R12S Rear brake issue

BillA · 07-18-2007, 05:53 AM

Has anyone had a problem with the rear brake on an R12S
with ABS?

In particular the amount of force required on the brake
lever. Initially the force was a little higher then I
expected. I assumed it was designed that way because of
the high compression of the motor. (resulting in lots of
engine braking) As time when on the force required
became larger. At about 10K miles holding the bike at a
stop on a small hill became almost undoable. I then
tried bleeding the rear brake and the problem went away,
for awhile. Now with 11.2K miles the problem is back.

I have swapped bikes with another R12S and I would guess
that I have to push 10 times harder. That only works up
to a point and then I get no additional braking no
matter how hard I push.

Have Fun, BillA.

tomn · 07-18-2007, 06:18 AM

Did you think about a visit to a dealer.

BillA · 07-18-2007, 06:24 AM

It is scheduled for next week.

Bob Hancock · 07-18-2007, 07:23 AM

Hard to say other than trapped air in the line. I'd take it to the dealer for sure. Mine is doing fine, now at about 5,000 miles, fwiw.

ktmduke · 07-22-2007, 05:19 AM

Yes, I have the same problem ... I put it dpown to an ABS idiosyncrasy, as it is only really apparent at low speeds ... at higher speeds it seems better (not perfect but better).

I would be interested in what your dealer has to say ... I have a particular 'communication' problem (really) with my dealer ... as I do not speak enough German to fully explain the problem and I live in Zurich, Switzerland.

By the way, I just completed the 4 day Centopassi event (www.centopassi.com) in the Italian & Slovenian Dolomites ... the only R1200S to do so....it performed fine over dirt, gravel, hairpin cobblestone bends and of course the fast sweepers....who says you need a R1200GS

English · 07-23-2007, 08:13 AM

I got my '07 R1200S with 1,700 miles on it. It's always had virtually no back brake. That makes it quite difficult on full-lock turns and holding still at lights.

It's due for it's 6,000 miles service now so I'll get them to take a look at it then.

We did try pressure bleeding it a little and it seemed to make no difference. Personally, I can't see that this can be a problem that could be cured with bleeding. It would seem to suggest frozen pistons to me, but I can't see how that could be possible on such a new bike.

BillA · 07-23-2007, 06:06 PM

English,

Sounds like your symptoms are exactly what I am experiencing. As I stated I
thought it was inherent in the design.

I agree that bleeding (looking for air) should have no effect. BUT, After I
bled the rear I got additional/proportional travel in the brake lever and a
working rear brake. (only later to have the symptoms return.) I have done a
little looking on the net and there are a number of approaches to ABS. Some are
pumps (heavy, assume that this is not used) some store fluid under pressure and
release pressure as needed. Just speculation, ABS issues??? (Since it has
lasted longer than four hours, guess it should see a doctor)

Bike goes in tomorrow.

Keep in touch.

Have Fun,
BillA.

English · 07-25-2007, 08:45 AM

Hey Bill, what was the verdict when you took your ride in?

Alan.

BillA · 07-29-2007, 04:37 AM

The Bike is in the shop and they agree that there is a problem.
At this point there are no fault codes. We are waiting to hear back from BMW.

Have Fun,
BillA.

flash1034 · 07-29-2007, 10:29 AM

Please let us know. My rear brake sucks too.

Flash

BillA · 08-03-2007, 06:43 PM

Got the bike back from the shop and all seems fine. Not exactly sure what was done but lots of brake and not a pressure required. I am leaving Saturday morining for a trip to Cape Brenton for a couple of weeks. If the repair holds up, I'll find out what they did and pass on the information.

Have Fun,
BillA.

English · 08-03-2007, 07:51 PM

Great. I'll be waiting for what they did.

Alan.

ktmduke · 08-13-2007, 10:43 PM

any update on what they did Bill ? ... a few of us have the same issue and would appreciate the information

English · 08-13-2007, 10:48 PM

Quote:

Originally Posted by ktmduke

any update on what they did Bill ? ... a few of us have the same issue and would appreciate the information

Oops, I forgot to update on this. They fixed mine at the 6,000 miles service on Friday (quoting from the service ticket):

Caused by brake master cylinder loose - not able to function with return spring.
Checked for faults - none - removed and reinstalled pads and caliper - bled rear brakes - reattached master cylinder - problem solved.

Dr. Curve · 08-14-2007, 02:03 AM

You should be able to lock up the rear at any time.........unless the ABS is on. Check your pad surface for glaze, or evidence of oil smudge. Check disc and clean both their surface and the surface of the pads with acetone or strong alcohol. Bleed of course. Change to Dot 5.1 (non-silicon) brake fluid if you wish. It is especially for ABS, and resists water absorption much better than dot 4 fluids, while having a wider working range of temperature range as well. Trail braking in the mountains is how a lot of us old people run in the switchbacks..............so that rear should always be ready to grab.

throttlemeister · throttlemeister's Garage

Quote:

Originally Posted by Dr. Curve

Trail braking in the mountains is how a lot of us old people run in the switchbacks..............so that rear should always be ready to grab.

Not if you have a rear brake like the one on my R11S.. It only has two options: no brake and full lock. Fortunately, I don't use it in switchbacks (but I did learn how to do it, and it does work well) and it's pretty much useless when braking hard on the front anyway, but still.

More on topic: can you just home-bleed the brakes on the R12S with ABS? I don't have the manual for the R12S, but I do for the R12RT and that bike is basically impossible to bleed at home without special tools from BMW and even then you still need a dealer visit to reset the computer to allow the ABS to go active again.

Dr. Curve · 08-14-2007, 06:58 AM

Do you need a dealer reset even if the key has never been turned on during the whole bleed operation? I was not aware of that.

throttlemeister · throttlemeister's Garage

Like I said, I don't know about the S. Since the caliper is only half the system with ABS and you also need to replace fluids and bleed the ABS unit. On the RT touching the brake system means the computer goes into error and disables the ABS until reset.

Dr. Curve · 08:53 PM

Throttlemeister, and others. I do not believe that you need to have a factory readout to bleed the new, non-servo type, ABS brake systems on the new R12S Bikes. I bled mine........and it bled just fine. No readout Faults. Strong hard grip at lever, "same as it ever-was, same as it ever-was....." and as we all know, the new twin has got the grippers and great control. Just remember.......the reservoir cap requires a special BMW tool to be removed.........don't do the brakes unless you note the cap's different ness...........ahead of time.

throttlemeister · throttlemeister's Garage

That's good to know. Wonder why they made such a weird and annoying procedure on the RT.