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The arm of my LSPV!! has a bend in it and I wonder if that's normal.
88 Pickup 2wd, Deluxe (long bed, x-tra cab)
Would Straightening the bar give me more contact at the drums, or overextend some internal component and mess up the valve?
I want to get as much contact between shoe and drum as possible because the truck has a lot of weight, and no sag.
The BPV adjustment screw is maxed out as are the star adjusters. Also, the entire system is new, including the brake fluid, and everything is tuned as much as possible.
Any input would be much appreciated.
BPV Arm has a bend on the right side, right up near the valve.
Last edited by MichaelKLerner; Aug 23, 2022 at 09:59 AM.
Reason: Added year and model description
It's actually called the LSPV - Load sensing proportioning Valve.
It would help us a lot to know the year of your truck, 2 or 4 wheel drive, and so forth.
You might want to go to a Toyota parts site, and find the right year, etc, for your truck, and see what the bar looks like. You might also check the FSM for your vehicle to see what it looks like in there. It will also have the procedure for properly adjusting the LSPV.
For example, here is the picture from the FSM for a 86-89 4WD 4Runner. You can see that the stock, from-the-factory part is straight. However, a small bend like that can be used to fine tune the valve to your particular needs, if the normal adjustments, the mounting plate and the shackle #2 (in the picture), are not adequate.
The correct adjustment procedure is shown further down in the FSM.
Without a brake pressure gauge, it's going to be just a guess to get it adjusted correctly.
Personally, I would just bend it back straight. Then put the set plate back in it's original position. It's been over five years since I have fixed my LSPV. But I do remember that the plate could be moved up or down, and that adjusts the pressure to the rear brakes. More weight on the bed of the truck the more pressure is needed for the rear brakes.
Last edited by snippits; Aug 22, 2022 at 01:57 PM.
It's been years since I put it on so I'm not sure, but I believe it does. I only got rid of it because it was rusted, required freeing up at least once a year, and finally one of the lines to it rusted out. Are you sure the self-adjusting mechanism that attaches to the emergency brake is free?
By "self adjusting mechanism that attaches to the e-brake" do you mean the star adjustment wheels? Yes the star adjusters are new, lubed, and adjust as expected
The Set Plate, no. The valve can be moved up and down a small amount on the Valve Bracket. The main adjustment as I remember it, however, is how Shackle 2 and Shackle 1 meet. You can see that the shaft on Shackle 2 is a fairly long, threaded shaft, that goes up through Shackle 1. The long bar from the valve attaches to shackle 1, and shackle 2 attaches to the rear axle. Thus, you can see how it adjusts the angle the bar is at.
I might be thinking backwards on the adjustment, but as I recall, the farther down the bar from the valve is, the less pressure to the rear drum brakes. As the rear end is lowered by the weight in the bed increasing, the bar is lifted up, allowing more pressure to be applied to the rear brakes. Thus, if you adjust Shackle 2 so it's lass far through Shackle 1, you get more pressure to the rear brakes to begin with, and as weight is added, it increases.
From the looks of things, that bend in your bar will lower the brake pressure to the rear. If you want more, straighten the bar out.
Excellent thanks. I got under the truck and manually moved the bar. It's like bench press. And I can feel it's at the end of its range. So now I am satisfied I have done all I can reasonably do with the stock configuration.
It's been a long time since I replaced the LSPV, so calling it a plate was wrong I think. What I was talking about was what 2ToyGuy mentioned...the bracket. It does move up and down just a little bit. But I do think 2ToyGuy is right about the main adjustment. I think I tried adjusting the rods, and ended up putting it back the way it was. The witness marks, rust, grime, and etc. got me back to the factory adjustment.
Anyway, like I said earlier, you will need a break pressure gauge, and what ever else was mentioned in the repair manual to adjust it correctly. I know some of us go down a dirt road unloaded, and hit the brakes hoping that the rears don't lock up with a moderate amount of brake pressure. If the rears lock up, then it's definitely too much brake pressure.
sorry to rain on the parade, but the arm in '87 and '88 4runners is not straight from the factory, it has the same bend as the one the OP has in his truck. the curve allows the arm to clear the spare tire (in the horizontal plane), and it also has a bend in the vertical plane, though not as pronounced as for tire clearance.
if you want max braking, disconnect the arm where it attaches at the axle, and secure the arm tightly to the bottom of the bed. this opens the valve in the LSPV to allow maximum flow during brake application. from my experience, you won't harm the valve in the LSPV by doing so.
Aug 21, 2022 | 08:22 PM
