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Brake calipers

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jcatnite

jcatnite

Jedi Knight
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Wanted to bounce something off you guys. I'm at the end of a front suspension rebuild and was trying to decide if I wanted to rebuild the front calipers. The reason that I am considering it is that neither caliper seems to release completely after applying the brakes. Once I pumped the brakes back up (and released the brake pedal) I noticed that it takes both hands to rotate the hubs when they were very free before I pumped the brakes to reseat the pad. So my question is: do you think the calipers aren't returning because they need to be rebuilt or is there something going on in the master cylinder that would prevent the pressure from being totally released? I'm leaning towards the later of the two but I do know that the PO replaced the master cylinder right before I bought the car. Thanks for the help in advance.
JC
 
Jc, were you having any trouble before the rebuild? I take it you havent changed the M/C. Did you fit new rotors? everything properly bled? New pads? a little bit of drag may be expected till new parts bed in some, have you bolted on the wheel and tried to spin them that way? i would guess that there may be some residual air in the line, let them sit a day or two and rebleed them.


mark
 
Disc brakes do not fully release until there is enough centrifical force from the spinning wheel to release them.
They should not be locked up but they will be snug until you spin the wheel a few times.
Dragging brakes are usually a sign of bad rubber brake hoses.
And if they are 10 years old, change them.
Collapsed hoses are bad but when they burst when you need the brakes most, that's worse. All these rubber hoses had dates on them, if you see 60s, 70s, 80s, change them.
 
The PO changed the master cylinder right before I bought the car. It didn't really help the brake problem as it was a collaped hose that was causing trouble in the first place. I fitted new rubber hoses and bled the system as one of the first projects. Before the suspension rebuild, the driver's side front tire was difficult to turn by hand. Not impossible but difficult. I always thought it was the caliper not releasing all the way (one of the reasons I changed the hoses)During the rebuild, I fitted all the normal suspension bits but also through in new bearings and seals for the hubs. I've bought new rotors and pads but went back with the old ones until I was sure that I didn't need to rebuild the calipers. I didn't want to ruin $80 dollars worth of new rotors till I got the issue sorted out. I'll take it down the road and see if the brakes free up a bit. If they don't, rebuild kits are pretty cheap for the calipers and I now know that we aren't allowed to seperate the two halves and hone the bores so I'm not as scared of it as I was this afternoon when I posted my question. Any other ideas are more than welcome but I think that if they don't release, it would be calipers that sat with the pistons in one position for a long time or perhaps some sort of port in the master cylinder that is clogged.
JC
 
All good advice Mark. I plan to do just that. Thanks for the help,
JC
 
JC i would also make sue that there is free play at the pedal linkage to the M/C. I broke all the rules when i rebuilt my calipers. havent had any troubles with them. i replaced all the seals and and the cups. i did not hone the bores as they looked fine.


mark
 
You may want to work the calipers in and out a few times.
I've done that on occasion.
Remove the pads and pump the brakes until the piston comes out a bit (not too far!). Then pry it back in and repeat this about 20 times. This often helps things.
 
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