View Full Version : Carbon bar clamp torque
Veloo
03-01-2020, 10:01 PM
Working on a friend's setup with a Ritchey stem with a max faceplate clamp of 5 Nm.
Ultegra 6700 lever clamp force is 6-8 Nm.
Bars are carbon Forte Pro.
Do you typically back off on the torque when it comes to carbon bars?
Add carbon paste to these spots?
zmalwo
03-01-2020, 11:16 PM
carbon paste then barely enough torque for the bars to not slip when you hit a pothole. any more torque than necessary is like asking for trouble
Pinned
03-02-2020, 12:46 AM
The bars should be textured where the stem clamps and along the shifter clamping areas as well. The texturing provides plenty of friction giving the ability to reduce the torque below the bars' maximum. I definitely don't go to the maximum torque unless needed.
Jef58
03-02-2020, 05:02 AM
I go 4nM on my 3T bars. They are labeled 5-6nM max depending on 4 or 2 bolt faceplates and have a rough surface to grab. A 2 bolt is 6 max. 5nM is tighter than you think using a regular allen wrench, to me, 4nM is plenty tight.
axel23
03-02-2020, 08:18 AM
I just came off a ride yesterday. Look 585 with Deda carbon bars torqued to the Deda stem at 4nM. I hit a pothole and the bars slipped down (I was riding on the hoods). I went home and tightened them to 4.5nM.
I go 4nM on my 3T bars. They are labeled 5-6nM max depending on 4 or 2 bolt faceplates and have a rough surface to grab. A 2 bolt is 6 max. 5nM is tighter than you think using a regular allen wrench, to me, 4nM is plenty tight.
Clancy
03-02-2020, 11:58 AM
carbon paste then barely enough torque for the bars to not slip when you hit a pothole. any more torque than necessary is like asking for trouble
I took a piece of carbon steerer tube that I had cut off from a new carbon fork, slide a stem on it and proceeded to try and crack the carbon. I stripped out the stem bolts at something like 18nm w/o any damage to the carbon steerer tube.
Not something I’d try on a new fork, but a fun experiment.
Interesting to see OEM stems that obviously come from same factory. One will have 5-6nm stamped on it, another 5nm, another 6nm.
Now another fun factor, how accurate is the measuring device. In a shop we had four new Park clicker tongue wrenches. When set at 5 nm, the actual readout when connected to a digital torque wrench ranged from a little less than 4nm to just over 6nm.
And, another fun story. I once watched a BMC mechanic build up a new TT frame and never once used a torque wrench. The bike was being prepared for TJ at the Tuscany Worlds. BMC had a TTT training camp in a small town prior staying in the same small hotel that I was at. When I asked the mechanic why no torque wrench, he just kind of scowled at me at point at his hand.
Good torque wrench and tighten to stated values. But in reality, there’s some room there for some leeway. I really believe that torque values are there because many people do not over-tighten, they don’t tighten enough. That’s been my experience watching others wrench.
mktng
03-02-2020, 12:12 PM
Vibe carbon stem and bar. Torqued to marked spec. Think it was like 5nM.
No issues.
Yet ..
vincenz
03-02-2020, 12:13 PM
I use 5Nm on all my carbon parts and never had any issue with slipping or cracking. Seems to be the sweet spot.
Mikej
03-02-2020, 12:20 PM
"max torque" printed on one component does not mean the other component can take it. Its the maximum, not the "optimal" for your application. Check the papers on the bars, see what the manufacturer recommends.
I use a short handled hex or torx wrench and my calibrated wrist or thumb. No slippage or breakage yet.
Matthew
03-02-2020, 01:13 PM
I just removed some Deda bars from a bike. I don't have a torque wrench and the clamping area was indented pretty good, but I have a tendency to tighten past what is needed. While removing the shifters I had to wiggle back and forth to remove from the bar. It practically sawed through the bar. Bits of carbon were falling to the ground. It actually made a hole in the carbon. I switched to aluminum. Same model of bars featured in another thread that showed they sheared off below the shifter. Scary
I always stop short of max torque and use carbon paste.
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