Stripped stem bolts - salvageable?

[KJMUNC]

I have a great Deda Mag 00 stem that I was tightening before I heard the dreaded "pop" of two of the bolts stripping the threading out of the stem. I was using a torque wrench and it was set below the recommended torque for the stem. Bolts are Ti and stem is magnesium alloy.

I hate to just toss the stem as it's in excellent shape and is crazy light and stiff. Plus it goes perfectly with my early 2000's-era C40.

So does anyone have advice on how to salvage the stem? I'm assuming retapping might be possible, but given the material involved I didn't know if the mag alloy would allow for that like standard aluminum stems would.

Any thoughts/advice are greatly appreciated.

[colker]

Have the same problem on two 3TTT record stems: hbar bolt stripped the threads on the stem.

[Ken Robb]

Heli-Coil? OTOH I would be worried that the stripped threads happening under such careful circumstances might indicate metal fatigue that could lead to catastrophic failure. I have always favored STURDY stems over light ones.

[Tickdoc]

if you balance stem cost v catastrophic stem failure = new stem nearly everytime.

[mtechnica]

Couple things, don't use a torque wrench, every time I hear about people breaking **** on a bike it's from using a torque wrench. Second, helicoil would mean drilling to remove material and tapping it to a larger thread which is questionable from a safety perspective on a light stem... toss it and don't use the torque wrench next time.

[Black Dog]

You would have to re-tap with a larger bolt diameter. This can be a problem. Perhaps a helicoil.

[ColonelJLloyd]

if you balance stem cost v catastrophic stem failure = new stem nearly everytime.

I don't like the alarmist and over-the-top caution you sometimes see on forums, but I agree here. I can just imagine an "oh sh**" panic stop in which the bolts pull through the compromised threads.

[MRB]

You would have to re-tap with a larger bolt diameter. This can be a problem. Perhaps a helicoil.

^ in addition you would have to finish threading the new bolt holes with a bottoming tap (square tap), and not a tapered tap, because the drill holes do not go all the way through the stem. But the issue of Magnesium vs Aluminum that the OP asked about should be pretty much irrelevant.

[benb]

If you've got the rig you could probably drill a whole right through the snapped bolt and extract it that way. Should be relatively easy given the location of bolts on a stem.

If the Ti bolts were not the original that might have been the issue with them snapping with the torque wrench. Torque settings on stems are for the bolts the manufacturer intended to be used.

Of course if it's old and was possibly overtightened without the torque wrench damage could have been easily overdone.

Couple things, don't use a torque wrench, every time I hear about people breaking **** on a bike it's from using a torque wrench. Second, helicoil would mean drilling to remove material and tapping it to a larger thread which is questionable from a safety perspective on a light stem... toss it and don't use the torque wrench next time.

People who are just getting started need to learn how to use a torque wrench just like other tools. I've had plenty of cases of "pro" bike mechanics improperly fastening parts on my bike since they thought they had a "calibrated hand" and didn't use a torque wrench.

I had my cranks fall off in a cross race once after the bike had been in the shop. He didn't use a torque wrench. Took it back to complain (I was able to attach the cranks back on well enough to finish the race as I had tools) and he went and put them back on again with improper tools and of course they were not torqued correctly and would have fallen off again... shook my head and left. This was before the modern crank designs, it'd be a little harder to make that mistake now even without a torque wrench but it was a good example.

[benb]

if you balance stem cost v catastrophic stem failure = new stem nearly everytime.

No kidding.. I had to resist telling a rider I saw with a Thomson X2 on a group ride last weekend about mine that got the cracked face plate along with all the anecdotes about others having the same problem here on this message board.

[weaponsgrade]

Personally, I wouldn't want to ride a stem like that, but if the hole is deep and the bolt is short, maybe there's still enough thread at the end of the hole that can be reached using a longer bolt.

[oldpotatoe]

if you balance stem cost v catastrophic stem failure = new stem nearly everytime.

And this is from a dentist...listen to him!

[Tony T]

I wouldn't use it and I would email Deda (dedausa@dedaelementi.com)

[jinbok]

happened to me recently.. i just bought new stem..

[TimD]

Using a hacksaw, cut it in half. Use the more interesting half as a paperweight.
Since it is magnesium, light it on fire. Gather the neighborhood kids first. Do not hold in hand.

[KJMUNC]

Using a hacksaw, cut it in half. Use the more interesting half as a paperweight.
Since it is magnesium, light it on fire. Gather the neighborhood kids first. Do not hold in hand.


haha.....best response so far. yeah, I think it's a just going to become a paperweight at this point.

Thanks for the thoughts! :beer:

[Bentley]

I think the idea of setting it on fire is brilliant. We used to do it with worn out Lawnboy mowers. Also cut it into strip and weight it and drag behind your bike at night.

[ultraman6970]

Mag stems arent famous for their reliability, they look cool tho.

[merlincustom1]

Couple things, don't use a torque wrench, every time I hear about people breaking **** on a bike it's from using a torque wrench. Second, helicoil would mean drilling to remove material and tapping it to a larger thread which is questionable from a safety perspective on a light stem... toss it and don't use the torque wrench next time.

I don't get this advice. It seems purely anecdotal. The manufacturer knows its product and recommends a setting. Maybe torque wrench not calibrated properly, user error, prior overtightening set up the failure, different bolts, etc. I'll err on the side of science over feel every time.

[mtechnica]

I don't get this advice. It seems purely anecdotal. The manufacturer knows its product and recommends a setting. Maybe torque wrench not calibrated properly, user error, prior overtightening set up the failure, different bolts, etc. I'll err on the side of science over feel every time.

Yeah I've heard that too from my friend that is a bike mechanic at a shop and broke his carbon fiber steerer tube. There are a few things you should torque like the 5mm bolts on hollowtech 2 cranksets but cranking stems to their max torque is a recipe for disaster, you only need to tighten them enough that nothing moves. Whatever though, I don't break anything so I'm good.

[Tony T]

….but cranking stems to their max torque is a recipe for disaster, you only need to tighten them enough that nothing moves.

OP didn't torque to max torque.

[Peter B]

if you balance stem cost v catastrophic stem failure = new stem nearly everytime.

Stems are cheap. Dental work is not. :help:

[fogrider]

Couple things, don't use a torque wrench, every time I hear about people breaking **** on a bike it's from using a torque wrench. Second, helicoil would mean drilling to remove material and tapping it to a larger thread which is questionable from a safety perspective on a light stem... toss it and don't use the torque wrench next time.

+1. easy to say use a torque wrench. I use short allen wrenches and don't over tighten. grease the bolts and tighten in a cross pattern.

there have been stem holes are drilled short and bolts bottoms out. if there is any material behind the hole, drill through and tap it out and get longer bolts. but I agree, if there is any doubt to it holding, toss it and use a new stem.

[Fatty]

Stripped stem bolts - salvageable?

The bolts, probably.

The stem, probably not.

[jamesau]

Wouldn't be surprised if the stem's threads were suffering from some minor corrosion before they stripped. Mg/Ti combo has a large galvanic potential and have to imagine the Mg's protective coating breaks down first at the threads (from both mechanical wear and galvanic corrosion).
As others have suggested, the stem is toast.
(Also, I might think the torque spec for a Ti bolt would be different than a steel one).

[MikeD]

+1. easy to say use a torque wrench. I use short allen wrenches and don't over tighten. grease the bolts and tighten in a cross pattern.



there have been stem holes are drilled short and bolts bottoms out. if there is any material behind the hole, drill through and tap it out and get longer bolts. but I agree, if there is any doubt to it holding, toss it and use a new stem.


I can easily overtighten 4mm head stem bolts even with a short handled Allen wrench.

[fogrider]

I can easily overtighten 4mm head stem bolts even with a short handled Allen wrench.
I'm sure you can, but don't. And I've stripped my fair share of threads. I just don't think a torque wrench is the magic bullet. For a stem to handlebar with 4 bolts it's important to tighten a little at a time and in a cross pattern. And check the tightness of the bar often.

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[Tony T]

I'm sure you can, but don't. And I've stripped my fair share of threads. I just don't think a torque wrench is the magic bullet. For a stem to handlebar with 4 bolts it's important to tighten a little at a time and in a cross pattern. And check the tightness of the bar often.


Us mere mortals do the same, but with a torque wrench. :)