BikeMan62

Hello everyone i've just signed up here. Been off the bike for a few years and now preparing my bike for summer. So i have a torque wrench and normally i don't use it. I just go by feel and over the years i've never had any issues. However on reading all my maintenance manuals i was wondering if i should use this torque wrench i have? Problem with these wrenches is you don't know for sure how accurate they are and i've heard of guys over torquing a bolt and breaking it because the wrench was out of calibration and didn't click so they kept torquing and wham the bolt go's.

Anyway with that said i did get the wrench out and used it to tighten my seat collar bolt that secures the seatpin. I have a Campag carbon seatpost. So reading up on torque levels in Lennard Zinn's book he gives a max torque of 10Nm or 88in-lbs. No minimum torque given so i assume that's the torque Campag think you should use. On tightening to 6Nm that seems really solid and it doesn't move or slip. Normally you don't need to horse a seat tube collar up as tight as that (10Nm). As long as it doesn't move or slip you're good to go.

To cut this saga to a close has anyone any idea why Campag specify a high torque level like that for a carbon seatpost?

Gary

fietsbob

It is the post being clamped , by the frames seat post binder Band clamp..

Un Known is the precision of the fit of the post in the frame. given the post making company is separate from the frame making company,

this is completely Un known ..

Try visiting the Bike shop You Got the bike from .. ? (never owned any Carbon bikes , Myself.)


I tighten bolts from experience , if it doesn't let the post slip doen its tight enough..
(The grit infused carbon assembly paste is assumed you Know about already)


There are torque charts given for the bolt sizes (5x0.8, 6x1 etc) in general (more applicable to Automobiles)

greased bolts have a different torque spec than dry Bolts , then there is the differences in the actual metals Used for the bolts

and the piece they're threaded into . Aluminum will strip before steel nuts or thread tapped into those different metals ..


as to your last Why Question, You may try calling the Campagnolo USA , company national representative Headquarters.

BikeMan62

Standard 31.8 seatpost going into a 31.8 inside diameter seat tube.
I am from the UK so will contact Campag UK. Just thought some people might have some ideas or opinions about torque. That's a relatively high level for a seatpost collar.

fietsbob

I'll add 31.8 is rarely 31.800, precise to the thousandth of the mm,

the tooling boring out the frame seat tube bore is subject to variation from at least tool wear in the production run.

your frame uses the Campagnolo made clamping Band for Carbon composite seat posts?
(or the one from the Frame company?)

BikeMan62

Yes it is. On most good quality frames it is damn close to it or right on it. Otherwise people wouldn't be able to fit their seatposts without undue effort. Plus mine is bang on the measurement. I have no problem with seatpost fit, it is not an issue. I'm talking about torque and why Campagnolo specify a maximum torque of 10 Nm as opposed to most other situations where a much lower torque is perfectly adequate.

fietsbob

Aerospace may be that fussy, Bike making is not. are You A Machinist by trade? or do You Know any?

I have Hand reamed My steel frame to fit 1 particular 27.2 post ( I used it as the go-no-go gage
to know when to stop cutting, (27.0->27.2)
but other 27.2 posts dont fit the same . because not all parts of Bikes are made to exacting standards..

Have a Machine shop turn out a 31.80 bar for calibration purposes , hundredths of a MM will probably be close enough.
use your Precision Digital Caliper to measure it accurately for analysis,

NB:It is a Metric equivalency for an Inch and a Quarter after all , or more precisely 1.25196850394"

Quite oversize.. in road bike seatposts ..

alcjphil

Campagnolo cannot specify torque levels for seat post binder bolts. The only torque level that they can control is for the saddle clamp. Don't confuse the two

BikeMan62

No, you're wrong, they can specify the clamping force they expect the mechanic to tighten to on a carbon seatpost. Check out the advised torque in Lennard Zinn's "Zinn and the art of road bike maintenance" 10Nm or 88in-lbs with no minimum torque advised.

alcjphil

The clamping force needed depends on the type of clamp.Campagno cannot control the seatpost clamp that a frame manufacturer will use. therefore their seat posts will be able to withstand reasonable clamping force. Some clamps require less torque than others depending on design. If you read the OP again you will see that the torque is much too high for a binder bolt,it is what you would use for a saddle clamp

AnkleWork

Who specified 10 N-m?

HillRider

A minor point but is the seatpost really 31.8 mm? The most common seatpost size, other than 27.2 mm, is 31.6 mm. 31.8 mm is a very common size for handlebar/stem clamps.

Zef

To the OP:

As far as I can find, the torque range for the Campy Seatpost Clamp is between 4 and 6.8NM (36-60 in-lbs). So the carbon seatpost should be able to withstand being tightened within that range....but it is best to tighten only until there is no slipping up and down or side to side. The seat rail clamp torque value for Campy seatposts is 22NM (124 in-lbs).

-j

Earl Grey

Yeah, that - the only source that has been mentioned is Zinn, but then the OP keeps asking (rhetorically) why Campy would specify it.