[Samurai81]

I did the LWB Vitara front disc brake upgrade, Subie master cylinder upgrade and Cultus sport (Mazda 323) rear disc conversion several years ago. I was not overwhelmed by the braking improvement and was surprised at having to replace the rear discs every few outings. I got through the local 6 monthly road worthiness checks and had other issues to be concerned about but recently the rear main seal on the G16A gave out at the same time as the front seal on the gearbox so it went into the shop for a birthday. At the same time I asked them to check the pressures to the brakes. They got 50 units (psi or bars?) all round which would mean the rears being smaller are doing all the work. I want some action up front but they dont seem to know how to achieve it without replacing the master cylinder (which is the correct one according to the Zuwharrie article by my mate Crowhorse

http://bbs.zuwharrie.com/content/topic,57063.0.html.

Anyone?

Steve.

[86slowsierra]

proportioning(sp) valve ?
http://www.spidertrax.com/s.nl/it.A/id. ... category=8

should help you swing the bias back to the front

[Samurai81]

I have one of those spidey proportioning valves. Trouble is I'm only getting 50 pressure units to the front and the back. This is apparently just the ticket for the rears but not enough for the fronts. I need a Harry Potter valve that magics up more pressure for the front.

[BenT]

Hey Steve

Given you have calipers designed to go on the rear with small pistons, you should be fine with equal pressure front and back. Your proportioning valve must be not working though if they are measuring the same pressure front and rear.

The smaller piston in the rear calipers mean they will generate less force and do less work, not more, which is exactly what you want.

If your discs are wearing out quickly something else is wrong - eg. a residual pressure valve in the rear line or handbrake sticking on.

I used to run a Subaru master when I ran stock front brakes on the rear, but switched back to the standard master when I put the Galant calipers on and got much better brakes and less pedal effort as a result. A bigger Suby master is really only needed with rear calipers with big pistons -eg stock fronts, and is a bit of a band-aid just to get enough volume for the big pistons to prevent a long pedal travel.

Putting the stock master cyl back on will give the magic pressure increase you are looking for.

Ben

[mcwilly]

So if u run front sierra calipers all round the pedal will travel further?

[zukmeista]

Yes because it will require more fluid to activate the rear brakes.

[Samurai81]

Mmmm so now I have to see if I can find the original master cylinder.....oh oh.

[mcwilly]

Mine almost goes to the floor now