brakes

[stevo1980]

Fitted new calipers and brake pipes, still using old pads and discs, should there be any friction when turning wheel while jacked up I can do it by hand easy but seem to be rubbing is this normal. I have felt my wheels after 10 min motorway drive and they are warmish, Discs red hot but I expect this.

[California Dreamin]

Depends on the degree of rubbing. All brake pads 'sort of' rest against the brake discs, relying on the design of the piston seal to rock the piston away from the disc (by a fraction of a millimeter) when the brake is fully released.
If it were me....I would be double checking that the brake pedal is fully returning to its stop and that there is clearance in the (plunger rod) to master cylinder and therefore, no reason for the calipers 'NOT TO BE' released.



You obviously took every care to ensure that the pads were totally free in the new calipers....

Martin

[stevo1980]

Whats the plunger rod and what do you mean pads totally free in the new calipers.
steve

[CovKid]

Plunger is attached to brake pedal and by 'free' he means the pads should not be so tight against the casting of the caliper so that they're tending to stick and make it harder for them to retract when pedal is lifted. Sometimes accumulated rust will do it.

[stevo1980]

the calipers are new so that's ok. can I adjust the thing on the brake to release the piston more ?

[California Dreamin]

Ooooh dear! mechanic basics, lesson number......

When the pedal is fully released the tandem pistons in the master cylinder should align with the ports to allow fluid from the reservoir to flow into the master cylinder. At this point there cannot be 'any pressure' in the system as it would just release to the reservoir...in other words, you know the callipers are not being pressurized and the pistons NOT being pushed onto the discs.
Trouble is....IF and I say if because it's not likely, the pedal isn't fully returning to it's stop, or for what ever reason the rod going into the master cylinder is partially pushing in the master cylinder piston, the brake fluid pressure cannot fully release.....like resting your foot on the brake pedal which would partially operate the brakes.

All you need to do is look up at the pedal box and 1) check the brake pedal is fully returning to it's stop and 2) that there is a small amount of free play in the operating rod BEFORE it starts to push the master cylinder.

The other comment I made was to ensure that when you slid the old pads back into the new callipers they should have been loose (completely free) before the pins and anti-rattle plate were fitted. (Just meaning that once released after braking they freely move back from the disc's).
A little bit of brake grease (plastilube or similar) should have been applied to the brake pad edges, retaining pins and piston contact points (rear of the friction surfaces)


Martin

[stevo1980]

cheers for that I will check the brake pedal now, all the rest you said about pads was done to that.

[stevo1980]

Just checked the pedal and yes it is fully in the up position and I can shake the pedal back and forth a couple of mill free play

[California Dreamin]

Soooo

It seems perhaps you maybe just a little worried after doing the repair....and all is OK.
Martin

[stevo1980]

Yeah its my first time doing brakes and yes I feel a bit nervous as its our first big trip to cornwall in it after spending all winter getting it right. just need to build my confidence with it, settin off in a couple of hours, fingers crossed.