Brake Disk

[skyhook]

Hi all

Just a Qs for you all, Is it pos to rotate rear brake disk or is it only rotate 1 way,

In other words can i rotate disk 180 deg ?

[Buzzin (^_^)]

eh...what?
As far as I know it should only be mounted one way (so that left/right don't change) and a little arrow should be located on it to show the direction of rotation of the wheel.

But why would you want to? (disc wears on both sides)

[skyhook]

Thanks Buzzing, I was just wondering if it could be done, as my brake pads are wearing uneven, so new rear brake pads and pos a new rear brake disk

[McF]

What ho Skyhook, as Buzzin says you should only mount the disk in the correct way, as indicated by the "Drive" arrow.

In what way are your disk pads wearing unevenly? Are you able to post a photo?. It's an awkward angle to try and get a camera in and you'll need to be close, so make sure you use the "macro" setting.

If your rear brake is working OK and provided you have more than minimum thickness on your pads and the disk, just keep an eye on it and all should be well.

If the pads are wearing thin on one side and the thickness is getting low, replacing the pads will be OK.

Have you measured the disk thickness?, if that is more than 4mm you will be OK, unless it has warped.

You will need a micrometer, or vernier gauge (with Buzzin's modification) to measure your disk thickness. I'm at home for the Bank Holiday weekend, and can bring mine south when I go back to work. If we all manage another "Loomies" or "Ryka's" I can bring it along and measure up for you (perhaps we should have a mini "workshop").

Identifying disk run out is best done with a Dial Test Indicator, but a pencil and a steady hand are nearly as good.
Take a sharpened pencil, rest it against something secure on the bike (eg the swinging arm) and point it at the disk until it lightly touches the disk surface, the pencil should be at 90degrees to the disk, then keep it at exactly that position. Rotate the wheel (or get a friend to do it). If the disk is still flat and true, you will get a light pencil line around the disk. If you have run out, there will be parts where you have a gap between the pencil and disk and others where the disk pushes the pencil away. Don't move the pencil back, just keep rotating the wheel until the pencil touches the disk at it's "highest" point, then rotate again until you can see the biggest gap between pencil point and the disk.
According to Messrs Haynes, the maximum tolerance is only 0.3mm so it is difficult to measure this accurately without a DTI, but it you can see a gap more than a f*g packet thickness, your disk may be too warped and it's worth having it checked properly.

[skyhook]

Thank McF will deffo need to have me disk checked, as one pad is wearing down uneven and much more than the other pad.

Think I need to get a services kit for back brakes, or a parachute.......lol

Besides need an excuse for another meet up just so I can throw me leg over your pan and try it for size, so bringing down you micrometer and check me disk, nice to go like a rocket, beter still if I can stop when I need to...........lol

[McF]

It sounds as though the root of the problem might lie in your caliper.

If the brake is operating (evidence = brake is working and a pad is wearing), then the piston is probably working OK.

The caliper is a "floating" design, which means it slides on a pair of pins. If these are sticking, the caliper does not "float", one pad will rub on the disk all of the time and wear it away more rapidly.

The cure is pretty straightforward, and well worth doing as part of routine, preventative maintenance. you should be able to do this with wheel still in and without disconnecting the brakes.

Put aNTy on her stand, clean the exterior of the caliper and surrounding area (it's as well to clean the whole bike!). Remove panniers or anything else that is cluttering up the rear of the bike.
Remove the three brackets that fix the brake hose to the swinging arm and bevel drive.
Locate the 5 fastners on the Caliper Assembly
One is a small grub screw which conceals the pad pin. This is at the back of the caliper and easy to spot - it's the long pin that secures the back of the pads.
There are two identical bolts that fasten the caliper mounting bracket to the bevel drive
There is a hex head bolt towards the rear of the caliper, this is a "slider bolt" and goes through a rubber bush. It allows the caliper to float
At the front of the caliper is the other "slider bolt" with an Allen Key head; it also goes through a rubber bush.
Loosen the two "slider bolts".
Remove the two bolts fixing the caliper bracket to the bevel drive Then pull back the caliper assembly from the disk and move it to give access.
Remove the two slider bolts, give them a good clean and light coat of rubber lubricant (if you have it - if not, I'd use coppa slip (I use that everywhere ;D ;D), or even just just vaseline ( I wouldn't recommend grease as it can get "runny", especially with higher temperatures and end up where you don't want it). Be careful not to put anything slippery on or near the brake pads or disk )

The slider bolts might want a "polish" with some fine wire wool, I'd use some brasso or autosol for lubricant.

Be careful with the rubber bushes - they do perish and might need replacing. If aNTy is your only mode of transport, I'd order new ones (£7 plus postage)
www.wemoto.com/index.dyn?oid=5834217 - brake caliper fittings - Rear caliper boots
and wait for them to arrive

While you have the caliper out, if the pads need replacing, do that too (£16 plus P&P for the EBC standard, but you can get cheaper pattern parts).
Push the piston back in a little (special tool, or use the principle of levers and some Mark 1 brute strength) - watch out for brake fluid coming back out of the rear master cylinder.
Remove old pads
Fit new pads
Reassemble caliper with mounting bracket and lovely slidey pins (use some "Loctite" on threads!)
refit caliper assembly (again, use "Loctite" on the bolts)
refit brake hose brackets
pump rear brake several times to get pads in contact with disk

Test ride - Carefully!
If the pads have been sticking, you may notice a better/smoother acceleration, top speed and improved mpg

Post in and tell us how simple it was ;D

When you're happy with the rear, if those pins were causing the problem, do the same for the front brake - it's a very similar design.

You should be able to do each brake in an hour or less, providing Jan keeps you well supplied with mugs of sustaining tea.