Crack in carbon fork steerer

[Sittingduck]

Would you ride with a 1 " slight crack and indentation in the fork steerer, if you had an expander fitted to the top cap? The crack has possibly been caused by an overtightened stem bolt and runs vertically, adjacent to where the stem clamps onto the steerer. I can feel the indentation/ridge with my finger if I stick it into the steerer. There's a pic I can upload later on that shows the steerer... currently at work. Have been off that bike for the past 3 days as my instinct told me not to risk it but riding the creaky B bike is doing my head in, especially in this nice weather! I am 90% sure everybody will say "No - don't risk it", just wondered if having the bung inside there would mitigate the risk of it going crunch?

 

[Yellow Saddle]

That crack is very common with stems installed on carbon steerers without a spacer on top. Even expanders don't often sit flush on top and this too causes such a crack.

The crack will not travel if you remove the cause i.e. stem clamping it. If you put an expander inside and position it properly, you will be ok. Even better if you have a "spare" spacer below the stem that you can move to above the stem.

 

[Sittingduck]

The crack appeared when there was no bung inside the stem - I had removed it... I know, I know. Tut tut

I have experimented with moving spacers and the stem up & down to try and find a place where the stem doesn't come into contact with the crack but whatever I do there crack is inline with a some of the stem, somewhere! I had 2 spacers on top of the stem when it happened and one conical sytle spacer below, it's a SuperSix, if you're familiar with the headset/spacer. As mentioned, I will upload a pic this evening but don't fancy doing tomorrow's club run on the old creaky alu bike as I will get battered even more than on my carbon bike, unless I drop down a group.

 

[Yellow Saddle]

The crack appeared when there was no bung inside the stem - I had removed it... I know, I know. Tut tut

I have experimented with moving spacers and the stem up & down to try and find a place where the stem doesn't come into contact with the crack but whatever I do there crack is inline with a some of the stem, somewhere! I had 2 spacers on top of the stem when it happened and one conical sytle spacer below, it's a SuperSix, if you're familiar with the headset/spacer. As mentioned, I will upload a pic this evening but don't fancy doing tomorrow's club run on the old creaky alu bike as I will get battered even more than on my carbon bike, unless I drop down a group.

Here's a way to convince you that it is OK after you have put a solid expander in there.

Before you make changes. stand in front of the bike with the front wheel between your legs. Grip the wheel with your legs and violently (hard and controlled) move the stem/bars left right up and down. You'll see movement, particular up/down. Now make the change and you'll see the movement is gone.

 

[Sittingduck]

Just to mention that bthe crack doesn't run all the way to the top of where te steerer is cut. Rather it is in the middle of the remaining steerer!

 

[Yellow Saddle]

Alternatively, find a Cervello dealer. Cervello has a system of inserting a long steel tube down the steerer so that it rests flush with the top. This is epoxied in place. Then inside that goes a standard star nut. That will give you the extra peace of mind. Even failing that, the fork is not ruined, it can be repaired, but that's for another day.

 

[Sittingduck]

Ok nice - I'll give this a go later on then try to convince the OH I am unlikely to faceplant into the Dual Carriageway tomorrow

 

[Yellow Saddle]

Just to mention that bthe crack doesn't run all the way to the top of where te steerer is cut. Rather it is in the middle of the remaining steerer!

OK, I get the picture. This is easy to solve. Use the Cervelo method or get a machinist to machine a piece of nylon or aluminium that fits exactly inside and spans the crack. It must be a right fit, preferably a good press fit. Ask him to cut flutes in the cyclinder and then expoxy it in place. If there is no space for an expander above that, get him to drill a hole and tap it for the 6mm top-cap bold and use that as the actual anchor for the bolt.

 

[Sittingduck]

Do you think this would suffice?

http://www.chainreactioncycles.com/ratio-compressor-alu-top-cap/rp-prod128628

 

[Yellow Saddle]

I think you have found the solution to your problem. They even give the length - 50mm. Do a quick measurement to see if that will solve your problem and click Buy. From the picture it doesn't look like you can "sink" the compression cyclinder deeper into the steerer than the flange on top allows. Therefore, just make sure 50mm will cover the old wound first.

 

[Sittingduck]

Cool - I have already hit the buy button... seems a reasonable punt for a fiver (inc. p&p) ;-)

Thx for the help.

 

[gbb]

Out of interest, what length is the existing bung Sittingdick ?.
My Bianci FC forks bung was about 50mm long, I'm pretty sure my Ribble bung is about the same.
I'll have a look later, the proposed fix above could be of interest if in the future any of mine suffer similar problems.

 

[Sittingduck]

Out of interest, what length is the existing bung Sittingdick ?.
My Bianci FC forks bung was about 50mm long, I'm pretty sure my Ribble bung is about the same.
I'll have a look later, the proposed fix above could be of interest if in the future any of mine suffer similar problems.

Hi Gbb

Not sure off the top of my head. Hopefully the bung will be delivered Today and I will try to get time to measure both.