Over-torqued stem bolts - do I need to replace the handlebar (6061 alloy)?
I was replacing the stem on my bike, and decided to use my newly bought clicking torque wrench to tighten the bolts. I was quite surprised how tight 5Nm was feeling. Turns out I was not using the torque wrench properly - I expected it to start skipping once the dialled torque is reached, so I over-torqued the screws and the stem clamp cracked (it looked like it was made of cast aluminum, for what it's worth). I was tightening the four bolts gradually, so I think that the pressure was distributed fairly uniformly over the area of the stem clamp.
I can see an impression of the stem clamp in the handlebar tube where the stem clamp was. No cracks, but it is definitely deformed a tiny bit, barely visible, but all around the bar tube. Perhaps 1/10mm deep, but I'm guessing. My handlebar is described by the bike manufacturer as "Specialized AWOL, 6061 double-butted alloy, 31.8mm". The stem was a MTB stem with four M6 bolts clamping the bar. My question is - do you suppose the handlebar's integrity is compromised? If I am now risking the handlebar failing because of over-clamping, I want to replace it. Otherwise I'm super happy with the handlebar, and have no other reason to swap it. Many thanks for any input! |
If you actually dented it, then likely it's compromised. But a small nick like you might get at the corner of the clamp, may be OK.
There's no way I can make any kind of assessment blind, and often even pictures don't help, so follow the general rule "if in doubt-- throw it out". Often mechanical decisions are more about psychology than technical considerations. I'll willingly ride compromised parts on a bike, if I either trust them, or have decided that they can break without it causing a crash or injury. OTOH- I like to have complete confidence in my bike, and don't want to be wondering about some part I don't trust, So a bar that's visibly dented at the stem clamp, is a goner for me. |
I can't say if your bars will break. But if they do it's likely to be a while from now (and you've forgotten about the current incident) when they're under a lot of stress. Not when I'd want a bar to break. Andy.
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The price of a bar is a lot cheaper than a visit to the emergency room.
Cheers, David in Alaska |
Thanks for the replies, everyone. New handlebar it is.
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i chipped a fsa slk handlebar last week when it slid downwards on the stem while i was checking for tightness. I replaced it with an aluminum version. Sage advice by David .
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