FleshThorn

My seal job that turned into a bearing job has now turned into a load proportioning valve job. I was unable to get any brake fluid past the valve although I could get fluid at the bleeding fitting. I already have a new OEM assembly on the way, but I am having trouble getting the old one free from the frame mount. I have used a little heat and PB Blaster and hoping a 48 hour soak will work. Anyone run into a frozen in place proportioning valve before ?

Magnusian

You bought a replacement LSPV?

Cancel the order if you can, get a manual bias valve, infinitely cheaper.

FleshThorn

Uhhhh.....I guess it is too late to cancel the order.

FleshThorn

After actually reading about switching to a manual valve I see how much simpler it will be. I will see about cancelling the order and getting a manual valve.

waskillywabbit

iTrader: (-1)

Searching does work and it will save your money and headaches.

I freed my lspv with a sawzall right into the trash.

:wabbit2:

Magnusian

I used a hammer and a grinder to remove the rest of mine, which the PO left on after putting in a manual valve.

OP, you should mount the valve inside your cab, it'll require some customization of the brake lines but it's easier to adjust the bias on the fly when you don't have to stop, pop the hood, adjust, and then hope you adjusted it enough or you'll have to do it again.

FleshThorn

I spent the morning installing the Summit brake bias valve. I sit it at about half way for now. I am still checking for brake line leaks. Hopefully all of my recent repairs are good to go.

razed

Do you get fluid from the LSPV bleed valve?
Yes: that's good.
No: replace the LSPV; or clean it really well.

looks like a mod doesn't get it. Last thing anyone should suggest is a truck that locks up the rear brakes first. Anyone suggesting bypassing factory installed safety devices could potentially be held liable for any damages resulting from an accident attributable.

jbtvt

Why all the hating on the LSPV? Seems like it would beat having to dial in a different bias every time you load and empty the truck. But I've been running on front brakes for a year now so maybe I shouldn't talk...

Been wondering the same thing though, has anyone out there gotten theirs working again?

Seems like every thread I've read (many searches) they just tear it off, which I'd really rather not do, if they're gonna lock rather it be the front at least. Was gonna try compressed air one of these weeks, possibly but hopefully not followed by disassembly.

razed

cant blame you for not wanting to remove it. anyone responsible should not remove it or sugest anyone else remove thiers.

basically it allows full brake pressure to the rear brakes in case the front brakes fail. an adjutable valve elsewhere will most likely not do the same and could cause total brake failure.

razed

Not sure what you mean.

the lsp-bv tees off the right-front brake, which is split from the front circuit of the master cylinder, giving front brake pressure to the valve.
a failure in the rear should not affect the front brakes since both circuits are seperated even though both are connected to the valve.
another line connects the other circuit of the master cylinder to the rear brakes through the lsp-bv
if the line with front brake pressure fails / loses pressure, the lsp-bv ignores the load in the rear measured by the lever and allows full pressure from the rear circuit of the master cylinder to be applied to the rear brakes.

it's a safety, all around.

more load / weight in the rear should apply more brake pressure to the rear brakes due to the action of the lever connected to the rear axle.

a failure of the front brakes causes the rear brakes to receive pressure irrespective of the load. a failure of the rear brakes is seperated from the front brakes because of the valve and full brake pressure can be applied to the front brakes if necessary.

That is something a manual proportioning valve will never be able to accomplish.

jbtvt

Well, good to know about the full pressure override if the front cyl dies, yet another reason not to tamper with some the all knowing Yota engineers put together. I for one will definitely be sticking with an LSPV. Hopefully it'll be possible to get the existing one flowing again, they are pricey!

razed

sorry if i came across harsh. the trucks were build the way they were for a reason and for someone to come in and say mod this cause it works better is foolish, unless the person takes responsibility for their advice when it doesn't work and compensates you for damages.

newer, like since 1980 pass cars usually have the brakes split left front and right rear are one circuit and right front and left rear are the other circuit from the master cyl. that sort of guarantees that if one side of the mc fails, there is one front and one rear whell to brake. trucks reall cant do that and theres a reason antilock brakes took longer to get onto trucks than cars and its because of the wildly varyed loads a truck can carry in the back and the first step was 'rear' anti-lock which guaranteed that if the front brakes failed, the rears would not lock up and spin you around and then things got better and 4wheel anti-lock came out where each wheel could be braked seprate from the others.

now, if your truck only goes offroad, do what you want i guess. but if your on the streets anythign you do that can put other people at risk, or even yourself at risk should be avoided unless your willing to accept it, i guess.

the best a manual prop valve can ever hope to do is bias the brakes according to your adjustments. if you one day carry more weight in the back and forget to adjust the valve and your brakes fail and you slide into a minivan and kill peeps... nota good thing, right?

and if you see mention of zip-ties on the lever to hold it up so you get full pressure to the back brakes, you should ask them if their going to take responsibility for any damages too. it's a dumb suggestion that can be fixed either by adjusting the lever where it mounts to the rear axle or the lsp-bv itself... the former works okay for a mild lift [maybe 3-4"] and the latter takes pressure gauges and stuff to do.

Numbchux

Done it? Because if not, all you're doing is speculating, which is far worse than those of us who have done it, and know that in practice removing the LSPV and simplifying the braking system makes for a much more reliable setup.


ASSUMING for a moment, that you're still running stock drum brakes in the rear (modification is bad, right?), it's nearly impossible to have too much pressure to them, as they're not really strong enough to lock, even with an empty bed above them.

So that means, as you put more weight in the back, you're only going to have MORE traction on the back tires, and therefore be LESS likely to go sideways in an emergency.


Most trucks don't have an LSPV. The brake bias is setup for an empty truck, and stays like that.


A couple years ago, we bypassed the LSPV on my buddy's '87 4Runner, bled the system and went for a test-drive. Numerous hard stops on gravel, and all 4 locked up simultaneously. Substantial improvement in braking force from the rear, and no more likely to go sideways. That's right LESS likely to hit that minivan full of children.

Of course, a couple days later, we pulled it in the shop and it got a manual valve and rear discs. For similar stopping power, and much more reliable.




I agree, on paper, 25 years ago, the LSPV system was pretty slick. But age has proven it to just add failure points in the system.

waskillywabbit

iTrader: (-1)

:wabbit2:

razed

Maintenance would have fixed that.



Too bad you don't get that, though.
It's better to cut things in to pieces and make a hodge-podge of solutions, right?

razed

It's common knowledge that drum brakes are more efficient than discs due to the larger swept area. It's also common knowledge that disc brakes recover from "fade" more quickly than drums.

So, you have drums in the back and discs up front.

And you never wondered why?

jbtvt

You're testing it wrong. It's not while stomping on the brakes and locking up all 4 that the modification is dangerous. It's the borderline lockups, when you've only partially depressed the pedal and the rear has too much bias where it will lock up and slide out while the front keeps turning. (How are you so sure that all four lock up at exactly the same time using this test anyway, it's a difference of milliseconds, which you wouldn't even be able to see, let alone feel. Not to mention you're saying they're not strong enough to lock up, and next paragraph saying you locked them up when testing?)

It will probably work fine for 99.99% of people, 99% of the time, but once in a while on a slick or snowy road I can definitely see this mod causing problems. Like a safety harness on the roofs, it's quicker to skip wearing it, but that one guy in 5000 who slips and dies every year sure wishes he hadn't skimped out. It's on there for a reason.

And BTW, it's not dated, still on most models new Tundras - http://www.tundrasolutions.com/forum...proportioning/

With ya on the frivolous lawsuits though Corax, people should do what they want, but take responsibility for the consequences.

waskillywabbit

iTrader: (-1)

In spite of what many of you guys think we don't just moderate on a whim or ban folks at will.

Razed was a person previously banned who resigned up so they were banned again when it was discovered.

The thread was edited to reflect their removal.

:wabbit2:

Numbchux

I ask again

Answer it before you respond again. Because if you've done it, and you're still so bitter about it, you did it wrong. And if not, you have nothing to add.




Thanks for the assumption about our testing. No, we did not just go out and slam on the brakes. I'm the crew chief for a stage rally team, we completely re-plumbed the braking system in one car for hydraulic handbrake and ABS delete, and installed a manual balance valve in the process. This is a ~300awhp monster, and it works great in competition and on the street. I have spent hundreds upon hundreds of hours ice racing. I know what brake bias and oversteer feels like, and how to set up a suspension and brake system for the best control.

So, the more detailed story on that situation. Empty 4runner, top off, gravel road (pretty much worst case scenario). Did it a few times from speed, lean into the brakes until they just barely lock up and we couldn't tell which was locking first. So we brought a chase car to watch....still couldn't tell.

I would not have been comfortable leaving it that way for any period of time. But we had rear discs and a manual valve ready to go in very soon, so we just waited.

The fronts should lock noticeable sooner than the rears on a low-traction surface, as there's more weight transfer on pavement.



My point in mentioning this, is not to recommend it as a realistic option, but to demonstrate the strength (or lack thereof) of the stock rear drums.

I have also heard that with the stock drums and a manual valve, opening it all the way still isn't enough pressure to be of a worry at all.


You'll also notice I said NEARLY impossible. I said it that way for a reason. With an unloaded rear end, and removed balance valve, they can be locked up on gravel.




Cars are a compromise. Every aspect of them. There are reasons for how everything is built, and keeping cost down is always on the list. Just because Toyota (or any manufacturer, of course) made it that way, doesn't mean it's perfect for every use. You can ALWAYS improve upon a design, making it easier to service, or more reliable, or even just catering more to your uses and needs.