Front brake suddenly grabs? - BMW S1000RR Forums: BMW Sportbike Forum
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  • 2 Post By BMW_388
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post #1 of 7 (permalink) Old 03-19-2019, 03:22 PM Thread Starter
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Front brake suddenly grabs?

Hi All, last December I flushed the brake fluid with castrol SRF and a vacuum bleeder. I have the GS911 but a quick forum search reveals that it is not needed for normal bleeding, so I didn't use it.

Since then I rode about 4 times (been raining a bit here in California). 2 out of those 4 times, in each ride there was once when I think the front brake suddenly grabbed a bit, then it releases. Needless to say it was a bit scary. The first time I was pretty upright. The second time was this past weekend, when I was 40-45 degrees into a left turn. When I got home and put the bike on the center stand, I noticed that the front wheel was not really turning relatively freely by hand. After I freed the front wheel with a bit more force, then it started turning relatively freely by hand again.

I took a look at the rotor surface but couldn't see anything obviously wrong - not warped or scratched. The pads seemed ok too. There are no obvious fluids or material around the calipers besides the normal brake dust.

Any one had a similar experience before? Not sure what else to check next. I was going to sell the GS911 so I have it in a sealed box at the moment, and I don't think there will be any codes on this, so I haven't checked.
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post #2 of 7 (permalink) Old 03-19-2019, 03:39 PM
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Why would you sell a tool that is so critical if you own a BMW motorcycle? It may just sit around and collect dust, until the day you really need it to check codes or reset the oil / service reminders.

As to the brakes, you should have bleed the system using the GS911 pump / module cycle process. You should maintain the brake fluid yearly. Flushing the complete system via past the pump is not going to happen just using a vac bleeder system. You need to cycle that pump with the 10 second or 20 second cycle. Whatever it is for the GS911.

If you are experiencing brake issues after messing with it, you need to sit down and bleed out the system again properly.
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post #3 of 7 (permalink) Old 03-19-2019, 05:19 PM Thread Starter
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Quote:
Originally Posted by BMW_388 View Post
Why would you sell a tool that is so critical if you own a BMW motorcycle? It may just sit around and collect dust, until the day you really need it to check codes or reset the oil / service reminders.

As to the brakes, you should have bleed the system using the GS911 pump / module cycle process. You should maintain the brake fluid yearly. Flushing the complete system via past the pump is not going to happen just using a vac bleeder system. You need to cycle that pump with the 10 second or 20 second cycle. Whatever it is for the GS911.

If you are experiencing brake issues after messing with it, you need to sit down and bleed out the system again properly.
Thanks! Well, I'm selling the GS911 because I got the ICOM D from BMW. I work on my car a lot and decided to move from the old and legacy K+DCAN to ICOM, so I thought I'd get the ICOM D for working on the motorcycle too.

Alright, looks like I should have cycled the module. How come the forum threads kept saying that it's not needed then?
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post #4 of 7 (permalink) Old 03-19-2019, 06:28 PM
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Is there more to this story? Did you change the levers or did you remove the brake lever for some reason? It could be that the front brake lever is not returning fully, therefore keeping pressure in the system. As it gets hot it will grab. The other possibility would be brake dust built up on the pistons in the caliper. When's the last time you had them out and gave them a good clean? Saying that the whell doesn't turn easily points to both of these as possibilities, or maybe the forks are twisted.
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post #5 of 7 (permalink) Old 03-19-2019, 07:15 PM Thread Starter
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Originally Posted by skapan View Post
Is there more to this story? Did you change the levers or did you remove the brake lever for some reason? It could be that the front brake lever is not returning fully, therefore keeping pressure in the system. As it gets hot it will grab. The other possibility would be brake dust built up on the pistons in the caliper. When's the last time you had them out and gave them a good clean? Saying that the whell doesn't turn easily points to both of these as possibilities, or maybe the forks are twisted.
Thanks for the ideas! I didn't do anything else. I have not cleaned the pistons at all (~7000 miles now), I'll give that a try! Forks look ok, and I didn't feel anything after running my hands over them several times, as I was cleaning them. I had a fork seal leak last year, which was fixed by SF BMW under warranty.
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post #6 of 7 (permalink) Old 03-19-2019, 07:45 PM
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@xldy Please clarify your initial post. Are you saying the front applied itself while riding or it just grabbed more than usual when you applied the front brake? I interpreted the latter. In any case it sounds like your calipers are due for a good cleaning. Mine seem to need cleaning every track day or race weekend to prevent excessive drag like you described..
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post #7 of 7 (permalink) Old 03-20-2019, 02:23 AM Thread Starter
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@xldy Please clarify your initial post. Are you saying the front applied itself while riding or it just grabbed more than usual when you applied the front brake? I interpreted the latter. In any case it sounds like your calipers are due for a good cleaning. Mine seem to need cleaning every track day or race weekend to prevent excessive drag like you described..
Hey Bob.. Sorry I was unclear. No, I believe it's the former, it grabbed a bit by itself. I don't trail brake (on the streets), I always try to enter at a speed I can control. And the first time it happened I was in a straight, so there was no reason to squeeze the brake at all...
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