Topic: Unusual binding symptoms.

[Angiey2002]

Hi Guys.
Cant figure this one out. I have put a 400 caliper on my 550 as it was the only one available and I was led to believe they are interchangable as long as you use the pivot arm for each individual bike as the 400 has a slightly wider space between the two mounting holes than the 550 but the other hole fittings are the same ie static pad adjuster onto the forks, pivot arm hinge etc. Cleaned out the piston barrell, seal groove etc and everything working fine on the moving piston side. After bleeding etc and discovering it was binding I removed the caliper again and without disconnecting the brake hose pumped the brake and I can actually see the pad retracting a fraction after releasing the brake lever so I know it is working ok. When I assembled it again I set the adjuster on the pivot arm, everything ok but after closer scrutiny I discovered that the moving piston had pulled the static piston onto the pad and it is the static pad that is causing the binding. The adjuster bolt that I had set was now loose because of the other pad pulling the pivot arm over to its side of the disc Can anyone point me in the right direction? Are the 400 and 550 compatible as they look the same although the 400 is slightly wider but as I said above if you use the 400 pivot arm it should be ok. I noticed it does sit a little bit higher on the disc but not enough to be a problem I wouldnt have thought.
Thanks.

[Head]

Can you post any pictures?? They might say a thousand words? Take a straight edge and put on the caliper mounting arm and see how it lines up with the disk,when I put another disk on my 750's this is what I had to do to see how much I had to shim the mount on the fork leg.
The binding sounds similar to what you describe,but with out seeing the parts it is hard to say
If they inter change able?

[Bodi]

I read your description several times and it still doesn't make complete sense.
To check if the parts will fit, pull the whole (mounted) caliper assembly away from the wheel fairly hard (against the spring) or squeeze the lever. Look at the cailper inner face on either side (not the pad face) - it should be almost exactly parallel with the disc surface (using new pads). If it isn't, you have some geometry problem either in the caliper arm or axle spacers.
Take a look edge-on from the front: the pad surface must be completely on the disk surface, and the top of the pad should be a few mm below the top edge of the disk.
To adjust the spring screw setting, loosen it (turn clockwise at the adjusting end) a few turns and push hard on the caliper against the disk to force the piston in a mm or three. The caliper arm should then swing freely a tad if you rattle it back-and-forth. It should not move more than just perceptibly up-and-down - worn pivot if it does. Lift the front wheel free of the ground and spin the wheel. Tighten the adjuster (ccw) until the inner fixed pad contacts the rotor and slows the wheel. Turn the adjuster about 1/4 turn cw, and tighten the locknut. Check again, tightening the locknut usually takes up about 1/4 turn and it will be dragging again... fiddle until the locked setting is about 1/4 turn free of pad contact. That's it. Only pad wear or turning the adjuster will change this setting (make sure the inner pad is fitting in the caliper OK, some edge play is necessary for it to swivel flat to the disk... some brands are too tight and need the edge filed smaller to work properly).
If it still drags, bleed and bleed again. If that doesn't work, clean the piston seal groove with a bronze brush wheel and Dremel type tool... then bleed and bleed and bleed and bleed again.

[754]

Try this,

unbolt the mounts to the fork, then apply brake and get someone to hold it...now the mounts should be where they would like to be (unless they are hitting the fork) if it has a gap it will show you how much to shim..

[Angiey2002]

Hi Guys
Thanks for your replies. Took the caliper off again  and everything seems to line up ok. Pivot arm working fine, moves freely, pads parallel to disc. Still binding a bit so I took it for a short run and when I got back it was ok. Possibly could have been the pad was just a tad thick and the run was enough to shave it enough to stop the binding. Still dont know the reason for it binding as it was really stuck and still do;nt know why it has freed itself. I'll take it for a longer run today and see how it goes and keep an eye on it in the future.
One last question. Does the stationary pad have to be adjusted on an ongoing basis as it wears?
Thanks guys. Much appreciated.
Angus.

[754]

If you had a used pad, it probably has to run in, moreso if there was a difference in disc diameters.

 I never run the adjuster bolts, not since about 76, if I chrome or polishthe fork legs ,I cut the adj threaded boss right off and smooth it out.