"warped back disc"

[Mattthebat]

MOT yesterday had an advisory of a warped disc, anyone know what causes this? without appearing to be thick.....

£168 for new one , fluddi buck!

[Boro Jake]

Could be a number of reasons, mainly due to heat/wear.

Surely you can pick up a decent second hand one off ebay?

[Mattthebat]

Strangely enough I'm on EBay now ...

[Stu]

Get it checked out You can have a little bit of warp on it it could still be within tolerance

Best to find. if cause too

[mealexme]

maybe you went for a really hard ride out then washed it straight away? Because i am pretty sure putting cold water on hot disks can warp them

[Fozzie]

Is your bike shaft driven?

I read recently the extra stresses of shaft drive can cause the back disc to warp easier. That may well be wrong but it could be a cause

[Mattthebat]

Mentioned this to BMW , "warranty doesn't cover wear and tear" bast!....

[Mattthebat]

maybe you went for a really hard ride out then washed it straight away? Because i am pretty sure putting cold water on hot disks can warp them

 

That could be the reason. Possibly..

[whitedevil]

Could be caused by a seized piston thats been pressing on the disc causing it to get hot and warp. happened to my gpz and actually split the disc.

[Mattthebat]

Could be caused by a seized piston thats been pressing on the disc causing it to get hot and warp. happened to my gpz and actually split the disc.

 

Ouch!

Took it to another garage "general wear and tear " it's only intermittent at very slow speed under 5mph. Cheapest on eBay is £130

[Tango]

Bonniebird had this on her bike......just a sticking piston on the front calliper causing the pads to drag on the disk and overheating the disk itself. Also make sure that the calliper is floating OK....that'll do the same thing if it's not.

[Stu]

Bonniebird had this on her bike......just a sticking piston on the front calliper causing the pads to drag on the disk and overheating the disk itself. Also make sure that the calliper is floating OK....that'll do the same thing if it's not.

 

i dont think it will be floating with it been a rear?

to be honest i have never seen a floating rear but i could be wrong

[Tango]

Bonniebird had this on her bike......just a sticking piston on the front calliper causing the pads to drag on the disk and overheating the disk itself. Also make sure that the calliper is floating OK....that'll do the same thing if it's not.

 

i dont think it will be floating with it been a rear?

to be honest i have never seen a floating rear but i could be wrong

I thought all callipers floated? I'm sure the ones on my Trophy had movement in them......even the rear. The callipers do the same job whether front or rear and the floating allows the calliper to centralise on the disk so equal pressure is exerted on both sides of the disk by both pads.....otherwise the pressure on one side could distort the disk and cause warping and poor braking.

But I could be totally wrong.....

[lucky]

Hello

With out knowing who did the MOT,the swing on the brake tester or a run out figure....

An intermitant warped rear disc on an R1200GS could be:

A dirty caliper or disc, the pins seize in the caliper body. This is the most likely and cleaning the caliper will lessen the effect.

Do you have a pyramid hugger? or touratech? these apply pressure on the caliper when the pads are half worn also cause the caliper to drag after that. causing pedal fluctuation

The disc mounts could have corroded causing the disc to rise in one spot,

the disc carrier could have warped really unlikely but do check the carrier flange by the bolt holes for cracks. A fault reported by very few people on other forums.

or worse case the wheel bearing could have excessive play.

or just a warped disc

If you have servo assisted brakes please be aware that pre 2009 the system is calibrated for organic rear pads after that and on non ABS sintered pads are used.

But as its only an advisory item and you only feel it at low speed why change the disc if it has plenty of life left. measure the disc and compare that figure to the minimum thickness on the disk. i think its 4mm from memory.

If you do change the disc its worth noting that to do this you need to remove the rear wheel as the disc comes of that side.Then remove the plastic guard three torx 30 then the caliper. Then the 5 disc bolts are loctited in and the release temprature is 80 degrees.

The bolts are one time use ( according to BMW) and are accessable from the non exhaust side in a cut out/ dished section in the final drive just below the plastic mudguard.

You can only undo one bolt at a time hold the disc in place by selecting first as this will stop the rear wheel turning the engine has enough compression to stop the wheel turning.

The bolts are wheel torx 50, the brake disc is a torx 40 deep reach the caliper is torx 45. Im would reccomend covering the torx 40 with rubber hose so it doesn't mark the paint on the rear drive.

The disc bolts are done up to 33nm, the caliper to 23nm the wheel bolts are 60nm.

Sorry for the ramble

Hope it helps ran a GS for a while and picked up a few things.

Anything else just PM me

[Stu]

Bonniebird had this on her bike......just a sticking piston on the front calliper causing the pads to drag on the disk and overheating the disk itself. Also make sure that the calliper is floating OK....that'll do the same thing if it's not.

 

i dont think it will be floating with it been a rear?

to be honest i have never seen a floating rear but i could be wrong

I thought all callipers floated? I'm sure the ones on my Trophy had movement in them......even the rear. The callipers do the same job whether front or rear and the floating allows the calliper to centralise on the disk so equal pressure is exerted on both sides of the disk by both pads.....otherwise the pressure on one side could distort the disk and cause warping and poor braking.

But I could be totally wrong.....

 

ooops sorry i thought you was on about the disk

and no all calipers dont float mine are fixed front and rear

its usually single pot calipers that float as they only push on one side 2 pot or 4 pot calipers are usually fixed as the pistons centralise

[Tango]

its usually single pot calipers that float as they only push on one side 2 pot or 4 pot calipers are usually fixed as the pistons centralise

Ok...thanks for that Stu...that makes a lot of sense. I guess I'm basing it on my knowledge of older bikes that didn't have the sophisticated brakes of the more modern machinery.......

[Stu]

yeah a lot of the older bikes had floating calipers infact i even think some of the old 4 pots where floating too theres some strange set ups out there

i thought your bike was a newish one?

[Tango]

yeah a lot of the older bikes had floating calipers infact i even think some of the old 4 pots where floating too theres some strange set ups out there

i thought your bike was a newish one?

My Trophy was '97 which is the last time I tinkered with brakes (rebuilt the callipers because of a sticking piston)

My "new" one is '03.......and not touched that yet.....and hope not to have to either.....

[Stu]

my TL is a 97 model and has fixed brakes no slides to seize up anywhere

im guessing its down to manufacturer on what type of brake system they decide to use

anyway lets get this back on topic

so check for a seized piston or slides and possibly budget for a rebuild of the brake caliper

another thought is make sure the pistons in the caliper retract back when the brake pedal is released as it could be a collapsed brake line stopping the brake fluid flowing back

[Mattthebat]

Hello

With out knowing who did the MOT,the swing on the brake tester or a run out figure....

An intermitant warped rear disc on an R1200GS could be:

A dirty caliper or disc, the pins seize in the caliper body. This is the most likely and cleaning the caliper will lessen the effect.

Do you have a pyramid hugger? or touratech? these apply pressure on the caliper when the pads are half worn also cause the caliper to drag after that. causing pedal fluctuation

The disc mounts could have corroded causing the disc to rise in one spot,

the disc carrier could have warped really unlikely but do check the carrier flange by the bolt holes for cracks. A fault reported by very few people on other forums.

or worse case the wheel bearing could have excessive play.

or just a warped disc

If you have servo assisted brakes please be aware that pre 2009 the system is calibrated for organic rear pads after that and on non ABS sintered pads are used.

But as its only an advisory item and you only feel it at low speed why change the disc if it has plenty of life left. measure the disc and compare that figure to the minimum thickness on the disk. i think its 4mm from memory.

If you do change the disc its worth noting that to do this you need to remove the rear wheel as the disc comes of that side.Then remove the plastic guard three torx 30 then the caliper. Then the 5 disc bolts are loctited in and the release temprature is 80 degrees.

The bolts are one time use ( according to BMW) and are accessable from the non exhaust side in a cut out/ dished section in the final drive just below the plastic mudguard.

You can only undo one bolt at a time hold the disc in place by selecting first as this will stop the rear wheel turning the engine has enough compression to stop the wheel turning.

The bolts are wheel torx 50, the brake disc is a torx 40 deep reach the caliper is torx 45. Im would reccomend covering the torx 40 with rubber hose so it doesn't mark the paint on the rear drive.

The disc bolts are done up to 33nm, the caliper to 23nm the wheel bolts are 60nm.

Sorry for the ramble

Hope it helps ran a GS for a while and picked up a few things.

Anything else just PM me

 

Thank you very much for all of the above, I do have a pyramid hugger, this could be the prob, as you say I think I'll keep it on the thickness is well over 4mm , but I've got the details of how to change it now !

I'll do it in the spring I tink.

Cheers to all who helped !