Rear brake fluctuations?

SPCK111

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Right, here’s a thing

Bikes first mot the other day 2016 GSA. Everything was fine apart from when tested on a rolling road the rear brake was showing flucations on the brake test dial. Quite a bit apparently. The bike shop checked everything and it all seemed ok.

Service carried out by BMW this weekend and I mentioned it to them. They did the same rolling road check and again the same fluctuations happened. They checked everything, for warped disk, pads, wheel and the lot and couldn’t feel anything on a test ride, nor could I for that matter.

Any ideas?

DKH
 
Did it Pass its MOT or fail on this point?
 
Passed fine. Didn’t even get an advisory. But shouldn’t be doing it. I’m a bit OCD about my vehicles.

I wouldn't worry about it.

Just make sure the discs are clean, get on with riding it :)
 
Yes well I will and do. It’s still under warranty and if there’s something wrong with it then it needs sorting. It also eats rear brake pads. Now I know they do anyway. I’m on my second set this year. Less that 1000 miles short of the service interval so I don’t know if that’s connected or now
 
Ok, so that's more information.....

It shouldn't eat pads at all. You should get 12,000 miles at least out of a set of rear pads.
 
Apparently the water cooled RT1200’s are the same. Mate of mine works on police bikes and he says they all do it

There’s a thread on here somewhere about the LC’s Going thought rear brake pads as a high rate
 
Well mine must be unique then, as they last at least 12,000 miles... and I use my rear brake all the time.

So maybe I'm just lucky.

But I also ride with toes on pegs and keep well away from rear brake pedal until I need it...
 
Well mine must be unique then, as they last at least 12,000 miles... and I use my rear brake all the time.

So maybe I'm just lucky.

But I also ride with toes on pegs and keep well away from rear brake pedal until I need it...

I very rarely use the rear brake alone. Only the front which with linked brakes used the rear as well of course

Heres that thread

http://www.ukgser.com/forums/showthread.php/32552-Brake-pad-wear?highlight=Brake+pad+wear

http://www.ukgser.com/forums/showthread.php/404136-Brake-pad-wear?highlight=Brake+pad+wear
 
Well I'm the opposite. I rarely use the front brakes.

I use engine braking mostly, occasionally front brake, slow control using rear brakes.

I wonder if my brake system pressurises differently then?
 
Ok..... so here's a wacky idea.

It seems that some people have this problem and some don't. What if it is to do with rider style, and how the linked brakes work.

A) I rarely use my front brakes. But I do use my rear brake a lot. I use it for slow riding, at every junction, stop sign, parking, manouvering etc. and I get great mileage out of my pads (12000 miles or more easily).

So when I dab my rear brake, it pressurises my rear caliper and applies the pads on disc. The system also applies a little bit of front brake as they're linked. But when I release the rear brake pedal, it depressurises the rear caliper and releases the pads from the disc. As it should.

B) You rarely use your rear brakes.... and you get very poor mileage out of pads and discs.

So when you apply the front brake, it pressurises the front calipers and applies the pads to the discs. It also applies the rear pads to the discs. But when you release the front brake lever.... I wonder if the rear pads are left engaged, and not released quickly. So now they drag for a while... wearing out the pads and discs unnecessarily.

It might be resolved by dabbing your rear brake pedal to pressurise the caliper and then releasing the pressure as the rear brake pedal comes back to position? Releasing the pads from the disc.

Just and idea... and maybe a flaw in the system which can't easily be detected due to this weird condition...
 
Using the rear brake only, does not activate the front brake, but using the front brake only will activate the rear. That is my understanding of how the linked braking system works on the GSs. I also think that the OPs rear pad wear is extremely excessive.

I changed my pads on my 15 GS at 14,000 miles, and they were still less than half worn. Most of my riding is in the mountains and on country roads, so using the brakes more than motorways for instance.
 
Well I'm the opposite. I rarely use the front brakes.

I use engine braking mostly, occasionally front brake, slow control using rear brakes.

I wonder if my brake system pressurises differently then?

I'm the opposite to you and rarely use the rear in isolation.

I changed the rear disc and pads on my last one at 29k miles and they still ok when it was stolen at 33k. I bought the bike with 13k on the clock so may have had a pad change before I got it.

It is weird that there is such wide variences in people's experiences.
 
Ok..... so here's a wacky idea.

It seems that some people have this problem and some don't. What if it is to do with rider style, and how the linked brakes work.

A) I rarely use my front brakes. But I do use my rear brake a lot. I use it for slow riding, at every junction, stop sign, parking, manouvering etc. and I get great mileage out of my pads (12000 miles or more easily).

So when I dab my rear brake, it pressurises my rear caliper and applies the pads on disc. The system also applies a little bit of front brake as they're linked. But when I release the rear brake pedal, it depressurises the rear caliper and releases the pads from the disc. As it should.

B) You rarely use your rear brakes.... and you get very poor mileage out of pads and discs.

So when you apply the front brake, it pressurises the front calipers and applies the pads to the discs. It also applies the rear pads to the discs. But when you release the front brake lever.... I wonder if the rear pads are left engaged, and not released quickly. So now they drag for a while... wearing out the pads and discs unnecessarily.

It might be resolved by dabbing your rear brake pedal to pressurise the caliper and then releasing the pressure as the rear brake pedal comes back to position? Releasing the pads from the disc.

Just and idea... and maybe a flaw in the system which can't easily be detected due to this weird condition...

The rear brake pedal applies the rear only.
The front brake lever applies the rear brake first then the front brake.
If an average rider uses only the front brake, and does not touch the rear brake, the brake usage count will be around will be around 1.5 to 2 times that of the front. you can check all this and more on a Nav 5 or 6,.
If one rides in town a lot and use the front softly you are probably using mostly the rear and not knowing it.
 
Ah good info everyone.

That might explain it then. If you're constantly dabbing the front brake, triggering the rear calipers all the time.

Or the master cylinder, or ABS pump is faulty creating a slight pressure on the rear calipers when there shouldn't be?
 
Why do so many GSs develop large amounts of travel in the rear brake lever? Both bikes I've had have done it. The dealer will bleed it and it will be OK again for a thousand miles, then I notice the travel is starting to increase again.
 
Why do so many GSs develop large amounts of travel in the rear brake lever? Both bikes I've had have done it. The dealer will bleed it and it will be OK again for a thousand miles, then I notice the travel is starting to increase again.

strange,both mine have never done it:nenau
 
I remember reading on here recently, that one bike that was suffering premature brake pad wear in the rear was finally pinned down to the calliper being out of alignment. My last GS did not suffer from excessive pad wear, but it did suffer from the rear brake requiring bleeding routinely.
I tend to use my brakes together, with the exception of slow speed balance, where normally rear only as required.
 
Glazed rear disc?... get some 1200 grit on it and removecd any glazed areas... used to happen on older stuff where its got too hot etc ... if your rerar pads are rubbing, it will be getting hot for sure :)
 


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