zactaylor

Hello all,

Looking for some advice.

I noticed at the beginning of last summer that there was a tiny 'line' on my carbon steerer tube just above the lower stem bolt. I actually just thought it was cosmetic marking, so have been riding on it ever since. Over the winter, the bike has been 'parked' while I have been on the winter machine, so I decided to drop the fork out just to be sure.

When I removed the stem, it was immediately apparent that it was not what I thought. There was a crack running down about 1cm from the mark I could see (covered by the spacers). It looks as though the lower stem clamp bolt has, at some point, been overtightened and 'compressed' the steerer tube.

To assess just how bad the damage was, I removed the expander bung and checked the inside. I could indeed feel a 'bump' where the line was on the inside of the tube.

Although I think I (sadly) already know the answer, could somebody answer for me: is the fork 'toast'? The mark was originally noted in June/July 2023 and I was riding it until October, and it never got any worse (from what I could see). However, now I have seen it 'properly' I am uneasy about riding it. The bung is actually very long (by modern standards) and comes right down all the way past the stem inside the tube.

Is it time for a new fork?

I wanted to attach images, but as I have only just joined the forum I can't. Bit of a silly rule?

Thanks in advance!

mpetry912 

I sure would not ride a carbon steerer if there was an obvious crack. It will fail at the worst possible time, with disastrous results.

I have seen some ways to sleeve them using a carefully sized plastic insert and epoxy but not as a repair technique

If you do get a new fork, spend the 20 bucks extra and get the expansion nut that supports the thin wall carbon steerer better than a star nut

/markp

grumpus

Never ever ever use a star fangled nut in a carbon steerer.

grumpus

If it's a particularly good fork you could probably have it repaired, but if you can easily buy a suitable replacement that's probably the way to go.

travbikeman

Curious if your fork has a steerer tube with something similar to the following:


Or is it a star nut/clamp like this:



If it's like this last image, and if you are on a new bike still under warranty, you might want to speak further with your LBS on this. An incorrect clamp may have been used.

Barry2 

I can’t see any reputable carbon shop repairing a steerer/fork !

What brand/model/year is the bike?

Barry

choddo

No. Our local one only do frames and wheels.

Camilo

Nobody uses a star nut with a CF steer tube and neither did the OP. He referred to the expander bung that was in it.

JohnDThompson 

Likely. Take it to a bike shop, where it can be assessed in person.

Spam mitigation rule. You can upload pictures to an "Album" associated with your user account, and other people can link to them from there.

Crankycrank

When you can post a photo that will be the most helpful. Without one no-one can say anything with any accuracy. Sometimes there are layup seams that get confused with cracks or damage so there is that possibility but I would suggest taking it to at least 3 different shops to get an in-the-flesh check which should be the most accurate way to do it.

grumpus

He wrote "I removed the expander bung" and "The bung is actually very long (by modern standards)" - I think that's pretty conclusive evidence that he doesn't have a star nut, and knows what he's doing.

zactaylor

Hello everybody

Thank you for all your replies.

I sent the photos to Carbon Bike Repair UK who are a highly-regarded repair shop in Leatherhead. They confirmed it was a clamp fracture.

I am going to contact the manufacturer for a new fork.

I will upload the photos (as I can now) so if anybody would like to add anything feel free!