Front brakes binding

[iDemonix]

Hey,

In the process of getting the bike to an MOT ready state. Last year it got an advisory for binding brakes, they've always been that way. Anyway, got the front wheel in the air, took the callipers off and:

- Replaced all dust seals
- Replaced all piston seals
- Replaced half-calliper O rings
- Cleaned out all the gunky shit (there was loads of grey sludge behind the pistons and inside calliper passageways)
- Used a dremel to polish each piston - all had loads of carbon-like build up on the first few mm - I got nearly all of them looking really nice, a few had some pitting but nothing major
- Drained all old brake fluid

Now, put the wheel back on, fitted callipers and spent about 1 hour straight bleeding the fucking things. Took absolutely forever to get any pressure anywhere, had to bleed top banjo bolt and both callipers about 30 times each. Put it all back together. Binding exactly the fudging same as before!. I'm at a bit of a loss, the callipers were in a fairly bad state beforehand, now they're freshened up, cleaned, new seals, new fluid and yet still they bind.

What else could it possibly be? I'm thinking tomorrow I'll try and lower the amount of fluid in the M/C see if that makes it any different but I'm getting towards the end of my tether with these brakes! The back one barely works and the front ones never stop working!

[dobbslc]

Have you checked the pads move freely on the pins and in the caliper body? Correct pads & not cheap stuff?
If you had loads of shite in the calipers you might need to check the master cylinder as well.
It might be worth checking the wheel is in the right alignment like spacer positions etc, see if the discs run in the centre of the caliper cut outs.

[Neosophist]

Discs will always drag on the pistons.

Binding is when they dont release off enough to cause just a bit of drag. How easy is it to push?

The MOT tester will know that when they check the brakes.

The only way the brakes will bind is if the pads are somehow wrong and cant move
The pistons / seals are dirty and sticking

Since youve done them ovre i think it will be ok, take it for a ride and use the brakes a bit, make sure theres not a lot of drag that makes it hard to push

[arsey30]

Did you clean out the white/grey oxidation/corrosion from the dust seal grooves?
Apply grease [rubber or silicon] to the dust seal and pad end of the piston only, keep grease away from the hydraulic seal , or the piston will try to slide through it, instead of being gripped.

Often the disc will free up a little when bedded in after a few miles use after assembly.
Spin the wheel, how many revolutions does it spin? I aim for 2 or more, but after a run a little more.

I would not use abrasive on the piston as they are hard coated to prevent corrosion and wear, use brake cleaner or fluid.
If the part that sits out in the air is really dirty/corroded use Scotchbrite on the pad end of the piston that does not go into the hydraulic seal.

[dobbslc]

As arsey30 says the seal is what pulls the piston back a bit after application. Red rubber grease is great for lubing the seals you can get a small pot off ebay and it lasts for ages.
And yeah did you clean all the crap out of the groves?

[iDemonix]

Yeah cleaned out the grooves, it probably spins about half a rotation when it's in the air. I'll take it up/down the road see what it's like and maybe take some fluid out the M/C.

Ultimately I think I'll just save up and do the SP1 modification after summer. Maybe a new M/C too.

[iDemonix]

http://www.ebay.co.uk/itm/151285353765? ... 1423.l2649

Just won those!

What model M/C should I be looking for, keep my eye out for an 03/04 CBR600RR M/C+lever? Braided lines I'm presuming most any will fit so long as they're the right length.

[dx400r]

I have some adapter plate for those calipers skuttling around the garage from before I went to NC35 forks if that helps.

[Morespeedvicar]

Remember they'll prob want a rebuild too, as there 10 years old now!!!!

[iDemonix]

dx4, let me know a price, although I'm not sure I'll stick with NC30 forks yet!