Brakes spongy after fitting 325mm discs and pads

Z

Zikim

Active member
A couple of months ago I upgraded the front brakes on my prefacelift with 325mm discs & pads, since then the pedal feel has been spongy and not the solid feel that I previously had. I have bleed the brakes twice, first time using the conventional method and second time using power bleed and INPA to cycle the ABS unit.

Since then the pedal feed has improved but is still not right. I have inspected the operation of the caliper when the pedal is pressed and there seems to be sideways movement as well as in & out. Is there something wrong here and is this the problem?
 
"I have inspected the operation of the caliper when the pedal is pressed and there seems to be sideways movement as well as in & out. Is there something wrong here and is this the problem?"
Which bit is moving sideways? piston as it moves in and out or caliper on the carrier .......What condition are the bushes in on the caliper there may wear on those allowing xs movemnent? i assume the parts were second hand?
 
All you've done is replace caliber carrier and disk so should be no pedal change.
Schoolboy question but you have got them on the correct sides? Bleed nipple at top?
I'd agree next re checking calipers are tight on the sliders and then a general check of all bolts correctly torqued up. Slider pins tight??
That's it - nothing else except start to check the rest of your system in case co-incidence and it's something else gone wrong..
 
If you let the system run dry then it is probably air/moisture still in there. I left my E36 sat for months with no fluid in and it took a number of fluid flushes to get it right. Get yourself some fresh fluid and try again, and of course do not recycle the fluid back into the system.

Failing that it is possible that the master cylinder seals have failed as is sometimes the case.
 
Toe-side said:
"I have inspected the operation of the caliper when the pedal is pressed and there seems to be sideways movement as well as in & out. Is there something wrong here and is this the problem?"
Which bit is moving sideways? piston as it moves in and out or caliper on the carrier .......What condition are the bushes in on the caliper there may wear on those allowing xs movemnent? i assume the parts were second hand?
Click to expand...
There is movement in the caliper sideways as the piston moves in and out. The calipers are new units so the bushes are also new.
 
cj10jeeper said:
All you've done is replace caliber carrier and disk so should be no pedal change.
Schoolboy question but you have got them on the correct sides? Bleed nipple at top?
I'd agree next re checking calipers are tight on the sliders and then a general check of all bolts correctly torqued up. Slider pins tight??
That's it - nothing else except start to check the rest of your system in case co-incidence and it's something else gone wrong..
Click to expand...
Yes they are on the correct sides with bleed nipple on top. I will be checking the tightness of the slider pins but they were torqued up when I fitted them.
 
This movement of the calipers concerns me. I have the same calipers retrofitted and once they are fitted, pads sorted and pedal depressed once they are rock solid. No movement at all. In fact a sod to retract the calipers enough to remove old pads.
Are the pads bedded in and nice even friction are on both sides of the disk?

If all the above is in order you have to start checking the rest of the system, bit by bit based on the pointers in all the above posts
 
simonlpearce said:
Does the pedal hold pressure?
Click to expand...
Once the pads bite the pedal holds firm.

The 1st time the pedal is touched it feels spongy and if pressed again within a few seconds it has a firm feel.
With the engine off, if the pedal is depressed a couple of times the pedal is solid even if it is pressed minutes later, pointing to the fact that the vacuum has been used up and there is no air present in the brake lines.
 
Thanks for all the responses.

Took the calipers off yesterday and the problem was that the inner pad on both sides that has the 3 pronged spring attached. Although the spring was inside the piston it was pushing each pad away from the top of the piston by about 3-4mm, hence on pressing the brake peddle there was the initial sponginess. I had to trial re-bending the 3 prongs of the spring so that the the pads sat flush with the piston.

First time I have known this to happen, but brake pedal feel is a lot better and will have to wait for the pads to re bed-in to get the full benefits. Incidentally the pads are Black Diamond Predator.
 
Glad you fixed it. Needed that dismantle and check approach.
Def. an odd one. I've head of one of the prongs getting bent but never what is in effect too long and not seating.
 
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