brake questions

White Noise · Mr Dudwee Joined: 17 Dec 2004 Karma :

i have a few questions regarding brakes and wonder if anyone can answer them
cheers

1) what sort of gap should there be between the pad and the brake disc when not in operation?
2) in normal operation there should be no contact with the disc and the pad, i am sure no contact!
3) what actually pulls the piston away from the disc once the brake lever has been released? it the hydrallic pressure?

i am asking this as i have reattached the back brake to my bike and the pads grip the disc but don't seem to pull the pads far away enough from the disk when realised!
could this imply a problem with the master cylinder?
Cheers
WN
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Mr.Everready · World Chat Champion Joined: 28 Mar 2003 Karma :

look at your front pads ! Very Happy

You should see no space between the pad and the disk. It isnt like a push bike.
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feef · Energiser Bunny Joined: 11 Feb 2002 Karma :

There's near enough no VISIBLE gap between the pads and disk... it's just not exerting any pressure on the disk with them when "pulled back"

in some cases, you can even hear an ever so slight drag on the pads when wheeling the bike about with the engine off.
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skyline · Scooby Slapper Joined: 20 May 2004 Karma :

In operation there should be no contract correct, but it may still look like they are very very close

mchaggis · World Chat Champion Joined: 10 May 2004 Karma :

Normally, the movement of the disc will push the pads slightly away, and the rubber piston seals will do a fair amount of retraction too. They are dragged out by the piston as it moves, and will pull it back to return to their original shape.
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White Noise · Mr Dudwee Joined: 17 Dec 2004 Karma :

its just on my ride to work this morning i used very little back brake and a lot of front, then once i got to work i touched the discs and the back one was hot and the front was cold implying that the rear pads have been rubbing the rear disk! which is not normal and not good as i fear i will warp the disc!
I have just put new seals in and the brakes don't seem to retract enough! Crying or Very sad

I figure i am looking to be able to ride the bike without touching the rear brake and the disc should not be getting hot!
Looks like i will be taking the calipers off again tonight!
WN
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LustyLew · World Chat Champion Joined: 19 Apr 2004 Karma :

I have a similar problem on my ER5 front caliper. It kept binding so I did as you, stripped the caliper and replaced the seals. It still wasnt right, so it's been off again and cleaned up by the garage. It's still a bit 'iffy', so it might be the master cylinder or lines that are screwed.
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Big Pete · Spanner Monkey Joined: 18 Jul 2004 Karma :

It does take some time for the pads to bed in again after the caliper has been off, You need to give it a decent run and some good brake use before you can easily say if its a seal/caliper problem. This is even more of a problem if the discs are seriously worn.
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White Noise · Mr Dudwee Joined: 17 Dec 2004 Karma :

The pads are the old ones as they have got a far amount of material left on them,