Help with compression plug and carbon steerer



biserker1

New Member
Jan 17, 2011
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Building a project bike and have a fork with carbon steerer. I cut the fork down using the park tool cut guide, hacksaw, tape, etc. First time cutting carbon fiber and it turned out great. I need to put a compression plug in there for the top cap.

I can't seem to find a video on the internet for install or type of compression plug to use. There are so many choices and types. Anyone have a good plug recommendation?

The steerer comes 5mm above the stem, as per the manufacturers recommendation. The is my fist compression plug install.

thanks!
 

CAMPYBOB

Well-Known Member
Sep 12, 2005
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What brand of fork are you using? Some manufacturers recommend specific types/brands of expander plugs.

I've used FSA, Douglas, Easton (one of the best, but I do not believe Easton sell them separate from their forks and a no-nameplug. They all work well for me.
 

e_guevara

New Member
Jul 15, 2004
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Any brand expander plug will do IMO.

The purpose of the expander plug is to preload the headset bearings onto the headtube and fork before tightening the stem. Once the headset has been properly adjusted (no more play), the expander plug doesn't have to stay on - except as a cap on the steerer.

Beats having to install a star nut into a carbon steerer.
 

biserker1

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Jan 17, 2011
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I am using a bontrager *** lite fork, like Easton, they do not sell their plugs separate. - I saw the video above. My fork needs to extend above the stem, it looks like the plug sits in the fork on this video. does it make a difference?


thanks
 

CAMPYBOB

Well-Known Member
Sep 12, 2005
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The expander plug is located inside the steerer tube. It is typically located inline or partially inline with stem. The expander plug is expanded into place to the furnished torque specification with the stem/spacer stack in place, but with the stem clamp bolts just snug to the steerer tube (not fully tightened). The compression cap is bolted onto the expander plug and with the stem clamping bolts loosened, is drawn down the spacer stack and stem thereby preloading the headset bearings.

There's some variation to the procedure by manufacturer, but it's fairly straightforward. Manufacturer websites such as FSA's, usually have downloads of the owner's manuals available. These will familiarize you with the specifics of installation.

Bontrager forks with carbon steerers were breaking steerer tubes with regularity a few years ago. Bontrager was recommending only certain stems be used in order to avoid failure. You might want to send them an email for a listing of what stems/compressor plugs are approved for your fork. Or not.
 

alienator

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Jun 10, 2004
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biserker1 said:
I am using a bontrager *** lite fork, like Easton, they do not sell their plugs separate. - I saw the video above. My fork needs to extend above the stem, it looks like the plug sits in the fork on this video. does it make a difference?
Does what make a difference? If you mean the location of the plug, then yes it makes a difference. If goes in the fork steerer, ideally (or such is the common belief) at a height in the steerer that'll put it above the bottom and below the top of your stem's steerer clamp. FWIW, the steerer should be high enough above your stem's steerer clamp that with a spacer on, the top of the steerer is on the order of 2-3mm below the top of the spacer (There's some fudge in that number depending on the manufacturer and who you talk to). Cutting the steerer to such a length helps prevent the cut edge of the steerer from fracturing secondary to clamp forces.
 

biserker1

New Member
Jan 17, 2011
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Originally Posted by alienator .


Does what make a difference? If you mean the location of the plug, then yes it makes a difference. If goes in the fork steerer, ideally (or such is the common belief) at a height in the steerer that'll put it above the bottom and below the top of your stem's steerer clamp. FWIW, the steerer should be high enough above your stem's steerer clamp that with a spacer on, the top of the steerer is on the order of 2-3mm below the top of the spacer (There's some fudge in that number depending on the manufacturer and who you talk to). Cutting the steerer to such a length helps prevent the cut edge of the steerer from fracturing secondary to clamp forces.
Got it! Thanks! Very new at the repair aspect of cycling - thanks for your patience.