Rear Brakes on F650GS Twin

[Luna]

I have a question for those who have the F650 twin - do your rear brakes feel mushy/almost non-existent????

I bought my 2009 used in March of last year with ~9200 miles. It now has ~13k miles. The rear brakes have always felt extremely inadequate. We bled the lines last Sept (just the main line for the rear - not the ABS module/lines). And yesterday we replaced the pads (with EBC carbon) and bled the line again. No real improvement.

Should the rear brake on this bike feel like that? Is there air in the ABS module/lines? (No ABS dummy light coming on.) Could there be something wrong with the caliper (hubby said it looked fine to him)?

Let me hear your experiences/opinions!!!

[shelion]

My rear brake feels neither mushy nor non-existent. It's not nearly as powerful as the front, obviously, but I can feel it when it kicks in. Two things to check/do: inspect the brake lines. Rubber lines degrade and lose pressure over time and it's the pressure in the system that engages the pads. If you didn't replace the all the fluid in the rear circuit when you replaced the pads, try that first. Buy a new, sealed container of fluid when you do it. Brake fluid degrades over time and sometimes just replacing all the fluid does the trick. If new fluid doesn't take care of it, put a braided stainless brake line on and see if that helps.

[Georgeinva]

First thing to check the the rear caliper. Grab the rear disc with you finger with both thumbs on the caliper. You should be able to push the caliper toward the disc. Then it should "float' on the mounting pins.
If all is good with the caliper check the brake pedal. It should return to the stop screw with minimal free play.
The ABS unit can not be bleed separately, unlike ABSII. If you have air in the pump it will not throw a fault. Air does not normally accumulate in the pump. The only way for air to get into the pump is improper bleeding or if you have replace a line or the the pump its self.

[Luna]

George,

We *did* replace a brake line last year - the front one, to accommodate handlebar risers. But I've had this problem even before we did that. I'll have Pat check the caliper and pedal like you said.

Thanks for the tip!

[patrick1moon]

The caliper works as you stated. I had it completely off to bleed it and replace the pads. I think there is still some air in the line or something.

I am not at home now but is there a bleed valve on the ABS block or the Foot pedal master cylinder?

[Root]

Interesting and potentially helpful thread. I will watch developments. The rear brake on my 2011 F650GS has always had less "bite" than the front. The effort seems more relayed than direct. At 6200 miles, it's passed two dealer checkpoints and has new fluid. Feels the same despite the maintenance.