Ok I know this has been discussed b4 on here more than a few times but the search tool isn't popping anything up so i cant find the old threads. Does anyone know the part # for the t bar style valve replacement one from summit or jegs( and also what they call it). I just noticed mine leaking yesterday from the bottom and don't want to pay oem price for a new one. Thanks
The stock unit works on load( the more in the bed the more the pressure! After market units control the pressure front to rear only!
If you dont haul anything just cap the t behind passenger front wheel and delete it. Looks alot better as well.
Still need a proportioning valve to do it correctly. If you hauled something all the time, then you could delete it totally. The LSPV limits brake pressure when there is no load in the bed. It does this so that the brakes don't lock up during a panic stop.
LSPV applies high pressure from front brake line to rears increasing brake pressure when there is a load. Hence why the rears will howl when you go too low without adjustment of the LSPV. Sorry you got it bass ackwards.
Haynes Repair Manual #92075 (Toyota Pickups 1979-1995)(4runner 1984-1995) Chapter 9, Page 15, section 9: "1) Due to the fact that disc brakes are non-self-energizing, they require more hydraulic pressure than drum brakes to function properly. Added to the fact that, conversely, drum brakes require less hydraulic pressure to be efficient in any automotive system is the fact that they are usually fitted to the rear of vehicles, requiring even less pressure than the front discs because most of the vehicle's weight is transferred forward during braking. 2) If the hydraulic pressure were the same to the front and rear brakes, the rear drums would be locked up almost every time the brakes were applied with force. The load sensing proportioning valve (LSPV) allows a portion of the rear brake hydraulic pressure to be applied to the front brakes, thus providing for smoother, more controlled stops." If I'm wrong, I apologize. My Haynes Manual hasn't failed me yet.
I wont argue the point. Trust me, I know I'm right on this one. Learned it in school at UTI. The rears always have less pressure than the fronts. If you follow the line to the front it goes to the front brakes portion of the master cylinder which is high pressure. When a load is applied the LSPV adds metered high pressure from the fronts to the rear "t" thus adding more rear stopping power. I deleted mine and have no probs whatsoever . Even in wet condition panic stops. I like Haynes as well...
That makes sense, maybe we found a flaw in the manual. I was working on the assumption that in our case the master cylinder plungers are the same in our setup and that the pressure sent to both front are the same. If that were the case, then the Haynes would be correct. Any unused volume or pressure of brake fluid could then be redirected forward. I have seen, on other vehicles, different sized plungers for forward and rear lines. And in that case, the reverse would be true. I consider this debate open until we know the facts....
We don't have equal plungers. Our design as with many others is a step-bore style design. But fair enough.
So basically i can remove my valve at the rear with out any rear lockup... under normal braking that is.
the LSPV is a dynamic brake pressure system (adjust front TO rear) as load is added in the rear. So when you lower, the LSPV thinks there's heavy **** in the back (lol those 3" drops) and it'll lock up hence the extra brake pressure sent to the rear.
Yes. And I'll advise it. I've been driving mine that way for 2 months now in all driving conditions and havent had a single problem under panic stops or anything. It's just a touchy subject for some who don't understand how it works and because it's part of the braking system. The only reason I would say to keep it is if you intend on hauling anything with the truck. If you were local I'd let you drive mine to prove it.
Man, I'm tempted to just drop this subject, but I think it's important. Just like anything else on this site, it's your call. I would be extremely hesitant to advise anyone online to make a call like such as this. The last thing I want is for someone to read on this site that it's OK to completely delete something such as this only to find out that it caused them to lose control of their vehicle, resulting in property loss or even injury. We don't all live in Southern California and I'm guessing that icy winter conditions probably haven't been a part of your weather for the last two months (unless you've visited the Sierras recently). The members from the north are going to deal with a lot less traction at times than us boys from the south. Would I drive my truck without one here in FL? Maybe until I was able to get one shipped to my door, every rain storm I see cars slide off of the road because of "black ice" and the inability to handle their cars. While their loss of control isn't due to the deletion of an LSPV, I am not taking any chances with my project over a simple to install $35 part.
