I've been frustrated with slipping even with proper torque (if under). I've now had two cracked steerer tubes that have needed to be cut down below the usefulness for me. (They loosen, then the movement/impact of the steerer tube in the headsets cause the stem to crack the top of the steerer tube.
Going aluminum. Any recommendations? Looking for a lighter weight if possible.

I'm in sympathy with your thoughts about carbon steer tubes. I just bought my first carbon steer tube fork for my track bike. Now I'm a little worried myself.

I'm at a loss. Tens of thousands of carbon steerers are in use without such problems, and reports of same are relatively rare. I don't mean to infer improper installation or maintenance, but losing two is getting beyond simple bad luck.

Maybe in the search for light weight you've chosen beyond what you should personally be riding? I trust there's no grease on the stem or steerer, that no one pulled a silly and installed a star nut, or that the stem is one of the ones that is incompatible with carbon steerers (the old Thomson wedge clamp was not a great idea for carbon, and some of the pinch areas or top/bottom edges on other stems are sharp and dig into the carbon. Maybe the bore of the stem is out-of-spec and too large to grip tightly, or out of round and stressing the steerer too much. Improperly faced head tubes or improperly seated headsets, as well as spacers (if any) that aren't cut perfectly parallel can also cause this sort of problem.

I'm just saying, maybe it's not the carbon steerer that is the cause of your pain. Maybe it's a bad/wrong stem or something obscure with the installation. Remember, the steerer that Hincapie broke at Paris-Roubaix was aluminum, so you might not be buying the insurance that it would initially seem.

Easton EC-70 is a pretty nice fork with an aluminum steerer. About 450g vs 350g for my EC90 with a carbon steerer.

What about using some of that Tacx dynamic assembly paste for carbon? It's supposed to help with slipping carbon posts, etc. It adds a little friction so that you don't need to use as much torque. I've not used it yet personally but I've heard good things about it.

Something is wrong for that to happen twice. Carbon stems on carbon steerers can be a little worse than others but even there with a little roughening of the inner surface of the stem it's no problem and you can use some toothpaste if you need more holding power (much cheaper and easier to find than the special pastes).

The only things I can think of that would cause it on properly installed equipment would be a very flexible steerer or more than 30+mm of spacers, which causes the same problem of flex and creeping of the stem.

I'd be curious to know what brand(s) caused that much problem. Sounds like a poor job of installation or a poor quality fork. I've taken scrap cutoffs from a carbon steering tube, mounted a stem on the tube with no internal support and tightened the stem, with two larger than average 6mm bolts, far beyond the recommended torque and got no damage at all. I'll have to try it with an internal support to see if I can create some damage.

As long as the proper support is installed, the steering tube is cut 2-3 mm above the stem and a 5mm spacer used on top, there should never be a problem.

There are a few stems that are no longer on the market, known to cause some pinching of the tube. Stick wiht brands like Deda, ITM or Ritchey and you should have no problem. It doesn't take much torque to hold a stem in place, particularly with the added aid of the top cap.

There are two tricks that will pretty much eliminate the problems you've been having.

The first one is to buy a tub of tacx dynamic assembly compound it is very grippy and somewhat gritty and will solve the slipping problem.

The second one is to leave enough steerer tube to put one 5 mm spacer on top of the stem as without the spacer the stem can concentrate stress on the top lip of the steerer causing a crack from the weight and leverage of the stem trying to bend the steerer foreward and down, with the steerer over the top of the stem by around 2 or 3 mm you eliminate this stress point.

Hopefully this helps if you decide to give it another shot.

. . or that the stem is one of the ones that is incompatible with carbon steerers (the old Thomson wedge clamp was not a great idea for carbon. . .

Whoa! That's the exact stem I was going to use on my track bike! Now I'll have to find an alternative.

This all seems weird to me. I am 6'2" and around 220 pounds and I have never broken a steerer. I have ridden Mizuno, Easton, and Reynolds forks with Easton, Thomson, Deda, and FSA stems and never had an issue beyond the POS tightening ring that Easton sends with their forks. Something else has to be going on. Have you used the same compression plug each time?, is the plug too low and you are crushing the top of the steerer? I did break the mizuno fork, but that was brain jarring pothole in a crit at 30mph and it didn't snap, it just cracked at the crown and I didn't realize it until after the race. Not much weight penalty between alloy and carbon steerers, it just seems odd to break steerers.

Weird is right. I have yet to have any issue with any carbon steerer, no matter what kind of stem I used. Given the state of the art, I'd say there had to be some other issue that was going on that maybe you weren't aware of.

Whoa! That's the exact stem I was going to use on my track bike! Now I'll have to find an alternative.

The new X2 is carbon-friendly, and one of the strongest stems out there.

I've been frustrated with slipping even with proper torque (if under). I've now had two cracked steerer tubes that have needed to be cut down below the usefulness for me. (They loosen, then the movement/impact of the steerer tube in the headsets cause the stem to crack the top of the steerer tube.

Sorry, but I smell user error. I can't quite tell what you're suggesting "loosens," but whatever it is, it's not right. At my shop, we build probably four to six bikes a day with full carbon forks - mostly Reynolds Ouzo Pros - and never see any of them come back. Get a good fork and a good stem and use a torque wrench, or - no offense intended - have a better mechanic than yourself do the job.

For what it's worth, Reynolds says the old-style Thomson stems are great, because of the way they distribute the load around the steerer. Again, however, don't over-torque them or most steerers will wrinkle in plies (I have seen this). Still, I'd recommend a Thomson X-2 (or X-4 if you're huge), but Ritchey, FSA, Easton, etc., all work fine.

Thanks for all of the ideas. I was just about to go have a pro take a look at it when I had discovered it had actually cracked, probably on some very rough road on a decent at the base of Mt Diablo. I hadn't expected it to crack.

Easton EC90 sl with a Ritchey WCS stem, using the external new Easton expander rather than the traditional expander plug. Maybe some grease got on the steerer tube, but it seems clean. Used a Park torque wrench to 45-50 inch pounds. Spec'ed to 5nm by Ritchey, (Easton won't supply a spec. Fear of Liability?)

Why is park useing inch pounds if all the bike part manufacturers are spec'ing nm? I don't ever remember seeing a spec of so many inch pounds.

I don't know why I was getting slipping stem either. My other Easton ec90's expander plug won't hold. It slips all the way up when tightened. I know that I have never gotten grease on the inside of a carbon tube, but it will not hold!

I was using 2cm of spacers.

If I go the carbon route again, I'll have an LBS install it. I could have very well done something not quite right or very very wrong. It isn't rocket science though.
Thanks for the EC70 and the Taxc paste ideas guys.

I'd be curious to know what brand(s) caused that much problem. Sounds like a poor job of installation or a poor quality fork. I've taken scrap cutoffs from a carbon steering tube, mounted a stem on the tube with no internal support and tightened the stem, with two larger than average 6mm bolts, far beyond the recommended torque and got no damage at all. I'll have to try it with an internal support to see if I can create some damage.

As long as the proper support is installed, the steering tube is cut 2-3 mm above the stem and a 5mm spacer used on top, there should never be a problem.

There are a few stems that are no longer on the market, known to cause some pinching of the tube. Stick wiht brands like Deda, ITM or Ritchey and you should have no problem. It doesn't take much torque to hold a stem in place, particularly with the added aid of the top cap.

I have done the same experiment, using a carbon steerer remnant and an older MTB stem with 5 mm allen head bolts. I tightened the stem until the carbon finally cracked (I think it was Reynolds) and while I did not use a torque wrench, I can say that I was putting a LOT of torque on those bolts using a 6-inch Bondhus allen wrench.

I do notice that most stems will leave some minor edge marking on the surface of the steer tube, mostly where the internal bore of the stem contacts the steerer tube. These marks are not cracks and can be removed with 600-grit sand paper.

AlexCad, that's the exact same setup I've been using for the past year, an EC90SL and Ritchey WCS stem. I initially used a USE Ringo-starr, which is very similar in concept to the Easton external expanding spacer thing. I found it to be pretty crappy and the headset ended up loose a lot. I switched to an expanding internal plug during the initial set up of the stem and headset, got the preload the way I wanted it and then took the plug out and just use a alloy topcap now, with nothing else. It's stayed perfect for >2k miles so far. The only thing I did out of the ordinary set up wise, was I wiped down the steerer tube and inside of my stem with rubbing alcohol first to get rid of any oils/grease that might have been on there. Maybe that would help?

Good Luck!

I'd definately use an expander plug. If placed properly it provides reinforcing outward presure where the stem clamps onto the steerer. Goodluck.

Yea ding ding ding...get the hell rid of the bear trap (that thing Easton uses to set the headset preload). I am supprised they are still shipping those...that is your issue. Get a standard expander (no not a star nut). The issue is the bear trap loosening...that thing is junk.

Yea ding ding ding...get the hell rid of the bear trap (that thing Easton uses to set the headset preload). I am supprised they are still shipping those...that is your issue. Get a standard expander (no not a star nut). The issue is the bear trap loosening...that thing is junk.


My bear trap that came with my Easton fork is now safely on the bottom of Pearl Harbor. It can no longer cause any harm. It should corrode away within a few years.

I'm about 210 lbs and Carl Strong recommended the Alpha Q GS-10 for me. It does have a carbon steerer, but with an aluminum sleeve that you cement into the top of the steerer. This allows you to use a standard (included) star nut, and prevents any undue stress from the stem. You may want to consider this model. I've been really happy with the ride, and it was fairly simple to install (if you are a moderately-skilled wrench turner).

Jim