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Old 01-24-21, 11:10 AM
  #8  
DaveSSS 
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Join Date: Sep 2008
Location: Loveland, CO
Posts: 7,212

Bikes: Cinelli superstar disc, two Yoeleo R12

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A picture is a must to advise on the extent of the damage. If you've cut the steerer long enough for 10-20mm of spacer (or more), you may just be able to cut off the damage. I do some unusual things with carbon steering tubes, like glue in a thread insert, rather than use an expanding plug. I've also extended the length of a steering tube by 10-15mm, using JB Weld epoxy, at the same time that I installed the permanent thread insert. As a mechanical engineer and machinist, I know what I'm doing. I want more than half of the stem clamp length to be the original steering tube.

I just finished eliminating the expanding plug on both of my newest frames. I take a 1" or 1-1/8" start nut and grind the OD so it just slips into the steering tube to use as my thread insert. I plug the steering to the appropriate depth with foam rubber and fill the entire upper 30-40mm of the tube with epoxy. Once it's cured, it's rock solid. With my current frame, I set the star nut deep enough so a future owner could saw off up to 15mm of the steerer to lower the stem, if needed. Any more wouldn't leave enough length for the 15mm headset top cover and the 40mm stem clamp height. To actually extend a steering tube, a copper tube coupling with a 1-1/8" ID is slipped over the steerer and serves as a precise mold for the extension. After the epoxy cures, the mold is removed.

Last edited by DaveSSS; 01-24-21 at 12:32 PM.
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