Carbon Steerer Tubes -- Safe ?

Hi:

Anyone have any negative experience, or know of any involving carbon -vs- alloy or steel steer tubes ? I just built a bike for my wife and used a Ritchey fork with an alloy crown and dropouts but the steerer and blades are carbon. I haven't heard of any issues that don't involve some sort of damage first, but thought I'd ask.
I have nightmares of the thing fracturing as she hits a bump going down a big hill or something - hopefully the typical stresses involved have been engineered and accounted for by a wide margin... and I am just paranoid
I used a compression type top plug and didn't overtighten the stem bolts to the recommended torques, was very careful cutting it to length, sanded any burrs left from cutting, etc etc..

thanks !

George

Nah....I've cut a bunch of carbon steerer tubes (4 or 5), and steel and alu as well. Haven't had any problems in the past 10 years of doing this. Especially using a compresion plug, and being careful about the stem clamping, as you have done, you should have nothing to worry about.

Lots of discussion on running a small spacer above the stem with carbon steerers (C'dale factory rep recommendation). Logic being that the stem should have full contact.

If you remember about a little less than a year ago, Bontrager came out and said Hincapie crashed at Paris-Roubaix because he was testing out a "carbon steerer tube". Whether it was actually a carbon steerer tube or just an excuse for a failing part, we will never know but just thought I'd tell ya.

__________________
Lemond Tete De Course
-Sram Force
Trek T1

He was testing carbon rims. The steerer tube was actually aluminum, but it wasn't the regular Madonne model.

^ the guys at Trek kept saying that the steerer was damaged in a previous crash; and I'm pretty sure it was an aluminium steerer. He definitely crashed, but I guess we'll never know how the damage actually occurred. There's a cool pic of it -- I'll try find it


Well, I knew there was a recommended maximum spacers, but I didn't know there was a recommended minimum

"The number and placement of spacers does have an effect on the fatigue life of an aluminum steerer tube. Running less than 5mm of spacers under the stem can concentrate or "point load" a great deal of stress in one spot on the steerer. Therefore, Bontrager recommends a minimum of 5mm, and a maximum of 40mm of spacers between the stem and the headset to maximize the fatigue life of the steerer.
Scott Daubert
Trek Bicycles"
http://www.velonews.com/tech/report/...s/11432.0.html

I cracked one, but it never failed on me while riding. I was foolishly experimenting with a few different compression caps and stems and I suspect I either scored the inside of the steerer pulling out the plug, or I overtightened the stem. The result, the fork is junk as it now has a 1 inch long vertical crack. On another bike that I've never felt a need to mess around with, I've used the same Reynolds fork/compression plug and Ritchey WCS stem for three years and it's completely fine. On the bike that had a cracked steerer I was using another brand of stem which does not wrap around the steerer like the Ritchey, but is more of a pinch closure. I also wasn't running a spacer above the stem. Now, on that bike, I put in a new Reynolds fork, will only use their compression plug, and a new Ritchey 4-Axis stem (with a spacer above). In my opinion Ritchey makes the most carbon friendly stem out there. More stack height, diagonal closure and opposing bolts. Plus they look good and are very light.

i have carbon forks with alloy steer tubes on 5 of my 9 bikes and have never had any problems out of them (knock on wood). i've used them for atleast the last 6 or 7 years.

Ah...someone brought up a good point...always follow the manufacturer's directions if they are specific to their own models - Cannondale, as another poster said before - says specifically NO SPACERS over the stem. Reason being that the top cap extends down into the steerer to keep it from crushing. Incidentally, I just got a new CAAD 9 and went through this - it comes with a star nut (!!!), and specifically says to use that, NOT an expander plug. I was rather skeptical....I've never used a star nut on a carbon steerer - but, it seems to work no problem. The inside of the carbon steerer on th Slice forks looks to be quite tough - no damage at all from inserting the star nut, and it's holding well.

wow, that's really interesting. I saw a used Cannondale Slice fork at the local shop with a star plug in it, and assumed some dickhead had wrecked his fork. The side walls of the Slice steerer are very thin, so that made me think the guy had REALLY screwed up.



I guess this means it's unwise to put a Slice fork on another bike without using this extending cap

Yeah, you gotta be careful when installing the star-nut - to be honest, I was pretty scared when I did it, because even though I have the starnut tool, it still took quite a bit of banging t get it to start the seating process. Once it started, there was no problem (ie, the wings on the nut had been bent enough to fit into the tube)



Exactly. But the one thing I can't figure out is - if you use an expander plug and put it in the correct position in relation to the stem, that should keep the stem from crushing the steerer tube anyway, and you don't need the special top cap then. Not sure what Cannondale had in mind when they came up with this unorthodox system

Hmm, not sure. Maybe it's a way of safeguarding against 'gooses' wanna have 10cm of spacers!

I'm still amazed how thin the walls of the Slice steerer are. The fork I saw was about 310g with the star nut!

Interesting comments. As far as using a spacer above the stem, I feel that it works well because there is no pressure over the top of the steerer from the stem. Plus it also gives a little wiggle room if I ever want to raise my stem a bit. As far as the expander not being positioned right, it's really not an issue with the Reynolds expander (or an FSA which I've also used) because it's a two piece expander and you can slide the inside piece down to an appropriate position before attaching the top cap (although use the top cap to help position it, since it's a pain when it falls inside of the tube). Persoanlly I like placing the expander so the top of the inside bolt is level with the top of the steerer.

The Cdale Slice starnut is not a regular starnut as used in an allow steerer. It's some special proprietary one. Not sure of the diff. Either use it or an expander plug, but mfg rep says defintely do not use a standard starnut. Like previous posters have said, follow mfg instructions.

Thanks Brian (and everyone else), I did notice when I followed the directions that came with the fork, that the compression plug reaches far enough down to protect the tube from compression the stem may provide). Seems pretty darn secure.
As long as the rest of it is engineered well and the support that the headset & bearings provide is good enough, I am hoping any torsional/torque from normal steering is well within the material failure tolerances at the dimensions the manf. used. I imagine there are lots of other places those forces find some compliance too (frame, tires, wheels, blades, crown)...
Seems like there is no systemic issue with these , definately makes me feel better.