agenkin

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!

FBinNY 

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.

Andrew R Stewart 

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.

md11mx

The price of a bar is a lot cheaper than a visit to the emergency room.
Cheers,
David in Alaska

agenkin

Thanks for the replies, everyone. New handlebar it is.

redtailfool

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 .