# Torque pressure for clamp -- carbon fibre frame



## Clicker7 (Aug 11, 2008)

Hi All:

I am wondering how much pressure to put on the front derailleur clamp (wraps around seat tube) when tightening after adjustments. This is and Ultegra clamp.

I've been using 2 fingers on my allen wrench and just tightening it to snug ( with fear of doing any damage to the carbon).

A couple of guys said to go to snug, then another 1/4 turn.

I figured that the seat tube must be reinforced as it gets toward the bottom bracket so it probably is pretty strong there.

I ride a Look 566 and there are no torque specs on their website ( not that it matters as I don't have a torque wrench yet).

Thanks everyone!

Joseph


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## budmol3 (Dec 7, 2008)

My 2008 Cannondale Synapse Carbon calls for 5-7 N-m (44-60 in-Lbs) . The components are Shimano 105, if that matters.


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## C-40 (Feb 4, 2004)

*???*

A torque value won't be of any value unless you own a small torque wrench. I've got lots of experience and don't need a torque wrench, but until you get that experience, you might consider getting one. I use a 4-5-6mm Y-style wrench with a firm twist of the wrist.

5Nm should never cause any damage.


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## Clicker7 (Aug 11, 2008)

Thanks Bud'

I don't have a Torque wrench yet, so when turning by feel how tight do you go on carbon.

Joe


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## Clicker7 (Aug 11, 2008)

Thanks guys, I picked up a BBB torque tool at my LBS.

Just to double check-- what is the correct torque for a Carbon seat post, CF seat tube, and Front Deraillieur clamp. Ive been getting different values from my local shop guys, and was just trying to find the most accurate info.

I am riding a Look 566, and can't find out anything on their website.

Also are there any websites that give Torque ratings or other useful tech stuff. 

Thanks all!

Joseph


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## wim (Feb 28, 2005)

Torque is not a pressure. It's a measurement of rotational force and applies only to things that turn or can be turned, like a screw or bolt. There's no such thing as a torque specification for a seat tube, for example.

Proper torque depends on the size of the screw and the design of the component containing that screw. Since there are so many makers of components, there's no exact torque value for a specific type of component. Here's a chart that'll give you some general torque values.

http://www.parktool.com/repair/readhowto.asp?id=88


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## TomH (Oct 6, 2008)

thats an expensive bike. surely you can afford 30 bucks for a beam torque wrench to do it correctly.


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## LO^OK (Feb 1, 2008)

Clicker7 said:


> Thanks guys, I picked up a BBB torque tool at my LBS.
> 
> Just to double check-- what is the correct torque for a Carbon seat post, CF seat tube, and Front Deraillieur clamp. Ive been getting different values from my local shop guys, and was just trying to find the most accurate info.
> 
> ...


If I was you I will contact Look's distributor and enquire. Torque figures depend on the component and materials specification. AFAIK there are no generic rules.


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## Clicker7 (Aug 11, 2008)

Tom H-- "thats an expensive bike. surely you can afford 30 bucks for a beam torque wrench to do it correctly"

Tom: I mentioned in previous post that I bought BBB Torque Wrench ($80) which is certified accurate to 4%.


Wim: Thanks for the link, that the kind of information I was looking for!


Joseph


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## TomH (Oct 6, 2008)

sorry, i missed that part. clickers are only accurate for about 3/4th of their range, with accuracy dropping off FAST. so a 0-100 inch pound torque wrench is realistically good for say 25-75 inch pounds. make sure you're in the wrenches useable range! the accuracy percentage ratings for torque tools are slightly misleading. a tool rated for 4% can be 10-20% off in certain ranges! or not, you really wont know unless you see a calibration report.


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## AlexCad5 (Jan 2, 2005)

wim said:


> Torque is not a pressure. It's a measurement of rotational force and applies only to things that turn or can be turned, like a screw or bolt. There's no such thing as a torque specification for a seat tube, for example.
> 
> Proper torque depends on the size of the screw and the design of the component containing that screw. Since there are so many makers of components, there's no exact torque value for a specific type of component. Here's a chart that'll give you some general torque values.
> 
> http://www.parktool.com/repair/readhowto.asp?id=88



That is really interesting. It explains a lot about why torque settings are relatively rare. I figured it was liability issue.


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## Clicker7 (Aug 11, 2008)

Thanks Tom:

Still it would be nice to know how much you can tighten a clamp on a carbon fibre seat tube without damaging the tube..... I'm a little obsessive with my first CF frame after 30 years of steel.

I called a half a dozen local mechanics and got a variety of answers from 4-5 nm to a full turn after it is snug??!! I'd be afraid of that one!

Thanks 
Joseph


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## wim (Feb 28, 2005)

*Minimum that does the job.*



Clicker7 said:


> Still it would be nice to know how much you can tighten a clamp on a carbon fibre seat tube without damaging the tube


You can use the angular position and the clearance between front derailleur cage and the tops of the big chainring teeth as a clamping force gauge. Set the position and the clearance to specs (thickness of a penny for the clearance), then tighten to 4 Nm. Shift the front several times on the repair stand and check angular position and clearance. If they stayed the same, go for a ride and shift the front a lot. If they're still the same after the ride, you're done. If they changed, try 5 Nm and do the test again. Chances are, 4 Nm will be enough.


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## Clicker7 (Aug 11, 2008)

error


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## Clicker7 (Aug 11, 2008)

Wim said:


> Set the position and the clearance to specs (thickness of a penny for the clearance), then tighten to 4 Nm. Shift the front several times on the repair stand and check angular position and clearance.


Thanks Wim:

I set it the torque a little over 4Nm, tested it for a while, and rode for an hour and it seems to be holding.

Joseph


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## Pieter (Oct 17, 2005)

Beware of under-torqueing, too. Don't be scared of clamping the carbon tube as hard as is necessary.

You might be sorry if the derailleur moves down the tube, or twists on it, under heavy shifting and damages the clearcoat. Or if it moves into the chainwheel with even more interesting results.

As for under-torqueing the stem-to-carbon steerer interface : a big no-no. My steerer has scratches and scuff marks to prove it.


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