Stem tightening

Discuss light weight issues concerning road bikes & parts.
Regret
Posts: 24
Joined: Wed Mar 28, 2012 12:53 pm

by Regret

So my bars were clicking when I pulled on them going uphill (a recurring theme I think). Took them off, applied carbon paste, torqued them just right, etc. Still clicking.

Next, check the stem. As I took it off I discovered that the guy who had assembled it had not tightened it very much. I pasted it and torqued it to spec (which seems to have cured the clicking noise) but am now in doubt. Because of the gap between the top of the steerer and the top of the stem (to allow for the cap) the stem gets more compressed at the top than at the bottom, and requires more turns to get to the right torque.

So do I:

Just torque both bolts to spec?
Torque the bottom one to spec and maintain the same gap at the top of the stem?

As a side I noticed as I was tightening the stem bolts the exact same clicking sound that I previously had when pulling on the bars - anything to worry about?

Thanks!

Geoff
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Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

As with all multiple-bolt parts, you should be 'evening-up' the tension on each bolt by tightening each incrementally (think: snow tires).

Regret
Posts: 24
Joined: Wed Mar 28, 2012 12:53 pm

by Regret

Geoff, that is my intuitive approach, but if I do that only one of the bolts will be torqued to spec. Is that just the way of it?

Bigger Gear
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Joined: Fri Mar 27, 2009 6:58 pm
Location: Wet coast, Canada

by Bigger Gear

Ideally, the best solution is to have a 5 or 10 mm spacer above the stem. The top of the fork would sit 2-3 mm below the spacer. That way the fork will pass through the entire section of the stem and clamping forces will not compress the end of the steerer. If you have a stem with a low rise you might be able to achieve this by using a stem with more rise and moving a spacer from below the stem to above.

PoorCyclist
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Joined: Wed Dec 07, 2011 1:26 am
Location: California's country side

by PoorCyclist

I lubricate the threads and the bottom of the bolt heads so they can reach a torque and (hopefully) unaffected by binding or friction. alternate so tighten to 4nm each, then 4.5nm, then 5nm

Never had a problem even though sometimes the gap is not EXACTLY even top to bottom.

Only had problem after going to LBS and they do me a favor by tightening my carbon stem to 6nm and I found a crack after I go home, that explain why they handed it back to me in a hurry.

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btompkins0112
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Location: Mississippi

by btompkins0112

Bigger Gear wrote:Ideally, the best solution is to have a 5 or 10 mm spacer above the stem. The top of the fork would sit 2-3 mm below the spacer. That way the fork will pass through the entire section of the stem and clamping forces will not compress the end of the steerer. If you have a stem with a low rise you might be able to achieve this by using a stem with more rise and moving a spacer from below the stem to above.


Or using a bung like the KCNC unit that has a larger surface area that extends from the top of the steerer and through the bottom of the stem, allowing for equal tightening force across the claming area.

Geoff
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Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

Regret wrote:...if I do that only one of the bolts will be torqued to spec.

No, I don't think so. You should not tighten one bolt completely, first, if you start with both bolts fully open and get them 'close' with a conventional Allen key, you can switch the torque wrench back and forth between the two bolts until they are both to spec. Assuming you have the steerer cut properly (with enough 'room' at the top) a good topcap for carbon steerers, you should be fine.

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Rick
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Joined: Sat Aug 29, 2009 4:30 pm

by Rick

PoorCyclist wrote:I lubricate the threads and the bottom of the bolt heads so they can reach a torque and (hopefully) unaffected by binding or friction. alternate so tighten to 4nm each, then 4.5nm, then 5nm
.


Lubing the threads and heads is actually a no-no.
The proper torque-stress relationships are almost always figured using NON-lubricated threads and heads. Loctite and anti-seize compounds are very mild lubricants and are acceptable on threads.
If you lube the thread and head, then the stress in the bolt becomes a lot higher for a given torque. You risk breaking bolts and/or parts.

Alternating, gradually increasing tightening is good though.

I wonder if the OP has a compression bung inside the steerer that is snugged up correctly to support the ID of the steerer ?

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Arky
Posts: 522
Joined: Sun Sep 23, 2007 5:06 am

by Arky

Minus the lubrication, here is the procedure you should be doing (as others have described):

http://www.woodcousa.com/bolt-sequence-index.htm

I would not do a circular pattern. I would do something like top to bottom on left and then top to bottom on right (repeat). You do not want to start out tightening both tops and then both bottoms.

PoorCyclist
Posts: 414
Joined: Wed Dec 07, 2011 1:26 am
Location: California's country side

by PoorCyclist

I use antiseize on Ti bolts, but I usually under torque them to 5nm if it says 6nm max.

just a little film of grease to avoid the head digging into the face plate or bind, e.g. when the beam of the torque wrench moved but the bolt didn't.. things like that.

So for the OP you want to check the gaps is somewhat even before you start (I use a 2mm hex key or something small).. apply same number of quarter turns alternatively to each bolt and finish with the torque wrench, ready to ride... don't think people bother to measure the final gap, do we?

Regret
Posts: 24
Joined: Wed Mar 28, 2012 12:53 pm

by Regret

Wow, thanks for all the answers.

Regret wrote:Ideally, the best solution is to have a 5 or 10 mm spacer above the stem. The top of the fork would sit 2-3 mm below the spacer. That way the fork will pass through the entire section of the stem and clamping forces will not compress the end of the steerer. If you have a stem with a low rise you might be able to achieve this by using a stem with more rise and moving a spacer from below the stem to above.

Due to my less than hypermobile physique I need as many spacers under and as few spacers over the handlebar as possible.

PoorCyclist wrote:Or using a bung like the KCNC unit that has a larger surface area that extends from the top of the steerer and through the bottom of the stem, allowing for equal tightening force across the claming area.
checked this on KCNC's homepage - looks like a good idea but I can't see how it will fit down the steerer tube on my Colnago EPS, there is no shim or anything that kan be removed - or have I misunderstood how it works?

Geoff wrote:Lubing the threads and heads is actually a no-no.
this is quite surprising to me - I have always had it pounded into me that you must never use dry bolts on a bicycle.


Arky wrote:So for the OP you want to check the gaps is somewhat even before you start (I use a 2mm hex key or something small).. apply same number of quarter turns alternatively to each bolt and finish with the torque wrench, ready to ride... don't think people bother to measure the final gap, do we?

The gaps start the same but the gap at the top is markedly smaller than the one at the bottom after careful alternate tightening.

barlo
Posts: 14
Joined: Wed Dec 22, 2010 3:21 pm

by barlo

I had the EXACT same problem. Turns out my problem was the headset. A year's worth of no service and it was filthy. I cleaned it up best I could and reassembled everything. Dead silent bike. Unfortunately the creak soon returned so it appears that my headset probably needs replacing. FWIW, I am running a full carbon, tapered (1.125 to 1.5) steerer with integrated steerer.

How I hated threaded steerers but this has been driving me mad!

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euan
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Joined: Sat Sep 05, 2009 11:20 am

by euan

yeah I would suggest it was the headset getting dirty, I had the same thing.
"Step forward the climber and all those who worship at the altar of lightness" - R. Millar

Geoff
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Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

Regret wrote:Geoff wrote:
Lubing the threads and heads is actually a no-no.
this is quite surprising to me - I have always had it pounded into me that you must never use dry bolts on a bicycle.

@Regret, that quotation was mistakenly attributed to me. I do not personally agree with that statement and believe that the stem bolts for both the steerer and the faceplate should be lightly greased on the threads and the heads.

Regret
Posts: 24
Joined: Wed Mar 28, 2012 12:53 pm

by Regret

Sorry Geoff, an inadvertent quote function goof.

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