Proportioning valve advice.

[broncoman6524]

I replaced my drums with discs, I now have a D44/14B all with D44 calipers, and a 85 C30 m/s. Brakes feel excellent but the rears still lock up first.

I've been looking into replacement proportioning valves.

Would it be smarted to get a single inlet/outlet, and just plumb it to the rear lines, and reduce ONLY the rear pressure.
Such as this.
http://www.jegs.com/p/JEGS/755192/10002/-1/10165
Or get a whole new distribution block and have full adjustability?
http://www.jegs.com/p/JEGS/762853/10002/-1/10165

 

[dremu]

Having replumbed the entire brake system on my sixpack, I would go with the first solution.

The factory combo valve does some other stuff besides proportioning, including the brake pressure difference switch, and I think something else which escapes me at the moment.

The adjustable valve is relatively cheap, is easy to plumb in, and will presumably solve your problem of widely different lockup pressures.

Adding anything else to the mix can make things much, much worse, and much harder to diagnose. Been there, done that.

-- A

 

[broncoman6524]

By brake pressure switch you mean?? Is there an idiot light that pops up?

It's a 77 that I've built from the frame, so it probally doesn't work...haha

Edit: What I was afraid of with just the rear adjuster is, If I lower the pressure to the rear lines. Say the M/c doesnt send much pressure to the fronts. This would cause my rear tires not to lock up, but the brakes would suck again. Or am I wrong in saying that?

 

[dremu]

By brake pressure switch you mean?? Is there an idiot light that pops up?

It's a 77 that I've built from the frame, so it probally doesn't work...haha

Edit: What I was afraid of with just the rear adjuster is, If I lower the pressure to the rear lines. Say the M/c doesnt send much pressure to the fronts. This would cause my rear tires not to lock up, but the brakes would suck again. Or am I wrong in saying that?

Yeah, the "BRAKE" light that goes off with the parking brake is also driven by the combo valve. I've seen people claim that it has a residual pressure circuit for the front too.

Anyway, the master should provide the same ratio of front-to-rear pressure at any pedal position, i.e. if the fronts are at a low pressure, the rears are too, because you've only got the pedal down a little

The only reason the fronts wouldn't get enough pressure is if there's a leak, at which point all bets are off anyway.

-- A

 

[ryoken]

the circuits are seperate... all your doing is sending a tad less to the back by adding the adjustable...

it's actually called a combo valve (edit, doh, too late!!). it contains the proportioning valve, metering valve and pressure switch (which yes, when below a certain pressure, lights the brake warning light)...

 

[broncoman6524]

Ok, that makes more sense now...kind dumb on my part. For some reason I was thinking. "Smaller bowl, less pressure"

Guess the smarter and for once a cheaper solution would be the single adjuster.