I’ve been running Tririg Alpha X bars on my bike (2017 BMC TM02) for about two years. The Alpha X stem mounts to the steerer tube via a single bolt wedge style steerer clamp, as many of you know.
During the process of installing Di2 on my bike, I noticed the steerer tube is “imprinted” where the stem wedge clamps to the steerer, see attached pic. Tririg recommends 15-18 Nm Torque on the clamp bolt, but I’ve normally torqued to 12 Nm without any issues. (I was nervous about the amount of torque on this single bolt, so I didn’t want to torque to 15 Nm unless I had issues with the stem slipping)
The lower edge of the indent looks like a crack to me. It has a sharp edge and as far as I’m concerned, it’s done and I’m going to replace it. I might ride it on the trainer until I get a replacement fork.
Has anyone experienced this with the Tririg style clamp? Any idea where I went wrong? How can I avoid having the same issue with the next fork?
This one is (2015 TM02). Lucky that my LBS saved my ass last week when they found there was “play” in it on my pre-race tuneup. They said I was one pot hole away from going down. Scary!
I’ve been running Tririg Alpha X bars on my bike (2017 BMC TM02) for about two years. The Alpha X stem mounts to the steerer tube via a single bolt wedge style steerer clamp, as many of you know.
During the process of installing Di2 on my bike, I noticed the steerer tube is “imprinted” where the stem wedge clamps to the steerer, see attached pic. Tririg recommends 15-18 Nm Torque on the clamp bolt, but I’ve normally torqued to 12 Nm without any issues. (I was nervous about the amount of torque on this single bolt, so I didn’t want to torque to 15 Nm unless I had issues with the stem slipping)
The lower edge of the indent looks like a crack to me. It has a sharp edge and as far as I’m concerned, it’s done and I’m going to replace it. I might ride it on the trainer until I get a replacement fork.
Has anyone experienced this with the Tririg style clamp? Any idea where I went wrong? How can I avoid having the same issue with the next fork?
Thanks.
As an engineer who’s looked at plenty of fatigue failures in my time (albeit accepting in Alu and Steel, not carbon… but still)…
I would be sh!t scared of riding on that.
If you do continue to use it, you’ll be needing the contact details of a really good dental reconstruction surgeon at some point.
I don’t think I’ve ever run anything close to those torque specs on a steer tube clamp. Maybe 5 nm(?).
In any case, did you note if the crack appeared below the steer tube compression plug? Those plugs are really help maintain the shape of the steer tube under high torque and I wonder if the alpha x was clamped below the plug.
As a composite scientist, this imprint should not be possible with a material as hard as carbon composite and so my very first thought would be an undercured resin in the steerer tube, or the resin getting plasticized from the mounting compound used on the steerer tube. What did you use when installing the aerobars?
As a composite scientist, this imprint should not be possible with a material as hard as carbon composite and so my very first thought would be an undercured resin in the steerer tube, or the resin getting plasticized from the mounting compound used on the steerer tube. What did you use when installing the aerobars?
Not sure what you’re asking for- I used the wedge clamp included with the aerobars, carbon paste, and torqued the bolt to 12 Nm (instructions specify to torque to 15-18 Nm).
As a composite scientist, this imprint should not be possible with a material as hard as carbon composite and so my very first thought would be an undercured resin in the steerer tube, or the resin getting plasticized from the mounting compound used on the steerer tube. What did you use when installing the aerobars?
Not sure what you’re asking for- I used the wedge clamp included with the aerobars, carbon paste, and torqued the bolt to 12 Nm (instructions specify to torque to 15-18 Nm).Asking about the carbon paste - what did you use?
As a composite scientist, this imprint should not be possible with a material as hard as carbon composite and so my very first thought would be an undercured resin in the steerer tube, or the resin getting plasticized from the mounting compound used on the steerer tube. What did you use when installing the aerobars?
Not sure what you’re asking for- I used the wedge clamp included with the aerobars, carbon paste, and torqued the bolt to 12 Nm (instructions specify to torque to 15-18 Nm).Asking about the carbon paste - what did you use?
Is the black piece part of the expander plug? You should take it out and inspect the inside of the steerer tube. Is it deformed on the inside as well?
Yes- the inside surface of the tube is not smooth. I can feel where the carbon has pressed in. I’m definitely not going to ride on this fork, but I don’t want to put a replacement on until I figure out the cause of this.
Is the black piece part of the expander plug? You should take it out and inspect the inside of the steerer tube. Is it deformed on the inside as well?
Yes- the inside surface of the tube is not smooth. I can feel where the carbon has pressed in. I’m definitely not going to ride on this fork, but I don’t want to put a replacement on until I figure out the cause of this.
I’m surprised there’s no metal insert like on other bikes.
I think the issue may be the BMC fork and not the Tririg bars. I had my BMC TMR02 fail in exactly the same way (hairline crack developing around the bottom of the stem) with a normal stem, clamped to no more than 5nm. It looks like someone else in the thread also developed the same crack on the same type of fork.
Also to note, while the torque spec on the Tririg is high, remember it’s a wedge system - a lot of that torque is lost to friction on the wedge device. 15 NM on the Tririg stem is not the same as putting 15NM on a traditional stem
One of the coaches of my tri team recently had the same problem on a Garneau bike. Tririg said they won’t help if there’s internal damage on the steer tube because they claim that means the compression plug wasn’t installed correctly. Please keep us updated on what they say to you.
I think the issue may be the BMC fork and not the Tririg bars. I had my BMC TMR02 fail in exactly the same way (hairline crack developing around the bottom of the stem) with a normal stem, clamped to no more than 5nm. It looks like someone else in the thread also developed the same crack on the same type of fork.
Also to note, while the torque spec on the Tririg is high, remember it’s a wedge system - a lot of that torque is lost to friction on the wedge device. 15 NM on the Tririg stem is not the same as putting 15NM on a traditional stem
This is all correct.
As we mentioned over email, that fork looks unsafe to ride. You should try to replace it immediately. DO NOT continue to ride with the fork in that condition, it could fail as others above have noted.
In general, the Alpha X Wedge clamp should not cause that kind of issue unless there is a problem either with the fork or the compression plug. When both are working properly, the system acts to sandwich the fork between the compression plug and the Alpha X wedge, and should not cause any cracking or damage. When one of those is at fault (for example, a missing compression plug, or one that is not installed properly), it can cause damage.
Especially given that your crack is at the center of the plug, and not on either side of it, strongly suggests there is a fault with the fork. I’m very sorry for the trouble, but we would recommend replacing the fork.
