05 rear brake issue question. - BMW R1200GS Forum : R1200 GS Forums
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post #1 of 13 (permalink) Old 23-Apr-2019, 01:42 PM (779) Thread Starter
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Question 05 rear brake issue question.

How far should I have to push down on rear brake pedal to get any noticeable braking? I can get the servo to kick in and actually lock the rear up on gravel but it’s about 3/4 thru the full foot pedal stroke. This is a new to me GS with less than 11k miles. The rear brake was very low on fluid when I got the bike and was not working. I just serviced all the brakes. I pulled all the brake calipers from mounts and removed pads and checked. Plenty of meat left in all of them. They hardly look worn. I cleaned calipers and the pins with brake cleaner. Cleaned up pins with a bit of sandpaper and lubed with anti seize. I coated the back of pads with anti squeal and reassembled. I flushed per Jim's excellent DVD's. Tested using GS911 brake bleed test and the rear failed. Bled the circuit and the calipers again. This time I got them to pass but I had to really push HARD on the rear brake pedal. Front passed as well but I had to pull lever really hard to get it to pass.
Took for a test spin. Fronts grab hard and fast with little movement. Rear you have to depress the brake pedal quite a ways but at the end of a long downward foot pedalstroke it will grab hard enough to skid and engage ABS. So my question is, should I have to push that far down on rear brake to get it to grab hard? It begins to slow a bit as soon as you engage but to get it to stop you have to almost bottom out the foot pedal.

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post #2 of 13 (permalink) Old 23-Apr-2019, 03:04 PM (836)
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Sounds like there is still some air in the line. I like to use a large syringe and push fluid through from the caliper back to the master cylinder. It's not unusual to have an issue getting the lines bled right from time to time. If you are confident that you have it bled properly then you may have a problem with the MC.
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post #3 of 13 (permalink) Old 23-Apr-2019, 04:27 PM (894)
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Originally Posted by Crawgator View Post
How far should I have to push down on rear brake pedal to get any noticeable braking? I can get the servo to kick in and actually lock the rear up on gravel but it’s about 3/4 thru the full foot pedal stroke. This is a new to me GS with less than 11k miles. The rear brake was very low on fluid when I got the bike and was not working. I just serviced all the brakes. I pulled all the brake calipers from mounts and removed pads and checked. Plenty of meat left in all of them. They hardly look worn. I cleaned calipers and the pins with brake cleaner. Cleaned up pins with a bit of sandpaper and lubed with anti seize. I coated the back of pads with anti squeal and reassembled. I flushed per Jim's excellent DVD's. Tested using GS911 brake bleed test and the rear failed. Bled the circuit and the calipers again. This time I got them to pass but I had to really push HARD on the rear brake pedal. Front passed as well but I had to pull lever really hard to get it to pass.
Took for a test spin. Fronts grab hard and fast with little movement. Rear you have to depress the brake pedal quite a ways but at the end of a long downward foot pedalstroke it will grab hard enough to skid and engage ABS. So my question is, should I have to push that far down on rear brake to get it to grab hard? It begins to slow a bit as soon as you engage but to get it to stop you have to almost bottom out the foot pedal.
I have an 06 Goldwing NON AB's and at 180K I had sorta soft brakes...Removed took apart and cleaned all calipers, two master cylinders and the hand brake And of course replaced all rubber pieces except the lines as I went. Why? Great shape and they dont move like all the other small rubber pieces. I have been rewarded with beautiful brand new feeling brakes. Dont know anything about the ABS module (?) on your 05 but if its got rubber bits in it I'd send it out and freshen it up too.
Thats my advice for your super low mileage 14yr old 05.
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post #4 of 13 (permalink) Old 24-Apr-2019, 07:19 AM (513)
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Quote:
Originally Posted by Crawgator View Post
How far should I have to push down on rear brake pedal to get any noticeable braking? I can get the servo to kick in and actually lock the rear up on gravel but it’s about 3/4 thru the full foot pedal stroke. This is a new to me GS with less than 11k miles. The rear brake was very low on fluid when I got the bike and was not working. I just serviced all the brakes. I pulled all the brake calipers from mounts and removed pads and checked. Plenty of meat left in all of them. They hardly look worn. I cleaned calipers and the pins with brake cleaner. Cleaned up pins with a bit of sandpaper and lubed with anti seize. I coated the back of pads with anti squeal and reassembled. I flushed per Jim's excellent DVD's. Tested using GS911 brake bleed test and the rear failed. Bled the circuit and the calipers again. This time I got them to pass but I had to really push HARD on the rear brake pedal. Front passed as well but I had to pull lever really hard to get it to pass.
Took for a test spin. Fronts grab hard and fast with little movement. Rear you have to depress the brake pedal quite a ways but at the end of a long downward foot pedalstroke it will grab hard enough to skid and engage ABS. So my question is, should I have to push that far down on rear brake to get it to grab hard? It begins to slow a bit as soon as you engage but to get it to stop you have to almost bottom out the foot pedal.
The way I read your symptom, it sounds like you get a nice solid feel from the pedal when it finally gets down far enough to do anything. This strikes me as a linkage issue rather than air in the lines, which tends to create a soft, "spongy" feel to the brake.

The linkage is not adjustable in the sense that you can set the pedal height to fit you, but there is an adjustment whose function is to assure that the master cylinder starts pressurizing the control circuit once the pedal's been depressed a wee small bit from its resting position (against the stop). See this thread on ADV Rider, in particular post #8. It is said to be a delicate adjustment and there's no reason for it to have gotten mucked up, but... if you check and find there is a lot of slop in there (that is, you find lots of play between pedal and stop), get your 2.5mm feeler gauge and try the procedure.
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post #5 of 13 (permalink) Old 24-Apr-2019, 08:44 AM (572) Thread Starter
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Yes sir you are correct! Another thing I have noticed after I did a test in the garage. Key on but engine off, I get a whine from servo as soon as the contact point is broke on the sensor for the pedal. BUT! I do not get active assist from servo until much further down, you can hear the tone change in the servo as I get further down and spinning the tire by hand I can feel the resistance as I get further down. I have the tank off and am planning on bleeding one more time. I have had it sitting in the garage overnight with a weight on the rear brake pedal. I'll check out the adjustment you linked to.

Based on this, am I to assume that I should be getting more brake much sooner? I do not have another bike to compare to and my last BMW with servo was an 05 RT 8+ years ago.

Thanks!

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The way I read your symptom, it sounds like you get a nice solid feel from the pedal when it finally gets down far enough to do anything. This strikes me as a linkage issue rather than air in the lines, which tends to create a soft, "spongy" feel to the brake.

The linkage is not adjustable in the sense that you can set the pedal height to fit you, but there is an adjustment whose function is to assure that the master cylinder starts pressurizing the control circuit once the pedal's been depressed a wee small bit from its resting position (against the stop). See this thread on ADV Rider, in particular post #8. It is said to be a delicate adjustment and there's no reason for it to have gotten mucked up, but... if you check and find there is a lot of slop in there (that is, you find lots of play between pedal and stop), get your 2.5mm feeler gauge and try the procedure.

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post #6 of 13 (permalink) Old 26-Apr-2019, 09:22 AM (599) Thread Starter
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I bled the brake circuit and rear caliper 3 more times. Not a bubble to be found. Took for a ride. Still works the same way. I think that is how its designed. Give you a bit of pedal travel with gradual brake application before servo kicks in.
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post #7 of 13 (permalink) Old 27-Apr-2019, 03:20 PM (847)
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Did you check the linkage?

Whizzy brakes, no FD drain plug, what's not to like?
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post #8 of 13 (permalink) Old 28-Apr-2019, 05:41 PM (945) Thread Starter
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Yep! 2.5mm. I am pretty much convinced this is the way it is supposed to be. Based on input from various sources who state theirs is the same way. Final confirmation will be in a few days when I go visit a bud with an 05 GS just like mine.

I have put roughly 185 miles on the bike so far. I'm getting use to the rear brake. It actually makes sense thinking about it now. The rear brake, especially with servo assist if not modulated correctly, has the potential to cause a rear washout if applied to abruptly. It seems that in the 1.5" of rear brake pedal travel, the brake force is incrementally applied without servo boost until the last 1/2" of travel. No official test or data to back this up just me trying it out on the center stand and on gravel road tests over the last 2 days. Thoughts?

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Did you check the linkage?

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post #9 of 13 (permalink) Old 29-Apr-2019, 06:44 AM (489)
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My 04 is about the same. I've had a couple bikes that allow a fair amount of travel before a hard grab.
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post #10 of 13 (permalink) Old 30-Apr-2019, 02:01 AM (292)
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I had this issue on my K1600 after a brake fluid change from dealer.

BMW told the dealer to put a 24lbs weight on rear brake for 24 hours to force the small air trapped in the line out. Brake pedal is now firm and feels great.

Prior to this the dealer tried all sorts of bleeding technique but non worked.

Ian

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