Snatchy front brakes R1150GS

[(RIP) Bin Ridin]

Have noticed that at low speed with light brake applied, the front brake works unevenly - i.e. the bike slows in pulses. Annoying when filtering.
Tried cleaning the discs with white spirit, no difference. Any ideas, please?

 

[Warthog]

I'm new to 1150GS's so I know nothing about ABS systems regarding symptoms if they go wrong, but any ABS issues aside, that sounds very much like a warped brake disc.

It seems likely that a slight warping would show-up more under light braking at slower speeds, as the bike has less forward momentum.

As I said, I'm no expert on BMW gremlins and diagnoses but if I was given that symptom on any other bike, warped discs would be my first guess. Other possibilities might be warn head bearings, or wheel bearings perhaps (Do GS's even have conventional head bearings??)

Hope this helps!

 

[Mzokk]

Sounds like a warped disk or disks. These bikes seem to be prone to it Mike O had several sets replaced under warrenty. I recon its because the disks are solidly mounted instead of floating and the calipers are prone to seizure unless cleaned regularly. A seized or semi seized caliper will overheat the disk which may lead to warping.

 

[wessie]

Have noticed that at low speed with light brake applied, the front brake works unevenly - i.e. the bike slows in pulses. Annoying when filtering.
Tried cleaning the discs with white spirit, no difference. Any ideas, please?

My 30,000 mile R1150GS has been doing this for a good while. Very slight pulsing at low speeds. No noticeable effect when braking heavily.

At the 24k mile service the BMW technician reported a warped disc but it had passed an MOT the week before so I didn't get it fixed. It has passed another MOT since and has not got any worse so I ignore it now. I'll probably get the disks replaced next time the pads need changing.

 

[(RIP) Bin Ridin]

Thanks guys, food for thought.

 

[(RIP) Kaister]

when bought my bike, i thought i had the classic 'warped disc' feel.

Tuned out the front m/c had been dripping on the caliper / disk and causing an on/off feel.

I emptied a can of brake cleaner degreaser over the whole lot and fixed the m/c cylinder seal.

all sorted

 

[sproggy]

At the 24k mile service the BMW technician reported a warped disc but it had passed an MOT the week before

A slightly warped disk wouldn't cause an MoT failure as long as the brake effectiveness wasn't affected. Still makes a bike unpleasant to ride, though, and is best replaced if it bothers you.

There is a safety issue relating to warped disks - the runout can knock the pads (and therefore pistons) back in the callipers so that when you apply the brakes nothing appears to happen since the first application is just taking up the slack that the warped disks have knocked into the system.

The amount of warp that would cause 'a slight pulsing' probably wouldn't have this effect, though.

 

[wessie]

The amount of warp that would cause 'a slight pulsing' probably wouldn't have this effect, though.

ding

 

[cookie]

A slightly warped disk wouldn't cause an MoT failure as long as the brake effectiveness wasn't affected.

it's a bit subjective what "slightly warped" means.

my MOT place will let "slightly warped" discs pass with a warning to sort it before next time.

"slightly more warped" & they fail.

 

[(RIP) Bin Ridin]

I am more inclined to think it is a disc contamination issue, will try proper brake cleaner.
What happened to carbon tet, can you buy it anywhere?

 

[cookie]

buy a tin of brake cleaner. useful stuff.

i doubt that's your problem though.

 

[Taipan]

I have this issue on my 03 Rockster which has servo brakes. Does your bike have servo brakes? If so its probably actually the rear brake grabbing.

Apparently, its the rear caliper on the combined brake circuit getting its reduced feed of pressure. The caliper pins are dirty enough to stop a smooth action and it feels like the brakes are grabbing. Try adding rear brake pedal pressure and see if that cures it.

On the advrider site there has been a lot of stuff written about this. Lots of people denied it, saying their pins weren't corroded enough for this to be the problem. Some even saying theirs were mint. But after following the extreme caliper cleaning procedure in this PDF they found out it was cured!

I havent got round to doing it yet and just add rear brake pedal pressure to counter it. So cant actually vouch for it myself. But many have tried it with good results. Worth a try?

 

[Mzokk]

Um...good article but I'd use fine sandpaper to de glaze the disks rather than wet and dry. Might be wrong but someone once told me once that wet and dry has a small amount of oil in it and not to use it to de glaze disks or pads? Anyone else heard this?