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undertorquing a seat's carbon stem clamp - did I chicken out?

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undertorquing a seat's carbon stem clamp - did I chicken out?

Old 05-06-10, 08:30 PM
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undertorquing a seat's carbon stem clamp - did I chicken out?

I've cleaned and re-greased the screws clamping the seat post on both my wife's bike and mine. Both are CF and the label says recommended torque 6.2Nm (55in-lbf), max 7.2Nm (65in-lbf). I used a beam-type torque wrench (TW-1) and made sure to measure while torquing steadily to avoid stiction. Beyond about 4Nm I started to be uncomfortable torquing it more. It didn't feel right to tighten more, at least not unless I find the seat is moving.

My philosophical question is whether I was too cautious. I believe the measurement technique and conditions were reasonably correct so I was surprised to see how much more room there would be for tightening.
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Old 05-06-10, 09:05 PM
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Get some Finish Line Fiber Grip paste and you won't need to worry about it.
It will make it so it won't slip even at he lowest recommended torque.
Once I started using it you will always use it, parts will never slip again.
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Old 05-06-10, 10:27 PM
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Torque recommendations are there for a reason but a good test is to try and twist the saddle with a bit of leverage with one hand and see if it budges the seatpost. If it doesn't move then you are probably fine.
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Old 05-07-10, 10:21 AM
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If the post doesn't move you're good to go.

Your beam wrench has what range? Common beam wrenches have a range of 250 ft-lb or more. Your spec is only about 5 ft--lb, and wrenches are generally considered inaccurate in the bottom 10% of their ranges.


Btw, the abbreviation is in-lb, not in-lbf (I presume the 'lbf' is supposed to stand for pound-feet, but the "feet" is out of place).
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Old 05-07-10, 10:57 AM
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in-lbf is inch-pounds-force. Thanks to our awesome English system of units, this is a rather confusing unit of measure, due to our common use of 'pound' as mass.

Some info:
https://en.wikipedia.org/wiki/Pound-force
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Old 05-07-10, 11:17 AM
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Originally Posted by DMF
If the post doesn't move you're good to go.

Your beam wrench has what range? Common beam wrenches have a range of 250 ft-lb or more. Your spec is only about 5 ft--lb, and wrenches are generally considered inaccurate in the bottom 10% of their ranges.


Btw, the abbreviation is in-lb, not in-lbf (I presume the 'lbf' is supposed to stand for pound-feet, but the "feet" is out of place).
His link to the TW-1 shows it is 0-7 Nm or 0-60 inch lbs.

jeanluc - put some tape on the seatpost with a small gap between the tape and the clamp, and see if it slips at all on the next few rides.

I have a tube of tacx assembly compound. It's not really grease, just a very fine plastic grit in a gel base. It works great on the seatpost.

Last edited by rm -rf; 05-07-10 at 11:20 AM.
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Old 05-07-10, 07:48 PM
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Originally Posted by rm -rf
His link to the TW-1 shows it is 0-7 Nm or 0-60 inch lbs.

jeanluc - put some tape on the seatpost with a small gap between the tape and the clamp, and see if it slips at all on the next few rides.

I have a tube of tacx assembly compound. It's not really grease, just a very fine plastic grit in a gel base. It works great on the seatpost.
Thanks for the suggestions. I'll try them. And you already answered what I wanted to say, that the TW-1 is the low torque wrench.
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Old 05-10-10, 05:57 PM
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Originally Posted by kenleekenlee
in-lbf is inch-pounds-force. Thanks to our awesome English system of units, this is a rather confusing unit of measure, due to our common use of 'pound' as mass.
A pound is not and never was a measure of mass. It is a measure of the effect of Earth-standard gravity on a standard unit of mass - on other words, force. Since gravity doesn't vary (at least not much) here on the surface of the Earth, a pound can be used to infer the amount of mass, and few people make the distinction.
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Old 05-10-10, 06:00 PM
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Originally Posted by rm -rf
His link to the TW-1 shows it is 0-7 Nm or 0-60 inch lbs.
Ah! Okay. Thanks. I didn't even see the link.



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