten the stem.

 

[ImmortalBach]

ImmortalBach,
Your tires and rims have a lot of rock scuffing. The Bosch wheel rim magnet has a large surface area. It is subject to rock strikes and can cause additional stress/leverage on the valve stem. Shit happens ya know. With time and use, a lot of stuff has likely been kicked up into your rear wheel and it's likely struck the Bosch wheel rim magnet/valve stem pretty hard. The valve stem has likely taken multiple hits over a period of time. Your last hit dropping down the ledge was one hit too many.

It's possible you may have overtightened the valve stem. To shear off the valve stem would require a significant amount of tightening on the valve stem nut in order to overstress and shear off the valve stem. It's possible, but not likely. Only you know how hard your tightened the nut. A rock strike is the more likely culprit based upon your rim and tire scuffing.

I also ride rocky terrain and my wheels take a lot of rock strike abuse. To avoid valve stem issues, I try to keep my valve stems as short as possible, i.e. just tall enough so that I can get an air pump on the valve stem. I realize you need to use a longer valve stem due to the Bosch wheel magnet system.

I do not care much for the cheap soft aluminum valve stems which come OEM on many rims. If you are currently using soft aluminum valve stems which have a conical rubber gasket molded onto the end, I would replace them with heavy duty valve valve stems. I've done this and have been very happy with long term use. I especially prefer the type which has a two piece valve stem, i.e. the rubber gasket is separate from the valve stem itself. Two piece valve stems tend to be more robust in strength and build quality.

Here are several examples of what I'm talking about:

Muc-Off Valve Stem

View attachment 134582



Velo Valve Stem - Sold on Amazon

View attachment 134583

One last note. I like valve stems which allow me to insert a hex wrench into the valve stem head to hold it in place while I tighten the valve stem nut. This prevents the valve stem and rubber gasket from twisting/turning and possibly damaging my rim tape as I tighten the stem.

View attachment 134584

I think you are probably right, an unlucky rock strike. For what it’s worth I was using cushcore brand valves. Shit happens

 

[Rod B.]

I think you are probably right, an unlucky rock strike. For what it’s worth I was using cushcore brand valves. Shit happens

Yes, it does brother

Cushcore makes a good valve stem. My Zipp Moto wheels look like they've been hit with a shotgun blast from all the rock strikes. I think it's just going to be one of those things you'll just have to keep an eye on. Maybe swap out the valve stems every once in a while.

Be safe,
Rod