Bought a bike online, took it to the physical dealer, he torqued my carbon stem over 6 NM when the limit is 5 NM

Discuss light weight issues concerning road bikes & parts.
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Rick
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Joined: Sat Aug 29, 2009 4:30 pm

by Rick

How do you KNOW that it was above 6 Nm ?

by Weenie


eppteink
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Joined: Sun Mar 25, 2018 9:05 pm

by eppteink

Rick wrote:
Tue Mar 27, 2018 9:41 pm
How do you KNOW that it was above 6 Nm ?
I have a 6NM key.

darnellrm
Posts: 215
Joined: Thu Sep 10, 2009 1:06 pm
Location: NC, USA

by darnellrm

What does that prove?

eppteink wrote:
Thu Mar 29, 2018 8:50 pm
Rick wrote:
Tue Mar 27, 2018 9:41 pm
How do you KNOW that it was above 6 Nm ?
I have a 6NM key.

eppteink
Posts: 3
Joined: Sun Mar 25, 2018 9:05 pm

by eppteink

darnellrm wrote:
Thu Mar 29, 2018 8:54 pm
What does that prove?

eppteink wrote:
Thu Mar 29, 2018 8:50 pm
Rick wrote:
Tue Mar 27, 2018 9:41 pm
How do you KNOW that it was above 6 Nm ?
I have a 6NM key.
Since I saw the screws were very tight, i´ve tryed to tight more just to check it wasnt over 6NM and it was.

waltthizzney
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by waltthizzney

as long as you didn't ride it im sure its fine

wingguy
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by wingguy

eppteink wrote:
Thu Mar 29, 2018 8:57 pm
Since I saw the screws were very tight, i´ve tryed to tight more just to check it wasnt over 6NM and it was.
So you were happy to tighten the screws to 6Nm? Then what's the problem? :wink:

Besides, screws that have been tightened then left stationary for any period of time can require more force to start moving them again than was used to tighten them to that point. Particularly if there's any sort of threadlock in there.

spinwax
Shop Owner
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Location: USA

by spinwax

Most torque keys that come with bikes or even the ones you buy are more of guide and many times not that accurate. I have checked many againt my zeroed and yearly calibrated torque wrenches and are not what they say more times than not. Most shops (not all) who use torque wrenches leave tension on them all the time, so they are torqueing literally hundreds of bikes way out of spec.

When I had my Retul fit studio/shop and was sometimes changing numerous stems out daily. I would say more than half of them were just torqued down by feel and way over manufacture's specs. It's amazing how many just tighten until "it feels fine".

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wheelbuilder
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Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

eppteink wrote:
Thu Mar 29, 2018 8:57 pm
darnellrm wrote:
Thu Mar 29, 2018 8:54 pm
What does that prove?

eppteink wrote:
Thu Mar 29, 2018 8:50 pm
Rick wrote:
Tue Mar 27, 2018 9:41 pm
How do you KNOW that it was above 6 Nm ?
I have a 6NM key.
Since I saw the screws were very tight, i´ve tryed to tight more just to check it wasnt over 6NM and it was.
This is by far one of the most ridiculous threads I have ever encountered. So you are using a 6nm key to tighten a bolt that was presumably torqued to 5nm "just to check?" So many things are wrong about this whole idea it would take 1000 words to list them. But most importantly...........who cares?

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4ibanez
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by 4ibanez

Urghh I dont torque my stems over 4nm. Inspect the 2 parts (mainly the stem you should be worried about I'd think). Buy a torque wrench and do it yourself (assuming your key is adjustable you could use it for most of the bike). I wouldn't trust a shop to setup my WW bike.

frankton
Posts: 1
Joined: Fri Mar 02, 2018 8:13 pm

by frankton

spinwax wrote:
Thu Mar 29, 2018 10:53 pm
Most torque keys that come with bikes or even the ones you buy are more of guide and many times not that accurate. I have checked many againt my zeroed and yearly calibrated torque wrenches and are not what they say more times than not. Most shops (not all) who use torque wrenches leave tension on them all the time, so they are torqueing literally hundreds of bikes way out of spec.

When I had my Retul fit studio/shop and was sometimes changing numerous stems out daily. I would say more than half of them were just torqued down by feel and way over manufacture's specs. It's amazing how many just tighten until "it feels fine".
Now this is the most inane comment here today! How could you generalize and assume that "most shops" keep tension all the time? Who would do that? Do you work at those "shops"? also, swapping stems all the time as some fitters actually do, It is really easy to feel what 5nm is like.

But I suppose some people get it, and others do not.

In the end, 5nm vs 6nm is not going to kill anyone or hurt anything.

bm0p700f
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by bm0p700f

In defence of the shop they may have had to tighten the stem bolts past the torque max to stop the stem moving. I have a couple of bikes like that, one with a Columbus fork and sedan stem another with a jenesus fork and Thompson stem and the bolts are as tight as I dare any less Nd the stem can start to move. So frankly op the issue may not be the shop. I am sure if you stem moved on a ride you would be in happy. The steerer tube will take a lot of load before failing, look at its shape, circles are strong. The torque limit is there so you don't round if the bolt head with a crap Allen key or damage the threads. So stop worrying FFS. The bolts have been set at that torque for a reason.

TheKaiser
Posts: 511
Joined: Thu Sep 05, 2013 3:29 pm

by TheKaiser

wingguy wrote:
Thu Mar 29, 2018 10:39 pm
Besides, screws that have been tightened then left stationary for any period of time can require more force to start moving them again than was used to tighten them to that point. Particularly if there's any sort of threadlock in there.
This ^^^^^

Proper maintainence technique to confirm a bolt is torqued properly involves backing the tension off the bolt, and then re-torquing it to the correct setting by taking it up to the limit again. Static friction between the bolt and stem will prevent an accurate reading of the current bolt torque due to that greater brakeaway force. I suppose you could use a paint pen to draw a line across the bolt head and stem to mark how it was aligned and the use that as a reference when you re-tighten it to see how the previous setting compares to the current one.

On a related note, potour mechanics often just throw a wrench on a bolt and give it a little force until they feel it tighten a bit to make sure things are secure and haven't loosened in the previous day/s riding. No torque wrench. This has been proven to gradually creep the tension up to greater and greater levels.

TheKaiser
Posts: 511
Joined: Thu Sep 05, 2013 3:29 pm

by TheKaiser

bm0p700f wrote:
Fri Mar 30, 2018 3:57 pm
In defence of the shop they may have had to tighten the stem bolts past the torque max to stop the stem moving. I have a couple of bikes like that, one with a Columbus fork and sedan stem another with a jenesus fork and Thompson stem and the bolts are as tight as I dare any less Nd the stem can start to move.
Out of curiosity, have you tried carbon paste on those stem/steerer interfaces? I don't see people use it much in that application for some reason. Seems like people reserve it for the bar/stem interface and seatpost.

DamonRinard
in the industry
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Location: Connecticut, USA

by DamonRinard

I remember a technical bulletin recommending against carbon paste on forks. Apparently some pastes (not all) are abrasive and can cut the fork.
Damon Rinard
Engineering Manager, Road Bikes
Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

thebubbatex
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Joined: Wed Nov 01, 2017 8:36 pm

by thebubbatex

DamonRinard wrote:
Fri Mar 30, 2018 11:38 pm
I remember a technical bulletin recommending against carbon paste on forks. Apparently some pastes (not all) are abrasive and can cut the fork.
Yep, it was a Trek bulletin that recommended against it on the sheerer tube. You can Google it.

by Weenie


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