for the Brake Pro.... and other

[buggito]

I got some time in front of me and decide to check why a have a spongy brake pedal when I open the rear brake line. So let's start from the beginning, one 3/4 master, two single piston front disc brake caliper, a regulator ( needle valve) 5 ft long ptfe SS braided tubing line, rear 4 pot caliper.

So when I bypass the rear brake the front brake feel right and work well, when I open the rear the pedal double the length of travel , I remove the bolt holding the cliper and have it free floating on the disc , symptom are the same , I think it's setting is *good, check the air, none, so I add a 2lbs check valve since the rear caliper is higher than the master, still spongy.

So I start to think my long PTFE Stainless Steel braided line is flexing and should be replace by a hard line, do you think it could be the culprit ?

[plkracer]

If it's a large 4 piston caliper, it could be requiring more than the master can put out. Will the rear brkes lock up, and does the cylinder max out?

[Bugpac]

is the rear bleeder at the absolute top? if it is not try to remove the bolts and rotate it enuff to put it there and then bleed them.....make sure to leave the pads on the disk somehow, they dont have to be all the way on to bleed them...

[flyerrider]

That is a lot of steel braided line. *I would run a hard line. and for the $20 it will cost you at pep boys it should be a cheap experiment

[LiveWire]

I thought I read that a stainless braided PTFE line will actually expand less than a hard line. The Formula Cross and Extreme had no hard line on the and have good brakes. They will lock up all four wheels. They have two dual piston in front and four piston in the rear with I believe a 3/4 master cylinder. Having pistons on each side of the rotor should not consume any more fluid. Each side should back off half as much as a floating caliper.

[buggito]

plkracer, the rear caliper is one of a front gsx 1100 , I think it use less than one front ( trailer disc brake).

bugpac, yes the bleeder is on the absolute top, I try to bleed it out as you say with the same result.(out of the car , bleeder straight up)

flyerider, that what I think happen, but don't want to tear everything until somebody confirm that it could be the case.

LiveWire , that what I read somewhere to

I think I have no other way than trying the hard line, like flyerider say the hard line are cheap test, just pain in the neck to work with.

[DesertDrifter]

Buggito, we are running braided line on all four wheels of our R16's at similar lengths if not *more, and we are not having any issues. I would say a bigger master cylinder would be better maybe 5/8". Hope this helps.

[plkracer]

Originally Posted by DesertDrifter\";p=\&quot

Buggito, we are running braided line on all four wheels of our R16's at similar lengths if not *more, and we are not having any issues. I would say a bigger master cylinder would be better maybe 5/8". Hope this helps.

Make that 7/8, 3/4 is 6/8, and 5/8 is smaller.

[DesertDrifter]

[smilie=banghead.gif] * *

[brandon]

If your line runs up from the master cylinder and then back down to the caliper you might try bleeding it at a fitting that is the high spot because air can get trap there .