Disc and pad change - not as easy as I thought!

[horsemeat]

Hi all,

After a bit of advice as this is driving me mental. I recently had my two year brake fluid change and had a nice firm brake pedal. So I decided to replace my front discs and pads as while they weren't on the limit, they looked crusty as hell. Anyway I've re assembled everything in the usual manner, and found my brake pedal to be spongy (after seating the pads!!). There's visible movement in the front caliper, when you apply the brakes you can see them clamp down, and when you release the pedal they spring back. It's clear why the pedal is spongy!

My only thought is that in pushing back the pistons to fit the pads, I've introduced air into the system somehow. So it compresses and then expands, pushing the caliper out of position. But I can't figure out how the air has gotten in?

The other option is incorrect pads/ assembly but I have re checked all my work, and compared the new pads to the old ones in case I'd ordered the wrong ones. They appear to be seated perfectly and all bolts torque up correctly.

Not wishing to cause a horrible accident I have booked it into a garage. In the meantime I was hoping you'd have some ideas! Am I correct in thinking air is my problem? If so, how has it entered the system and do I have a more serious issue?

Callum

[Dan_FR]

The piston is supposed to retract upon releasing the pedal, otherwise the brakes would bind

Does the free play in the pedal go away when you pump the brakes? If you then hold the brakes on, does the pedal slowly sink to the floor?

[horsemeat]

Thanks for the reply!

That makes perfect sense, but I was concerned about the amount of movement. Its quite noticeable!

I haven't tried holding the pedal down but yes, the free play goes away when I pump the brakes. It returns soon after though.

Thanks again Dan.

[99hagued]

Probably just need bedding in, drive it for a week or two and see how you get on.

[Dan_FR]

New brakes do need bedding in before they bite properly, which means pressing the pedal harder than usual for the same braking effort. Unless the pedal is nearing the floor I would get the new pads bedded in and see how it is from there. Unless you've opened a bleed nipple or allowed the piston to 'pop out' you won't have introduced air into the system

When was the fluid last changed? It could simply need doing and the new pads (and reduced friction during the bedding in process) have highlighted this.

[horsemeat]

Fluid was changed in Feb. It was a definite improvement at the time, Id like the bite back!

Tried what you asked. If I pump the brake it firms up but if I then hold it on it gradually lowers.

I should say the brakes do work, the pedal travel is just really long. Disconcerting!

[horsemeat]

To update this: all is well again.

I wish I had a reason but I got in the car one morning and the pedal feel was as sharp as it's ever been. This is of course after paying for another fluid change (no effect) and replacing all the caliper bolts / fittings (no effect).

Bizarre, thanks for the help

[Dan_FR]

They just needed bedding in mate, there's a lot less friction until this happens so you find yourself pressing the pedal a lot harder/further than you normally would