Brembo business - pads touching normal?

[Kookaburra]

Gradually been fixing up the safety and performance of a single disc 1985 R65. New disc, pads and pins, braided hose and fluid 12 months ago. So now time to flush through and change the fluid after fitting a speed bleeder in place of the rusty standard part. On a test ride brake works better than previously however pads appear to be grazing the disc and squeaking a little when I rotate the front wheel. I am new to having disc brakes on a bike (showing my age here) so question is whether this is normal. Suspect it has something to do with the state of the calipers and seals but haven't been in there yet. Would appreciate any comments from gurus.

Want to say a big thanks to montmil for the excellent photosequence and commentary on changing the timing chain. It made the job very easy and I now have an impressive sequence of white dots on all the electrical connectors- looks like airhead dominos.

[montmil]

Kooka-  A very slight, non-pressure contact of the pads to disc is not uncommon. You do need to break in the new pads by doing several firm stops from a semi-sporty speed. Repeat 10-12 times. If your disc has the wear ridges that occur due to the placement of the disc's drilled holes, the pad break-in should produce better braking performance.

If you still have the squeaks after breaking in the pads, try a small dab of anti-rattle paste on the back of the pads where they contact the brake piston.

Did you fit organic or metallic pads? Organic good. Metallics will wear the disc muy pronto.

And thanks for the kind words regarding my timing chain adventure.

[Barry]

Pads dragging on the disk is not that unusual. It's down to stiction possibly due to corrosion on the caliper pistons which rely on the hysteresis in the rubber seals to drag them back off the disk. The pistons have to be reasonably free to move for the rubber seal to work in that way.  

With all the work on the brakes did you remove the pistons for inspection and general clean Up ?  If not you might see an improvement just by removing the pads and exercising the pistons in and out a few times. You will very likely find one that wants to move before the other. Hold back the mover with a G cramp which will force the other one move. With clean pistons and good seals you should be able to spin the wheel with no brake drag at all. It tends not to last between brake overhauls but that's how they should work.  

[Kookaburra]

Don't you love the gurus - managed to get stiction and hysteresis in the one sentence! Awesome - Having had fun looking up hysteresis I went out to discover the brake lever seems to have gone almost solid overnight. Plenty of stiction and no hysteresis. Looks like I'm going to have to pull the Brembo apart. Two steps forward one step back.

[arvo92]

I recently did a complete re-build of brakes. I installed new pistons, seals, lines etc. Pretty much the whole set. After this I also have a very very slight contact with the brake disc and I can re-assure that it gets better by the day as the new brake pads are working themselves to adjust to the existing grooves on the brake discs.

Your brembos should be better than my ATE's as the pistons are stainless steel. I would definitely open the calipers up and clean everything. That should do the trick.

[Justin B.]

The pistons in the Brembos on my '82 were anodized aluminum...