First Gen Tacoma Build Advice
- Thread starter HAB
- Start date
Clutch
<---Pass
Yeah...forgot to add that...not going to help you in your situation.
Jump on Tacoma World and see where others mounted theirs.
No need for an air tank on mine, since I have an e-locker. I just use one of those hand held compressors for airing up the tires...and use a cordless impact wrench for flat changes.
DaveInDenver
Middle Income Semi-Redneck
The Toyota name is the LSPV, meaning load sensing proportioning valve.
The theory goes that as the suspension squats the rod pushes a plunger in the value up on the frame, which allows more brake fluid to reach the back brakes. If you follow the plumbing you'll see a hard line goes into the valve on the frame and the soft line from the axle goes up to it. On the axle the soft line splits to a pair of hard lines on the axle running to each wheel.
The factory sets the system to give just enough pressure not to lock up with an empty bed. There's a whole procedure in the service manuals on how to do it. This adjustment is why the bracket on the axle is threaded, you move the end of the rod up and down to set it.
The problem is when you lift the truck it appears like you've removed weight from the bed so the system actually reduces rear brake pressure further and effectively turns off the rear brakes. To solve this you can use the threaded adjuster, but it's usually too short to work. Some people bend the rod, which works if you can get it right but of course you never do, not to mention it's a permanent mod that doesn't allow you to life more or go back to stock.
So the bracket was invented I believe by Moses on his first mini truck. If you measure the amount it offsets it happens to be usually 2 or 3 inches. So it's a kludge, but it works and is simple.
As you have noted it all of this might solve the brake issue but doesn't solve your issue. Thing is the LSPV isn't the most sophisticated device in the first place. When new it works fine IMO and if you maintain it and take time to adjust things it can work after you lift. But usually it's only working marginally. So the alternative is to remove it altogether. However if you just bypass it you get way too much rear braking and will lock up the rear long before the front. On pavement this is a pain, on dirt it's a significant pain and on snow and ice this is suicidal.
Hod rodders have been faced with this problem forever. So they have simple proportioning valves they use on their custom brake systems. You do some searching to figure out what that mean, (I'd use "toyota mini truck brake proportioning valve" or something like that). You can get brake balance working with those just fine but the problem is there's no load-vs-no load change so you usually end up leaving some braking performance on the table when you're fully loaded. But it would let you eliminate the LSPV if you wanted.
Thanks for the detailed reply, that's helpful. I did look up the factory spec for ride height in the service manual yesterday and measured, I'm only about 3/4" up from stock in the rear, so in theory it probably isn't working too badly. The seller told me 2", but either he overstated, or the springs have just sagged with age. I'm not likely to be changing the rear load that dramatically often, so a set and forget manual valve would work fine for my use. I'll look into that.
DaveInDenver
Middle Income Semi-Redneck
Yeah, indeed, many people use hot rod proportioning valve with success. The truth is the LSPV works really well in theory but isn't the most useful in practice. Most of the time it's adjusted too far attempting to prevent the rear from locking up that even loaded it's preventing much rear brake actuation anyway. With a dial you can get the rear working really well daily and when you load it you just don't gain any additional help. But in reality the extra cargo isn't adding that much additional weight that needs to be stopped anyway and the front are doing 75% of the work either way.
