BMW S1000R

Main S1000R Boards => Maintenance, Servicing, and Mechanical => Topic started by: Knobnose on December 18, 2018, 11:53:37 PM

Title: Brake fade
Post by: Knobnose on December 18, 2018, 11:53:37 PM
I started to experience brake fade at the beginning of my last trip - soft front brake lever with excessive travel. One pump gives proper lever feel.
I bled both front and rear resulting in no improvement. Called around to a bunch of N.Cal.BMW dealers but the nearest one that could look at it was in Las Vegas, so I made an appointment and rode there.
They had the bike ready in a couple of hours and told me “the computer said the brakes were fine but they bled them anyway”. I test rode it down the street, did a hard stop from 30mph and the lever came back almost to the bar. I asked them to give it a try and they agreed there was still a problem and took it back into the shop. They determined that the system “was slowly losing pressure”, ordered a new master cylinder and replaced it the next morning under warranty. The brakes felt fine so I continued East. Within a hundred miles or so the problem was back.
I lived with it for the rest of my trip by just giving an extra little pump which works  fine as long as braking can be anticipated but not so much in a emergency. I adjusted the lever all the way out which gives enough travel get the bike stopped without pumping but prevents my small hand from covering the brake.
I’m taking the bike in  to a Bay Area dealer next month and wondering what I might suggest to them.There is a lot of ABS related plumbing under the seat and I wonder if that fluid gets changed with a normal bleed or if air or moisture could be lurking there. The fact that the brakes were fine for a while is puzzling. There in no evidence of a leak anywhere that I or the mechanic can see.
Any ideas?
Title: Re: Brake fade
Post by: beech on December 19, 2018, 06:46:34 PM
The fluid in the ABS system gets changed with a flush that uses the shop computer or a GS-911. It is far more involved than a quick change.
On the other hand I have a friend with a different model BMW that had the same problem with the rear brake of that bike. Two dealers and three brake bleeds and the fade remained. We put the bike on the lift and gave the rear system a through bleed, I ran a pint of fluid through that system. About half way through that small bubbles started coming out. We worked on it until no more bubbles. The system has been fine since. Hard to convince a shop there is a problem. You did the right thing by quickly taking the bike back for a demo and letting them realize there is still a problem. Your brakes should not act like you describe of course. Sorry for your frustration. You may have to tackle this problem on your own to get the intensity of work needed.
Title: Re: Brake fade
Post by: rogracer on December 19, 2018, 10:04:52 PM
You might try adjusting the driving modes (which alters ABS behavior and front/rear linking), as well as shutting off the ABS completely, and see if the problem remains.  If it changes or goes away it may point to an issue in the ABS valve body.  I wouldn't be surprised if there is some air in it.   When I asked the dealer at my last service if they cycled the ABS pump when they bled the brakes, they told me "no" they just "bled it".  I was kinda shocked by that but at least they were honest.  Even the GS-911 has the ability to cycle the valve body, so the dealer was lacking in this regard, and maybe yours was too.
Title: Re: Brake fade
Post by: beech on December 20, 2018, 09:53:00 PM
I know most riders seldom get a chance or purposely activate the ABS while riding. I have a down hill dirt driveway and lock up my wheels at least once a month to get that ABS pump running. As the above post confirms, I don't think all dealers do the complete proper bleed sequence, much less clean and push back the pucks to get that trapped fluid out. There really is a lot to it. I use a GS911 and it is a big nanny looking over your shoulder to do a complete job.
Title: Re: Brake fade
Post by: Knobnose on December 20, 2018, 09:57:56 PM
Thanks for the suggestions, I’ll report back next month. I think that part of the problem is that communication with the mechanic gets filtered through the service writer at large dealerships.
Title: Re: Brake fade
Post by: Fistuk on December 23, 2018, 09:01:50 AM
I had a similar issue, but the breaks would not fade while riding. On occasion  I needed to pump the front lever a few times to get the pressure up on start up. After that - the lever would be fine and break feel would feel OK.

There was also some brownish goo clearly visible in the front break reservoir  - that would disappear when the break fluid got warmer (maybe it was sucked into the system)

The fluid was changed - two times in a row about 3 months apart and it solved the problem initially, but it would reappear. The techs at the garage told me that the second fluid change was 'deeper' process in which all of the fluid from the system (including the ABS pump) was flushed. The more involved process requires the shop computer to be connected.

The third time it happened, they could not get the pressure up to spec after flushing and they changed the front master cylinder (and flushed the system completely again). This seems to have solved the problem, although it only has been two months so it may be too soon to tell.

By the way - the bike is two years out of warranty but they still picked up most of the cost of the new master cylinder - without being asked to do so.
Title: Re: Brake fade
Post by: rick_lee on December 25, 2018, 04:34:32 AM
Was just gonna post the same problem.  My bike is parked until I fix this, and it's about six mos. out of warranty.  I bought some Pentosin DOT4 LV today and will try to burp the system tomorrow.  Really hate this issue and don't want to pay to have what looks like a factory or design issue fixed.
Title: Re: Brake fade
Post by: rick_lee on December 25, 2018, 06:27:16 PM
Well, I just did a traditional bleed, was extra meticulous, used a rubber mallet on the calipers, an air compressor suction attachment on the bleeders screws, and, well, it's a whole bike now.  That took at least 1-1.5" out of the lever travel.  Braking is super sensitive now and will take some getting used to.  I hope this does the trick and the problem doesn't come back for a while.
Title: Re: Brake fade
Post by: rick_lee on January 30, 2019, 05:50:41 AM
And one month later and the lever is getting spongy again.  I did 1000 miles this past weekend, rode to SoCal and back.  I did a lot of lane splitting and stop and go in LA traffic.  Now lever is going farther down.  Not as bad as it was, but also not as good as it was after the last bleed.
Title: Re: Brake fade
Post by: podders on January 30, 2019, 04:21:21 PM
Perhaps try rebuilding the front brake master cylinder, I had a quick google and found this.

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=6&Q=master%20cylinder%20repair&Sort=2

BMW appear to like chucking complete components on which must cost hundreds(at retail...) to solve the problem when in reality, its a few quids worth of rubber seals that actually need replacing, same as the common water pump issue.

I'm guessing that's because of time but its not the way to do it IMHO.
Title: Re: Brake fade
Post by: beech on February 03, 2019, 05:47:12 AM
BMW does not sell the rubber bits inside the front brake. They are glad to sell you another complete unit for $459. Maybe a cross check with manufacture would lead to a secondary source. But if under warranty all you can do is complain. I agree with you that this is a nasty business model.
Title: Re: Brake fade
Post by: rick_lee on February 10, 2019, 04:39:05 PM
I changed my front pads yesterday, which was a super easy, almost enjoyable job.  Although it was time to do it, I also figured the extra pad meat would reduce the lever travel a bit.  Once done, I took it out for some very spirited bedding.  No joy.  Lever is coming way too close to the grip.  I could feel the pads getting bedded and biting earlier and harder.  But the lever is just about to the point that I'm going to have to park the bike again until this is solved. 

The OP's having a whole new MC installed and still having the problem afterwards makes me loathe to just start replacing stuff until the root cause is tracked down.  I finally got the MotoScan app working the other day and am wondering how hard a job it is to do a full flush with ABS cycling via the app.  Or do I need to take this to a pro with a GS-911?
Title: Re: Brake fade
Post by: beech on February 10, 2019, 04:49:23 PM
Boy, what a pain you are having, sorry. I use a GS-911 on every brake bleed I do for myself or other owners. It does in my opinion make a difference. You could cheat and take the bike out and activate the ABS on dirt or grass (and do another bleed) but that is a weak substitute. Seems someone in your area should have the tool. Personally I would not own a BMW with out one. Just something that has to be in the tool box, cost of doing business. One brake bleed at the BMW shop (they have the correct tools also) would pay for the GS 911 tool.
I agree that a detailed brake bleed is where you need to start at this point. And flushing more fluid through than would seem reasonable.
Title: Re: Brake fade
Post by: zombie on February 10, 2019, 08:27:26 PM
*Originally Posted by beech [+]
Boy, what a pain you are having, sorry. I use a GS-911 on every brake bleed I do for myself or other owners. It does in my opinion make a difference. You could cheat and take the bike out and activate the ABS on dirt or grass (and do another bleed) but that is a weak substitute. Seems someone in your area should have the tool. Personally I would not own a BMW with out one. Just something that has to be in the tool box, cost of doing business. One brake bleed at the BMW shop (they have the correct tools also) would pay for the GS 911 tool.
I agree that a detailed brake bleed is where you need to start at this point. And flushing more fluid through than would seem reasonable.

If your BMW shop charges over $500 for a brake bleed, you need a new shop.
Title: Re: Brake fade
Post by: beech on February 11, 2019, 01:39:12 AM
Yeah, I know, the new gs911 is not cheap. Just saying that owning the tools for work pay off in the long run. I allocate 1.5 to 2 hours for a serious S bike bleed flush. Cleaning pucks, double flushing, using piston retractors all that stuff. Probably I go too slow. Sprits bottle of water with some detergent in it for any fluid on the bike or calipers. That sort of thing. If your inclined to use a shop, then don't waste money on tools but remember you are at their mercy now. When someone I know asks me to work on their bike I charge money as your point of tool cost is well taken.
Title: Re: Brake fade
Post by: Fistuk on February 11, 2019, 04:36:59 PM
*Originally Posted by beech [+]
BMW does not sell the rubber bits inside the front brake. They are glad to sell you another complete unit for $459. Maybe a cross check with manufacture would lead to a secondary source. But if under warranty all you can do is complain. I agree with you that this is a nasty business model.

I got the same response when I told them there are instructions on how to rebuild the Nissin MC. Their logic was that they cannot take responsibility for rebuilding a part of the vehicle which can directly affect rider safety... Looks like an excuse to me but I could not argue with them.

Since they covered almost all of the cost of the new MC and warrant the repair, it seems like a good deal but I agree this is a wasteful maintenance policy.

My brakes are working perfectly since the MC was replaced - so they obviously analyzed the issue correctly.
Title: Re: Brake fade
Post by: SimonUK on February 11, 2019, 05:57:33 PM
*Originally Posted by beech [+]
BMW does not sell the rubber bits inside the front brake. They are glad to sell you another complete unit for $459. Maybe a cross check with manufacture would lead to a secondary source. But if under warranty all you can do is complain. I agree with you that this is a nasty business model.

I ma not sure what rubber bits you are referring to, but you can buy a piston and seal kit for a front claiper - https://www.kfm-motorraeder.de/cms/en/genuine-spare-parts/bmw-spare-parts?itemid=34117714801
Title: Re: Brake fade
Post by: beech on February 11, 2019, 07:56:22 PM
I was thinking in the master cylinder on the handle bar. If your caliper puck seal was leaking the only way would be to the outside where you would see the mess in a hurry.
Title: Re: Brake fade
Post by: podders on February 11, 2019, 08:00:25 PM
*Originally Posted by SimonUK [+]
I ma not sure what rubber bits you are referring to, but you can buy a piston and seal kit for a front claiper - https://www.kfm-motorraeder.de/cms/en/genuine-spare-parts/bmw-spare-parts?itemid=34117714801

He would have needed these parts for the master cylinder, not the caliper, which is a doddle to get for any of the Japanese bikes I own , which are nigh on 40 years of age....
Title: Re: Brake fade
Post by: CrazyBiker on February 12, 2019, 08:36:14 PM
Cycling the ABS pump for a comprehensive bleed is not going to help with leaking seal issues.
On other hand, I didn't need to cycle the pump on my S1000RR and the brakes feel fine if not as great as the R.
Title: Re: Brake fade
Post by: rick_lee on February 22, 2019, 04:28:36 PM
*Originally Posted by Fistuk [+]
My brakes are working perfectly since the MC was replaced - so they obviously analyzed the issue correctly.

My brakes worked perfectly after my last bleed too.  Felt like a whole new bike.  The problem is that, well, the problem returned after about 500 more miles.
Title: Re: Brake fade
Post by: rick_lee on March 04, 2019, 03:38:32 PM
Bled it again on Saturday.  Lever did not change at all after bleeding at the calipers, but got a little better once I did the master cylinder.  I went riding for a bit yesterday and it just wasn't the way it had been.  So I bled only the MC again, saw a few tiny bubbles and the lever got a lot stiffer.  What the hell is causing this and how to fix?  No point in replacing the MC if there is a design flaw with the stock one.  Bike isn't old enough to have worn seals.
Title: Re: Brake fade
Post by: beech on March 04, 2019, 05:35:43 PM
Vibration can foam the oil in the reservoir. The K1300S series had to add a open cell foam pad to the reservoir and a weight under the cap.