Smokin Joe
Squire
- Location
- Bare headed cyclist, Smoker
+1.
spacers on carbon steerer
- Thread starter huttster
- Start date
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GrasB
Veteran
- Location
- Nr Cambridge
+1 When get instructions with the fork, stem & steerer tube plug that conflict with each other what do you do? I also think that different manufactures are guarding against different issues & using different compromises in their recommendations so what solves one potential problem causes another.Stem and carbon fork manufacturers clearly haven't got their act together, yet - their parts are not cross compatible and they are pointing fingers at each other as well as blaming "user error".
GrasB
Veteran
- Location
- Nr Cambridge
If you over torque the stem bolts then you can distort the steerer tube shape if it's not supported, however if you do support the tube you can crush the carbon layers so it breaks in a different place... the fundamental problem is that you've over torqued the bolts on the stem but it doesn't stop people blaming the thing that broke rather than their own ham-fisted mechanical work.
In response to reported breakages, A recent Trek service bulletin recommends spacers above AND below the stem. I think the spacer between stem and headset prevents local distortion of the steerer (due to the stem clamp being not perfectly round, or overtightened) in the region of the headset top bearing, which otherwise results in point overloading of the steerer.
Only somewhat related to the insertion of the bung, and another different failure mode.
Stem and carbon fork manufacturers clearly haven't got their act together, yet - their parts are not cross compatible and they are pointing fingers at each other as well as blaming "user error"
http://velonews.comp...bulletin_121428
Thats really interesting, you are certainly right about the fact manufacturers have not got their act together.
At first I was confused by all this as in my mind if the fork is supplied with a carbon steerer of a certain length why is it therefore not safe to use the entire length of the steerer as it was supplied !, why would they supply a fork with a steerer that is to long and therefore not safe to use until its trimmed down ?. but realise its about the point of load and its this which seems to be causing some difference in opinion especially amongst manufacturers.
How do you reposition the star fangled nut within the steerer then ?
GrasB
Veteran
- Location
- Nr Cambridge
You DO NOT! you use something like the BBB Powerhead
I am assuming when I go to remove some of the spacers that came on my new bike im not going to find one of those ??.
GrasB
Veteran
- Location
- Nr Cambridge
A star fangled nut should never be used on a carbon steerer, it damages the steerer tube as it's inserted. I've never seen a manufacture use a star fangled nut in a carbon steerer only something like that or a proprietary equivalent (iirc reynolds embed a thread in their steerer & a proprietary plug)
Smokin Joe
Squire
- Location
- Bare headed cyclist, Smoker
I believe Boardman did.
Sorry if this is a stupid question but how do you re position them. Do you expand then slightly out and then push them into place and tighten further ?. I understand the point where they need to sit lower than the bottom edge of the stem on carbon steerers so want to check mine
Zoiders
New Member
- Location
- Ice Station Zebra
I don't think it's a compatablity issue but a quality issue.
Faced with an expensive recall do you either
A - Shell out all that money replacing what should be a modular and adjustable system but isn't because the weave quality was not good enough on the steerer tube to withstand the bung plug (which is quite frankly shocking considering the small amount of loading involved)
B - Change the instructions and blame the customer for quite rightly assuming it should be adjustable when it turns out not be?
They went with the second cheaper option.
Faced with an expensive recall do you either
A - Shell out all that money replacing what should be a modular and adjustable system but isn't because the weave quality was not good enough on the steerer tube to withstand the bung plug (which is quite frankly shocking considering the small amount of loading involved)
B - Change the instructions and blame the customer for quite rightly assuming it should be adjustable when it turns out not be?
They went with the second cheaper option.
OP
OP
huttster
Well-Known Member
- Location
- southend on sea
Can only tell you how i did mine,loosen the stem bolts first then loosen the expander plug,when i loosened mine it fell all the way down,retrieved with my sons remote control car aerial
,repositioned the expander by turning until it just about didnt drop down,moved into position then tightened to a specific torque,spez site says 9N-m,replace cap,tighten bolt in cap to remove play in steerer,then tighten stem bolts to a specific torque,mine says 6-m 
youngoldbloke
The older I get, the faster I used to be ...
It is worth examining your particular plug and take it apart to see how it works. The ones I have used have needed to be snugged up tight in position in the steerer tube before replacing the top cap bolt - as in the Hope Hed Doctor video linked to above. The top cap bolt alone does not expand the plug, but is used to preload the steering before tightening the stem bolts. It is also a good idea to lightly grease the threads of the bolt that expands the plug, as this is quite fragile, being threaded externally to expand the plug, and internally to receive the top cap bolt, and it can be snapped off quite easily if overtightened. But keep any surfaces that meet the carbon steerer spotless and grease free. Some plugs cannot be re-positioned anyway as they have a lip that positions them at the top of the steerer tube, so if you wanted to lower your stem by a large amount you would either have to cut the steerer, or replace the plug with one that allowed you to re-position it and keep lots of spacers above the stem.
GrasB
Veteran
- Location
- Nr Cambridge
My Boardman has a carbon steerer... however if you look closely at the steerer it actually has a thin walled aluminum tube in the middle of the steerer tube, this is what the SFN is gripping not carbon fibre.
Hi Guys
Just read through this very interesting thread and thought I'd add my two pennies worth. We use full carbon forks on our carbon frames and if a customer really wants the bars lowered we use a small 3mm spacer underneath the stem as 3 mm really does not make much difference to the bar height. Leave at least a 10mm spacer above the stem and if you need to cut the steerer and its a DIY job, then after correctly marking where the steerer needs cutting (2mm above the stem and spacers) use two stems lightly clamped onto the steerer with a gap between for the saw blade -- this method helps to keep a straight cut on the steerer. The tensioner when loosened (not too much as it can come apart and disappear into the fork) can then be pushed gentle down into position. Place spacers and stem loosely on steerer then lightly tighten tensioner so forks are held firmly and still moving freely -- then tighten up stem bolts. I always recommend following Park Tools guidance info. My link
Just read through this very interesting thread and thought I'd add my two pennies worth. We use full carbon forks on our carbon frames and if a customer really wants the bars lowered we use a small 3mm spacer underneath the stem as 3 mm really does not make much difference to the bar height. Leave at least a 10mm spacer above the stem and if you need to cut the steerer and its a DIY job, then after correctly marking where the steerer needs cutting (2mm above the stem and spacers) use two stems lightly clamped onto the steerer with a gap between for the saw blade -- this method helps to keep a straight cut on the steerer. The tensioner when loosened (not too much as it can come apart and disappear into the fork) can then be pushed gentle down into position. Place spacers and stem loosely on steerer then lightly tighten tensioner so forks are held firmly and still moving freely -- then tighten up stem bolts. I always recommend following Park Tools guidance info. My link
