spongy brake problem and useless hand brake

[gasman]

after fitting twin pot calipers to my fxgt and braided lines the feel in the brake pedal is quite spongy, unlike how it was before i fitted all the bits it was solid as a rock.

the pedal is hard-ish if your going allong and press the brakes lightly, but if you slam on the brakes they are soft as.

i bled the master clyinder then continued to bleed the lines untill there were no more air bubbles with the outlet from the line i connected to the nipple submerged in brake fluid in a bottle so i can be sure of this.

also my hand brake is totaly useless. the adjustment on the cable on the back of the hand brake lever is at its max and there is still lots of life left in the rear pads so i dont know what else can be done.

so my questions are:
-what is wrong
-how do you bleed your brakes
-what pads do you use on your car that get occasional track time with out any brake fade.
-how do i fix my hand brake so that i can lock up the rear wheels and do 180's

[Grrrrrrr!]

I'm guessing these are the twin pot brakes of a superstrut ae101/111?
If so it could be the caliper slider pins (or whatever they are called) could be sticking. This means instead of the caliper sliding smoothly to clamp onto the disk the caliper is bending the pads to make contact with the disc.
Take the caliper off, pull the pins out, clean all the rust and gunk off and put a little anti seize compound on them being very careful not to leave too much around, you dont want it on pads or rotors.

Mintex m1166 worked well for me, rotor wear was quite high, but when i changed pads i also:
1) changed rotors to DBA slotted ones
2) went to a couple trackdays
3) used the brakes harder on the road
so of course they wore a lot faster.

A pressure bleeder is great for doing brakes. pressurises the entire system and just pushes the fluid thru.
Start at the wheel from the master cylinder and then work to the next furtherist away.
Generally with RHD cars this is left rear, right rear, left front, right front.

[Pelo]

Your master cylinder may be too small. The twin piston calipers displace more fluid than the normal ones. See if the MC from the donor car will fit.
Are the bleed nipples at the topmost point?

[neo]

I also had this issue after after doing the same thing to my 101, but also included a wilwood prop valve.

I find you 'need to pump the brakes up' before they feel hardish to one application.

However, if I lock off all the brake hoses, the pedal is firm as.. and again all bleed proerly

Maybe it is the mastercylinder not being big enough... hummm (or the fact I had no front pads left last time I went out??!)

[Santa'sBoostinSleigh]

mine was fine....
AE111 SS front calipers, AE111 rear calipers and rotors (same size as AE92 but larger diameter rotor) and AE92 master cyliner/lines/bias valve


handbrake, you probably just need to tighten it

[gasman]

meh

that sliding pin was seized on one of the calipers and when i was trying to losen it it snapped off.

couldnt find a replacement so i went to pick a part and got some carriers off a curren and the fitted fine with no mods apart from the fact that they now place the caliper further out from the hub so now the pads overhang on the disc. so now im trying to get a hold of some stock 275mm discs which would fit and fill the gap left behind.

i also did some measuring and found that the twin pot calipers actually have less piston surface area than the stock ae92 gtz single piston so the spongy pedal couldnt of been because of the master clyinder displacing not enough fluid. the curren piston area is larger still and so should give me even more force on the pads.

using the twin pot calipers with the curren pads i found that the pistons were too close to the edge of the disc and wernt clamping near the center so i used the curren calipers with the larger single piston, which fixed that problem and now the pedel feels almost as good as before i started and also brakes alot harder when your moving but when your standing still it still sinks.

i now have some twin pot calipers and one good carrier left for sale if anyone wants them and 2 machined down and resurfaced discs to swap with some stock 275mm items.

my handbrake is still poos tho and the adjustments are at their max

[rollaholic]

i couldnt say for sure on an AE92 but you might find that the handbrake has an adjustment at the rear of each caliper too - a bolt you undo with a allen key type screw underneath it. tightening or loosening this screw adjusts the handbrake travel on that caliper accordingly.

its supposed to be self adjusting but they do get thrown out sometimes. back the adjustment on the lever right off before you adjust at the caliper, and keep spinning the disc as you thread it down to make sure you dont make it too tight - i usually turn it till it stops the disc from turning easily, then back it off a half turn or so. once both sides are equal you can adjust the cable travel as needed.

[Grrrrrrr!]

meh

that sliding pin was seized on one of the calipers and when i was trying to losen it it snapped off.

i now have some twin pot calipers and one good carrier left for sale if anyone wants them and 2 machined down and resurfaced discs to swap with some stock 275mm items.

Hmmm, if i remember correctly there is a rubber bung over the end of the hole the pin goes into on the carrier. If you remove that, spray some crc etc into it each day from both ends for a couple of days then get a pin punch the right size you should be able to push it out. Then order a new pin and seals from revhead and you can either sell them as a complete set or use them. Better than junking them or selling them off cheap cheap.