LSPV adjustment after 2" lift

I fitted the lifted suspension to my 80 quite a while back and did not bother with caster correction or the LSPV adjustment. The truck drives fine so I thought I'd leave it for a while and see how it went. Well my brake warning light came on on the dash causing me to scratch my head a bit - anyway Rob correctly diagnosed that it was low brake fluid level. My take on why the brake fluid got low was that my front pads had worn quite significantly - after very minimal wear in the previous 8k-odd miles that I've driven the 80 and a lot of wear in the last 2k miles since fitting the lift, I believe that it's excessive brake bias towards the front due to incorrect LSPV set-up

So I decided that it's time for an LSPV re-adjustment The LSPV set-up has the valve etc mounted on the cross-member just ahead of the left (n/s) rear wheel and the rod/lever connected to a bracket on the rear diff-casing. There are different options to re-adjusting the overall set-up. I did some research on MUD and the general view is that the easiest adjustment for a modest lift of around 2-2.5" is to move the LSPV itself. Someone did the calcs and a 2.5" lift apparently needs the LSPV to moved downwards by a 1/4". Reading through the calcs, I see that the theoretical adjustment is in fact 4.8mm which the Americans have converted to 1/4"

Anyway, I figured that I would aim for a 5mm downward adjustment (working in tenths of a mm is pretty much impossible in the gloomy wheelarch with encrusted mud and Lincomb bank vault liner ).

The plan of attack is to brush the crud off the LSPV, particularly on the 2 bolt and the slots in the bracket that the LSPV sits on. Once you've gently removed the bulk of the muck (gently because you have fairly delicate brake lines there), mark the current position of the LSPV. I just marked the very top of the LSPV by scratching a mark with a screwdriver.

Here is a pic copied from MUD with marks drawn on. You can see the 2 nuts to be loosened clearly in the middle of the LSPV body.


Once the nuts have been loosened, I gave the bolt-ends a few judicious taps with a brass hammer - obviously be careful not to destroy brake lines and unions I used a long screwdriver as a lever on the top of the LSPV to level it downwards. Because of the accumulated muck, it moves fairly slowly, so it's easy to slide it down gradually until you have it in the desired position



Tighten the nuts and the job's done! Find a loose surface with ABS disabled and test to see that you have the balance roughly correct. The fronts should still lock just before the rears.

Hope that helpful for anyone else that hasn't adjusted their LSPV yet! It's a very straight-forward job - removing the left rear wheel (not essential but makes access much easier) and loosening the 2 nuts on the LSPV are the sum total of "mechanics" involved

Cheers,

That is one clean LSPV though after shouting at the truck for the last two hours trying to bleed the front calipers i will do the valve when i replace my rear calipers. Was going to rebuild them, but after just inspecting them i think i will go all the way.

I found there was enough adjustment on the axle end (the threaded rod) when I did mine.

right i need an answer

did a lift over the weekend and left this job until today ..

i tried undoing the bolts 1 snapped and the other is super tight . didn't want to shear it off so looked at the other end of the lspv where it mounts to the axle ..
the adjusting rod is pretty corroded so not even gonna try and adjust it ..

I've undone the bracket that bolts to the axle and made an extension piece so the bracket now bolts up about 1 and half inch higher than it did
i think its like shortening the adjusting bar
...

Will this work?
have i gone the right way ? ( raising the bracket or should it be lower )
have i added to much?

does this make sense

When I did the normal 2" lift on my 70, I originally added 2" to the existing adjusting rod, but then decided to convert the proportioning valve to manual adjustment. I did this for two reasons:-

1) I have junked the back seats, and fitted an equipment box and table, so the load in the back is basically constant, so no need for the valve to vary.

2) I hate superfluous fittings!

If anyone wants to know how to convert the valve, just ask.

Roger

Alright I'll ask then

How do you do it?

I'll take the valve apart and get some pics. I'm making a new wall cabinet at the mo, so give me a couple of days.

Roger

Picture 1 shows the LSPV valve as it is now. The rubber cover is a bellows I had spare. I shortened it and glued in a rubber bung.

Picture 2 shows the valve with cover removed.

Picture 3 shows the adaptor removed.

Picture 4 shows the adaptor and circlip (circlip is the original).

Picture 5 shows adaptor from another angle.

Picture 6 shows underside of adaptor.

I used the original steel washer that is held in place by the circlip. You need a threaded upstand (a long nut with the edges ground down so that the circlip will fit, or make one from suitable tube that you can thread). The adjuster is a cut down bolt, around 8mm dia, with a suitable locking nut. The squared off end is so you can hold the adjuster so you can tighten the lock nut. I soldered the upstand to the washer.

Once fitted, clamp off the front brakes and drive the car (slowly) and then brake. Adjust the adjuster to nearly lock the brakes. Remove clamp and re try. At the MoT, the tester was surprised at the effectiveness of the back brakes. Certainly on the road, the retardation is better.

Roger

Does it matter which pipe goes into either of the two ports on the valve? I can see the one that goes to the axle but what is the significance of the two pipes going into the valve??is there any sequence?

Thank you for taking the time to show us this Roger.

A simple but effective solution.

Simple but wrong. The valve alters the amount of pressure at the rear brakes which is a variable, even if the weight of the vehicle is unchanged the distance between the body and axle will vary according to how hard you are braking. @BAt21, as this is running alongside your other 'pedal travel' thread I will just throw in a quick heads up. When braking the front of the car pitches down and the rear up, how hard you brake and how much weight you are carrying will dictate how far the body moves away from the axle. Braking just the rear wheels without any front braking effort will not lift the body the same amount so the adjustment is simply wrong. Or to put it another way, after setting the LSV with just the rear brakes just not locking, and then braking again with the front brakes will lift the rear higher as the front dips, in other words even less braking (which would be correct) but, the reality is maybe no effort at all, this is completely different to the roller testing that was mentioned. It seems many are happy with 'close enough' brakes but, for me it has to be done properly. if you want it done right then pay to have the pressure setting done correctly, of course if you are happy with close enough...................................

Can't explain this anymore as my head hurts, I will wait until I throw the gauges on, who knows the amount of difference it will make when done correctly may be minimal.....maybe?

regards

Dave

I am following this with interest and while i like the idea of just moving the LSV but i do question how that will work when new factory suspension will sag 2 inches as it ages and (i assume) remain in spec .

I am also baffled as to what i can do if the LSV is activated by body roll and my HD towing set up on the rear and HD sport on the front (meant to cope with the weight of a winch bumper i haven't actually got yet) means i have very little body roll at all even under heavy braking .

Is this why i want to stamp on the inventors head every time i hear the abs rattle ?

Dave's right. The correct way to do it is in the workshop manual. However the procedure is for a standard car and there are no official figures for one with suspension or other relevant modifications. I still think if the valve was seized in such a position as to put all the pressure within the limits of the switch on to the rear wheels it would be safe on the road. Only guessing though.

The spec for the rear brake pressure is 45 kg / cm plus or minus 6 kg, so it's not what you'd call a tight tolerance. I'd like to know what kg difference moving the valve body has. The FSM actually says the primary adjustment should be with the arm. Which is what I do. The real world problem with trying to move the body is that the nuts simply snap off.

Can anyone confirm which way I need to adjust the link on the threaded rod on the back axle to compensate for a 2 inch lift? Up the threaded rod or down the threaded rod ?
I was going to just lower the LSPV .......the nuts are loose and not seized....I gave them a tap on the end with a copper hammer but the LSPV seems very reluctant to move down so thought I'd just try adjusting the other end .

To be fair, why do our trucks even have this when we all have ABS... It doesn't make sense.

Because they don't all have ABS Beau. The GS doesn't. But why fit it to the GX and VX - is a very good question.

Gotcha! I wonder if the brakes would operate better without that then? Anyone removed/bypassed the LSPV?

In the past I considered fitting one of those rally style brake bias adjusters but as Dave pointed out in the postings some time back, this is a constantly variable equation. Personally I don't think that it's something that's very finely tuned by the LSPV but the more the front dips, the more the LSPV compensates.

If you had a truck which you never changed the weight of (difficult with fuel load or course) and you only ever braked with the same force, you could set the brakes and forget. But in real world braking this simply isn't the case. However, I do wonder with a very heavily laden truck such as mine, just how much lift do I get when I brake. There is a limit to how much braking force I can apply before I lock up (no ABS and at the point the tyres slide, in theory the vehicle stops pitching.

Now I know it was unpopular with the purists the first time I said it, but the opportunities for having an FSM brake set up are almost non existent; even more so now that Trevor has closed. But I still maintain that I get a decent enough set up by driving forward and braking hard, then reversing up and braking hard and noting the difference in brake effect. Yes it's not perfect and the LSPV is deigned to wok going forwards, but it does give you somewhere to start. I then adjust the rod a bit at a time until I get a good balance and can brake hard going forward on a fairly loose surface to the point that the rear wheels aren't locking up quickly. If you shoot backwards and the brakes slam your head into the seat then you've probably too much rear bias.

The proof is in the brake pad wear and that has been pretty even. But then I started towing the Metalian trailer with the very high nose weight. The stopped the vehicle lifting at all under braking and suddenly I started eating rear pads. This tells me that the rear brakes are not being closed down sufficiently. It was interesting that on mountain passes the fronts weren't heating up but the rears were boiling. I plan to adjust the nose weight of the trailer rather than mess with the brakes which are otherwise fine.

Well , I've just adjusted the link on the threaded rod on the rear axle upwards by 5mm and will see how that works , still have 10mm more upwards adjustment .

I tested it last night pre - adjustment and the front disc's were getting very hot after several stops on tarmac where as the rears were warm.

TBH the lift has been on the vehicle for several years with no issue's .....just I've just rebuilt front axle , brakes and rear brakes so thought I'd have a play with everything known good .

As for why the GS has no LSPV and the VX do's I would wonder if it's not to do with the fact that the GS was a 5 seat vehicle and the VX an 8 seat vehicle .....that's a lot of extra weight if fully freighted .

We always had bias adjustment on our Rally car's either with a twin master cylinder set up and bias adjuster to the pedal box that's pretty much infinitely adjustable or a more simple detented valve in the rear brake line on the trans tunnel as we also ran all the brake lines inside the shell .Also a hydraulic handbrake.

This was more about being able to get the rear end loose and just about locking under braking so we could flick it left or right into the corner and then steer on the throttle......a good thing in a nimble RWD Escort or Manta....not sure I'd be doing that in a loaded cruiser .