[bohuler]

Just a quick one, i've done a search but still not really clear. i'm going to upgrade my drum brakes to discs, using the snake racing gear i've been trying to flog my no one wants. It uses the front calipers and disks meaning you need a proportioning valve. What I was wondering was if I upgraded the front at the same time to vitara discs and calipers, would i still need a proportioning value? And also, does it matter which model/year I get the vitara calipers and discs front? Last time i was at center road wreckers there was a couple of vitaras and would hate to grab the wrong ones
Cheers
Dave

[mnemonix]

Regular vitara calipers are identical to sierra ones.
You need the LWB vitara brakes for them to be an upgrade.
You'll most likely still need a proportioning valve even if you use those on the front.

Do some research on the residual pressure valve in the rear drum brake system. It caused all sorts of grief with my rear disk conversion.

[bohuler]

WTF is that valve? Where do i find it and what does it do?

Is it the factory proportioning valve that comes with the car?

I checked on low range off road and they have a kit that gives you new rear hard lines with a valve which is what i was thinking the easiest way to go if i need the valve.

The only reason i was going to change to disk brakes is first of all, easier to clean the mud and shit out of and as said before, I have got the conversion kit and can't seem to flog it.

The drivers side rear drum is full of oil atm and the axle seal has been leaking for months, so i thought seeing I have a spare sierra that has pretty good front calipers and disks i'd convert one of the 2 spare rear diff housings to calipers and at the same time convert the the spare front housing to vitara calipers (along with new bearings and all the other shit that you do).

That way when i put the stuff on my car, all i have to do it put it on the hoist and drop the whole rear diff off, remove the center and put the center on the new housing and reinstall. and with the front the same.

(altho is dropping the front housing off as easy as the rear cause you have the steering stuff attached to it?)

Dave

[Reubs]

bohuler wrote:

WTF is that valve? Where do i find it and what does it do?

Is it the factory proportioning valve that comes with the car?

The proportioning valve controls braking power to the rear end as required by a lever controlled by the angle of the rear axle connected to a valve on the rear brake lines.

They can be found on Vitaras, coily Sierras and Jimnys.

Just a guess here (i don't really know), but maybe a coily one would be easiest to fit on a leafy Sierra.

[bohuler]

I know what the proportioning valve does, it was the "residual pressure valve" that i had no idea about what it is and where it is Or is it that same damn thing just a different name?

[mnemonix]

All drum brake systems have a residual pressure valve to ensure the line remains charged with (residual) pressure. So the hydraulic action acts on the pads as soon as the pedal moves.
A disk/caliper system does not do this as the caliper always remains at the required position. The caliper piston seal is responsible for pulling the piston away preventing brake drag.

If the residual pressure valve is not removed, you can suffer constantly riding brakes, excessive pad wear and heat. Think of it like driving with the hand brake engaged a couple of clicks all the time.

It's usually a part of the master cylinder, but can be inline in some systems.
I worked around mine by doing a brake master cylinder upgrade (subaru) at the same time, as these are designed for rear disk brakes as standard.

Plenty have upgraded to rear disks without issue. Many have not.
Food for thought.

[bohuler]

So the best way of going about it is to upgrade the master cylinder as well or just find the residual pressure valve and piss it off? If the residual presssure value is an inline valve I just need to remove and bypass and not upgrade the master cylinder?

At the end of the day, im only running 215/75/15's so its not quite like i need the excess brakes capacity running 31's need

Brakes are not something that you want to fruck up big time cause the first time you find out they don't work is when you want to stop

[86slowsierra]

http://www.auszookers.com/index.php?nam ... c&p=101428

http://www.auszookers.com/index.php?nam ... c&p=225105

[Built4thrashing]

What i know others have done is use LWB vit disc and calipers in the front, some sort of rear disc kit (there are many available) and replace sierra mastercly with one from a forrester. The forrester MC has a larger internal bore but still bolts upto the sierra booster. Ill tell you about it tonight at meeting.