Scraping disc brake

[Yellow Fang]

I seem to be having real problems setting my rear wheel so that the disc brake rotor doesn't scrape against the pads. A thief tried to steal it, but only took the mounting bolts. I've screwed the disc brake actuator back on, but I can't seem to adjust it so that it sits straight between the two pads without scraping one of them. Any ideas?

 

[Steve Austin]

Is the disc warped?

 

[Mr P]

IIRC Your calliper/actuator will have some way of setting the pads up so they don't rub on the disc....some have adjusters for both pads....others just one and you use washers behind the mounting bolts to position the whole unit (including the fixed pad) then set the adjustable pad

 

[jay clock]

washers.... you may need very thin ones to adjust it this way or that. It helped me solve a graunchy brake. You can buy them at an LBS at £400 each, or find a little diy shop, or even ferret around in your tool box....

 

[Jonathan M]

washers.... you may need very thin ones to adjust it this way or that. It helped me solve a graunchy brake. You can buy them at an LBS at £400 each, or find a little diy shop, or even ferret around in your tool box....

+1. If some scum tried to remove the caliper then they've probably lost some of the thin shims that youm probably didn't even know were there in the first place.

 

[Yellow Fang]

I'll see if I can get some. I read a web site that advised loosening the mounting bolts and applying the brake to centre the pads. I've just tried that. It seems to have helped somewhat although I can still detect the odd scrape, and I haven't actually ridden it yet. I don't think the rotor is dead straight, but I don't think it was before either.

 

[Cubist]

Try the same loosening and retightening sequence again, only this time hold the brake on, and nip the bolts up to fingertight at first, then alternate between the bolts putting an eight of a turn or so on at a time. Don't over-torque them, they really don't need to be massively tight.

 

[02GF74]

there are two (at least) type of brake calpier mountings. ( look at where the bolts are in photos below)

the older type - IS mount - have bolts in line with the wheel axle - and use thin washers - or shims if you wanna get fancy - to centre the caliper. the shims can be as thin as 0.2 mm - if you are desparete, make them out of a coke tin - dirll 5 mm hole then cut round hole with scissors to make a shim.

more recent calipers - post mount - have a slotted hole - so you centre it up, then do up the bolt.

one of these methods will sort you out

 

[Jonathan M]

there are two (at least) type of brake calpier mountings. ( look at where the bolts are in photos below)

the older type - IS mount - have bolts in line with the wheel axle - and use thin washers - or shims if you wanna get fancy - to centre the caliper. the shims can be as thin as 0.2 mm - if you are desparete, make them out of a coke tin - dirll 5 mm hole then cut round hole with scissors to make a shim.

more recent calipers - post mount - have a slotted hole - so you centre it up, then do up the bolt.

one of these methods will sort you out

Well, if you've used Manitou forks for most of your MTB'ing time, they've always used the post mount system. It used to be derided as too heavy etc, but I see that many frames & forks now use post mount in place of the (misnamed??) international standard. They're much easier to set up as well!

 

[Yellow Fang]

there are two (at least) type of brake calpier mountings. ( look at where the bolts are in photos below)

the older type - IS mount - have bolts in line with the wheel axle - and use thin washers - or shims if you wanna get fancy - to centre the caliper. the shims can be as thin as 0.2 mm - if you are desparete, make them out of a coke tin - dirll 5 mm hole then cut round hole with scissors to make a shim.

more recent calipers - post mount - have a slotted hole - so you centre it up, then do up the bolt.

one of these methods will sort you out

Neither of these look like mine. I have a Hope mini disc on the back. What is this slotted hole of which you speak?

 

[Jonathan M]

The slotted hole is on the caliper, so that there is s few mm of lateral movment in lining up the caliper on the disc.

I'd hazard a guess that the frame mount is an International standard mount, where the bolt goes in sidways and through the frame mount, screwing into the caliper body.

The post mount requires the bolt to go through a hole on the caliper, then screws into the post mount. Commoner on forks, fewer frame manufacturers seem to have taken up the post mount on frames.

 

[02GF74]

Neither of these look like mine. I have a Hope mini disc on the back. What is this slotted hole of which you speak?

the top one, you can see the 2 holes for the bolt holes - the bolts are in line with the axle.

the lower one, you can see allen bolts already fitted - if the bolts were not there, you'd see the slotted hole - allows the caliper to move to and fro.

here is another claiper, this time without the bolts fitted - notice the holes a not circular but elongated.