How to centre hydralic disc brakes

[fido]

Is this possible?

My front disc is rubbing and when pulling the brake I can see the disc itself being pushed inwards. All of which leads me to assume that it's a bit squiffy.

Apologies if this is a common topic that I should have searched for more thoroughly but I'm on the mobile at work and it's a bit of a pain in the bum.

Many thanks

Fido

 

[RedBike]

For most brakes you do this...

Loosen (but don't remove) the bolts holding the caliper on.
Pull the brake on, which will cause the caliper to move and automatically center. Tighen the bolts while holding the brake on.

For others you sit there adding or removing washers / spacers until the gap is just right.

On cheaper disc brakes only one pad moves so the disc will move slightly when you apply the brakes. You need to manually adjust the fixed pad so it's as close as possible to the disc without rubbing.


If this is a new bike then take it back and get the shop to sort it. If this is an older bike then whats changed to make the brake rub? Is the rotor bent?

You could also have a sticky piston. It's quite common for one piston to move slightly more than the other.

 

[Piemaster]

What I do (and I'm no expert here) is firstly make sure the wheel is sat in the dropout correctly. Then slacken off the two allen bolts holding the caliper on, squeeze the brake on and retighten the caliper at the same time.
There will probably be other opinions, probably better, but the method works for me.

edit: Redbike can obviously type faster than me

 

[bad boy]

For most brakes you do this...

Loosen (but don't remove) the bolts holding the caliper on.
Pull the brake on, which will cause the caliper to move and automatically center. Tighen the bolts while holding the brake on.

For others you sit there adding or removing washers / spacers until the gap is just right.

On cheaper disc brakes only one pad moves so the disc will move slightly when you apply the brakes. You need to manually adjust the fixed pad so it's as close as possible to the disc without rubbing.


If this is a new bike then take it back and get the shop to sort it. If this is an older bike then whats changed to make the brake rub? Is the rotor bent?

You could also have a sticky piston. It's quite common for one piston to move slightly more than the other.

This post is spot on.

 

[fido]

thanks folks, I'll give it a whirl.

 

[Jonathan M]

This post is spot on.

AGree, Fido, check what mount you have first, and then if it is post mount use Redbikes excellent advice in the first part of his post.

If it is International Standard (IS) then check some of the websites about caliper alignment, IS can be much more of a faff than post mount.

 

[fido]

They were Hayes Nines and I've done as advised and it's was just the job it would seem so ta very much one and all.

 

[RedBike]

Hayes nine are great brakes, way more powerful than anything else i've tried in that price range. However, they do have a reputation for rubbing.

 

[rogerzilla]

With IS mount Hopes you have to put shim washers between the mounting plate and the caliper. This is easier to do if you take the pads out so you can see exactly where the disc is in relation to the caliper body.

If the disc only rubs for part of the rotation, it's bent. You can improve its truth by bending it by hand. The sort of runout you get on a thin bike rotor would be completely unacceptable on a car, where runout has to be about 0.05mm or less.

 

[02GF74]

The sort of runout you get on a thin bike rotor would be completely unacceptable on a car, where runout has to be about 0.05mm or less.

hmm, you sure? less than 0.3 mm is the spec. on Kawasaki Z1000 A1 rear disc - but I'll bet it would be similar on a car .... will check the Haynes manuals tonight

 

[rogerzilla]

I think the difference is that the thin bike and motorbike discs have some compliance, whereas a car disc is an absolutely solid lump of cast iron. A typical figure is more like 0.10mm, but I think it's 0.05mm for my car.