Rear brake and/or ABS fault?

jacksdad63

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Hi, I'm having problems with the rear brake, cannot find the answers on here, so yet another ABS post :oops:
Bike: R1200GS, made on 11 Jan 2007, 0307, with option X0630, I-ABS Generation 2 brakes.
The rear brake has got about 5 inches of travel, then barely bites, but if also using the front brake, it feels very firm and works well. Rear pedal only, when moving I can literally stand on the pedal before I get a slight amount of stoppage!
If I pump the rear lever it does build up enough bite, today it only just passed the Mot, the tester said it was borderline though
On a 'normal' bike I'd say the rear brake cylinder is leaking inside, there's no external leaks and the system isn't losing fluid anywher.
Any ideas please?
Thanks, Mike
 
Is it servo brakes ?? If so have you checked the rear brake fluid level in the modulator ? The fluid level sensor might have failed (I’ve had it on a couple of customers bikes) so they’ll be no low fluid warning light on the instrument panel
 
I don't think its servo brakes. The build sheet shows the details as I posted. The front ABS sensor has got about 50 slots, each 6mm wide, which I think is the nos servo, as that has more like 100 'narrow' slots. It doesn't make any strange noises, there's just that rear lever travel and lack of power, unless the front brake is applied first.
Last documented brake fluid change was 16 years and 50k miles ago.....
Pads were changed 3,000 miles ago, EBC HH pads all round, they are coming up for renewal already! The last owner lived in London, must have been on the stoppers all the time!
Think a fluid change is needed, with the new pads, how would I go about doing a ful fluid change?
 
Last edited:
recco change is every 2 years... bleed the brakes and go from there - likely introduced air when pads were low / got changed

ABS 2 links front lever to the back brakes - which likely explains why it seems normal at time

FYI even when fully bled and no faults u get almost no braking from the rear - just activation of the rear ABS - drive the bike properly and its never on the road when slowing down so u can save wasting time getting a massage
 
Thanks again for the comments, I think first I'll change the fluid in the rear brake line and caliper. I had a quick look earlier, it's like gearbox oil...must be the stuff from that 2008 service for sure!
Can I just pump out the old fluid using the brake pedal, and topping up the resovoir, like a standard brake job?
If yes, I'll see how things go, but I'm wondering if a full fluid change is worthwhile, the bike is 17 years old, done 75k miles and no record of brake work other than pads change and that one fluid change so long ago, which could have just been a top up or worse!
 
There are quite a few videos on utube that might help you out. Such as this.

You're lucky you don't have the servo. I've never attempted mine with the servo, I'd rather pay someone else to do it.
 
usually you can just bleed the brakes like a normal person - suck old dirty crap from reservoir and fill with clean fresh fluid, tease brakes on and off to see if any air in master cyls wants to pop back in the reservoir...

get a flexi pipe and a tall container where the other end of the felxi pipe can sit in a bit of old fluid and an 8mm ring spanner -gently squeeze the brakes and then crack open the the bleed nipple... a tiny quantity of dirty fluid and maybe air comes out - then keep the lever the lever pulled fully in / down, and nip up the nipple, repeat about 4 times top up the reservoir and keep going till the clean stuff comes out - then tighten nipple fully

repeat on the other front caliper and move to the rear pedal - watch the joke reservoir that almost holds enough for about 1.5 pedal strokes

if that ends up with a crap feel on the lever and the pedal - u might need to try a proper bleed with diagnostic tools and running the ABS pump

your situation may end up more complicated - as no one bothered u may have an issue will corrosion in the master cylinders

if you find no trace of air and still have a nasty spongy feel - you may have ripped the master cycl seals running full stroke on a rusty bore.... brake fluid sucks up water and causes corrosion - add in budget junk to make components with and it ends in tears
 
Thanks again for the replies. I've had a look on YouTube, plus I've got brake bleeding tools I use in my jap bike restorations, so I'll change the fluid in the rear lines and see how it goes. I've craked open the bleed screw and pumped the lever a little, the fluid is like syrup! Hopefully that solves the fault, a nice easy job!
Ive rebuilt dozens of car and bike calipers over the years, hoping this job goes smoothly!
 
Today I've finally got time to work on the bike, I've changed the fluid in the rear brake, just pumped it through/topped up the pot, only used about 150ml of fluid, just kept going until it was clean: the stuff in the vacuum tool pot was filthy! Dark brown, and a few solids, I can't believe the bike has been dealer serviced from new, yet the brake fluid must never have been changed. Lots of BMW annual inspections and services, including fitting new pads!
I've not had time to ride it yet, I'm going to replace all the brake pads and change the front fluid first, then see how it stops, thanks again for the input :thumby:
 
Stahlbus: Does anyone know which thread I'd need for the 2007 GS? I can measure the fronts as I'm going to flush them, but don't want to do the rear again! :D
 
Motorworks in Huddersfield list them,
TIJ650 said:
…….and buy a GS-911 too. Know expensive, but handy for ABS bleed and other stuff 🤔
Click to expand...
I've found lots of ebay listings for Chinese GS-911, cost about £70, are these any use? I'd like to flush the entire brake/ABS sysytem to renew all the fluid, as despite the full service history I don't think its ever been changed!
 
Wouldn’t fuck with the Chinese ones. Up to you though.
I’ve used the GS911 abs bleed, but never noticed any difference afterwards. With my bike, the air somehow gets in the rear line. I bled 2 years ago and still fine. The speed bleeder worked well and is very good quality. Stahlbus also do a quick oil drain valve, but really don’t see point. 🤔
 
I won't be buying a Chinese GS-911: they don't work on Windows 10, they use XP...must be some very old junk!
Hoping to get out for a ride tomorrow, inbetween the monsoons :oops:
 
A quick update!
The rear brake is working really well now, took a few miles to get everything settled, now when I apply the rear pedal alone, there's still a bit extra travel than I'm used to, the brake does work well.
When I've applied the front brake lever alone, I press the rear pedal, and its almost solid, pressing it does increase the rear braking effort, but only a little....is this how the linked brakes work? Never had such a set up before, I've tried 'emergency' stop just with the front lever, it certainly slows down well :D
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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