Loosening screw

RowCycle

Hello,

The screw that goes vertically down the middle of the fork (headset top nut?) on my bike comes loose, I guess due to vibrations and the fact that my stem doesn't quite sit flush with the washers above and below.

Is there something I can put on the thread to keep it from loosening in normal riding, but can still be undone by me when I want to remove it?

Thanks for the help

P_Tucker

PTFE tape will work, or nipple lock. Singger.

double u tee

Hi,

Try to loosen your stem tighten down on the top bolt and apply a small thread lock also, then when you have tightened your top bolt do the stem!
I hope it works for you as I did the same thing on mine.

Wayne

RowCycle

double u tee wrote:

Hi,

"apply a small thread lock"

Wayne

?

Thanks Wayne

sheffsimon

RowCycle wrote:

double u tee wrote:

Hi,

"apply a small thread lock"

Wayne

?

Thanks Wayne

google loctite threadlock

fludey

Your stem shouldn't be flush anyway there should be a 2mm ish gap from the top of the stem to the steerer. The force to tighten this bolt down should only be light, depends on forks and stem but on mine it's only 2nm so don't go cranking it up. Are you sure it coming loose and not the star nut inside the forks moving up, which would say it's been overtightened at some point or just fitted badly and wants replacing, or do you have carbon forks with a carbon steerer in which case you shouldn't be using a star nut and it should be an expansion fitting...not got oil on it have you if it's one of theses?

If you use thread lock use a light weight one, not one that locks solid otherwise you may find it bonded fairly well to the nut in the forks which once set will just spin when you try to remove it next time.. :shock:

rafletcher

It doesn't matter really about it coming loose - though it's annoying I'm sure. In fact I'm amazed it is coming loose - I've never experienced that happening. So I'd say it's possibly not done up tightly enough!

As you no doubt know, once you've set the preload with it, and then tightened the stem bolts to maintain it, you can back off the top bolt by 1/4 turn or so. Fludey is right that the top of the steerer should be 1-2mm below the top of the stem otherwise you won't properly pre-load the headset bearings - but I suspect your's is ok of you'd feel the slack in the headset when riding.

I'd be surprised if (with steel or alu steerer_ the star nut was moving up. If it is it's well and truly knackered!

RowCycle

fludey wrote:

Your stem shouldn't be flush anyway there should be a 2mm ish gap from the top of the stem to the steerer. The force to tighten this bolt down should only be light, depends on forks and stem but on mine it's only 2nm so don't go cranking it up. Are you sure it coming loose and not the star nut inside the forks moving up, which would say it's been overtightened at some point or just fitted badly and wants replacing, or do you have carbon forks with a carbon steerer in which case you shouldn't be using a star nut and it should be an expansion fitting...not got oil on it have you if it's one of theses?

If you use thread lock use a light weight one, not one that locks solid otherwise you may find it bonded fairly well to the nut in the forks which once set will just spin when you try to remove it next time.. :shock:

Thanks all for the advice.

Maybe I didn't explain myself well. The top surface of the stem is not exactly perpendicular to the fork steerer. Therefore at the top, the washer doesn't sit flush with the stem, and I think this and the vibrations of the road slowly work the screw loose.

fludey

Sounds like your steerer has been cut and not very well it should be parallel with the stem just 2mm lower, might be worth trying another 1mm spacer if that cures it get bike shop to cut your steerer to sit straight and 2mm lower.

Hope that helps :?

k-dog

RowCycle wrote:

Maybe I didn't explain myself well. The top surface of the stem is not exactly perpendicular to the fork steerer. Therefore at the top, the washer doesn't sit flush with the stem, and I think this and the vibrations of the road slowly work the screw loose.

That shouldn't matter as long as it's not too off - the cap should be resting on the stem not on the steerer - as others have said there should be about 2mm between the top of the steerer and the top of the stem - so that the cap tightens on the stem not the steerer (which would be pointless in loading the bearings).