CB550K Front Brake problem

[davidrsmith]

Hi

I have just managed to get my CB550K3 on the road, after about 10 miles the front brake started complaining. When I applied the brake it worked correctly, but after I released the lever it sounded like one of the brake pads was touching the disc, and made a hell of a noise.
I haven't had a chance to look at it yet but I assume that the piston isn't retracting properly when I release the lever. Can I put some sort of lubricant on the piston to help it move smoothly?

Many thanks
Dave

[hairygit]

NO! The most likely cause will be a stiff pivot, which will need dismantling and greasing, but thankfully you don't disturb the hydraulics doing it, so no need to bleed the brake afterwards.

[deltarider]

Sqealing of the front brake is an all too common phenomenon with our bikes that a lot of us will run into sooner or later. The pivot can but is not so often the problem. When you lift the front end, is the brake dragging? A slight drag is normal ofcourse. We need some more info like what pads you are using? Is the nylon ring under the pad on the left side?

[davidrsmith]

Hi

Thanks for the replies, I don't know what make of pads are in the bike, they were the one's it came with, when I checked them out they had lots of material left on them so I refitted them. Yes there is a nylon washer between the pad and the piston. Hopefully I will get a chance to look tonight otherwise it will be the weekend.

Thanks
Dave

[deltarider]

See if they're chamfered. If yours are EBC, I have some more tips.

[Johnwebley]

Maybe the piston seal needs changing. If it becomes hard through age it will not retrace the piston causing the pads to drag.

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[Bryanj]

There should be NO drag when you spin the wheel if the brake is adjusted correctly.

most common faults, if adjustment of screw is correct, and in order are:-

(1) pivot seizing
(2) tiny hole in master blocked
(3) Caliper seal dragging/piston corroded
(4) flexible s collapsing

[Rob62]

You dont mention if the caliper piston is new or has been out for cleaning and new seals. My recollection of running these machines year-round was the need for regular attention to the front caliper to prevent brake binding caused by ingress of road shite and salting.... but if everything is new it may be just in need of correct adjustment as already mentioned.

[davidrsmith]

Hi

I have just managed to have a quick look, the front brake is definitely dragging. I tried adjusting the caliper bracket adjusting screw, it didn't seem to do very much and I couldn't detect any movement in the caliper, and the brake dragging didn't appear to change. I did loosen the caliper retaining bolts slightly and the front moved freely..
When I got the bike I did the road muck off the pads and cylinder housing and I did bleed the brake. So I think its probably time to get some new seals and take it all to bits clean it, grease the pivot pin and put it all back together.

Dave

[deltarider]

Sorry, I used the wrong word: drag. What I meant to say is, when you spin the wheel you'll hear the pad is near the rotor. Did you adjust by the book?

[Rob62]

Is the caliper leaking? If not the seal must be working ok....sometimes the outer part of the piston (the bit that stays on the outside of the seal) can become corroded and can cause the piston to stick in the caliper. Take the pads out and carefully pump the piston out half way and see if there is any corrosion or dirt on the piston. If so gently clean it off and press the piston back in, keep an eye on the fluid level while doing this.... as long as the piston isn’t heavily pitted or damaged this will be ok. Obviously the best option is a full strip and overhaul but the above can be a quick fix.

[deltarider]

This is what I always use: http://www.ate-info.de/en/details/produkte/ate-bremszylinder-paste-180-ml
With the front wheel out, free movement of the pivot is easily checked. Just swing it. It's still not clear to me you have the brake dragging or just the sqealing that most of us know.

[K2-K6]

http://www.sohc.co.uk/index.php/topic,11445.15.html

We have discussed before and you may find some useful additional info to help you look through your system in the above link.

[davidrsmith]

When I was riding the bike it sounded like squealing, but when I checked the front wheel with the bike on the centre stand the front wheel needs both hands to get it to rotate. I did put a micrometer on the disk and it is true. I have just been reading the haynes manual, it suggests smearing the piston sides with brake fluid and exercise it slightly after checking it for pitting and corrosion.

[matthewmosse]

I used to get this most winters, my fix, pop caller in half, gently pump out the piston a few mms and clean up with a toothbrush, dry first then with wd40. Apply copper slip, wind piston back in using a G clamp, repeat until the piston was free to push back by hand, and could be seen to slightly sink back a bit after pumping the master, if you look closely. At this point I knew it was a good move to grease the pivot, copper slip every bolt and the backs of the pads, making sure none was going to get onto the brake disks or friction surfaces. That worked for about a decade and so far I have not had to do much apart from change brake fluid every so often purely because that should be done every few years or so. That said the cb250 nighthawk did need a proper rebuild as did my bmw sidecar so it doesn't fix every bike every time but it has kept my cb500 in operating trim for a lot of miles.