Agentbolt

So I had a bike shipped up and mailed to another bike shop, and then reassembled at the other bike shop. I got it out of the shop, started riding off, and suddenly the handlebar is like turning in my hands, but not the wheel. It's barely attached.

So I get it home (like 10 miles away) and sure enough, the handlebars seem to be moving independently of the fork. I see this big inviting nut at the very top of the headset, so I tighten it up, and viola, it feels tightened. So I get on it, and bike a mile or so, and it starts getting sloppy again. It's loose again. Crap.

So I get off, tighten it again, same story. Stays tight for like a mile. So finally I decide to REALLY tighten it. I tighten the crap out of it. As I'm doing it, I hear a loud crack, and suddenly it's loose again. And if I try tightening it again, as soon as I get it moderately tight, it makes the crack sound and loosens again. So I clearly overtightened something and maybe broke something.

After doing a more thorough investigation, I realize it's the frigging stem clamp that was loose, not the star nut. I tighten the clamp, and tighten the star nut as best I can without it snapping loose again, and now it feels fine. The fork is plenty tight.

So my questions are:

A) What did I break?

B) What exactly does that star nut at the top of the headset adjust anyway?

Any verbal thrashing you guys are going to dish out at me for adjusting stuff without having any idea what I was doing, trust me, I've already given it to myself tenfold.

DMF 

Not nearly enough info...

Got pics?

Ashen

The star nut is just to set the proper tension on the bearings. The stem being clamped down is what actually holds everything in place. So to properly adjust your headset, you would loosen the stem, set tension using the star nut, crank down the stem bolts. All to proper torque blah blah etc. I'd guess the crack was the star nut slipping in the steerer.

Agentbolt

Okay, sorry no pics but I'll try to clarify.

It's a Surly Long Haul Trucker bike. It has a threadless headset. There's a 5mm allen bolt at the top of the headset, it's the adjustment for a threadless headset. I cranked down on it too hard until I heard a snap or crack, and now I can't tighten it much without it making the same snap/crack sound and instantly loosening again. Just wondering what I broke, and what exactly the stupid thing does in the first place.

davidad

The top screw is used to preload the headset bearings. The stem is held in place by it's screws. Once they are tight you could take the top cap off. This explains it better. Book-mark this site.
https://www.parktool.com/repair/readhowto.asp?id=65

DarkCloud

+1

Good and complete explanation.

HillRider

What I don't understand is why you didn't IMMEDIATELY return to the shop that assembled the bike as soon as you found the problem.

My take is that they neglected to tighten the stem clamping bolts when they assembled the bike but, since you noticed it right away, why on earth did you continue to ride it? Count yourself as extraordinarily lucky that you weren't involved in a very serious accident.

LarDasse74

I, too, have heard the sickening crack when tightening a headset. In my case it was the headset top-cap cracking. This is fairly easy to do with a plastic top cap - they are strong enough to preload the bearings and no more.

Replacing a top cap should not cost more than $5 or $1 (for a fancy one).

Not to make you feel bad, but you really should have gone back into the shop when the stem slipped the first time - you could have been seriously hurt if the bars slipped at the wrong moment.

Even if you fix the cracked top-cap (i think), adjust the headset, and clamp the stem down yourself you should call the shop and tell them their techs might be a little to sloppy - mistakes like that can cost a person his life.

operator

so basically the op tightend tehs hit out of the hS c amp because ;he thought that ti would suecure sthe stem but t obviously didn't. It's the ste m bolt sthat do it. Well gg

probaqbly bultlled the starnut thorught the ****in sterrer

LarDasse74

HAHA!!!

That is the most kickass drunken post EVER!

Agentbolt

Very likely so, but I have no idea what that means. I don't know the anatomy of a headset too well. All I know if before I effed with it, it was tightening a LOT more than it currently can, because as soon as I get even a half turn it cracks again and loosens. Something's definitely different, so I figured I'd broken something. I don't know what you're referring to when you say something like "it preloads the bearings"

A little more background I guess, I didn't specify because it didn't have anything to do with my question. The handlebar felt fine until I was about 6 miles away from the bike shop. Not precisely that far, but it was obvious I was more than halfway home. I'd been dropped off at the shop, so the bike was my only way home. I was closer to home than the bike shop by the time it was noticeably loose. It wasn't so loose it was spinning in my hands until I was pretty much home, and by the time I'd gotten off and was walking it because it felt REALLY squirrely when I tried getting on it after stopping.

Step ONE when I got back was to call the bike shop and tell them they screwed up the buildup of my bike when it was delivered. They offered to re-do the repair if I brought the bike back in. I couldn't get back there because I had a currently unsafe bike in my hands as my only means to get around. So I told them I'd fix it myself and asked for a refund, and for the mechanic who worked on my bike to get a talking to. The shop owner refunded my money and promised to chew out the mechanic.

Obviously that was a mistake, because I had no idea HOW to fix the bike, but it seemed simple enough at the time. I tightened the top cap, it felt firm, I figured problem solved. Obviously I was wrong. If it makes ya'll feel any better, I DID take a small digger when I took it out the next time, when I tried mounting it the wheel heeled way over while the handlebars stayed in my hands, and I fell off, giving me a pretty clear indicator I'd missed something. Lesson learned.

Anyways, so the current situation is I can't tighten the end cap as much as I could before I overdid it, and I'm getting the impression that if the stem is clamped on tightly now (it is) that it's not a safety issue. If that's the case, I'll just have them see if I snapped something off in there next time I bring it in for a tuneup (to a different shop obviously), which it's due for soon. Thanks for the info, all.

DarkCloud

Well, if you spend 5 mins in educating yourself, you could handle most of the basic bike stuff without breaking a sweat.

In any case, you really NEED to pay attention to some issues if you want to enjoy your bike without any problems.
The headset is one of the things you need to be aware of.

As other already said, the top cap is used to set the preload on the headset bearings. Since your stem was not properly fixed, tightening the top cap is a very bad idea since it will put too much pressure on the bearings, and could ruin the headset in some extreme cases. Additionally, the steerer/handlebars will be stiff and you don't need any of that.

I would really recommend to perform a proper adjustment of all this. It's a 5 min operation, you learn some stuff and it may help you avoid some problems later.
The algorithm is the following:
- Completely unscrew the top cap. Look inside the steerer and observe the star nut. See how the star nut bites into the steerer and how the top cap screw will screw in the star nut.
- Un-tighten the handlebar stem. Observe how the stem fixes itself on the steerer. Try to slide the stem up and down on the steerer and look at the headset bits.
- Understand that the stem needs to be at the good position in order to not let the steerer move vertically (shake) but not to press too hard on the headset bearings (stiffness)
- Now, start to screw to top cap back and go until the stem is at the good position (i.e. you just begin to feel that the top cap screw is harder to screw). Do not overtighten!!!
- Tighten the screws of the stem. Be careful about stem orientation wrt. to the wheel. Tighten the screws in a diagonal pattern. Be firm, but stop when you feel it's right (difficult to judge) or when you (visually) see that the stem starts to tighten (very slightly deform) at the vicinity of the screws. In any case, check whether the stem is solidly fixed to the steerer.
- Screw just a bit more the top cap, in order to be sure that it doesn't unscrew by itself. Since the stem it's now holding everything in place, the top cap is not needed to do something after that. In the extreme case where you cannot tighten correctly the steam cap (i.e. you reached the screw end course and the steam cap is loose), then that means that the star nut moved inside the steerer. It's an easy fix too, but you can also let the LBS to do that.

cycle_maven

Get a new star nut, and if your top cap is plastic, a new top cap. Pound the old star nut out and install the new one. Adjust the headset properly, and you're done. Star nuts cost a buck or two. A bike shop could do this for you in <5 minutes.

imi

oh man!

Ex Pres 

Sorry operator, way too much punctuation.

Panthers007

This is often a mistake made by newer mechanics:

You want to tighten the stem-cap a little before torquing down the stem-bolts. Use a torque-wrench and set the bolts to the manufacturer's specs - going from one to the other slowly increasing the torque until they are the same. Then check the stem-cap and check for any play in the headset, and making sure it moves freely side-to-side when the front wheel is lifted and the bike tilted.

jrs665

It is not a nut but a bolt. The bolt you tighten pulls up a nut that spreads a piece of plastic made out of a few parts like a skirt, the plastic skirt will have cracked. If it brakes entirely , the bolt and nut will fall to the bottom of the tube.

maddog34

Is there a specific reason you feel compelled to "answer" a 13 1/2 year old thread?

pdlamb

Bring this thread back to life!

SJX426 

breaks not brakes! Is there anything like a partial break, really? If it is broken, it is broken, period. Even if the parts don't separate, the functional intent is compromised.

wheelreason

lmao...

DMF 

I *think* I was being ironic. Either that or the OP was vastly expanded in the millennia this thread has been dead.

Necrosis, people. Respect it.