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Old 09-29-2012, 11:28 PM   #1
Nacho911 OP
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F800GS front brake off/full on

Has anyone noticed that the F800GS front brakes seem to either be all off or you touch the lever and its full on to lock up? Mine seems to be this way. I washed out the front last week on easy terrain. New tires, well cleaned. Bam washout and a few broken bones later, I was like WTF just happened? Friend took my bike to get a wash and said my front feels like it is under hard braking at the lightest touch of the lever.
The front tire was easy on, off for tire replacement, I don't think I fkd up the pads when it did it. Tested fine with a spin of the wheel after.
Any ideas?
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Old 09-30-2012, 01:37 AM   #2
Loutre
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Originally Posted by Nacho911 View Post
Has anyone noticed that the F800GS front brakes seem to either be all off or you touch the lever and its full on to lock up? Mine seems to be this way. I washed out the front last week on easy terrain. New tires, well cleaned. Bam washout and a few broken bones later, I was like WTF just happened? Friend took my bike to get a wash and said my front feels like it is under hard braking at the lightest touch of the lever.
The front tire was easy on, off for tire replacement, I don't think I fkd up the pads when it did it. Tested fine with a spin of the wheel after.
Any ideas?


You have a screw on you front brake (on the lever). If you turn it you modify that factor going from "soft" to "hard" (it modifies how hard you have to pull on your lever).
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Old 09-30-2012, 02:28 AM   #3
LukasM
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Originally Posted by Loutre View Post
You have a screw on you front brake (on the lever). If you turn it you modify that factor going from "soft" to "hard" (it modifies how hard you have to pull on your lever).
That is incorrect. While there are some high tech master cylinder that can do it like the Brembo RCS, the stock MC obviously does not offer the ability to change motion ratios.

The only thing you can adjust with that screw is the position of the lever from where you start your pull, not how hard you have it pull. Depending on your hand size it might feel to you this way, but that's only because your muscles can generate less active force if you go away from the ideal length.

This MC can change motion ratios:





To the OP,

Dual discs off road are always going to put out quite a bit of braking force, so you have to be careful modulating them. I don't find it quite as much of a problem as you do, but you could try lower friction brake pads, a master cylinder with different bore size or motion ratio, a single disc conversion,.... Quite a few options.
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Old 09-30-2012, 07:45 AM   #4
JRWooden
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Abs?

Is the bike ABS-equipted?

Has anybody monkeyed with the front master cylinder lately?
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Old 09-30-2012, 01:09 PM   #5
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Thanks for all the replies. My bike does have ABS. At the time of crash it was off, as I was on dirt. No one has fiddled with the master cylinder. Maybe going from a K60 front to a TKC 80 is a big difference in grip on the dirt.
After I heal up, I'm due for the 20,000km service, I'll have them have a look at the brake. I have had issues both front and rear with spongy brakes. They've been bled at the dealer before. The rear had hug travel before lock up and now is great. On our last 5000km trip doing the Washington Backcountry Discovery Route it seemed my front was sloppy, I even bought fluid, but never used it. I thought I needed to bleed it.

Then this washout lockup shit. Hmm maybe there is more to this than I thought
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Old 09-30-2012, 01:39 PM   #6
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My guess is the tire change. Nobbies wash out in the dirt unless treated carefully. When I switched to the k60 front I noticed I could grab a handful of front brake on gravel and the tire was stable and resisted washing. I think it's the shallow chevron that helps there.

Sorry to hear about the crash
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Old 09-30-2012, 02:14 PM   #7
JRWooden
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Originally Posted by Nacho911 View Post
Thanks for all the replies. My bike does have ABS. At the time of crash it was off, as I was on dirt. No one has fiddled with the master cylinder. Maybe going from a K60 front to a TKC 80 is a big difference in grip on the dirt.
After I heal up, I'm due for the 20,000km service, I'll have them have a look at the brake. I have had issues both front and rear with spongy brakes. They've been bled at the dealer before. The rear had hug travel before lock up and now is great. On our last 5000km trip doing the Washington Backcountry Discovery Route it seemed my front was sloppy, I even bought fluid, but never used it. I thought I needed to bleed it.

Then this washout lockup shit. Hmm maybe there is more to this than I thought
If ABS was OFF and the master cylinder was "as delivered" ... I've got nut'n ...

A buddy of mine had and issue where in an ABS-design front master cylinder was installed on his non-ABS bike and caused a problem similar to what you experienced ....
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Old 09-30-2012, 08:23 PM   #8
sorebutt
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I find it takes a lot of pressure and lever movement to make the front brakes work. After riding my 800gs a lot I got on my ST1300 and put myself on the gas tank the first time I used the front brake.

They usually make dual sport bikes with front brakes that aren't very sensitive so the brake won't lock up too easy off road. Most brake problems are the brakes being too soft, which can be caused by air in the line, spongy lines, etc. I can't think of anything that would make a brake more sensitive. You should have some free play in the lever and then a gradual build up of pressure as you pull on the lever. The lever can't build prssure instantly. Your tire turns freely with out the brake on. The only think I can think of is gremlins.
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