Load Sensing Proportion Valve (LSPV) and suspension lift

[BlueRock Junior Member Find all posts View Profile Close BlueRock]

I've noticed that all my brake dust is settling on the front wheels.
And, the brakes don't seem to be performing as well as I think they should.
So, I suspect the rear brakes aren't doing much.

The most likely culprit is the Load Sensing Proportion Valve (LSPV).
I assume I need to adjust this to compensate for the 3 inch suspension lift, in the back.

But, how do I do that?

There's an adjustment mechanism, next to the spring.
But, it seems pretty useless, given the angles involved.
I suspect I might need to install some kind of bracket extension, in order to bring the spring higher up on the panhard rod (closer to the chassis).

Will that work? Will it make a difference? Are there any tricks to fiddling with the LSPV?
I have dual-rate OME springs with ABS.

BlueRock

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

With brake dust settling on the front wheels, can mean that the pads are getting low, and with that, they can become hot very quickly making stopping distances longer.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Rear brakes only do about 5% of the stopping. If you don't believe me try stopping
using the handbrake only.

Cheers
LeighW

[williade Avid PP Poster! Find all posts View Profile Close williade]

A 1" spacer block on the LSPV should compensate for new position of the Panhard rod.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Rear brakes only do about 5% of the stopping. If you don't believe me try stopping
using the handbrake only.
Cheers
LeighW

That will only prove how terrible the handbrake is. It has no bearing on the foot brake at all.
(The handbrake uses a tiny little drum brake, whilst the foot brake uses disc brakes, both front and rear).

[williade Avid PP Poster! Find all posts View Profile Close williade]

Agreed about the handbrake. But the rear disc is more like a Saturn ring around the drum of the HB and is only a single piston caliper compared to the 4 piston calipers in the front.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

That will only prove how terrible the handbrake is. It has no bearing on the foot brake at all.
(The handbrake uses a tiny little drum brake, whilst the foot brake uses disc brakes, both front and rear).

I was generalising, in a modern braking setup, under light braking the rears do about 5% of the braking if any. Under heavy braking they do about 30%. Getting back to the original question, would be better if the load sensing valve was returned to it's proper setting, though it will not make a spectacular difference to the braking. It's main function is to stop the rear wheels locking before the fronts which causes the back end to drift around under heavy braking.

The dust on the front wheels is normal as they do most of the stopping. In my cars I have never had to replace the rear brake linings, generally only heavy brake users have to. Pays to drive sedately!

Cheers

LeighW

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

Rear brakes only do about 5% of the stopping. If you don't believe me try stopping
using the handbrake only.

Cheers
LeighW

Tried it, the rears lock up...lol

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Tried it, the rears lock up...lol

haha, surely you had a slippery surface.. Mine is a struggle even with new pads.

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

haha, surely you had a slippery surface.. Mine is a struggle even with new pads.

Was done on the road, no slippery surface involved. You need to adjust the handbrake cable at the handbrake leaver. I had an 80 series before the Prado, and we all know how poor the handbrake is on those, but with a bit of adjustment at the leaver, it worked a treat. It may require a few small washers to get the cable to a suitable tension.

[wadzy6 Lurker Find all posts View Profile Close wadzy6]

with reference to the original question, i recently installed a 3 inch lift. i got my mechanic to cut off the old tag which is attached to the panhard rod and make a new bracket and install it onto the new adjustable panhard rod. i only just got this done today so i will see how it goes. it would be best to buy a prado manual book (like max ellerys) because there is certai ndistances and angles that need to be maintained. or just get a good mechanic to do it

[BlueRock Junior Member Find all posts View Profile Close BlueRock]

Sweet! Let me know how this works out.

I have Max Ellery's book, and on page 319, it shows a picture of the LSPV with dimension 'C.' Any idea what they mean by the 'short' model vs 'long' model? I have no idea which one I have. The difference is apparently 2 mm.

BlueRock

[KZJ95W Lurker Find all posts View Profile Close KZJ95W]

long wheelbase and short wheelbase?

[KZJ90 Member Find all posts View Profile Close KZJ90]

Tighter spring, better brakes. There is never too much brake force at rear. Useless valve, better if there would be only straight line over it.

[BlueRock Junior Member Find all posts View Profile Close BlueRock]

Bracket extension installed

I finally went ahead and dealt with this. I searched in the hardware store and found some 40 mm x 2mm steel with holes in it that I could conveniently cut into a bracket extension. I then did a few calculations to figure out how much to raise mounting point by (where the spring mounts to).

Length of Panhard rod (bolt to bolt) = 94 cm
Length to centre of mounting bracket = 72 cm
Length to centre of spring mount pivot point = 76 cm
My rear suspension lift = 70 mm
Distance from axle to bump stop = 15.5 cm

So, the adjustment required was to raise the spring mounting point by 70 x (76/94) = 57 mm. However, to be safe, at maximum compression when the axle hits the left outer bump stop (if it ever actually hits that), at the current height, there needs to be a minimum distance of 15.5 x (72/94) = 12 cm between the top of the bracket and the frame. This means that the top of the bracket extension can't exceed the top of the current bracket by more than 3 cm. If it's more than that, there is a chance it might hit against the frame at maximum spring compression.

Here is a picture of what the final solution looks like...



And, from the other side...



As the original bracket bolt was quite rusted, I managed to bend and snap it, when removing it. But, some quick work with the angle grinder saved it enough so that it still works (but it's not adjustable any more). That angle grinder seems awfully useful!

I've tested it, this evening, and the brakes feel and respond much better than before. The pedal doesn't seem to be as sluggish. I've washed the rims, so I'll see where the brake dust settles, over time.

The 222 mm figure mentioned in the Max Ellery book (on page 319) seems completely bogus. Moreover, they got the A and B adjustments backward. My 'C' measurement is something like 240 mm.

Cheers,
BlueRock