Non existant rear brake.

[Frankiesan]

Hey guys + gals

My rear brake hasn't been right since the day I melted it post seizing (when it snowed).

Firstly the rear disc cracked across 2/3 of the disk..

Then the replacement was 2 or 3mm too thick in places, which is outside of manufacturing tolerances. This made the rear lever 'pump' back when braking and made it shudder like hell. (Not nice or fun)

So a new disc was fitted but it still felt like it travelled a long way and didn't seem to have well any force to it.

On Saturday, using the advice of turning the calliper upside down and tilting it. My self and a friend used one of those vacuum pump things to drain the old fluid out and put new stuff in.. Now plenty of bubbles came out of the original fluid and it did take quite a time to get the air out of the lines but none the less it ran clear and did tighten up. We noticed also that the callipers weren't coming out uniformly at all. Without taking them apart they were given a good scrub and clean with paraffin making them move better.

The main problem lies in the pedal I think. See it travels 30mm before you feel any pressure back (it's 15mm on my mates blade), post that 30mm it only took another 20mm or so and it'd fully lock the back wheel. (If it was an airlock it'd still be spongy right?)

Looked at adjusting the pedal but since it obviously has never seen Acf50 or any form of lube in its entire life it's a bit rusted and the adjuster won't budge (nor do I wanna break it)

Got on it this morning after it not having a day of riding (so if the fluid had air in it from being shaken in my bag whilst riding it would have settled out) and the rear is almost gone, it's like a spoon brake can feel it starting to affect your speed but in no way strong enough to counteract the torque of the engine.

Do you guys think it's the adjustment in the pedal or airlock or needs rebuilding due to pistons?

Also that link to the Aprillia forums never loads for me at work so I've not got a clue what goes on in the other posts I've seen about rear brakes.

Also does anyone know what kind of or what model the rear calliper is? I'm gonna get a mate to re-build it (unless you guys come up with something)

[Frankiesan]

Right after writing a big post and getting logged out....

I've been searching all morning for a piston and seal kit.. Not sure if this is promising or not to be honest as I have no idea what the model / part number for the rear caliper is

http://www.1tail.com/sa/p/Brembo_-_Seal ... P4-32_.htm

http://www.moto-racing.co.uk/ccp51/medi ... %20Kit.jpg - This has 4 pistons in it so not sure if it's right.

http://www.yoyodyneti.com/category.aspx?categoryID=3017 - American Company

http://www.tawvehicle.com/brembo_hp_rear_caliper.htm - I'm sure I've read somewhere that the rear caliper is the same as Aprilia RSV Millie and Duke Monster 696 + 750SS(99-02) so using the chart at the bottom you get a Billet Rear Caliper Kit code of 120.A441.10


http://www.speedzilla.com/forums/genera ... ipers.html - Long ass thread but says once again that KTM can source them...

Think the big issue here now is not the pistons, cleaning them or refitting them but in getting the right bloody O-Rings. So any one of you guys out to make a profit? buy/make/acquire a shed load of them and put a post up selling them on Aprilia and duke forums.

[pod]

My sympathies, the rear disc you now have is useless if its that far off whack.
The brake can be made to work.If
The pedal pivot is lubricated.
Pull the footrest plate off, remove pivot screw and grease pivot, loctite threads on reassembly.

You have 10-15 mm free play at the pedal.
The adjuster needs freeing , soak in plus gas , and add heat to free off.
Any less and the brake will bind after use, same goes for a dry pivotl, causes brake bind

The caliper pistons are free to move.
Remove caliper and hold in one piston at a time using the jaws of a big spanner, pump out the other piston, clean with a toothbrush and lots of water and relube with Brembo grease before pushing back, repeat for other piston.

All the air is bled out.
Get a look at the Aprilia link somehow, the caliper needs to be removed and inverted ,bleed fully upside down with bleed nipple uppermost, then tilted about 45 degrees and bled again.You will notice right away when its fully bled.
Repeat again after a day or so of riding if it goes spongy again.
Fluid changed annually at least.
The TAW sight is great lots of good info.
Strange that pistons but not seals are available.
Cheers
Pod

[Frankiesan]

Thanks for the info Pod.

The faulty disc has been replaced as it was outside manufacturing tollerances (which are in Nm so when your talking mm they (EBC) didn't argue and had it returned)

We did turn the caliper upside down tilted to the side (maybe not 45 deg though) I'll give it another go tomorrow plus the extra tilting and see what happens.

Can I just confirm what your saying about the pistons?

I can pop one out at a time ?

I've never taken a caliper apart before so I've gotta ask, isn't there brake fluid at the other side?
If so how am I gonna get the other one out? I'd have a big air bubble when I put the other one back in right?

Also if I follow your instructions will I need to replace the seals or will they be ok if I leave them alone?

[pod]

Dont pump the pistons out of the seals, just 8- 10 mm or so proud, enough to clean them.
I use a 12 adjustable spanner with the jaws open over one side of the caliper and one piston, while pumping out its partner.
You dont take anything apart , just remove the pin and pads , secure one piston , pump out its partner , clean with brush.
You can take the whole shebang off, remove master cylinder, reservoir and caliper, use a screwdriver in place of the push rod to pump the master cylinder, easier at the bench than kneeling beside the bike, the brake light switch has a connector just under the rear of the fuel tank.
Oh, paraffins not a good idea, soapy water and a toothbrush is all you need.

When the piston is clean it should push back with thumbs .
Brembo grease or red rubber grease can be sparingly applied to the pistons before pushing home for the final time.

I find the final bleed is easiest with the M cylinder mounted but the caliper free to be inverted. Put a block between the pads when bleeding.

[Frankiesan]

Oh, well we already did that with the cleaning of the pistons then.. guess we should re-do and grease like you say.. was gonna do it tonight but something came up .

will have to wait til next week now....

[mandie82]

Frankie if you have any probs.. give our stu a ring this weekend... think you will be seeing him on saturday at the jumble sale thingy!