Just fitted some new carbon bars to my new five. I used a Ritchey torque wrench (which comes preset at 5nm) and some carbon paste. Both parts are sold by Richey specificaly for fitting of carbon parts.

Whilst tightening the clamp bolts up (i made sure the gap on the top and bottom were equal, and also tightened the bolts in the correct order of 1 top other side bottome and vice versa) all bolts were nipped up at equal presure to the point of just geting to the start point of torque being acheived. Whilst finishing the 4 bolts upto torque the 1st 3 bolts tightened to the torque no probs. Whilst tightening the last bolt i could here a cracking noise just before the bolt reached torque. I backed the bolt off and tried again. Again same thing, backed off again and loosend all bolts off and then tried again all in the same order. This time all good.

I have heard horror stories of carbon bars failing etc so am just a bit paranoid. I fail to see how they have been over tightend as the bars go upto 8nm max and the ritchey torque wrench is preset at 5nm and is the tool specificaly for the job. the noise sound like a split second of a tree branch/stick being twisted and craacking if you get my drift. noise lasted max about 1sec each time before the bolt being backed off sharpish.

What do you all think?

I think you stay with alloy ones if you are worried.

Stuff makes noise, is my detailed opinion, i got a loud cracking noise last night from the motorbike as I bolted the petrol tank back on and I’m pretty sure it wasn’t cracking 🙂 It was the thread catching on the lip of the mount and then popping loose, crack. This could have been something similiar, perhaps the faceplace.

surley you only need to tighten them enough to stop them turning in the stem

i like to tighten main things like brake calipers and bars to the recomended torque settings. hence bars are 5nm and that why i tightend them to 5nm.

No signs of damage to the bars but the cracking has me a bit worried.

Thomson stem by any chance?

Doesn’t matter actually, bolts creak occasionally (just more so in Thomson IME), it’ll be fine, stop worrying.

Hi Nick

Stem is the standard orange jobbie, it was more of a cracking noise than a creak.

Think i will just ride it and see how it goes, and listen and watch over the next few rides for any signs of failure/stress lines etc

cheers for the advice

STOP!

Cracking is not a good thing with carbon, but it may just have been the clear lacquer that made the noise.

I’ve had carbon road bikes for a few years now, kitted with all carbon bits Ritchey) and my MTB currently sports CNC monkeys and seatstem – trust me when I say that you do not have to torque them up anywhere near what you might consider necessary(compared to alloy. The friction between carbon surfaces is different (assumin ur fitting the bar into a carbon stem?).

Just nip them up evenly, give it a test ride…jump around on it and I bet u’ll find it’s enough. I’ve never had a carbon failure yet, road or MTB.

If ur really concerned, feel free to email me 😉

The clamping (crushing) force resulting from the same torque (eg 5Nm) applied to a dry (unlubricated) bolt-thread will be less than for a lubricated bolt-thread.
The torque is a measure of the energy applied to the screw. Bolts have nuts on the end , screws screw into things (like stems).
Lubrication will enable a greater (crushing) load to be applied to the plastic pipe for the same given torque.
When is a plastic pipe not a plastic pipe?
CFRP is mostly plastic, that is why its called Carbon Fibre Reinforced Plastic.
Carbon fibre is fancy string, CFRP is plastic with fancy string in it (a composite).
Similar to asbestos in asbestos-cement, rebar (steel) in reinforced concrete, sawdust in Bakelite, wattle and daub etc.
CFRP is anisotropic.

Problem is bone dry stem bolts most likely.

Take the bolts out of the stem, lubricate the threads with a small amount of lithium grease, re-insert the bolts and torque to the correct pressure.

This happens ALL the time, I’ve never so much as even snapped a stem bolt, let alone damaged a handlebar before…