Brake System Flush | 48K Mile Service - Part 3

[Lee]

Could that be because the servo type brakes had separate systems, the wheel circuit and the actuating (?) circuit? The new system runs from master cylinder through the ABS unit and to the calipers (I am pretty sure).

Frank

I believe that's the reason.

[Grumpy Goat]

Sure as heck can't do any harm to follow the steps recommended by the GS-911 people!

Agreed. Works a treat and if anything just uses up more brake fluid, which is inexpensive anyway. Considering what its function is, we should do this service annually at least.

[Grumpy Goat]

This was done on the older Servo ABS bikes. BMW does not call for it on the newer bikes but I still do it to exercise the ABS pump.

And that is a very good reason in itself. Unless you have a panic stop every now and again, you don't really know that it is in working order. Exercising it at least annually can give good peace of mind, if nothing else.

[Grumpy Goat]

The new system runs from master cylinder through the ABS unit and to the calipers (I am pretty sure).

That is my understanding also. All brake circuits (front and rear) pass through the ABS pump, although unless ABS is activated it is probably a passive thing. Here is a nice diagram.

[mspratz]

My hose is very tight.

That's enough of that kind of bragging. This is a family forum!

[BobAin'tStoppin']

Is there a separate bleed fitting on the abs unit? I just bled my brakes and the lever is quite soft. Used the harbor freight vacuum kit. It works well, but no air came out. Haven't got a ride in yet to confirm that the bike will stop properly. Lever has been soft since new. My new Himalayan has a great lever feel. Very firm. But the front brake is kind of a joke. Four fingers if you really need to stop.

[Duckbubbles]

Is there a separate bleed fitting on the abs unit?

I've had the tank off several times and did not see any bleed nipples on the ABS module. The brake bleeding instructions also does not say anything about bleeding at the ABS module.

Frank

[BobAin'tStoppin']

Thanks for the info. Saves me taking off the tank to check. Every BMW I’ve had with abs has spongy lever feel. Guess I’m used to it at this point.

[Grumpy Goat]

Thanks for the info. Saves me taking off the tank to check. Every BMW I’ve had with abs has spongy lever feel. Guess I’m used to it at this point.

Lee said that it was the LC boxers that had such a feel to the brake, although I am not sure why that would be. I can attest that my S1000R with ABS has a completely different feel. Nothing spongy about it and the progressive braking range is much shorter. Some (including the previous owner) think it is "grabby".

[Lee]

Thanks for the info. Saves me taking off the tank to check. Every BMW I’ve had with abs has spongy lever feel. Guess I’m used to it at this point.

Lee said that it was the LC boxers that had such a feel to the brake, although I am not sure why that would be. I can attest that my S1000R with ABS has a completely different feel. Nothing spongy about it and the progressive braking range is much shorter. Some (including the previous owner) think it is "grabby".

It's hard to describe, it's almost like there's a little too much free-play in the lever.
A longtime master tech I talked to after buying the bikes was also confused why the Wetheads had a different feel to the brakes. He was not a big fan of the feel.

I don't mind grabby. I'm one of the few who liked the feel of the older Servo ABS brakes.
You got instant results with those

[Grumpy Goat]

It's hard to describe, it's almost like there's a little too much free-play in the lever.
A longtime master tech I talked to after buying the bikes was also confused why the Wetheads had a different feel to the brakes. He was not a big fan of the feel.

I don't mind grabby. I'm one of the few who liked the feel of the older Servo ABS brakes.
You got instant results with those

I'm with you on that, i.e. the preference for a high firm feel. I can still feather the brakes with that but when you have two different bikes with different brake feels (?) feathering can be a bit of an eye opener, especially when going from one bike to the other, progressive to firm.

[Duccrazydave]

I remember the first encounter I had with BMW servo brakes. Was at my dealer in Charlotte for some Ducati parts. As was always the case, I took a Beemer out for a demo ride. Not sure what year, but it was an RT. Wonderful ride and great brakes. Upon returning, I was backing the bike (downhill) into the parking spot. Killed the ignition, then had quite a scare when I lost the normal feel at the lever!
Just like a car. No run, no assist.


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[Olgry1]

Is there a separate bleed fitting on the abs unit? I just bled my brakes and the lever is quite soft. Used the harbor freight vacuum kit. It works well, but no air came out. Haven't got a ride in yet to confirm that the bike will stop properly. Lever has been soft since new. My new Himalayan has a great lever feel. Very firm. But the front brake is kind of a joke. Four fingers if you really need to stop.

I have had luck in the past bleeding the master cylinder to firm up the brake lever.

To do so you remove the lid on the master cylinder. Then very SLOWLY you squeeze the ball on the very end of the brake lever with your right pointer finger. If you squeeze the brake lever too quickly brake fluid will shoot out of the reservoir and get on your painted surfaces.

After you have squeezed the brake lever almost as firmly as you can you want to slide your pointer finger off the ball at the end of the lever. The lever will quickly spring back to it normal position and in that process will send a "shock" through the brake line. You then repeat this process a few times over the next minute or so. Sometimes you will see bubbles immediately as you slowly begin to repeat the process. You then wait 5 or so minutes to let air bubbles move through the system and up to the master cylinder.
After the five minutes or so you then once again slowly squeeze the brake lever and look for bubbles flow out of the brake line into the master cylinder.

You continue the process until the air bubles get so small you can hardly see them flow out of the brake line into the master cylinder.

[Grumpy Goat]

I have had luck in the past bleeding the master cylinder to firm up the brake lever.

To do so you remove the lid on the master cylinder. ...

Sounds interesting. Couldn’t hurt I suppose. I will try this tomorrow before the garage gets too hot.


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[BobAin'tStoppin']

Brake lever feel: I've had the whole gamut over the years.
≥≥ Kawasaki H-1 had drum brakes. Instant fade to no slowing down. That one was pretty scary.
≥≥ Yamaha RD350 was my first bike with a disc on the front. What a revelation. Can't remember the feel of it, but the stopping power was awesome.
≥≥ /5 bikes had pretty mediocre drums with a firm feel
≥≥ Wifey had a 1200 monster city with a nice firm feel to the front.
≥≥ Yamaha TDM850 had premium hardware all around. Nice feel.
≥≥ Yamaha FJ-09 was ok, as was Guzzi Breva
≥≥ R1100RS, R1200GS, F800ST, R1200R, R1200RS all spongy feel but the bike stops fine. They just don't bleed out to firm for me.
≥≥ My new Royal Enfield Himalayan has a very solid feel but the front brake is like wood. Needs a four finger grip if you want to stop in a hurry.