New front disc and pads for my ST... what torques ?

[Sibbo]

The second hand but very good front single disc has arrived from Germany and a set of pads from Motobns. I'm a little worried about fitting them, the disc is fairly straight forward but I don't know the required torques and my Haynes manual doesn't tell me .Does anyone have the numbers ?

The next is fitting the disc pads ... minor embarrassment but I've never fitted pads before and have no idea how ! I need the torque settings for the Allen bolts and maybe a link to a Youtube with someone showing me how ?

All help appreciated !

[barryh]

No torque settings involved in changing pads unless the caliper is removed which is unnecessary. You only need to knock out the two pad retaining pins and that's easier to do with the caliper mounted. I'm not one for videos as they all talk far to much before getting to the point. The only difficulty you might encounter is that the pistons will have to be retracted to fit the thicker new pads. There are special tools to do this but I always use a piece of wood to lever them back or sometimes a small G cramp to force them back in. Note that pushing the pistons back will increase the fluid level in the master cylinder so keep an eye on that.

If you already have the caliper off, an official book figure for the dual piston caliper mounting bolts is very elusive but Snowbum recommends not to exceed 20 ftlbs which is what I have used in the past without problems. He also lists 17 ftbs for disc mounting bolts.

[Sibbo]

OK, thanks for that, quite low torques .

How about the disc retaining bolts ?

[barryh]

Snowbum gives only the one figure of 17 ftlbs for the M8 carrier to wheel bolts. 17 ftlbs is about right for an M8 8.8 bolt. Are you bolting the disk to the Carrier which would have originally been riveted ?

[Sibbo]

No, I'm replacing the whole unit that the disc is riveted to.

[barryh]

17 ftlbs will be correct then.

[Rob]

If you have never had your caliper apart, you may want to consider it:





I replaced the lines, as well, and was lucky enough to have found pistons (R65 ATE) at Motobins when they still carried them.

[SteveD]

Well worth opening them up I agree.
Grant & me found much crud like that and four split piston wiper seals when we recently opened his front Brembos. Replacing the seals gave the brakes a much better feel.

[Sibbo]

OK, said he nervously.

[SteveD]

A little something I prepared earlier...

I had a go at renovating the Brembo calipers on my R100RS...here's the pictorial.

Remove the calipers from the bike, then split the calipers by removing the two bolts.

I'm lucky enough to have access to disposable, single use only surgical grade procedure towels. They're lint free and make a great rag to use to wipe bits clean.






I should've cleaned it much better....


Compressed air can also be used to force them out, but this is very easy and won't damage the piston lip if you're careful. Just lever them up. If the piston won't budge, then try the compressed air I suppose. In the past, I've resorted to whacking the caliper half against a block of wood to knock the piston out, when the air didn't work. In that case it did dislodge the piston enough to make the removal easier.


The mark is easy to clean up with some 1600 wet and dry, lightly lapped. I did replace the front caliper pistons with new ones, and used the best pair of the six used pistons I had for the rear caliper. I also lightly lapped the piston bore.



Remove the wiper ring, use a toothpick to lever it out as it won't damage the inner surface of the bore or the recess for the rubber wiper ring.


Once the wiper ring is out, give the caliper another meticulous clean, flushing the fluid passage, wiping inside the ring recess, cleaning the o-ring recess etc. Then, use a little brake grease to lube the wiper ring, and reinstall. As you can see, I've used the pbr rubber grease as recommended by the local airhead BM Motorcycles shop here in Ringwood, Victoria. There are other products. I lightly coated the pistons to reinstall them too, but brake fluid would also work there.


The real thing..



Just push the piston back in with your fingers, then reinstall the piston seals. Coat the piston seals with the rubber grease too. It helps to preserve them, keeping them supple. As it's a specialist brake grease, it doesn't melt and won't contaminate the discs. I just rubbed it onto the seal, coating it, not a thick goopy cover, more a light smearing.


Now, same treatment to the o-ring...then place it into it's recess at the fluid passage hole. This picture shows too much...it was cleaned up more before bolting it together.


I then added the bolts and aligned them to the lower half, o-ring in place, then carefully tightened it all up, ensuring the o-ring stayed in place.


Back on the bike and then to prime with brake fluid.

I find the retrograde technique quickest. That uses a 50ml syringe with some tubing attached to the bleed nipple.
The brake fluid reservoir has its lid removed and most old fluid is removed previously. That way spillage and paint damage is avoided. Then I carefully flush the brake fluid up into the caliper and fill the reservoir from the bottom end. Once a bit has gone in, have a look in the base of the reservoir for fine contaminants and remove it before proceeding.
Once filled correctly, pump the brake lever carefully to ensure you're happy. Lid back on, pump the lever....go for a ride, careful at first until you're confident it's all good.

Parts in ukp fr M'bins...2012 prices.
16.50 x 2

19.50 x 2


Hand model: me. Photographer: me.

I did that with mine a while back, and we did Grants about a month back. It's easy enough. Be surgical, more so than I was in the link.