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Discussion Starter · #1 · (Edited)
Hello all. I finally got my act together and recently installed some ss brake lines and new pads for the front and rear on my 2014 fz09. I'm new to this and pretty much followed along forum posts from here and some youtube videos. Front brakes are great and a huge improvement. However, rear brake feels really weak. I can just about bottom out the pedal and really never feel much bite. I can see the caliper moving around upon applying brake but it doesn't seem to really do much past that. If using only rear brake, takes a good while longer to stop than before. There are no visible leaks. I've bled/evac/filled twice with no change. I took out the pads as well and pumped the brakes to clean the piston but everything looks good. Any thoughts? I was expecting to need to use less foot pressure similar to the front with the new lines. Was this the wrong expectation or this there another adjustment to be made? I greatly appreciate the help.

I've attached a photo of with and without brake applied. 20170507_131207.jpg 20170507_131228.jpg
 

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I would say your problem is air in the brake line. Doesn't take much. Did you bleed them by using a mini-vac tool? Were you careful not to allow the reservoir to run dry during the bleed process?

If you don't have the mini-vac tool, first ensure the reservoir is full, then pump the rear pedal several times quickly....then while holding it down slightly open the bleeder valve...allow any air to escape and re-close while keeping the pedal depressed. Do not allow the pedal to travel up while bleeder valve is open. Use a capture hose on the bleed nipple and get a helper if possible.

Your photos of the piston travel are very similar to my bike.
 

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Discussion Starter · #3 ·
Yeah used a mini-vac, never let it dip below half to make sure air never went in. Ran about 4 full reservoirs through it on the second go and never saw bubbles at the end.
 

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Alright, just finished giving that a try with a fresh brake fluid bottle, no change I'm afraid.
You didn't detect any air/bubbles upon bleeder valve opening? In looking at the FZ brake line, it looks like it could trap air in that bend, but no more than the front line crossover.
 

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Discussion Starter · #7 ·
No air at all, I went ahead and tried a "reverse" too with leaving the cap off the reservoir and applying the pedal to see if anything bubbled out the other direction with the bleeder closed, but no dice there either. I'll try to tie it down overnight tonight and see if anything changes.
 

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You say the caliper moves around, how exactly? It should only move to squeeze the pads together. The mount should not move. Is the caliper mount correctly slotted into the swing arm?
What do the wear marks on the pads look like, the same on both/full coverage of the pad? How much free play is there on the pedal?
 

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The M/C has 'lost its bleed'. Keep pressing slowly over and over, and air will come out and you'll gain pressure again.

Sent from my SM-G903W using Tapatalk
 
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You say the caliper moves around, how exactly? It should only move to squeeze the pads together. The mount should not move. Is the caliper mount correctly slotted into the swing arm?
What do the wear marks on the pads look like, the same on both/full coverage of the pad? How much free play is there on the pedal?
The FZ caliper is a one-sided piston assembly...thus the caliper must slide on pins in order to apply brake pad pressure to the rotor on the non-piston side. On my Suzuki, its a dual-piston assembly, so the caliper is firmly bolted and does not use slide pins. Both pistons push their respective pad against the rotor.
 

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Discussion Starter · #12 ·
Gave that a shot, lifted the caliper up straight, tiny air bubbles appeared, ran 2 reservoirs worth of fluid after to make sure. Then went ahead and applied the break lever slowly too over and over. I'm afraid it still just feels spongy. M/C rebuild time? Sorry just not sure where to go from here if I can't really find air and it seems to be drawing/evac'ing in a decent amount of fluid with each press. Just no real pressure. Really appreciate the help everyone.
 

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Are you sure you're keeping the bleeder closed while you're pumping and not releasing the pedal until the bleeder is closed?

Unless you have a leak in the line, there really isn't anywhere for air to suck from except the reservoir and the open bleeder.
 

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Has to be a reason. What exactly was done to the rear assembly? Any shims missing? Was the master cylinder messed with in any way? Will it pump up to pressure?
 

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Discussion Starter · #15 ·
Yeah I made sure bleeder was closed before releasing the pedal. Only thing I've touched was the new lines and new pads. No shims missing either, all pieces are accounted for. It's really not getting up to pressure in the same way as the fronts did, if i pump up then hold and crack the bleeder, there's not much pressure difference, it still "bottoms out" the pedal but not like before. Could air have just gotten stuck in the m/c with the new line?
 

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if i pump up then hold and crack the bleeder, there's not much pressure difference, it still "bottoms out" the pedal but not like before.
Sounds somewhat like you have a restricted line. I hate to say it, but you might try putting back on the OEM hose. I hate working with brake fluid.
 

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After installing steel brake lines and new pads the same thing happen to me. The front brakes worked great but the rear was spongy and way to much travel in the brake pedal. Turns out I cross threaded rear caliper bolt. I knew I screwed up because the rear brake assembly would not retract after brake pedal was pushed down. Retapped rear assemble then ordered a used assembly from eBay for 50.00. The FZ has many parts that are very soft aluminum and easy to cross thread. Take your time and use plenty of grease and always finger tight first. Hope this helps.
 

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The FZ caliper is a one-sided piston assembly...thus the caliper must slide on pins in order to apply brake pad pressure to the rotor on the non-piston side. On my Suzuki, its a dual-piston assembly, so the caliper is firmly bolted and does not use slide pins. Both pistons push their respective pad against the rotor.
I know, but he said the caliper moves "around". It should only move very slightly when fluid pressure is applied. Unless the piston was pushed back into the caliper.
 

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If you had rubber lines you could clamp the line and see if the pedal goes solid. I guess you've checked for leaks?
 

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Tie the brake pedal all the way down, as tight as you can and leave it overnight and check it the next morning.....or whenever you can and see if it's good to go or not.
 
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