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Discussion Starter #1
I have 4 pad Brembos and a 999 style radial m/c on my 916 and just did my first track day with this setup yesterday. I quickly found that I have a very squishy brake lever after braking hard at the end of the long straight at Putnam. The lever is very hard with very little lever travel before brake engagement until after a very hard braking event, then I see something like 60-70% lever travel before brake engagement. I can “pump” the lever and reduce most of that travel. I cant imagine there is any air in the system, due to the very firm lever otherwise.

Is this a problem with my combo of parts or an issue with something else?
 

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What brake fluid did you use ? What kind of brake lines ?
 

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Discussion Starter #3
Braided lines, and the routing goes from the M/C to the right side caliper, then crosses over the fender to the left caliper. The brake fluid (I believe) is Dot4, and I cant vouch for the brand... Eyeing the Brembo RCS M/C’s in the classifieds, think that and a flush with a quality fluid would fix it?
 

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Discussion Starter #5
So this means I shouldn’t get those pretty M/C’s :( I guess I can redirect that money to a slipper clutch.
 

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The parts you have are great. It must be the brake fluid boiling. Either water in the fluid or the pads are dragging causing extreme heat.

Raise the front of the bike and spin the wheel to check and see if the pads are backing off after using them.


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think that and a flush with a quality fluid would fix it?
Depending on how much moisture the brake fluid has absorbed from the air, the fluid will at some point boil — causing the system to behave like there's air in the system.

Fresh DOT 4 brake fluid from a sealed container will boil at a higher temperature.
 

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Discussion Starter #8
The parts you have are great. It must be the brake fluid boiling. Either water in the fluid or the pads are dragging causing extreme heat.

Raise the front of the bike and spin the wheel to check and see if the pads are backing off after using them.


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Good catch!! The brakes are dragging enough on the front wheel that it only spins a revolution or so before stopping.. What could be causing this/How can I fix it!!

Still gonna change the fluid, sounds fun.
 

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You can either remove the pistons in the caliper and hope that fixes the issue, completely rebuild the calipers, replace the calipers.

Years ago the issue occurred on my bike. I was finally getting faster and toward the end of one of the session the front brakes went mushy and I could smell the fluid. Sticking calipers was the issue.
 

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Several random thoughts:

Did you align the calipers before torqueing them down? If not, they're probably dragging.

The newer M4 calipers paired with an RCS pump are better IMO, particularly on the track. Better pad selection too, me thinks.

I believe that some racing associations have banned the over the tire brake line routing. A Y-line or dual lines might be worth considering.

All that said, I start with fresh fluid and ensuring that the calipers are aligned.
 

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Discussion Starter #11
Several random thoughts:

Did you align the calipers before torqueing them down? If not, they're probably dragging.

The newer M4 calipers paired with an RCS pump are better IMO, particularly on the track. Better pad selection too, me thinks.

I believe that some racing associations have banned the over the tire brake line routing. A Y-line or dual lines might be worth considering.

All that said, I start with fresh fluid and ensuring that the calipers are aligned.
Align the calipers? Nope, didn’t do that cause I had no clue I needed to. Would you be so kind as to give me a quick break down?
 

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Me too. WTF does that mean?


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As mentioned earlier, it's the brake fluid. Get some FERODO or similar brand high temp brake fluid. It will fix your problem...with proper bleeding.
 
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Aligning calipers is the process of torquing down the axel, pinch bolts on fork, and calipers to keep the wheel spinning freely. It is described in the repair manual.
 

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Most people refer to that as aligning the “forks”.

The OP does not have radial calipers. With axial calipers alignment is totally dependent on fork alignment.

And I would disagree with the guy in the video. The fork alignment should be done before aligning the calipers. If the forks are misaligned while doing the caliper procedure and then you move the forks to align them, you have just moved the calipers out of alignment.

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Definitely sounds like old fluid which has absorbed moisture, but rebuilding the calipers can make a big difference too. Clean, smooth piston, fresh seals, and a dab of red rubber grease can make a big difference when it comes to "releasing" the disc.
 
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One thought, if you went with the 999 brake pump aswell, then you need to get your head into how it works, its brilliant, but you need to know how.
Itll stack air forever unless you learn there is a screw internally that makes it self bleeding, quite brilliant.
Look down the cup/canister.
 

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Discussion Starter #19
One thought, if you went with the 999 brake pump aswell, then you need to get your head into how it works, its brilliant, but you need to know how.
Itll stack air forever unless you learn there is a screw internally that makes it self bleeding, quite brilliant.
Look down the cup/canister.
I loved the radial M/C's on my 05' 999s, so I thought they would be a cheap addition to the track bike. The bleed valve in the reservoir was confusing at first, but its a brilliant idea after you know how to work it.

Ill be pulling the calipers off soon, along with flushing the system and will rebuild the calipers if needed. Going to have to wait on the RCS masters, a slipper clutch is in line before anything else!

Thanks for all the suggestions guys, hopefully I can get it back together for a trip to NCM before the summer is out!
 

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I loved the radial M/C's on my 05' 999s, so I thought they would be a cheap addition to the track bike. The bleed valve in the reservoir was confusing at first, but its a brilliant idea after you know how to work it.

Ill be pulling the calipers off soon, along with flushing the system and will rebuild the calipers if needed. Going to have to wait on the RCS masters, a slipper clutch is in line before anything else!

I'd do master cylinders way before a slipper clutch.


I'm a bit curious--what's different about the 999 masters and what do you have to do to set up/use/maintain them?
 
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