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Today I bled the front and rear brakes on my new-to-me 2013 R1200RT. I've been bleeding brakes on BMW's for many years so what happened has me baffled.

I used Valvoline Dot 3 & 4 fluid from a new, unopened can. I replaced the stock bleeder nipples with Speedbleeders front and rear so it was an easy one-man flush. At no time did the fluid levels in the reservoirs get low enough to draw in air. I found no air in the existing fluid. Prior to the flush, the rear brakes were solid. I took care to not let brake fluid run down on the brake pads. Where some brake fluid accumulated on the caliper, I sprayed with Brake Cleaner.

Here's the dilemma. Following the bleeding, the rear brake feels mushy as if air was in the system. I cannot come close to purposefully locking up the rear brake or causing the ABS to activate.

Does anyone have a suggestion?
 

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Today I bled the front and rear brakes on my new-to-me 2013 R1200RT. I've been bleeding brakes on BMW's for many years so what happened has me baffled.

I used Valvoline Dot 3 & 4 fluid from a new, unopened can. I replaced the stock bleeder nipples with Speedbleeders front and rear so it was an easy one-man flush. At no time did the fluid levels in the reservoirs get low enough to draw in air. I found no air in the existing fluid. Prior to the flush, the rear brakes were solid. I took care to not let brake fluid run down on the brake pads. Where some brake fluid accumulated on the caliper, I sprayed with Brake Cleaner.

Here's the dilemma. Following the bleeding, the rear brake feels mushy as if air was in the system. I cannot come close to purposefully locking up the rear brake or causing the ABS to activate.

Does anyone have a suggestion?
Take speedbleeder off and rebleed using stock nipple. I've also experienced overnight "firming" up of a mushy lever...when tiny air bubbles have worked their way to reservoir and dissipated.
 

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I'm very interested in this post because I don't have an understanding of how the front and rear brakes are "tied" together.

You obviously have a front and a rear MC. If the front brake lever also has control over the the rear brake caliper, maybe pulling in the front lever and holding it there with a bungee cord overnight could force a bit of unseen air out of the system. I have never needed to try the same with a rear brake pedal.
???
 

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First of all you need to remove all the brake fluid and do a complete flush. The RT uses DOT 4 or better. You said you mixed in DOT 3 and DOT 4 together. Go to the auto store and buy either 2 small cans of DOT 4 or DOT 5.1 brake fluid. DOT 5.1 has an even higher wet boiling point than DOT 4.
Do NOT confuse with DOT 5, that is a silicone base fluid used for professional racing applications without ABS and the silicone will eat your seals in a heart beat.

I have a 2012 and I installed the speed bleeders. I used DOT 5.1 and bled the brakes with no difficulty whatsoever. Unless your speed bleeders are defective they are OK to use. If your not sure which fluid to use then make sure you use DOT 4 and nothing less rated. To be on the safe side never use old fluid after the container was opened. Atmospheric moisture gets in the can as soon as you open it and then it sits in the can and will deteriorate the fluid over time with out even using it. Trust me on this one from experience.

Now one more thing about boiling points listed on the cans. The dry boiling point is the temp with ZERO moisture content in the fluid. This is what you have with a factory sealed can. Now when you open the can you expose the fluid to moisture from just being exposed to the air. That is where the WET boiling point comes in. This is more realistic because of obvious reasons. The numbers they used are based on an average of 3% moisture after opening the can. This is why you need to get the highest WET boiling point fluid you can find. This was my reasoning for using the DOT 5.1 fluid. It is just a bit more forgiving if I extend my brake bleed intervals for whatever reason.
 

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Discussion Starter #6
You said you mixed in DOT 3 and DOT 4 together.
I wasn't clear in my original post.

The brake fluid I used was from a factory sealed container that Valvoline states is a DOT 4 fluid that also satisfies the requirements for DOT 3. Valvoline container label calls it a Syntentic DOT 3 & 4 Brake Fluid. See this link.

So I am confident I used the correct fluid and that is not the source of my problem.
 

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Keep bleeding the rear and it will firm up unless there is a problem with the brake system. I guess if putting a trap on the front brake overnight might help put something heavy on the brake pedal overnight.

Did you shim you calipers open during the bleed?
 

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Discussion Starter #8
Did you shim you calipers open during the bleed?
No I didn't. Based on my experience, that is required if you are trying to purge the system of air following a component replacement or caliper overhaul, etc. I have never had to remove the calipers to push the brake pads into the cylinder during a normal brake fluid flush.
 

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No I didn't. Based on my experience, that is required if you are trying to purge the system of air following a component replacement or caliper overhaul, etc. I have never had to remove the calipers to push the brake pads into the cylinder during a normal brake fluid flush.
Interesting. I need to bleed the brakes on my bike and I would love to skip the tire and caliper removal.
 

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Discussion Starter #10
Things looked better tonight. I re-bled front and rear brake circuits again and found no evidence of air in the lines. It seems the rear brake is better than last night. I can lock up the rear wheel and cause the ABS to activate. However, it still doesn't feel as "solid" as it did prior to the brake fluid change.

There are several things I can yet try, including:

- Back flushing the circuit from the bleeder nipple to the master cylinder reservoir. I've heard that often removes air that stubbornly refuses to be flushed out during a normal brake flush.

- Removing the calipers and pushing the pistons back into the caliber cylinder to expel trapped air.

- "Tilting" the caliber to have the bleed nipple at the very top of the caliber to allow air to escape.

Whatever the solution, it will have to wait until next week. I am traveling with my son to the Top of the Rockies rally in Paonia, CO this weekend. I feel confident enough of the brakes in their less than perfect condition so as not to worry too much during the trip. We will be trying out new Sena bluetooth headsets on the trip. It will be a pleasure to be able to talk when necessary and wirelessly listen to GPS commands and music.

Thanks for all your tips and recommendations.

Later
 

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Interesting. I need to bleed the brakes on my bike and I would love to skip the tire and caliper removal.
JVB recommends pushing the pistons back to flush all traces of old fluid out. Personally, I had never bothered to do that, and I had just finished doing the flush on my '07 just a few days ago.
 

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Interesting. I need to bleed the brakes on my bike and I would love to skip the tire and caliper removal.
I've not pushed the calipers apart when I've bled the brakes. But if you want to, there's no reason to remove the tires and calipers. You can go to your local building supply store and get a bundle of wooden shims for a couple of bucks. These are the things that are used to shim door frames into alignment when mounting them in the rough openings in the walls. They'll slide in between the disc and the pads from front, back or top. And being wood, they won't scratch the discs.

I find shims useful for all sorts of things around the house and generally keep a pack around.

JayJay
 

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If you attempt to push the pistons back into the caliper body, be careful of 2 things.
1/. You are displacing fluid. If the bike has had a fluid change with worn pads, when the pistons are pushed back, that fluid will overflow out of the reservoir (and depending on what bike we are talking about, that reservoir will be in different places).

2/. If you push those pistons back, make sure they are really well cleaned and ideally lubricated with a smear of brake fluid or brake grease to allow the pistons to slide against their seals without damaging the seal in the caliper body.
 

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If you attempt to push the pistons back into the caliper body, be careful of 2 things.
1/. You are displacing fluid. If the bike has had a fluid change with worn pads, when the pistons are pushed back, that fluid will overflow out of the reservoir (and depending on what bike we are talking about, that reservoir will be in different places).

2/. If you push those pistons back, make sure they are really well cleaned and ideally lubricated with a smear of brake fluid or brake grease to allow the pistons to slide against their seals without damaging the seal in the caliper body.
Item 1/ is why I push the pads back before bleeding or adding fluid to the reservoir. The fluid will not drop below the minimum mark on the reservoir unless I have a leak or the pads are worn excessively.
 
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