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My borther had a pucker moment after his front tire valve stem let go. Tires replaced 2 years ago, he couldn't remember if valve stems were replaced. The shop he went to seems pretty decent and had no issues finding my rim repair when i replaced my tires and think their standard practice is to replace valve stems...
 

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Good PSA.

Personally, I always replace the rubber OEM ones with the metal ‘L’ shape type variety almost immediately.


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I never even thought about my valve stems. Just assumed the dealers replaced them with every tire change?
 

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As far as I know, my '09 still has the original stems. I meant to change them out this time, but didn't plan ahead. They don't appear to be degraded. So far. When I see cracking, they're done.

I would go to the angled metal stems, were I to change them. Somewhat contrary to my understanding of the physics:

I'm not going to add weight to the top of a rubber stem, as that will cause greater fatigue, compared to the very light weight plastic cap. Lots of outward force when the wheel is spinning, with many random jolts from the road. A lot of those shocks will not be perfectly aligned with the plane of rotation, which will cause the stem to flex. The more mass there is at the tip, the greater the force applied. The longer the stem, the greater the leverage which means more flex.

The vertical, thick sided tapered shape of the rubber OEM stems resist flexing quite well. So long as you don't overload the system.

The angled stems exacerbate this loading, in a huge way. Guaranteed to flex much more because they are longer, and bent out of plane with the principal loads applied. This is why they're metal, vs rubber. Metal does a much better job of resisting flex, which I expect can easily compensate for the load. Strength goes up at the square of volume. Twice as thick, four times as strong.

The real limiting factor would be the mass. Mass goes up, at the cube of volume. Twice as thick, eight times as massive.... Not a critical element, for a valve stem......
 

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I do my own tire changes and I change stems every tire change. They only cost a couple $$ and it seems like a false economy to not change them every time as a basic maintenance item. Like OP, I have had a stem fail and leave me with a flat tire, but thankfully mine wasn't while riding.


As far as I know, my '09 still has the original stems. I meant to change them out this time, but didn't plan ahead. They don't appear to be degraded. So far. When I see cracking, they're done.
The problem is you may not see cracking. The one I had fail looked perfectly OK until I tried to twist the cap off to put air in and the whole stem came off in my hand.


Mark
 

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My borther had a pucker moment after his front tire valve stem let go. Tires replaced 2 years ago, he couldn't remember if valve stems were replaced. The shop he went to seems pretty decent and had no issues finding my rim repair when i replaced my tires and think their standard practice is to replace valve stems...
yeah...that huge "grenade" valve cap is the culprit 100%

I've never ever seen this happen to any of my cars or bikes ever and other than my bike, i never change valve stems. They just don't fail, like ever.
On the bike i have 90 degree valve stems, because it's easier to check pressure and add/remove air to the front because of that huge brake disks.
 

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I do my own tire changes and I change stems every tire change. They only cost a couple $$ and it seems like a false economy to not change them every time as a basic maintenance item. Like OP, I have had a stem fail and leave me with a flat tire, but thankfully mine wasn't while riding.




The problem is you may not see cracking. The one I had fail looked perfectly OK until I tried to twist the cap off to put air in and the whole stem came off in my hand.


Mark
I don't disagree with anything you're saying. Rubber parts become less and less flexible as they age, a process which can occur at wildly different rates, based on environment. Ozone is particularly harsh.... Electric motors with brushes used to create ozone due to the small arcs created while running.

OP hasn't provided enough info to establish why the monster valve stem cap was able to cause the stem to fail..... All we know from what's been said, is the tires were changed 2 years ago. Is it a 4,10,20 year old bike?:O How old were the stems?

At some point, failure of an overloaded stem becomes virtually guaranteed. Mine are probably due, at 10 years old.

The OEM style rubber stem..... Can that be replaced without removing the tire from the rim? I expect not; seems like they should plug the hole in the rim from the inside, out.

I expect the angled metal stems use a lock but on the inside of the rim to lock them in place?
 

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As someone doing hundreds of tire changes each year....

I replace the rubber stems on any bike more than 5 years old- isn't a choice for customers it is just done-, since I have no way of knowing when or if they were ever done........ but-- the bikes with aftermarket metal 90* or whatever......... those I leave alone even though I have had way more of those come in leaking air than the rubber stems

just something about replacing the rubber stem for an aditional $1 (most) the customers appreciate, but replacing the seal on a metal stem for $5.00 they bitch about

and any of the bikes I know are heading to the track, if they still have rubber stems I do put in metal stems ..... or strongly advise they do--soemtimes thye just go new rubber when they are too cheap for their own good..........

All that said.......... I left in my original rubber stems for 8 years before going to metal ones and had no issues. I still know people who are on 15 year old + oe original rubber stems because they only wear out their tires about once every 7-10 years

alot of their life expectancy depends on sun exposure and the such.....
maybe even more so- if you use harsch chemicals to clean your wheels often
 
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The OEM style rubber stem..... Can that be replaced without removing the tire from the rim?
Nope, they pull into place from the OD of the wheel. You can change one by popping one bead off but if you don't have the equipment for an easy tire change on the 17" radials (to remount the bead you had to break) that doesn't help you much.


and any of the bikes I know are heading to the track, if they still have rubber stems I do put in metal stems ...
What metal stems do you use for this?


Mark
 
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