Torque

[Cassie]

@ tankman - re-mantling ... thats why I need the wrench.

 

 

Cassie .. post a pic pls

 

Looks exactly like that! The handle (which acts like the dial for torque settings)is very slid & sturdy.

I used it for the fist time this weekend and tightened everything I could possibly lay my hands on...amazing how "loose" some of my steerer nuts were!!

Edited October 31, 2010 by Cassie

[Johan Bornman]

Where do you guys get your torque values?

I have looked at ritchey and they say half the torque as others eg the stem. Ritchey say 5Nm others say 10 - 11.3Nm

 

At first these things seem confusing but there is some method to the madness.

 

Bike parts are generally affixed with 4, 5 and 6mm bolts. The torque these bolts can handle before shearing goes up with the thickness of the bolt. All things being equal, a 6mm bolt can safely handle more torque than a 4mm bolt.

 

Further considerations are:

 

1) Bolt material - alu will break before steel and must thus be tightened with caution.

2) Thread quality - poor thread will introduce more stress risers than smooth thread.

3) Adjacement material - a carbon steerer for instance is more delicate than an aluminium one.

4) Double or single pinch bolt design. A single pinch bolt arrangement such that on your seatpost, tolerates more error on torque than a double pinch bolt design such as on your stem.

 

A mechanic develops a feel for appropriate torque for given bolt diameters and materials over time. However, this doesn't save him or her from otehr faults that lead to failure at bolted points. For instance, a double pinch bolt design requires both bolts to be torqued very similarly. This requires an incrimental tightening technique where you gently get the bolts up to torque by tightening one, then the other then the other then the other etc until you reach torque. Very few mechanics know and understand this. Here a torque wrench is not even their saviour. They have to incrementally tighten the bolts, otherwise, the loosest one will work loose and the clamp cpi;d fail.

 

Richey uses 4mm bolts in the handlebar clamp and these require very little torque. Luckily there are four of them. Designs with just one bolt would require much more torque, as would designs where the clamp has more material than a featherweight race component.

 

I say get, and use a torque wrench for small bolts and understand why things should be done as recomended.

 

For larger torque values, notably cassette lockrings and square taper cranks, an error of 20 or 30% is irrelevant. Learn to do this by feel, but have someone demonstrate the appropriate feel to you.