Bandit 400 Rear Brake

alun111 · World Chat Champion Joined: 31 May 2007 Karma :

Hi, I was hoping someone could help me.

I took the rear caliper off my bike today to put some more copper grease on the back of the pads, as a couple of weeks ago I replaced the pads and the brake's been squeeling ever since.

So naturally this turned into a bit of a clean and then me trying to free one of two pistons that was seized. So, by pressing the brake pedal the free moving piston pops out a couple of mm, so i get cleaning it with brake cleaner, a toothbrush and some cotton buds. When that was done I moved on to the other one, I managed to get it to pop out by putting the pad in on the ok piston side and jamming a screwdriver horizontally through the caliper, this meant that when I pressed the pedal only the seized piston came out, and it worked quite well.

Now I had to re-seat the seals a bit when I pushed the pistons back in as obviously I had to peal them back a bit in order to clean.

Now my question is, could this affect the pressure in the brake system at all?

I took it for a spin and the pedal felt spongy so I bled the brake. I had GREAT difficulty in doing this at first, and then I managed to do it well, and fully, but now the pedal's got no pressure and It'd be quite dangerous to ride!

To begin with when bleeding the brake I managed to let the reservoir run right down, so i think i might have got a LOT of air trapped (maybe?) in the system, could this be why they're bled but are absolutely useless? Or, is it what I did with the piston seals that's buggered everything up?

Thanks very much for your time, I really appreciate it.

TUG · World Chat Champion Joined: 12 May 2007 Karma :

sounds like there was a bit of air in the system if it felt spongy. my rear brake squeels too atm but i put it down to the disc being a bit grooved from when the caliper seized.
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Haz ER-5, innit!

alun111 · World Chat Champion Joined: 31 May 2007 Karma :

Thanks for your reply but it doesn't really help me. I've bled the brake but the lever's got no pressure. Can anyone help me? I could really do with the bike tomorrow! Thanks again.

TUG · World Chat Champion Joined: 12 May 2007 Karma :

well if theres no pressure theres air in your system cos you havent bled it propperly or you put the seals back in wrong and its letting air in.
____________________
Haz ER-5, innit!

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

I would say you haven't bled them through properly. Some bikes are buggers for getting an air bubble on the banjo bolt onto the master cylinder. Another common (ish) problem is having the bleed nipple on the caliper at the bottom of the caliper (and of course as air rises in the system it is useless for bleeding the brakes with the caliper in place).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

TUG · World Chat Champion Joined: 12 May 2007 Karma :

i would suggest back bleeding if you bleed nipple is at the bottom of the caliper as the air will get forced up out of the mc, theres a guide on doin so somewhere on the forum, if anyone would like to post it up or you could use the search function.
____________________
Haz ER-5, innit!

TUG · World Chat Champion Joined: 12 May 2007 Karma :

i would also back bleed your bike too as you've said you've bled it twice now and still having problems.
____________________
Haz ER-5, innit!

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

TUG · World Chat Champion Joined: 12 May 2007 Karma :

couldnt you get a syringe and bit of tube undo the bleed nipple and with the syringe full of brake fluid force it back through that way? or have i got the wrong method?
____________________
Haz ER-5, innit!

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

alun111 · World Chat Champion Joined: 31 May 2007 Karma :

Cheers for all the replies. I think I have it sorted.

I had another go a couple of hours ago and i've just finished not too long ago. I took the caliper back off as I thought maybe the one of the pistons/both are sticking as I didn't lube them with brake fluid before I pushed them back in.

So I popped both pistons out as far as I could again without them coming out, and I gave them a REALLY good clean. I also took the dust seals right off and cleaned them and the surrounding area which seemed to be covered in sawdust-like powder.

Anyway, I lubed the pistons with clean brake fluid after cleaning them and pushed them back in, put the caliper back on and bled the brake. I seem to now have as much pressure as I did yesterday before bleeding the brake initially. It still feels soft though, but my brother and mum's bf both think I might have mixed the pads up when I put them back in so they need bedding in again. Sounds plausible. So hopefully, after a bit of riding they'll be back to normal, with two free pistons!

So, thanks very much for all your help again.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

alun111 · World Chat Champion Joined: 31 May 2007 Karma :

Yer, I realise this Keith, but I'm after a newer bike so I want to refrain from spending on this one, plus the gearbox is buggered anyway so i'm not gonna be selling it until I gain the knowledge to fix it. If I was keeping the bike and so on I would be stripping that caliper right away and replacing the disc too.

Thanks for your suggestion anyway, much appreciated Smile