Warped front disc

dippy · Oct 18, 2022

My front discs keeps in getting warped. With a new disc braking is perfect for the first 1000 miles then starts to feel like ABS is faintly kicking in then gets so bad over the next 2000 miles that it's difficult to use. I've had the calipers cleaned but no difference. 5 discs in the past 15,000 miles, taking the piss

I've booked it in with BMW proper this time but one question, 20,000 miles ago I changed the front fork springs for progressive ones. Suddenly had the thought that if I'd put the forts back on slightly out of alignment that it would cause this problem. Anyone think that could be the issue? And if so, how do I check as they "look" OK?

Or does anyone have any other idea why this would keep happening?

squibb34 · Oct 18, 2022

The fork question seems unlikely - the usual problem is overheating, maybe a dragging brake pad, which will normally leave witness on the disc face, along with some abnormal pad wear.

If you have stripped, cleaned & checked/renewed the seals in the callipers, then I'm wondering if this is the master cylinder piston failing to return cleanly. Presumably the ABS works as it should, with no codes showing.

Just occasionally, & I've only had this with a car, the actual hub surface can be distorted - in my case thought to be due to track day use by a previous owner.

dippy · Oct 18, 2022

Thanks for replying. Before I had the calipers cleaned one pad was nearly completely worn with the other quite fresh. I'm not sure the seals etc were done. From what you say then it would seem like the master cylinder could be at fault?
I dont know about the error codes, the place I used for any work has closed down and no way of finding out.

squibb34 · Oct 18, 2022

dippy said:
Thanks for replying. Before I had the calipers cleaned one pad was nearly completely worn with the other quite fresh. I'm not sure the seals etc were done. From what you say then it would seem like the master cylinder could be at fault?
I dont know about the error codes, the place I used for any work has closed down and no way of finding out.

Personally, bearing in mind that you seem unsure of what work was done on the problem calliper/s, I would start by removing them for a full strip down & check over. Park the MC idea for now.

This sounds like a sticking piston or slider pin that a simple external clean up may fail to correct. If yours, like mine, are Brembo, then rebuild kits are readily available for a sensible price.

This is simple DIY if you have the tools/skills/desire & frankly should have been checked when the first new set of discs were fitted.

Take care giving this to a dealer, unless they warranted the previous disc change in some way - it could turn out to be horribly expensive.

DJ123 · Oct 18, 2022

dippy said:
My front discs keeps in getting warped. With a new disc braking is perfect for the first 1000 miles then starts to feel like ABS is faintly kicking in then gets so bad over the next 2000 miles that it's difficult to use. I've had the calipers cleaned but no difference. 5 discs in the past 15,000 miles, taking the piss &#55357;&#56837;

I've booked it in with BMW proper this time but one question, 20,000 miles ago I changed the front fork springs for progressive ones. Suddenly had the thought that if I'd put the forts back on slightly out of alignment that it would cause this problem. Anyone think that could be the issue? And if so, how do I check as they "look" OK?

Or does anyone have any other idea why this would keep happening?

Are they OEM discs? Do you have the correct spacers/washers beneath or on top of the discs to make sure it is aligned correctly? If your wheel does not spin for 2(ish) turns without stopping you've got brake drag, and its most likely the disc is not sat where it should be.

The axel through the bottom of the forks will/should keep them square.

dippy · Oct 18, 2022

squibb34 said:
Personally, bearing in mind that you seem unsure of what work was done on the problem calliper/s, I would start by removing them for a full strip down & check over. Park the MC idea for now.

This sounds like a sticking piston or slider pin that a simple external clean up may fail to correct. If yours, like mine, are Brembo, then rebuild kits are readily available for a sensible price.

This is simple DIY if you have the tools/skills/desire & frankly should have been checked when the first new set of discs were fitted.

Take care giving this to a dealer, unless they warranted the previous disc change in some way - it could turn out to be horribly expensive.

thank you. yeah i know, piss poor that i dont know what work has actually been done! i've checked my receipts and it only specifies labour and as i said, they've, Bath road BMW, have closed now so cant ask them.

they are Brembo. i'll check out the rebuild kit. would this include a brake fluid change? that, i think, is beyond me

dippy · Oct 18, 2022

they would be OEM discs that i've used. the garage was an ex BMW dealer and kept half the staff and knowledge so i'd say they would have the spacer/washer all tip top. the wheel doesnt spin now due to the warping but was spinning fine with the new disc.

DJ123 · Oct 18, 2022

dippy said:
they would be OEM discs that i've used. the garage was an ex BMW dealer and kept half the staff and knowledge so i'd say they would have the spacer/washer all tip top. the wheel doesnt spin now due to the warping but was spinning fine with the new disc.

i would remove the discs and check what is on there vs what should be on there. If anything, for peace of mind knowing the discs mounting position is fine and the callipers are the next place to look.

squibb34 · Oct 18, 2022

dippy said:
they are Brembo. i'll check out the rebuild kit. would this include a brake fluid change? that, i think, is beyond me

Only to bleed fresh fluid through, into the callipers once checked & repaired - a one man job, but easier with two unless you have a vac system.

Here is the parts diagram - BMW list the repair seals & rubbers, but you may find Brembo far cheaper, particularly the discs: -

...... https://www.realoem.com/bmw/enUS/sh...72-BMW-F_800_GS_13_0B02,_0B12_&diagId=34_1665

Everything you need is available from Motorworks ........... https://www.motorworks.co.uk/parts/...-f800gs--09-2012---08-2016--86&sid=6RTBmYri7N

Micky · Oct 18, 2022

dippy said:
My front discs keeps in getting warped.

Or does anyone have any other idea why this would keep happening?

Because you keep using them :blast

140,000 miles on my 2008 F800GS on the original discs, 75,000 miles on the original pads ....

.... but yet dozens of tyres fitted

Use them hard and they'll warp ... but then that slows you down ...

:beerjug:

dippy · Oct 18, 2022

squibb34 said:
Only to bleed fresh fluid through, into the callipers once checked & repaired - a one man job, but easier with two unless you have a vac system.

Here is the parts diagram - BMW list the repair seals & rubbers, but you may find Brembo far cheaper, particularly the discs: -

...... https://www.realoem.com/bmw/enUS/sh...72-BMW-F_800_GS_13_0B02,_0B12_&diagId=34_1665

Everything you need is available from Motorworks ........... https://www.motorworks.co.uk/parts/...-f800gs--09-2012---08-2016--86&sid=6RTBmYri7N

Thank you for the info!

dippy · Oct 18, 2022

Micky said:
Because you keep using them

140,000 miles on my 2008 F800GS on the original discs, 75,000 miles on the original pads ....

.... but yet dozens of tyres fitted

Use them hard and they'll warp ... but then that slows you down ...

120,000 on my 2006 1200 and same discs so that's not the issue, 3000 miles, ok so maybe half is off road, is well below what they should last for

Halfa1200 · Nov 15, 2022

1.Check that the slide pins have not seized into the callipers.
2. If the pins have seized inside the calliper, remove them, clean them of the rust and grease the pins and inside the calliper but check that they slide backwards and forwards. If there is any play between the pin and the calliper, the calliper will twist and then lock preventing the calliper from releasing after you have released the brake leaver.
3. If there is any play you will need to replace the calliper and the slide pin.
I had to do this on my F700GS which I have from new. Brembo do not like using grease on their slide pins.
I find that the only grease that works is Copper Slip and I regrease them every 6 months.

dippy · Jun 30, 2023

so, eventually got round to cleaning callipers, thanks for all the advice by the way folks, much appreciated.
anyway, my first calliper clean and i was surprised at how little area there is to clean but brushed and spayed as much as i could. changed brake pads and disc. all back together and spinning showed that the disc was still catching in one area. finger against the fork and spin the wheel and yes, contact with finger lost at same place that disc catches.

so, and i can't believe i didn't do this first, took wheel off wife's 650 and put on mine, spun, and exactly the same thing, catching on a few centimetres.

I had booked it in to BMW but upon advice here i cancelled. so the problem is with the forks then. I'm guessing when i changed the springs to progressive ones that one fork is slightly out of alignment but one would think that the axle bolt would square that way right?

so from here i suppose I have to loosen all bolts on the forks, loosen axel bolt and see if i can get into a position that doesn't catch when spinning.

any thoughts folks?

RPMDAKAR · Jul 5, 2023

Unless the hub is actually machined out of line I cannot see that the forks should play any part in your problem, you swapped wheels right? did your wheel in her bike do the same? The only other suspect could be the wheel spindle (axle) if that's slightly out of true, but there again you would notice that when winding it into the fork leg surely?

dippy · Jul 5, 2023

RPMDAKAR said:
Unless the hub is actually machined out of line I cannot see that the forks should play any part in your problem, you swapped wheels right? did your wheel in her bike do the same? The only other suspect could be the wheel spindle (axle) if that's slightly out of true, but there again you would notice that when winding it into the fork leg surely?

Yes swapped wheels over. Well, put the wife's wheel in mine and used her spindle and the same catching seen. Yeah I don't get is, the physics of this doesn't seem possible. Surely if any part was out of alignment then the catching would be constant on the disc and not just in a small area

Oldrat · Jul 5, 2023

Are you a heavy braker?

If you’ve been braking hard and then leave your brake applied when stationery, the heat between the pad/disc dissipates at a much slower rate than the rest of the disc, and can lead to warping esp in floating discs.

dippy · Jul 5, 2023

no, not a heavy braker. but that wouldnt explain why my wife's wheel also catches

RedRick Esq. · Jul 5, 2023

Micky said:
Because you keep using them

140,000 miles on my 2008 F800GS on the original discs, 75,000 miles on the original pads ....

.... but yet dozens of tyres fitted

Use them hard and they'll warp ... but then that slows you down ...

I read an article ( cant find it) about warping discs becoming more and mor common on cars ( so i assume the same is for bikes)

First thing it said was that the metal used in the discs these days compared to years gone by is that is isnt as good - no doubt due to cost cutting / profiteering etc

But the other thing was that it is most common on automatic cars that rely on braking more to slow and then require the brake to be kept pressed to stop the car creeping forward as the discs heat up under the initial braking phase then that heat dissapates un uniformly through the pads and the rest of the disc the pads are not touching so in effect cooling a part quicker than the rest which causes warping

So on a bike comming off a motorway slip road as an example from 70 mph to a standstil then holding the bike on the front brake for a few seconds or longer could have the same effect ??

Of course that could be all bollocks

dean0n0 · Jul 5, 2023

Have you had a clock on them to see if they're running true? If there's any run-out it'll wear the high spots, not noticeable when new but a little wear will soon be felt and will only get worse.

Warped front disc

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