Keepig my stock 4 wheel disc brakes in mind, no LS1 swap etc.......

I know weight transfer to the front during braking helps the fronts, but wouldn't it also, basically, decrease the effectiveness of the rear brakes?

What about adding a prop valve to the stock brakes, and adjusting it so the rears basically did more, even though that would mean the fronts did less?

I mean, adjust the rears so that they reached lock-up, then adjusted it to just shy of that point. Giving them max pressure, but without lockup.

Worth it? Waste of effort?

 

I know this isan older thread, but that sounds dangerous.

 

thats great sounding, but if you set the back brakes to nearly lock on say dry concrete, then get on some slippery asphalt or wet roads, the back WILL lock up because the tires have less grip then when you set the p-valve. with the rear locking up, and especially without the front locking up, the rear will start to catch the front, and you'll turn sideways. so i would say BAD idea, sounds like it could work in theory, but in a real world application seems like a disaster waiting to happen

 

But....In 89, all 4 discs were the same size, so the rears were effectively doing more work than 87 discs were, as the 87 had rear smaller discs than the fronts.

Seems to me like, my 87 rears could be given more pressure, witghout it being "dangerous.

If wet vs dry rear lock up was a concern...do the test on wet pavement. So, the lock up was measured on wet instead of dry.

 

Do your test on gravel. Much easier to lockup.

You're talking about ditching your stock valve, right? And running 100% pressure to the front?

 

More the opposite....Reducing front pressure & increasing rear pressure, so the fronts have to do less & the rears can do more than stock.

All due to testing though, for any increase/decrease. In THEORY, it could stop better, if the rears helped more. After all, my rears were OUT COMPLETELY & the braking wasn't that noticeable. In fact, the fronts would lock easier, because of having to do 110% of the work.

 

You want to REDUCE front brake pressure? Why not just up the rear pressure and keep the front the same? That and get better tires.

 

Without putting in a whole near master cylinder, you can't increase to amount of pressure. All you can do is redistribute what you have. To add back pressure, ithas to come from somewhere. Only place to get it is from the front, meaning less front pressure=more rear pressure & vice versa.

 

Okay, maybe I don't understand the braking system like I thought I did. You have two ports coming off the master cylinder. Both capable of a set pressure. If you get rid of your stock prop valve you could set both to see 100% of that pressure if you wanted. However then you'd be locking the rears all the time. You're not splitting a set pressure between the front and rear. Each see their own individual pressure. Referring to a split system like if you removed the stock prop valve.

When I twist the dial on my adjustable prop valve (that is plumbed in line with the rear brakes) I'm not changing how much pressure the front sees.

 

also, the front have more weight on them when braking because of weight transfer when slowing down, so the front would need more pressure than the rears to lock up, so it makes more sense for the fronts to have more power/pressure

 

Well yeah, I don't think Stephen is saying the rears should have more than the front (at least I hope not), just that he wants to balance them out a bit more. I say just up the rear pressure by itself.

 

Well, the way yours is set up then, with the stock prop valve still there, your adjustable valve is just that...an adjuster for the rear only. It's not plumbed into the front, so really it's not a prop (proportioal) valve, just a pressure adjuster, for the rears only. You can only reduce the rear pressures, but never get more than stock.
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Exactly! Rear pressure more than the front IS a recipe for disaster. I basically just want the rears to get more pressure, than they do stock.

Step # 1 will be a 4th gen rear, for better brakes. Just not sure if that'll work with my Snypers now./ Might stick out. 1" or less I can handle. ANY more than 1" MAX, and no 4th gen rear....THEN, if I need/want to/think it'll help, I might try to adjustable valve idea.

 

That's not hard to do, they hardly see any pressure stock whatsoever.



Wait, are you talking about some sort of dual adjustable prop valve? That controls both front and rear from the same unit? I've never seen one of those.

Either way, you're complicating things. Can you give some reason why yanking it all out and just running a adjustable rear prop valve wouldn't accomplish what you want?

 

You will need to modify the proportioning valve(also called a combo valve) to allow more rear brake pressure. The stock setup severely restricts the pressure to the rears. You want to keep the factory combo valve in the system. There is a thread on here somewhere about modifying the combo valve by machining the end of the plug but I can't seem to find it.

 

Why do you want to keep the combo valve? It's useless if you want to have any control over the brake pressure.

I originally gutted the stock prop valve and welded the hole that's in the plug shut and reinstalled but realized it was just a bunch of extra adapters and clutter I could do without.

 

I may do a C4 IRS swap instead of a 4thgen rear axle. Either way, I'll do the rear swap first, then tackle the brake line pressure increase/decrease, front & rear.