[jacksonpt]

I noticed this today while tuning up my bike (front end was a bit loose). The Arc stem uses a single bolt/wedge setup to clamp the steerer... when tightened down, the bolt presses on the headset enough so the headset is not square with the frame, nor is the stem.

I can put a small spacer below the stem to fix it, but I've been riding it this way for at least a year now. Should I be concerned? The front end still feels tight and solid.

 

[richcreek]

see the skrew in the 2nd photo, under the stem, theres your problem. just grind that down some.

 

[GumbaFish]

Yeah I'd have to say that is no good, can you just cut the bolt down so it doesnt stick out like that? That seems kind of like a weird design.

 

[GumbaFish]

I'm not familiar with the design, but could you put some small washers where you insert the bolt so that way they take up some space and the bolt doenst stick out.

 

[binary visions]

I'm not familiar with the design, but could you put some small washers where you insert the bolt so that way they take up some space and the bolt doenst stick out.

He said he fixed it with a spacer... Jackson, I'd just pull the whole thing apart and make sure your top headset bearing is still smooth. If that's still smooth, I can't imagine what else would be damaged by running it like that.

On second inspection, pull the whole thing apart and make sure the headset bearing race & top cup doesn't have anything weird worn into it - odd grooves, metal flakes anywhere, etc. Not really a safety issue but if there's anything worn like that it could cause premature bearing wear which you should watch out for.

 

[GumbaFish]

Yeah, I am just wondering. It seems very odd that they would make a stem that would absolutely require you to run a spacer just so it doesnt scratch up your headset.

 

[kinghami3]

I agree with the Voice of Reason. It looks odd, but if it's solid and the bearings are still in good condition, I don't see any problems with it. It wouldn't hurt to grind the bolt down though.

 

[binary visions]

Yeah, I am just wondering. It seems very odd that they would make a stem that would absolutely require you to run a spacer just so it doesnt scratch up your headset.

Maybe an improperly spec'd bolt (too long)?

 

[jacksonpt]

It just keeps getting better and better...

I went back out move a spacer under the stem (I took the photo/posted this before I actually got around to moving it). The wedge clamp system is really nice, but you REALLY have to torque down the bolt to keep the step from twisting in high torque situations.

Well, low and behold, I broke the head of the bolt off. *shakes head* Not real sure how to get it off next time, but...

 

[narlus]

post a top pic; i'm still confused as to what that bolt is doing.

 

[binary visions]

post a top pic; i'm still confused as to what that bolt is doing.

It's a wedge type system, there's a wedge in the steerer clamp and the more you torque the bolt down, the harder it presses the wedge into the steerer.

Good luck with that, Jackson. I'd see if I could file a small slice in the bolt and try to extract it with a flathead screwdriver.

IMHO, it's a solution looking for a problem. Not much wrong with the standard steerer clamps. But what do I know anyway, I run a Thompson, another non-standard clamping mechanism

 

[GumbaFish]

Yeah I'd just get a new stem personally. I feel your pain, I somehow messed up my seat shim the other day. Its the retarded mechanical issues that get me the most mad. If I go off a drop or something and something breaks at least I know what I did, but the ones where you just scratch your head are the worst.

 

[jacksonpt]

post a top pic; i'm still confused as to what that bolt is doing.

Typical stems have 2 bolts that run horizontally that clamp the two sides of the stem around the steerer.

The Arc stem has one bolt that runs vertically. It threads into a small wedge inside the stem that slides along the steeter. The more the bolt it tightened down, the more the wedge is pulled up, which pushes it into the steerer.

Think about a small wedge used as a door stop. The door is the steerer, the floor is the stem, your foot against the stop is the bolt... not the greatest example, but it's all I can think of.

 

[BurlyShirley]

All i can say is, "what a stupid design" all steerer tubes are the same size, how can it be that they made the bolt too long?

 

[Wumpus]

The thing that bothers me is that the top part of the headset isn't/wasn't sitting flush. Seems like it would have gouged something. Plus, isn't that what holds the retaining ring in place?

 

[Transcend]

see the skrew in the 2nd photo, under the stem, theres your problem. just grind that down some.

Way to actually read the post there, Einstein.

You should be able to get the bolt out fairly quickly with an easy out. Not sure why they would spec a design like that, just to be different? Seems like a fairly complex solution to a problem that didn't exist. Elegant though, I'll give it that.

 

[jacksonpt]

You should be able to get the bolt out fairly quickly with an easy out. Not sure why they would spec a design like that, just to be different? Seems like a fairly complex solution to a problem that didn't exist. Elegant though, I'll give it that.

I'm hoping there is an easy solution like that. I'm going to try to get it apart this week and replace the headset (just to be safe). I love the stem (cheap, light, strong, elegant), and will buy another one in a heartbeat... I'll just pay very close attention to the bolt.

 

[jacksonpt]

OK, got it all squared away - thanks for your input.

I used an extractor bit to pull out the broken bolt shaft. It didn't come out easily, but it did come out. Luckily, the bolts Thule uses for their kayak carrier has the same thread and is even a 5mm hex. I dremmeled off about 1/4" of the bolt to prevent it from contacting the headset like the original bolt did. Everything seems good, and the front of the bike feels tight and solid.

I will still be replacing the headset at some point, but the urgency is lessened.

 

[Skookum]

Yeah I'd just get a new stem personally.