combined brake caliper advice?

[Phill]

Ok ive finally picked up the vfr rear end and noticed the rear brake caliper has two holes for brake lines.

I'm assuming one is the line from the rear brake master and one is from / for the combined brake circuit?

Any ideas? It probably wont matter too much and I can block one off no probs and use on as a supply, just not real sure which one?

It may just be a strip and test job but was trying to save myself the hassle and seals!
Cheers
Phill

[Hillsy]

I believe they're a 3 piston caliper and one of the holes operates 1 piston, the other does the remaining 2.

[Phill]

that'd be right!! what if I made a link pipe? overkill perhaps?
maybe I'd better strip it all down and check it out.

[letoy]

Hi there.
If you have a compressor you could use a bit of air pressure on one hole at the time and check which hole moves what.
Just a sugestion.
Cheers,
Fernando

[Booster]

Find which hole operates the single piston and ignore it, or put a vfr front braking system on and make use of the linked brakes.

[WATEVR]

is it possile to fit another rear caliper and how much do you use the rear you could just pissit off all together!!

[Gix11]

Nah, you need a back brake for balanced breaking with big pull ups. I learnt that one the hard way.

[Phill]

OK after a bit of soaking in the degreaser tub it all came apart.
Yes, three pistons. The centre piston is for the dual braking and is larger than the outer two so I'll block it off and use the outer two.
now if only I had a mill and alloy welder like Ben i could get the bastard to fit the bike.

[TurboKat]

So Phill, the centre inlet only controls the middle piston & the end inlet controls both end pistons, is that right?

[shift1313]

is using all 3 overkill? Id be worried about a piston never moving in the caliper, even if it is totally seperate.

[Phill]

Turbo, thats right, centre is one line outer two is second line.
Shift, wasnt real sure which way to go about that. If I leave it it may sieze in/rust, if i use it it may work harder than the outer two. stuffed if i know. I might try a link pipe between the two and see how it wears? might just be ok or might end up with f'kn fantastic rear brakes?
suck it and see i guess.
heres an idea. how about if i drill a hole from the two outer piston bores into the centre? one inlet line, same brake fluid and pressure, all bleed from one end? and thoughts?

Phill

[Large]

Isn't there a pressure over area formula that means different size pistons exert different forces?

(if not please ignore the above statement:))

[Large]

Although, now I think about it, the Nissins on my Kat had two different sized pistons....

meh

[shift1313]

yes there is large. You can figure it out fairly easy. its just figuring out the surface area or the piston. pi*r*r will give you the area of the piston(if the back was flat, should be close enough). then you can figure out the ratio. you have to figure that if you were hard on the front brakes and the rear on a stock vfr, all 3 pistons would be going anyways. What are the sizes of the pistons? if you have two(just for reference) 1" diam pistons and one 1.5" diameter pistons you are looking at 1.57" surface area for the two combine and 1.75" for the larger center one. if you feed them the same it would probably be okay. id have to sit and figure it out with actual numbers but id be willing to be they work out to be the same knowing honda engineers.

[Hillsy]

quote:Originally posted by Phill

Turbo, thats right, centre is one line outer two is second line.
Shift, wasnt real sure which way to go about that. If I leave it it may sieze in/rust, if i use it it may work harder than the outer two. stuffed if i know. I might try a link pipe between the two and see how it wears? might just be ok or might end up with f'kn fantastic rear brakes?
suck it and see i guess.
heres an idea. how about if i drill a hole from the two outer piston bores into the centre? one inlet line, same brake fluid and pressure, all bleed from one end? and thoughts?

Phill



I'd just pop out the middle piston and run the outer 2 on the one line. It's not gonna make that much of a difference for your rear brake.