Sticking brake

[marcusfordus]

How much pressure

I have been messing with the bike again whilst waiting for a caliper bought on ebay ( 7 days and still waiting :wank: ) and found the operation of the rear caliper a puzzle, not really covered by the old Haynes manual.
When all the pistons are manually pushed all the way into the caliper, I watched the operation of them by pressing the rear brake pedal only.
First comes the centre piston until it meets the pad and pushes the caliper body till it stops, which I think is the way it should work.
Next I see the front piston come out until it meets the back of the pad, followed by the rear piston until it meets the pad, and at this point all the brake pads are in contact with the disc and sitting what looks equal distance on piston movement.
Still causes the brake to drag and squeel on the ride up the street and back.
I adjusted the secondary master cylinder to the recommended distance after finding it 3mm out, but to no avail, same old problem.
Anyone else know if this is how the rear caliper SHOULD operate.
The plan is to swap the rear caliper and see if that is the cause, if it isn't, the PCV is the next item on the hit list.
BMF Sunday I shall be hunting.

 

[Trumpet]

Quote from Haynes manual.... " When the rear brake pedal is applied hydraulic pressure from the Master Cylinder is applied to the Centre piston of the rear brake caliper, and also to the centre pistons of the front calipers. The torque reaction of the front left caliper on the secondary master cylinder applies pressure to the two outer pistons on the rear caliper via the proportional control valve". As you say, there should be no hydraulic path from behind the centre piston to the two outer ones, and there is. My guess would be that somehow the centre hydraulics have broken through to the outer piston hydraulic path due to some defect in the caliper when you did your E stop .. Just be patient for the replacement and good luck bleeding the bugger.

 

[Trumpet]

Or to put it simply, when you press the rear brake pedal at a standstill, only the centre piston on the rear caliper should move.

 

[marcusfordus]

What if....

...the brake fluid is coming down the other line via a backfeed from the PCV, that should taken the pressure to the front calipers .

I think changing a bit at a time will be the final solution of getting to the bottom of this saga.

 

[ianrobbo1]

if you dont sort it will you be flogging your goodrich hoses???
I ask as I'm in the market for a "good cheap" set!! :}

 

[Stevebrooke]

if you dont sort it will you be flogging your goodrich hoses???
I ask as I'm in the market for a "good cheap" set!! :}

Like a vulture you are. Just circling around waiting to take advantage of someone else's misfortune. :m :}

 

[Trumpet]

Can't be, they are two separate circuits ? The PCV only comes into play when the secondary master is pushed from the LH front caliper, it reduces pressure so the secondary master doesnt lock up the rear brake.

The rear brake actuates the inner two pistons on the front via a delay valve, it isnt't connected to the PCV, it initally only applies the centre lh piston front, then as pressure builds brings in the centre RH piston to prevent fork dive when using back brake only. Im looking at the Hanyes picture in chapter 7.4 for this info. Is it wrong ?

You said that pressing the rear brake pedal pushes out the two outer pistons on the rear caliper. I can't see how the PCV could be doing that ..

 

[marcusfordus]

I'll rip it off....

...and start again.
Been at the BMF and picked up the whole braking system from a 5 mile old bike, it has everything still connected.The goodridge hoses are going onto the new stuff !!
Didn't have any money left to buy his wheel set up and discs, or mirrors, or swingarm, or any of his collection. The chap built a racing quad and used the Blackbird engine and electrics, everything else was up for sale.
So if anyone saw a mass of pipes and hoses being dragged across the showground, THAT WAS ME :neenaw:

When I get it all off I shall have a strip down of the rear caliper to see how the fluid is being pushed into the rear.

Forgot to say, all with genuine 5 mile old Honda brake pads too. Price ?100 for the lot, so I have a spare set of front calipers going begging. The HH pads will be swapped over to keep on the new prolites so, as new Hondas can go as well.
Quick sums in the head today, If I had waited till BMF time I could have had, all new brakes, discs, and wheels for less than what I have forked out for on the Prolite conversion with pads and a rear disc :xm
Chances of finding that lot again are Nil.

 

[Trumpet]

NICE ONE ! Get the hoses on right this time around :neenaw: No seriously, let us know what you find. A real puzzler this one.

 

[marcusfordus]

All sorted out

I was right about the rear caliper pistons operating as they do, middle one comes out straight away on the rear pedal, followed by the other two, so there is a route for the fluid through the pcv and delay valve as the new set up does just the same.

What I found on the old stuff was,
1: The rear caliper hanger needed changing, as I fitted the new gear and found a slight drag on the disc after a test ride, so fitted the new hanger as well, probelm solved there then.

2: The secondary master cylinder push rod fixing, that connects to the torque arm on the left hand fork leg, has a small metal bush fitted inside a brown plastic type sleeve. Seized and refused to budge until pressed out, the new one fell out so I knew I was onto something there !

So the emergency stop I did, moved the torque arm upwards, which never came back down fully, causing the rear caliper to stick and overheat, doing the disc in and some way affecting the caliper and hanger. Da Da :}

So I now have loads of brake spares, with standard perfect hoses, 5 miles worth of use and three sets of three pad pairs.

Rear hanger is going in the bin, all other parts can be sold on.

 

[Trumpet]

Wow, so they really are fully linked then, Haynes is wrong. Glad u finally nailed it. I need some new pads if they are cheep enough ... :-: all three sets

 

[marcusfordus]

So what....

are genuine Honda pads new then ?

 

[Trumpet]

Eh ? No, really, I need to replace all three sets of pads on my bird in the next few months, if ur selling the five mile old honda pads I'm interested. PM me
:k

 

[Jaws]

I hope you paid a decent amount for those bits and did not nick them for a few quidlets !

The Racing Quad is not a racing quad.. it is a quad used to get world speed records for deaf blind Graham Hicks..
It is used too promote the plight of deaf blind people and they have NO funding at all..

If you got the stuff really cheap best you make a donation before me or Pete at Blackbird Spares catch up with ya .. we both actively support the team with what we can.

We will stick an extra tenner on any bill to you and make a donation on your behalf ! ( Just joshing ! )

Did you take any time to talk to them about the project ?

They are very interesting people

 

[marcusfordus]

I did...

...chat with Rob about the quad, he said it got flipped once, but didn't say if it was using the nitrous kit at the time .
A lot of work went into building the thing, but they need help with the Honda electrics so their little sign said at the show.
He had a few bits left mid week when I spoke to him on his mobile, wheels in grey, standard exhausts, swing arm.
Could have kicked my self when he told me how much the carbon cans went for :bang: .

 

[R2B2]

So after all that it WAS the secondary master cyl sticking as I said at the start of the thread (posts no 2 & 15). Glad you got it sorted now.......

I am puzzled though that the outer pistons on the rear caliper are coming out with the rear brake pedal only :dunno: . Is this when the bike is stationary? When the bike is moving I would expect them to come out with rear pedal only (via torque reaction from the left front caliper), but not when stationary :dunno: :dunno:

 

[marcusfordus]

Try it....

..... yourself, get down on the floor and push your rear caliper back onto it's sliders ( pushes all three pistons back in a touch ). Pull the caliper back to give a gap between the pistons and pads, now look from underneath so you can see the pistons and press the rear brake pedal slowly. Middle piston comes out first, then the outer two.

You don't learn anything in life if things work correctly all the time, little puzzles like this make it interesting.

You need a minimum of 750ml of brake fluid to do a whole system, worth bearing in mind if you are going to tackle this job at home and think you have a bottle of 500ml brake fluid stuck on the shelf in the garage .

 

[R2B2]

You need a minimum of 750ml of brake fluid to do a whole system,

Ah....... I don't have to worry about that - I'm delinked! Only use a little bit now!

 

[Trumpet]

MARCUSFORDUS - you have PM :yo: You can donate any extra money you make back to the guy

 

[marcusfordus]

Have I

No PM as of yet