Front caliper wont fit on new rotors and pads!?

[_spetznaz]

i got a 1991 240sx with ABSi bought front rotors and pads off of tirerack all for the correct car.i go to put the stuff on and i retract the caliper piston and when i try to fit the caliper on... DOEST FITso i figure i didnt retract the piston all the way i wrestle with that, still no go.

has anyone had this issue? how far does a healthy caliper piston retract? the rubber boot is flsh with the caliper so it seems pushed back all the way but theres still some piston sticking out.

how should i go about this?:

i could re surface my current rotors and wear the pads down evenly until they're small enough to fit.

The rotor is supposed to be 20mm but when i measure it with a ruler it looks more like 21.5mm, maybe i could resurface that to get some extra room?

or maybe i could remove the shims on the back of the pads and try grinding that down?

grinding the piston is out of the question

im getting desperate if u cant tell, help a out pleeez

[gumby74]

Use an old brake pad and C clamp to press the piston back as far as it will go.The piston should be flush with the rubber seal, not sticking out beyond it.

[Rucca]

The piston should be basically flush with the caliper. Sounds like it is pushed in all the way but if you aren't sure just put an old used pad over the piston and use a C clamp to force the piston into the caliper all the way. Once the C clamp becomes very difficult to spin, you know you are bottomed out. Refinishing the rotors wont take of 1.5mm, well it would take about 5 passes with a brake lathe at least. Even with an extra 1.5mm you should be able to easily slide the caliper over the pads and rotor...

Make sure the pads are tightly hugging the rotor and the rotor is held firmly on the hub (use a lug nut to keep it in place if you need to). If the shims came with the pads, try to use them but you don't need them. If needed, ditch the shims for extra clearance. Either way, it sounds like you don't have the correct pads or rotor, your caliper piston isn't fully retracted, or you just aren't sliding the caliper around correctly...

[_spetznaz]

ok so the piston in the caliper has rust on the edges, is that preventing it?its got like 8mm left to go untill its flush with everything but its really hard, so hard that its not moving back anymore as if it bottomed out. im gonna try to clean the rust off, pb blaster that sucker, but is this basically a seized caliper? or what are some ways around this...

just brute force?

[Rucca]

A seized caliper is either the piston won't move or the slide bolts have rusted so much that the caliper won't swivel or move in and out on the slides. Make sure your caliper slide bolts are lubed up and moving freely (use wheel bearing grease, antiseize, or some thicker lube). You can clean up the piston a bit if you want. It is ok to sand the rust off a metal piston, just don't go insane and don't tear the rubber boot.

8mm of piston sticking out, though, is too much. Try pressing the brake to move the piston outward a bit (stick some wood or your old pads in the caliper to ensure that the piston does not fall out of the bore) and recompress the piston.

Also, when you say the rotor is supposed to be 20mm, I believe you are looking at the rotor repair limit. That is actually saying that a 20mm is the thickness at which a rotor should be discarded.

[_spetznaz]

ok rucca you've been of much help, im about to try to sand my piston a bit and see if it will retract some more, if that doesnt work, since you confirmed that 8mm of the piston still sticking out is wrong, then il have to get new calipers. il report back with my results, anyone else with some input feel free to post it

[_spetznaz]

ok i took the piston out byt just taking everything off then pumping on teh brake and the fluid pushed it out.the piston had lots of rusty **** on it and was slightly corroded(this isnt good but i didnt care) i sanded the crap off and cleaned it, slid back in no problems and fit over my new brakes with room for more.

now im pretty sure i introduced air into the system cause the brake pedal will go to the floor with hardly any notion to stop the car, so i needa bbleed them, il post up after i do that.

[_spetznaz]

ok i took the piston out byt just taking everything off then pumping on teh brake and the fluid pushed it out.the piston had lots of rusty **** on it and was slightly corroded(this isnt good but i didnt care) i sanded the crap off and cleaned it, slid back in no problems and fit over my new brakes with room for more.

now im pretty sure i introduced air into the system cause the brake pedal will go to the floor with hardly any notion to stop the car, so i needa bbleed them, il post up after i do that.

[_spetznaz]

bled brakes correctly including ABS actuator, and works now