Brake adjustment bolt won't stay put

[srw]

I've got what I think are Ultegra brakes (although the branding on the calliper is slightly different). They have an allen bolt (something like 2mm) on the top which adjusts the position of the left calliper relative to the right one. That bolt on the back brake just won't stay put, and keeps loosening itself, with the result that the distance between callipers gradually grows as I ride. Last night I had to retighten the bolt about half-way, which wasn't ideal. The front brake isn't affected at all, as far as I can tell.

Is there anything I can do to keep this bolt in place? I don't particularly want to threadlock it, because it's a useful adjustment to be able to have.

 

[Gary E]

Threadlock won't stop you adjusting it in future it'll just stop the bolt from moving due to vibration. You'll still be able to turn it with an allen key.

 

[Pauluk]

Is it a bolt that tightens right up to its head, or is it an adjuster that doesn't tighten in this way. If its a bolt that tightens all the way to its head then could the bolt or the threaded hole be damaged? If you loosen the bolt does it have excessive side to side movement? You could try a new bolt of the same size to see if that fits better and stays tight.

 

[srw]

It's an adjuster. The bolt itself is a tiny headless thing, which has no side-to-side movement at all.

 

[Pauluk]

Are these disc or V-breaks

 

[srw]

The brand is actually VNT elements - Van Nicholas's own brand - but the brakes are effectively a clone of the Ultegra ones. Road-style rim brakes if anyone's still confused!

And I was wrong about the front brake - it's also working loose, but not by as much. What would I lose by threadlocking the things?

 

[HovR]

What would I lose by threadlocking the things?

About the price of a drop of threadlock. Threadlock will make the thread a bit tighter to unscrew, but won't lock it solid. You'll still be able to adjust as needed.

 

[Gary E]

That's what I said!

 

[Pauluk]

Just noticed that on one of my bikes the V brake spring adjustment bolt has some kind of thread lock on it. Looks a bit like the threads painted blue.

 

[Gary E]

Yep, that'll be the thread lock.

You'll find it on the adjusters on deraileurs too.

It can wear down and become less effective, especially if you adjust regularly, so a re-application every now and then is a good idea.