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PostPosted: Fri Mar 07, 2014 7:05 pm 
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Posts: 719
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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PostPosted: Fri Mar 07, 2014 7:08 pm 
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i always use carbon paste...and in your case, i would go with the lower only when using the paste for assembly.

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Posted: Fri Mar 07, 2014 7:08 pm 


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PostPosted: Fri Mar 07, 2014 7:55 pm 
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You should always use the lowest value, otherwise you may damage the "weakest link" of the assembly.


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PostPosted: Fri Mar 07, 2014 7:58 pm 
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Joined: Wed Sep 20, 2006 1:03 am
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Location: Madison, WI USA
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


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PostPosted: Fri Mar 07, 2014 10:17 pm 
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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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PostPosted: Fri Mar 07, 2014 10:50 pm 
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Location: Madison, WI 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


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PostPosted: Sat Mar 08, 2014 12:30 am 
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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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PostPosted: Sat Mar 08, 2014 1:07 am 
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Location: Madison, WI 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


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PostPosted: Sat Mar 08, 2014 1:17 am 
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Awesome. Thanks.

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Posted: Sat Mar 08, 2014 1:17 am 


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PostPosted: Sat Mar 08, 2014 7:35 am 
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Joined: Tue Dec 23, 2008 2:57 pm
Posts: 676
Location: NYC
Do not confuse MAX torque with recommended torque...two very different specs. This topic has been covered comprehensively on this forum in several previous threads. EM3

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