Brake Shimmy

[jim123]

On my MOT I got an Advisory that there was "undulation" in the brake efficiency on the fronts of my R1200GS. I'm told that the discs tend to warp over time.

Rather than replace the Discs I was thinking of having them spun on a lathe to remove the distortions.

Has anyboby tried this as a fix?

 

[autogs]

i dont think that is an option on a thin bike disc,could be wrong im sure someone will be along soon to shoot me down though

 

[Deleted account 190920001]

Bike disks are too thin to be able to skim them. There is only a 0.5mm wear limit in them. 4.5mm new 4mm minimum according to the rep rom

 

[autogs]

phew

 

[Myke Rocks]

On a BMW car:

Bike disks are too thin to be able to skim them. There is only a 0.5mm wear limit in them. 4.5mm new 4mm minimum according to the rep rom

When you leave it in for a 40,000 mile service, it always seems to need brake disks, even if there is no noticible wear. When you query it, they tell you the disks are under the wear limit, but cannot tell you what this is.
Cleaned the lips of my son's Deauville last year. Whilst they were in the lathe, I checked the width. Well below Honda's stated limits, but, bugger it, I am not putting disks on a 13 year old work hack.
I did not skim them, only take the lip off them.
They work perfectly even though well under wear limits, though I doubt if I would wish to go road racing using them.
Ultimately, if you should decide to skim them, providing you take very little off, they may be ok.
An overly thin disk may increase the likelhood of brake fade, and the only way to find out is to suck it and see.

Myke

 

[BlueBird]

Bike disks are too thin to be able to skim them. There is only a 0.5mm wear limit in them. 4.5mm new 4mm minimum according to the rep rom

You couldnt give me the maximum permissble runout for the front discs and the minimum thinkness and runout for the rear could you

try cleaning the discs with brake cleaner or neat thinners it does make a slight difference in the wobble in my experience.

 

[Deleted account 190920001]

You couldnt give me the maximum permissble runout for the front discs and the minimum thinkness and runout for the rear could you

try cleaning the discs with brake cleaner or neat thinners it does make a slight difference in the wobble in my experience.

Max runout at the front is only 0.1mm at the circumference.
Rear is 5mm new 4.5mm minimum thickens and the max runout at the circumference is 0.6mm.

 

[BlueBird]

Max runout at the front is only 0.1mm at the circumference.
Rear is 5mm new 4.5mm minimum thickens and the max runout at the circumference is 0.6mm.

Kin'ell
I've got 0.04 on the left and 0.05 on the right.
Im on my 3rd set of discs in 70k,2 pairs of standard and a set of steptoes and they have all warped now,
Its doing my head in,must be the wheel where the discs mount to the wheel out of true.gona make a jig and have a measure up to see if it's that.