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satchel
11-09-2010, 05:42 PM
Has anyone adjusted your LSPV after putting a lift on?

During the spooky night run I couldn't get my rear tires to brake at all, they just kept pushing my front tires on the ice every time I tried to brake. I started thinking today that it is probably my LSPV.

The reason I'm thinking this is because the LSPV works by sending more or less pressure to the rear brakes depending on how close the frame is to the rear axle. That means if you add a ton of weight to the back of the truck and it squats, putting the frame closer to the axle, then it should send more fluid to the rear, and just the opposite if you remove weight and the frame returns to its normal height.

This makes me think that lifting the truck with my OME kit, which raises the frame up from the axles, would have the same effect as taking weight out of the back of the truck and reducing the rear braking pressure. I'm wondering if it threw it out of adjustment so much that no pressure is being sent to the rear.

Anyone heard of something like this before?

leiniesred
11-09-2010, 06:07 PM
Yeah, lifting the truck with springs makes the LSPV think the truck is empty. On Bob's FZJ80, we figured that with his lift we would be about right with the adjuster moved all the way to the high end. You'll have to ask BobinDenver if his truck stops the same before and after the lift.

On my '89 4runner, I found that the lspv was more of an empty truck/full truck switch. Not much in between. Once I got to 13.50" wide tires, I found I could run it in "heavy truck" all the time without locking up the backs. 37x12.50s also work fine in "heavy truck" mode and the truck stops better in heavy truck mode.

Chris
11-09-2010, 06:36 PM
On my FJ62 I added a rectangular scrap of 2x4 steel and re-mounted the LSPV on it effectively raising it 3.5" then adjusted the arm so it was parallel to the frame.

satchel
11-09-2010, 06:39 PM
I guess I didn't realize this was common knowledge to do this after performing a lift. Thank you for confirming my suspicion.

TIMZTOY
11-09-2010, 07:22 PM
ditch it for a adjustable proportioning valve (http://www.jegs.com/i/JEGS/555/63020/10002/-1?parentProductId=755192). if you dont want to do that. what i did for my 89 was cut the rod about 2" out of the valve. then riged up a bar so i could adjust it up and down and tighten it to stay there..

Jacket
11-10-2010, 06:19 PM
PM Crash if he doesn't post up to this thread. He's done some experimenting with the LSPV on his 80 to improve braking and should have some good beta for you.

Air Randy
11-10-2010, 06:32 PM
My suggestion is to take your LSPV off and throw it as far away from you as you can. No other mfg uses those things and from what I can tell they are just a source of poor brake performance especially as they get old and rusty and you start modifying your suspension.

Go to Davezoffroadperformance.com and buy this manual proportioning valve setup. I put one on my mini truck, it takes less than an hour to install and works great, you can dial-in whatever front to rear ratio works best for your rig.

TIMZTOY
11-10-2010, 06:55 PM
here's daves link. (http://www.davezoffroadperformance.com/forum/viewtopic.php?f=3&t=52)

nuclearlemon
11-10-2010, 07:04 PM
My suggestion is to take your LSPV off and throw it as far away from you as you can. No other mfg uses those things and from what I can tell they are just a source of poor brake performance especially as they get old and rusty and you start modifying your suspension.

Go to Davezoffroadperformance.com and buy this manual proportioning valve setup. I put one on my mini truck, it takes less than an hour to install and works great, you can dial-in whatever front to rear ratio works best for your rig.

or you could just buy it from summit off road, since that's where dave apparently gets them ;)

i'll be eliminating my lspv next summer just to get rid of the clusterf&%% of lines everywhere.

corsair23
11-11-2010, 02:45 PM
You can pull it and toss if you want, or just do a search here and on MUD on where to set it after your lift. Lots of threads on the subject. If yours was trashed I could see ditching it, otherwise they seem to work well enough...:dunno:

Air Randy
11-12-2010, 11:31 AM
They do seize from corrosion and modified suspension is a balancing act, far from an ideal solution.

But still I don't mind having it on mine. Not having to crawl under there every weekend to adjust a valve for Home Depot runs and then again Monday for the commute is nice. It seems to do what it's supposed to in my case even with OME rear springs.

I guess I don't understand why you would want to adjust your front to rear bias every weekend? Every other vehicle in the free world seems to function well without changing the brake bias between offroad, onroad, etc. You normally adjust the proportioning valve to what works well with your vehicle, tire size, typical load, etc then never touch it again.

Air Randy
11-12-2010, 11:33 AM
or you could just buy it from summit off road, since that's where dave apparently gets them ;)

You can, but what makes Dave's unit nice is he includes all the metric fittings and tubing you see with it. Makes it super easy to install. You can get the Summit unit direct but then you need to piece together the metric adapters, etc.

Uncle Ben
11-12-2010, 02:33 PM
So many re-engineers... :rolleyes: For those that are not smarter than MIT trained auto engineers the LSPV actually is a smart little device. The easiest way to keep it where it was calibrated is to mark the lever level at stock height then readjust after doing the lift and again after lift settles and your done adding major weight/modifications. Toyota actually has done quite a bit of math and if adjusted properly you will find even brake wear F&R. Adjusting it for more front bias so it feels like better brakes will get you machining rotors often due to warping....just saying....

Air Randy
11-12-2010, 05:32 PM
So many re-engineers... :rolleyes: For those that are not smarter than MIT trained auto engineers the LSPV actually is a smart little device.

I'm sure it was.....when it was working properly.

Now most of them are just a rusted rats nest of tubing.

If they are so wonderful, how come Toyota doesn't put them on every new vehicle they make now?

Uncle Ben
11-12-2010, 05:53 PM
I'm sure it was.....when it was working properly.

Now most of them are just a rusted rats nest of tubing.

If they are so wonderful, how come Toyota doesn't put them on every new vehicle they make now?

They do.....they just tied it into the ABS system along with A-Track.

satchel
02-26-2011, 08:27 PM
After taking the truck up to steamboat and sliding all over the place because the rear tires are not locking up and just keep pushing the truck, I thought I would start looking into this again. I actually took it to a local midas place just to see what they thought and they didn't have any input as to what the problem could be.

I have yet to change out the lspv, but have changed virtually everything else previously including the master cylinder. I did take the arm from the lspv and move it all the way up and all the way down with the truck in drive and my foot on the brake pedal and the rear tires still just keep on spinning. Any thoughts as to what this could be other than the lspv? The guys at midas just said that the rear drums weren't strong enough to stop with the v8 I've got in it, but I seriously doubt that. It's not like I'm accelerating during these tests, just letting it idle and the rear drums will not lock up at all. I guess I'll order that setup from Dave's on the previous page. Seen here: http://www.davezoffroadperformance.com/forum/viewtopic.php?f=3&t=52

One question about that setup. What do you do with the bypass line? I have a supply line in, bypass out, and line out to the rear brakes from my valve, but this only has 1 in and 1 out.

coax
02-26-2011, 08:43 PM
A few ideas, fwiw.

Any possibility that one or more of the rear cylinders are out of adjustment or frozen? Can you pull one drum on one side off and see the shoes moving at all?

I did take the arm from the lspv and move it all the way up and all the way down with the truck in drive and my foot on the brake pedal and the rear tires still just keep on spinning.

When you say this did you adjust the lspv at the frame end or the axle end? Not sure if/how much the truck is lifted, but for more than a very small lift it needs to be adjusted at the frame side to get enough adjustment. I'd say you are correct in that the V8 has nothing to do with the braking system unless you are power braking around corners :D

satchel
02-26-2011, 08:49 PM
Thanks for the input. The shoes are definitely moving, just not enough to provide pressure against the drums, and they are adjusted quite tight against the drums as well.

As for the lspv adjustment, I unbolted it at the axle and held the arm up as far as it would go on the lspv while my buddy had it idling in drive with the brake fully depressed and it made no difference, then moved it down as well and still no difference. I did permanently adjust it as high as it would go at the axle, no adjustment at the frame.

I'm guessing that the valve itself simply isn't providing enough flow through to the rears even when it is maxed out. I just can't think of what else the problem would be other than the master cylinder and that was changed already. Anyone know of a good brake place that would actually know and be able to test it well? I also looked for a brake pressure tester to see how much pressure I'm actually getting back there and I can't find one.

coax
02-26-2011, 09:40 PM
When you unbolted the axle end of the rod and raised it all the way up, did it max out with in the lspv mechanism or did it hit something on the body? Reason I ask is that due to the linkage of everything, if the lspv was improperly adjusted on the frame side, even raising up the arm all the way may still not redirect enough flow to the rear.

I'm having trouble putting down this thought into words.

Say the valve body on the frame was already mounted too high by 1/4 inch. Axle side adjustment might not make any difference if its out of spec on the body mount? :confused: So even maxing out the rod end upwards might not redirect enough flow? Unless maybe the valve is clogged or in some way broken, (or its all rusted out) it may be worth a try to adjust the valve down a 1/4 or 3/8 inch (marking the original spot) and see if that makes a difference, before going and trying to track down a pressure tester ($$$ money on amazon, but maybe someone in the club has one?) Even if you moved it down as far as possible so it was, in theory, as much rear-proportioned as possible, it may give you another test point. If it works, adjust as necessary. If not, than maybe the valve needs replacing??

Just a few more thoughts. Not sure if they are helpful :)

satchel
02-26-2011, 09:52 PM
When it was unbolted I raised it up all the way to the max of the lspv, there was still room to go up to the body but it would have broken the arm off of the lspv if I moved it up that far I think. When I finally adjusted it permanently I moved the arm up about 2 or so inches. Probably several inches from the maxed out movement I made when it was unbolted, but either way nothing made a difference. I guess to say it another way, I don't think it would matter if the lspv would have been completely removed from the truck during the adjustment. I moved the arm through the full motion of what the lspv allowed and there was no difference.

I absolutely appreciate the thoughts, it helps me think through things more thoroughly. I think at this point I'm hoping that the valve itself is bad being that I have gone through the full range of motion with no difference. Has anyone had one that was completely bad before? Is there something I'm missing, like maybe the rear was not intended to fully lock up? I don't see how that could be possible but maybe I'm missing something. Any thoughts on whether the drums can't handle the output of the v8, or switch to discs? These don't seem likely at all to me either but any thoughts are appreciated.

Air Randy
02-27-2011, 10:16 AM
After taking the truck up to steamboat and sliding all over the place because the rear tires are not locking up and just keep pushing the truck, I thought I would start looking into this again. I actually took it to a local midas place just to see what they thought and they didn't have any input as to what the problem could be.

I have yet to change out the lspv, but have changed virtually everything else previously including the master cylinder. I did take the arm from the lspv and move it all the way up and all the way down with the truck in drive and my foot on the brake pedal and the rear tires still just keep on spinning. Any thoughts as to what this could be other than the lspv? The guys at midas just said that the rear drums weren't strong enough to stop with the v8 I've got in it, but I seriously doubt that. It's not like I'm accelerating during these tests, just letting it idle and the rear drums will not lock up at all. I guess I'll order that setup from Dave's on the previous page. Seen here: http://www.davezoffroadperformance.com/forum/viewtopic.php?f=3&t=52

One question about that setup. What do you do with the bypass line? I have a supply line in, bypass out, and line out to the rear brakes from my valve, but this only has 1 in and 1 out.

If you really want to try and diagnose it, rig up a rubber brake line with the proper fittings that will allow you to bypass the LSPV. Bleed the rear brakes and see if that makes them work right. If so, you can get another lspv from Yotajim or a new one if they're still available. Or, get the Dave's unit ,install it and the problem is solved. Of course, you won't have all of the magical properties of the lspv, 300K brake life, anti-gravity, etc.:D

If the bypass doesn't work, and I'm assuming your new master cylinder is good, then it almost has to be a blocked brake line. Check all of your hard lines from the MC back to the lspv to make sure none of them are crushed or bent so far as to restrict fluid flow.

rover67
02-27-2011, 12:59 PM
Have you tried swapping out the master cylinder? Maybe the piston is not sealing right in there.

I feel like if it was a blocked line the pressure would come up eventually when you press on the pedal really hard. It seems like the fluid flow would just be really slow. That doesn't seem to be the case with your truck. It seems like there is just low pressure. The volume is actually fine, the pistons in the rear drums were moving nice and fast and were both kicking out way more than they needed to.

satchel
02-27-2011, 02:00 PM
Randy, good ideas. I might just go in that direction to help troubleshoot it. Not sure how I would tie into the bypass line though, maybe using a tee I guess.

Marco, I did change the master cylinder already but I can't guarantee that the problem was happening before I did it. The new one may be bad I guess.