low rear brake pedal

[bungie4]

Ever since my bike was new, its had a soft, low rear brake pedal. I just got the bike out and gave it a test drive and it seems worse, keep in mind i haven't ridden it 2+ years.

Checked fluid level, it's fine. Bled the rear brake, no change. Any ideas? I'm not equipped to bleed the abs unit.

[FJRoss]

I assume that you bled the lower right piston pair (linked brake) on the front as well using the brake pedal...?

(I know you're not new to this but thought I'd ask)

[bungie4]

I assume that you bled the lower right piston pair (linked brake) on the front as well using the brake pedal...?

(I know you're not new to this but thought I'd ask)

I didn't. I sold my service manual and don't remember which caliper it is linked to. I'll get it done this evening. I was supposed to bring the bike in for a fitness but no point with the brake like that. I cancelled the fitness scheduled for tomorrow morning.

So this because it's been pissing rain for the last 5 days

[FJRoss]

I assume that you bled the lower right piston pair (linked brake) on the front as well using the brake pedal...?

(I know you're not new to this but thought I'd ask)

I didn't. I sold my service manual and don't remember which caliper it is linked to. I'll get it done this evening. I was supposed to bring the bike in for a fitness but no point with the brake like that. I cancelled the fitness scheduled for tomorrow morning.

So this because it's been pissing rain for the last 5 days

Cold and crappy here as well (but the weekend is going to be great). Bleed the lower right front piston pair from the rear brake pedal and then do the rear bleeder again for a few pumps. That will likely fix it.

[raYzerman]

Right front lower bleeder is the one linked to the rear. Should work out. Nothing special to do because of ABS. Once front lower done, push a coupla squirts out the rear again....
Going for the cert, huh... sounds like good news!

[bungie4]

Right front lower bleeder is the one linked to the rear. Should work out. Nothing special to do because of ABS. Once front lower done, push a coupla squirts out the rear again....
Going for the cert, huh... sounds like good news!

Yup! I took it out for the longest ride I've done since NotCFR in igloomikfuktuk. A good 15km.

[Red]

Bungie,

Front caliper first, as said above. Speedbleeders do help. Also, let the brake lever snap back after each pump, rather than letting it go back slowly - you will move more fluid that way.
Works for me.

[bungie4]

Done . You guys called it. Thanks so much. Pedal is firmer than the day i bought it!

A surprising amount of air came out of that front set of pistons.

[SkooterG]

That soft brake pedal is a common occurrence on the linked brake system. And in my experience it's always the front caliper that is the culprit. I wonder why?

[escapefjrtist]

FWIW, to stay ahead of a soft rear pedal, I bleed the rear brake circuit annually. Seems there's always bubbles from the front caliper even after just a few months.

~G

[raYzerman]

I'll theorize front one is the longest length of fluid travel..... well, after all the good book says bleed the front one first.

[FJRoss]

I renew fluid and flush brake and clutch lines every two years. Maybe I'm lucky, but I have never had a lever or pedal go soft and need bleeding between services. Never had to do any clutch service except lubing the brass bushing in the lever or replace anything other than brake pads on either of the high mileage Gen II bikes I have owned.

[Hppants]

Ray - does your theory lend itself to the prominence of air in the front part of the linked circuit? BTW - this has happened to me before to. Is it that the length the air has to travel to get burped causes it to be a challenge? Or is it the fact that the bleeder is close to being the same height as the M/C reservoir? IOW - the bubbles don't get much "lift"?

Inquiring mind(s) want to know.

[raYzerman]

It's not really a theory, but best practice for any brake system, you should always bleed the longest length first (think cars, where X-linked front and rear). The longest line would have the largest volume of moisture-contaminated fluid and air, if any. Reservoirs are always above the master cylinder, the only part of the system that is gravity fed. After that it is all pressure and it doesn't matter the height of the lines. Remember too on these bikes the steel fluid lines run inside the frame right beside the engine and see a lot of heat cycles, in particular the clutch, and that fluid will darken much sooner than brakes since you're cycling the clutch much more than brakes.

General statement, but the older the fluid, the more water content in the fluid. If you want to prevent brake/clutch problems, do a full flush and bleed, note air bubbles can be from air entering around the threads of unsealed bleeder screws or a loose-fitting bleeder hose..... but once done, you can do a quick bleed every spring with very little fluid (if you calculate, approx. only 2 ounces or so in each system), so you only need the small bottle of fluid. Very unlikely you'll see any air in the system. Go two years if you like, but every year is best practice on an FJR.

[Festus]

I seem to remember FJR Pittsburgh and Powerman saying something about putting a weight on your rear brake lever and leave it overnight. Thoughts on that? There might have been more to it, that's all I remember from the conversations.

[Pterodactyl]

I normally replace brake fluid every winter on all our bikes. However, if a lever/peddle gets soft, a common occurrence on the BMW R1200/1250 bikes, I will hold the lever/pedal in the engaged position overnight. A small bungee on the front lever or a weight on the rear pedal does the job. Not much pressure is required. Theory, as explained to me, is that opening the circuit allows the air in the circuit to rise into the reservoir. I’ve been doing this for years and the next day the lever/pedal is always very firm.

[bungie4]

I seem to remember FJR Pittsburgh and Powerman saying something about putting a weight on your rear brake lever and leave it overnight. Thoughts on that? There might have been more to it, that's all I remember from the conversations.

I've bungied back my front brake lever overnight to help bleed a stubborn front. It works. Air bubbles rise to the highest point they can. If they make it to the master cylinder they can't get passed the piston until it moves and uncovered the port.

[Hppants]

I've also thought about the ABS pump block. After I flush the brake system, I exercise the ABS pump. That presumably exchanges old/dirty ABS block fluid with the clean fluid in the lines adjacent to it. Should I then Re-flush the brake system to remove that diluted fluid? Or is it diluted enough that in 2 years, it will get cycled out?

I suppose with enough coffee, I could lather myself up proper with this.... LOL

[Pterodactyl]

I've also thought about the ABS pump block. After I flush the brake system, I exercise the ABS pump. That presumably exchanges old/dirty ABS block fluid with the clean fluid in the lines adjacent to it. Should I then Re-flush the brake system to remove that diluted fluid? Or is it diluted enough that in 2 years, it will get cycled out?

I suppose with enough coffee, I could lather myself up proper with this.... LOL

The process for bleeding the ABS pump on BMW with the GS911 diagnostic tool calls for cycling the pump after flushing the brake fluid, then flush and cycle two more times. I do it once and call it good, but I also occasionally activate the ABS on our gravel road.

[FJRoss]

I've also thought about the ABS pump block. After I flush the brake system, I exercise the ABS pump. That presumably exchanges old/dirty ABS block fluid with the clean fluid in the lines adjacent to it. Should I then Re-flush the brake system to remove that diluted fluid? Or is it diluted enough that in 2 years, it will get cycled out?

I suppose with enough coffee, I could lather myself up proper with this.... LOL

The process for bleeding the ABS pump on BMW with the GS911 diagnostic tool calls for cycling the pump after flushing the brake fluid, then flush and cycle two more times. I do it once and call it good, but I also occasionally activate the ABS on our gravel road.

Seems excessive. I did my F700GS without activating the pump at all (other than activating while riding, before I got Motoscan) but will likely do it again next year anyway - it was a mess! Flushing x3 isn't going to happen!

For the FJR, I will activate by jumper (or on-road use after flushing). I don't bother with purging again afterward. Wouldn't hurt but doubt it makes much difference unless the fluid was horribly contaminated.