Which torque recommendation?
Moderator: robbosmans
When clamping parts together with different torque recommendation, which do you use? For example, clamping a stem to a bar. Stem has a torque recco of 4nm and the bars has 5nm. Which do you go with?
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A torque specification for a handlebar is nonsensical; a bar has no threaded parts.
I wrote a little post a few years ago answering this question in detail:
viewtopic.php?f=3&t=66911&start=5
If you're in tl;dr mode: use carbon paste on the bar/clamp interface, thoroughly grease the stem bolts and tighten them to the stem spec of 4 N-m. Remember to snug the bolts against the clamp until they're finger tight and then apply those 4 N-m in sequence and slowly. In other words, turn each clamp bolt roughly one turn at a time, alternating in an X-shaped pattern.
Cheers,
Jason
I wrote a little post a few years ago answering this question in detail:
viewtopic.php?f=3&t=66911&start=5
If you're in tl;dr mode: use carbon paste on the bar/clamp interface, thoroughly grease the stem bolts and tighten them to the stem spec of 4 N-m. Remember to snug the bolts against the clamp until they're finger tight and then apply those 4 N-m in sequence and slowly. In other words, turn each clamp bolt roughly one turn at a time, alternating in an X-shaped pattern.
Cheers,
Jason
Thanks folks. My example was made up, but in the manual for my Zipp SL bars it does indicate a max torque for it. I've also seen other carbon parts without threaded parts to have torque limits. That's what I was asking about. But it was answered. I will use the lower number. Thanks.
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- Posts: 668
- Joined: Wed Sep 20, 2006 1:03 am
- Location: Portland, OR USA
drainyoo wrote:in the manual for my Zipp SL bars it does indicate a max torque for it. I've also seen other carbon parts without threaded parts to have torque limits.
<Jobst>
Specifying a torque value for a non-threaded part hints strongly at incompetent engineering. (Or, more charitably, a moment of extreme engineering sloppiness).
A torque value is meaningless without thread pitch. This is equivalent to specifying a maximum speed in meters. In both cases, the value is means nothing on its own and more information is required.
</Jobst>
I'm glad you found the information you needed. While using the lower torque value, I'd still check very carefully to ensure that all parts are secure. At best, a handlebar that slips while riding is irritating. At worst, it causes a crash.
Cheers,
Jason
Thanks Jason. Got it. So using carbon paste essentially let's you apply less torque to the bolts and still get a secure grip?
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- Posts: 668
- Joined: Wed Sep 20, 2006 1:03 am
- Location: Portland, OR USA
Yes; carbon assembly paste inhibits slipping. I'd use it on bar/stem and seatpost/frame interfaces if slipping was a problem without it.
For what it's worth, carbon paste is essentially grease with very fine sand in it. Theoretically, you could easily make your own.
Cheers,
Jason
For what it's worth, carbon paste is essentially grease with very fine sand in it. Theoretically, you could easily make your own.
Cheers,
Jason
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