by-passing ABS on 1150 GS
 

Hi,

I have an 1150 GS which has a non-functioning front brake. I want to fit a new front master cylinder, and run two brake lines directly to the calipers. This will be a temporary fix, so I don't need to hear that it's dangerous/breaks warranty/stupid/etc (unless it really is stupid!).

I would like to make the workaround as simple as possible, so by-passing the ABS reservoir and by-passing any brake system junctions (ie, where a single hose goes to a t-junction and splits to two hoses onto the calipers).

Not being a BMW person, is there any weirdness that would prevent this?

cheers,
Doug

Brakes
 

If it is a servo model you can get the linkage piece from a non servo model and use a bm master cylinder no probs bypassing the servo. Have a look on ukgser.com there is a write up detailing this process.

Have you found why the front brake doesn't work? I very much doubt an ABS fault on a non-servo model would do that. it will always fail back to a non-ABS system. If it's just the calliper or master cylinder, just replace and bleed and the ABS sorts itself out.

If you have got some weird ABS related issue, then a straight master to slave connection just like any other bike will work.

If it's a servo bike it'll still work but I've no idea what the feel and brake distribution would turn out like.

BTW, if you are in the UK, partially removing an ABS system isn't legal. To be 100% safe insurance and MOT/VOSA wise either fix it so the ABS works or remove the lot and tell your insurance. Chances are none of this will make any practical difference but I'd hate for circumstances to leave you in trouble on that score.

Andy

cheers guys. the bike is not in europe, and I'm just trying to have a worst case get-me-going idea in my head. it's just temporary, until someone who knows bm's can look at it.

cheers,
Doug

Doug

My Servo-ABS pump failed while I was in Dubai, and cost too much to replace and could not be fixed by BMW. So I removed it and linked my brakes direct like a non-ABS model.
The bike's brake ability is the same as with Servo, no change, in fact, it is better now, I have more feel from the brake than with Servo, especially on low speeds.
I used standard braded hoses made by a motorcycle custom shop (Not BMW), cheaper than BMW. Use the same brake pads, master and brake cylinders, no change need for those, just get a brake hose company to make up the hoses and links, easy.
The wiring was a challenge, as I had to bypass some wiring to get the tail light and brake light working. I also had to add change-over relays on the brake light circuits to make the brake light work. Let me know if you like to know the details of how to wire the tail light after you removed the Servo-ABS pump, I made a diagram that will give you an idea how to do it.

It was my rear brake circuit that failed.
My bike is a 2002 GSA.

Good luck
Johan

hey,

OK, so I have the bike now. It seems just fluid loss from the master cylinder, and no damage. topped up with fluid, bled at the ABS unit and all seemed ok.

After a test ride, the front brakes gradually locked on. It seems the pistons don't return properly. I took the calipers off and it's all a bit dirty, and the pads are rusted. The pistons could be moved (carefully) using a screwdriver to lever them back, so they are not seized solid. when they are locked on, releasing some fluid releases the calipers grip on the discs. this also points to the pistons not being seized. the fluid coming out of the calipers is jet black, like old engine oil.

I decided to free them off, and then just not use the front brake till I get to Morocco and the BM shop in Casa. There's not much traffic on the roads here, so it's fine using the rear only.

That was all going swimmingly well, until the front locked up all on it's own while I was zipping along the road. This happened a couple of times, over 600 miles.

It seems to me that pressure is somehow building up and the half-release that should happen in the system (to pull the pads back a fraction) isn't happening.

Any ideas?

Mine did the opposite, no brakes on the rear system. After it was bleeded and checked by the dealer twice, it was ok for about 100km or so, then again the same problem. I did not want to get stuck with this problem further on the road, so opt to remove it. I hope you get yours sorted out.

Johan

so, the brake problem is now fixed. And erm, user error would be a fair description. Now dealing with a clutch issue, so forgot to post the fix incase anyone else suffers from a bout of stupidity :-)

the bike was involved in a spill, landing on the right-hand side. All the fluid leaked out of the master cylinder, which I replaced and bled at the ABS unit. Initially all seemed fine, but very soon I got the problems.

The symptoms I had (post-spill) were the brakes locking solid after about 5 times of using the front brake lever. In addition, three times in 3000 miles the front brakes came on by themselves while riding at 60-70 mph. Once they came on, they were locked solid. I opened the bleed valve on the caliper to release some pressure, and the brakes freed up.

A pint of beer to anyone able to spot the problem...

I have no experience of BMW's, let alone their braking system. Everyone I have spoken to about BMW brakes (on an 1150 GS) has said not to touch them as they are too complicated, and ABS/brake problems must sorted by a dealer.

I am used to Japanese bikes and brakes, and have stripped and cleaned many a caliper. So I do sort of know what I'm doing. And I got a bit carried away with the complexity of it all, and made some assumptions.

the cause turned out to be, the front hand-guard had rotated a little and the groove inside the hand-guard was no longer lined up with the lever. This means the lever was depressed ever so slightly. So, rather than riding without brakes, I was riding with brakes constantly!

so, I have re-learned not to jump right into the very complicated diagnosis and making too many assumptions. And to solve problems, you really should start at the beginning.

what an idiot... :-)

Live and learn! I've heard of bar muffs doing this, both on brake leves (poor fuel economy) and clutch levers (lack of speed, siezed two stroke).

Andy

It's the human condition; we always expect the worst problem. I've had the same issue with a hand-guard. How many times have you watched someone struggling to start a bike only to find that either they were out of fuel or it's turned off, or that the run-stop button was activated.:confused1: