Jerky inboard disc brake

[dickie]

I have an inboard front disc. At high speeds it works pretty well. At low speeds it is on/off causing the front to bounce up and down.

I've only experienced this on old worn discs on other bikes but this brake is only about 400 miles old. I haven't inspected the disc yet.

Any ideas?

[nsaints]

I scratched my head with this over a new inboard hydraulic disc a few years back. It was fine for 100 from new but then got worse with symptoms as you describe

Tried all the obvious stuff, in the end I decided the actual disc was made from inferior iron and had worn unevenly. So I bought an evergreen disc from scooter Centre
Solved the problem, with the old disc chucked in the scrap metal bin at the local tip

[dickie]

I scratched my head with this over a new inboard hydraulic disc a few years back. It was fine for 100 from new but then got worse with symptoms as you describe

Tried all the obvious stuff, in the end I decided the actual disc was made from inferior iron and had worn unevenly. So I bought an evergreen disc from scooter Centre
Solved the problem, with the old disc chucked in the scrap metal bin at the local tip

Thanks. That was my suspicion. I'll order one today.

[Warkton Tornado No.1]

I have an inboard front disc. At high speeds it works pretty well. At low speeds it is on/off causing the front to bounce up and down.

I've only experienced this on old worn discs on other bikes but this brake is only about 400 miles old. I haven't inspected the disc yet.

Any ideas?

I think the OEM discs were made of iron & quite probably would have been cast, allowed to 'rest' out in all weathers to relieve stress, then machined.

The disc you have may have not followed the same procedure & is now warped. You could try getting it skimmed in a lathe, but depends upon the amount of warping. If you have 'worked' the brake, then there shouldn't be any more material movement to come, so shouldn't warp further. It would be interesting to know if warping is the problem & if so, how much the run-out is.

I hope any replacement doesn't end up doing the same

[Storkfoot]

You haven’t said whether this is an original Campagnolo hub. If it is, then the disc is a good call and I can vouch for the Italian ones you have been referred to. You also need to check that it floats on the pins. I use copper grease on the pins, not too much mind.

If it is a Vietnamese made hub, I have no experience of them but I have read several posts over the years referring to pins coming loose and having an almost interference fit with the disc, which of course it shouldn’t especially if the circlip remains in place. I have also seen posts referring to having to replace the entire activation mechanism.

[Storkfoot]

Going back to this old thread, has anyone every had an original disc machined on a lathe or a grinding machine? If so, was it successful in getting rid of any jerkiness?

I know I could buy a new one, but the ones I have bought in the past, the Evergreen ones, only seem to be available in Germany.

Somewhere in the garage, I have two or three original discs. I’d like to reuse one of them if possible.

[steveg]

I know I could buy a new one, but the ones I have bought in the past, the Evergreen ones, only seem to be available in

VE Spares might have some Evergreen in stock

[Storkfoot]

I know I could buy a new one, but the ones I have bought in the past, the Evergreen ones, only seem to be available in

VE Spares might have some Evergreen in stock

Thanks, Steve. I made contact with them and they don’t stock them.

[Fast n Furious]

Going back to this old thread, has anyone every had an original disc machined on a lathe or a grinding machine? If so, was it successful in getting rid of any jerkiness?

I know I could buy a new one, but the ones I have bought in the past, the Evergreen ones, only seem to be available in Germany.

Somewhere in the garage, I have two or three original discs. I’d like to reuse one of them if possible.

Yes. They machine up quite well on a lathe. Just make sure it is clocked up concentic in the chuck first.

[steveg]

I know I could buy a new one, but the ones I have bought in the past, the Evergreen ones, only seem to be available in

Hi Paul
After I posted I remembered I got a newfren disc from them to fit an Evergreen hub!

VE Spares might have some Evergreen in stock

Thanks, Steve. I made contact with them and they don’t stock them.

[dickie]

Reading back, I never posted how I resolved this issue.

I found the problem to be that there was too much force exerted on the pins by the anti-rattle clip. As the pins are not equally spaced, that means that the disc can easily run out of true and lock itself there.

It was partly caused by the groove being machined too deep, but the primary reason was too much tension in the clip.

The remedy was simply to reduce the clip radius, or put another way, to bend the clip into a smaller ring. I can't honestly remember how I did that and manage to retain a fairly constant radius, but I do know it wasn't a drama.

Or I could have left the clip out, but that would have been defeatist.

[Storkfoot]

I found a couple of old original discs, one of which I have taken the circlip out of. I’ll take them down to the engineers in the next few weeks.