Author Topic: Nightmare of a brake problem - FZ6 S2 (Read 8416 times)

Shinigami · « **on:** 05 July 2015, 07:20:37 pm »

So, for a while i've been having issues with my rear brake, it's basicly chewing through pads in less than 1000 miles and doing so at an odd angle and uneven, also seems to be rubbing

Now i've replaced the rota & pads, completely cleaned the hell out of the caliper and pins, both slide pins baby smooth with 1500 grit sand paper (were ever so slightly rough) and greased them up.
Piston is pretty much spotless, no corrosion on it at all, with the caliper out and lever pressed then released the piston looks to retract a little though i've no idea how much it should.
Brake fluid also changed and lines bled.
Problem is still persisting today, went to feel the rota temperature and was red hot after little use of the rear, on centre stand it's clear it's not released the pads as it barely moves when try to spin it by hand

I've also now changed the seals and the issue is still occurring, it's driving me nuts

Any ideas?

The caliper is a single pot nissin caliper

Boris · « **Reply #1 on:** 05 July 2015, 07:49:14 pm »

Just an idea. Could the issue be with the rear brake master cylinder and not the caliper? Especially if you've cleaned and replaced everything.
I would personally disconnect the brake line whilst the bike is on the centre stand and see if this releases the pressure on the rear brake pads.
If it does it could be the master cylinder sticking.

If it doesn't, I'd be tempted to by a second hand unit from a breakers, as it sounds like one of them problems that you may never get to the bottom of and drive you to an early grave.

Shinigami · « **Reply #2 on:** 05 July 2015, 08:16:19 pm »

to sound like a complete newb, where about should I disconnect the line? Thoughts did go towards the cylinder..

however there'some other variables, I've noticed on the diagrams there should be shims behind the pads? these are missing, however I can't see how a shim would help the brakes release.

other is the bit the caliper attaches to, this appears to have a slight bend, I do not know if this is supposed to be like this or it has bent somehow? there's still a clear gap between this and the disc

Shinigami · « **Reply #3 on:** 06 July 2015, 11:06:47 am »

Additional symptom, had to ride it briefly today, the brake requires 2 pumps of the pedal to feel fully firm, after this it feels firm on 1 but then after moving off again it goes back to needing 2. And definitely still running. Disc was red hot

Fazerider · « **Reply #4 on:** 06 July 2015, 11:40:08 am »

Is the caliper misaligned, the mount bent or the disc warped (i.e. dish-shaped)?
Anything causing the pads to be held at a slight angle to the disc surface would give the symptoms you describe.

Shinigami · « **Reply #5 on:** 06 July 2015, 11:49:49 am »

I'll get some photos later its continued after disc was replaced at a garage so don't think it's disc or wheel alignment

Shinigami · « **Reply #6 on:** 06 July 2015, 12:26:18 pm »

Have a short close up vid

https://youtu.be/aiWkY76G50w

chaz · « **Reply #7 on:** 06 July 2015, 10:28:43 pm »

It seems to be draging this can be caused by quite a few things, the piston sticking. the presure not been released back into the master cylinder as Boris said, there must be a bit of free play on the lever so the piston in the master cylinder comes fully back when the foot lever is released.
the shims that are missing are anti-squeal shims.
Can the caliper slid on the 2 mounting bolts, the ones with the rubber gromits on, the way the brake works is the piston pushes the outer pad against the disc, which also makes the caliper slide outwards putting presure on the inner pad.
Is the hose ok, if you press the brake hard while nipping the hose with your fingers if it swells it needs replacing test over the full length, it can also swell on the inside and act as a non-return valve. releasing the bleed nipple would test this but be careful or you will have to bleed the brakes.

Shinigami · « **Reply #8 on:** 07 July 2015, 06:47:52 am »

It does slide on the pins by hand but not visually when the brakes are used, I'll try testing the line like you say, piston is spotless and visibly retracting as can see in the video if its not chucking it down tonight will test a few more things

Failing that anyone know a decent garage in Manchester who know their brakes? Rather fix it myself but think Mrs is getting bored of me nicking her CBF lol

chaz · « **Reply #9 on:** 07 July 2015, 07:57:43 pm »

I would look at the master cylinder, you shouldn't have to pump it to get a brake?

sarelt · « **Reply #10 on:** 08 July 2015, 01:43:19 pm »

Having to pump twice to me points to the master cylinder, try an new kit and also make sure you replace all the washers where the pipes connect. Why the pads wears off at an angle to me sound like the bracket where the caliper mounts on is maybe bent. This could put pressure on the side of the pistons preventing it from sliding back properly which creates the friction on the disks. Hope this helps.

chaz · « **Reply #11 on:** 08 July 2015, 04:00:15 pm »

It might have been damaged when the wheel was put in maybe after a tyre change, if the caliper carrier was not lined up with its slot onto the bar on the swingarm and then tightened up this could cause damage to the carrier but I don't know if it's possible? although I've seen blokes "mend" things by hitting with a hammer and if that doesn't fix it then it needs a bigger hammer, lol. erm it wasn't you was it?

Shinigami · « **Reply #12 on:** 11 July 2015, 06:44:43 pm »

trying a new bracket before master cylinder as i've managed to get one for £3, whereas a master cylinder is considerably higher cost and shouldn't have failed on such a low mileage bike, whereas the bike has fallen over twice on the right side so it's possible the bracket has bent

helmetvonthrob · « **Reply #13 on:** 12 July 2015, 02:07:10 pm »

Years ago I had the front brakes on my car go sticky, found out it was my calipers going oval. Stripped them down and honed them round, new seals, sorted!

If you can see the caliper 'relax' slightly when you release the brake then the pistons aren't sticking.

As a matter of interest, you said the pads were wearing unevenly, in what way? Something out of line would wear the front of one pad and the rear of the opposite..

Shinigami · « **Reply #14 on:** 17 July 2015, 04:04:37 pm »

There was barely any wear on the left pad (chain side of disc) but right pad was completely worn to nothing at an angle with nothing on the front of the pad left but a fair bit at the back, putting new bracket on and re-ckecking alignment of everything tonight after work

chaz · « **Reply #15 on:** 17 July 2015, 04:17:28 pm »

Don't know if this is even possible, you have the spacers in place that the wheel spindle goes through, I did loose one out when trying to get the wheel in but it was obvious? if you tightened it up with one missing F**k knows what woulg happen.

Shinigami · « **Reply #16 on:** 17 July 2015, 06:10:53 pm »

Doubt its to do with spacers is it didn't start happening in line with wheel being removed, which is why I think the wind blowing it over may have done something

chaz · « **Reply #17 on:** 18 July 2015, 08:53:11 pm »

you didn't say it had been over?

Shinigami · « **Reply #18 on:** 20 July 2015, 07:47:01 am »

Retard moment, thought I had. Not crashed or anything, the wind took it over when it was parked. Couldn't try the replacement bracket as discovered I don't own a socket big enough for the rear wheel nut. Did discover that there's a notable difference though when the front of the 2 slide bolts is unscrewed so looks like something somewhere may be bent?

https://youtu.be/JA54ByJTZzg

chaz · « **Reply #19 on:** 20 July 2015, 02:03:22 pm »

There should be a ring spanner in the tool kit if it has one, never use mine as I have a socket to fit, 32mm I think but yours has the later swingarm in so might be different?
It looks as though something is twisted?

unfazed · « **Reply #20 on:** 06 August 2015, 08:45:49 pm »

Only a few things can cause pads to wear unevenly on a single piston sliding caliper
A warped disc (Looks ok in the Video)
A bent bracket (highly unlikely, would take a lot of force))
Sticking slider/s
Worn sliders
A misaligned piston due to corrosion in the seal slots
Can you push the piston push in easily with your thumbs?
Is they much play in the caliper on the sliders with the pads out?

Shinigami · « **Reply #21 on:** 10 August 2015, 09:40:44 am »

I've changed the master cylinder and lines and still happening, piston is spotless and caliper does slide with pads pushed back but have a feeling it's the caliper bolt closest to the front its more difficult to bolt in so may have been misthreaded by previous owner? Ordered a replacement caliper from a breakers, that bolt side is where its wearing the pad down most,

Shinigami · « **Reply #22 on:** 21 August 2015, 10:07:14 am »

Replaced the caliper and its fixed now. Happy days!

unfazed · « **Reply #23 on:** 21 August 2015, 11:36:57 am »