expansion plug overtorque ?

Discuss light weight issues concerning road bikes & parts.
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Drpoomanchu
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Joined: Sun Feb 09, 2014 8:59 am

by Drpoomanchu

Hello all, new to the forum and cycling as well.. I need some guidance.. I bought a nice 2012 Fuji Altamira BLK SE and decided to build my own bike because i was liking road more than cross.. i bought the extra lite ultrastar expansion plug for my headset assembly. Fairwheel bikes sells this plug and gives install directions on their website. The thing is, the torque specs they give are for the previous model @ 15nm and are not the correct torque specs.. After i torqued it to 15nm it seemed like too much so i went to extralites website and they had actual torque specs of 7-8nm.. Im new to the carbon world and i dont know if i should be worried or not. I took it apart and looked over the steer tube inside and out. i dont see anything out of the ordinary and never heard anything odd.. any helpful insight would be great thanks

by Weenie


HillRPete
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by HillRPete

Especially with the expansion plug it is easy to find out how much torque you need, and it is absolutely not required to "crank it to 11" just in case. Once the fork is sitting tight (check by pushing the bike back and forth with the front brake pulled), you can just clamp the stem, even if well below max torque spec on the plug.

fdegrove
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by fdegrove

Hi,

TS is worried about over torqueing the plug and damaging the steerer in the process.
Personally I just torque it by hand ( I know it's not the best advise), if I feel it's slipping I tighten it a bit more.
Naturally you should not go above the max. torque the manufacturer specifies but I usually get away with much less torque than that.
After all its only need to get rid of excess slack in the bearings and that's it.
Once the stem bolts are tightened it can no longer slip upwards provided you use a top cap and tighten the stem bolts properly.
The system I use actually uses a bung as top cap so the steerer pipe can't be over compressed from the outside either.

Ciao, ;)
Being a snob is an expensive hobby.

Svetty
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Location: Yorkshire - God's Own Country

by Svetty

Just want to clarify that we are talking about the torque used in tightening the wedge bolt in the expanding bung and not the top cap bolt used to set the headset preload before tightening the stem bolts.

The former needs enough torque to make sure the bung cannot creep up the inside of the steerer when the topcap bolt is tightenened. In my experience this turns out to be around 7-8Nm. Carbon paste might help but usually the serrations on the outer surface of the bung ensure that there is decent grip on the inner surface of the steerer. The topcap bolt generally requires substantially less than this.

fdegrove
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by fdegrove

Hi,

It appears you're confusing the terms bung and plug.

In the case of the example I gave the bung and the top cap are actually a single piece.
The plug in this case is then the expander.

Ciao, ;)
Being a snob is an expensive hobby.

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Drpoomanchu
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Joined: Sun Feb 09, 2014 8:59 am

by Drpoomanchu

Basically im woried about it doing damage to the steer tube from over torqueing it.. I know carbon is strong but i also know it can be damaged... I really feel bad about overtorquing that should have known better.. I should have let a shop build it for me.. Im just the type that likes to say " I built that ". Should i not ride it after doing that or i there something i can do to check it..? Would you be worried about it or not...

goodboyr
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by goodboyr

Easy to check for damage by removing everything and carefully examining the inside and outside of steerer tube for signs of damage. My opinion is that you are fine.

fdegrove
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by fdegrove

Hi,

Should i not ride it after doing that or i there something i can do to check it..? Would you be worried about it or not...


You had the stem over the tube while doing that? No visible damage inside the tube or outside?
If yes and no, then you'll do just fine.

Ciao, ;)
Being a snob is an expensive hobby.

Valbrona
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Location: United Kingdom of Great Britain and Northern Ireland

by Valbrona

Last thing I would worry about. Carbon tubes can actually be very strong when you are pushing from the inside out in a uniform way, as with an expander. However, carbon tubes are very susceptible to damage when compressed from the outside in, like with a stem. When fitting your stem use carbon paste and err on the side of caution in respect of torque specs.

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Drpoomanchu
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Joined: Sun Feb 09, 2014 8:59 am

by Drpoomanchu

Ok, I did have the stem over the steer tube when I over torqued the ultrastar but it wasn't tight just loose.. I will pull it apart again today and look it over again... Nothing with the steer tube looked out of place or abnormal last night. Thanks for the responses.. Hopefully next time I post it won't be due to a mistake... :oops:

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madcow
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by madcow

Over tightening will not hurt the steerer tube at all. The reason for the lower torque value on the newer version is that the bolt head for tightening it is shallower and it may strip when installing or removing at the higher torque, but the bolt head will definitely fail before any damage can be done to the steerer.

by Weenie


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