Another brake problem.... binding

**oldeskewltoy** · 05-09-2008, 10:08 AM

Working on a friends AE86...

14 months ago the entire braking system was rebuilt, it worked fine at a track day, and drove fine for about 2-3 weeks before a shunt at a highway cloverleaf entrance bent a front wheel and an aluminum panhard rod

Move ahead 10 months. braking system (hydralics and mounting) are removed for powder coating/epoxy paint coating.

6 days ago... The car was brough over to my home garage. We put it up... replaced the crossmember, both front lwr control arms, the steering rack......... the entire rear axle assembly...... (extensive overhaul/restoration of undercarriage)
..... both rear calipers(factory reman - and epoxy coated), and using OEM kits both front calipers were overhauled and epoxy coated. New Brembo/Brady slotted rotors were installed with Porterfield pads

After bleeding, the car was taken for a 2 mile test drive(alignment close.... but still off a touch) the brakes were spongy. At the 1 mile point we pulled over and both hubs were warm to hot. We turned it around drove back to the garage and have been having the same issue now..........

Front calipers binding... rear calipers ok. Spongy pedal. solutions tried in the past 96 hours....
5 different front calipers... 3 different rights, and 2 different lefts
2 master cylinders
2 different flexible brake lines(OEM and Goodridge)

Comparing his brakes too mine...(I have an AE86 as well) When his brakes are pressed there is significantly more movement in his mounts/caliper and hardware then mine. His look semi drama filled, mine seem to just move the needed amount with little outward signs............ I have NO drag to speak of, his bind

We are stumped.... We have blown out the lines...we have "tossed" in the stock pads again with the same bad results. We have had the calipers open(bleeders/brake lines) and they still bind! 3 different calipers act the same! One was rebuilt by us using the OEM kit(with the pink grease), a second was rebuilt about a year ago, by a third party, the third is a 25 year old used one with tattered bits, but all moves and works.... three completely different calipers all responding similarly.......................

Any ideas???????????????????????

**VA61DETT** · 05-09-2008, 11:05 AM

Check your rotors maybe?
A mate of mine was having trouble with his mrs's lancer, had a new set of pads installed.
Within a few weeks, started having all sorts of brake trouble.
Ended up machining the rotors about 3 thou, all good now, apparently some issue with a slight taper being worn into the rotors??

Hope that’s somewhat helpful.

-A

**thechuckster** · 05-09-2008, 01:02 PM

did the stub axle get a big hit? maybe the caliper mounts are no longer true to the disk

... or what ^^ said about the disk being out of round and/or tapered.

Remove calliper, setup a dial gauge off the strut tube or calliper bracket and rotate the disk and watch carefully.

**Rodger** · 05-09-2008, 01:41 PM

See my thread.

http://www.toymods.net/forums/showthread.php?t=39800

After many many years I found the root of the problem of both binding brakes and loss of camber.

Regards

Rodger

**oldeskewltoy** · 06-09-2008, 01:55 AM

Hmmmmmmm, Rodger... I'll check that further....

BUT... we have now swapped back all the un-coated parts, along with swapping in the older Powerslot rotors. The driverside is now fine(using a POS part store reman caliper - with an SAE bleeder FORCED into the bleeder location). The other side POS caliper which had to go back - it had the OEM bleeder broken off inside, with another SAE stuffed in behind it!! We are getting the replacement later today. The passenger side IS better now... almost ok(tad too much drag........) but we both figured to put a "matched" set of calipers on it.

*IF* this works... what I don't understand is how our calipers don't work......??????? The front calipers on an AE86 are NOT rocket science... good, clean housing, good, clean piston, a few rubber seals and thats it.... so how can one rebuild work better than another????? Right now it is still speculation... but the rotors and the coating APPEAR to have worked in conjunction to cause a problem.....

Also... we MAY have two problems....... The spongy pedal seems to ONLY be when the engine is running now. The pedal is hard, and consistant when the car is off... start it and the pedal can go close to the floor with repeated applications of the pedal. Stop the engine... the pedal comes back to PERFECT.... start it again and again it gets mushy... turn it off again, and in 2 pumps the pedal is perfect again... with no air. We checked the booster procedure and the booster checks out..........

**oldeskewltoy** · 06-09-2008, 11:21 AM

update.......

Got the replacement caliper bled it and it seems pretty good. Took it out with stock OEM pads and the pedal was firm, and responsive. We then got back from the test drive... and my friend wanted to fit the Porterfields...

... and the problem came back! We swapped out the porterfields for the OEMS and everything was fine again!

The Porterfields had been used on this car previously(before the accident), well with the re-assemble there was no way of telling which pad was which(R or L) and so the porterfields had already be broken in on a "different" front end(prior to the total rebuild) The pedal was soft because the pattern of the porterfields, and the angle the pads had worn made the pedal not responsive(mushy) and the brakes weak(for they weren't properly bedded in to the current set up)

**Rodger** · 07-09-2008, 09:12 AM

Do the Porterfields fit the same in the caliper? Are they binding in their bracket?

They could, as you say have worn with a taper so that when you put them in in a different combination they can bind for a while but they should still release.

A spongy pedal when the brakes are binding is common to how mine felt.

Actually now I think about it more, Pads are tight against the rotor, the pedal is released and it either sucks the piston back leaving the pads in place and a gap to fill next pedal application.

Or

It sucks the fluid back because the piston is stuck, reducing the pressure in the lines and then when you apply the brake again it has to increase the pressure alot before it is enough to again move the piston a very small amount.

I can say though, with mine I never noticed any brake problem with the OEM RA23/28/40 hub/rotor/caliper, just could not get the camber I wanted.

It was when I moved to the RA60 hub and vented rotor and modified the caliper brackets to mount TN Magna calipers I began having the brake problem. Initially I thought I had a warped cailper bracket. It was flat but I noticed a difference in the gap at the top of the rotor to bracket and at the bottom of the rotor to bracket of 8 odd mm.

I now believe the thinner rotor of the RA23 had limited the un-square clamping of the RA23 caliper to not drag noticably.

To check if the stub axle is bent, use a set square positioned at four points around the stub at the oil seal end and measure the distance to the centre of the end of the stub. It could be bent down (most likely from the accident) or it could be bent forward, giving some toe in.

It only needs to be a couple of mm and the piston will pull off square in its bore, binding on the seal.

How is the camber comparison between sides?

Regards

Rodger