88FJ62 stock suspension measurements on Rear axel to Frame /Braking problem

[cruiserneck]

I am looking for the stock specs for the measurement of the rear axel to the frame. My 62 has a spring kit and I am having breaking problems that I have narrowed to the LSPV valve. I read posts where people had added a 2" spacer to the end of the load sensing spring that connects to the axel housing. I did the adjustment and added a 2" spacer and the brakes are much better, BUT if I could find the stock specs on the axel to frame distance, I could do a better calculation of the correct angle and hopefully tweak it to the maximum breaking benefit.

Had a small accident 35 mph on a moderately damp street where the front wheels locked up and the rears did not engage at all. This was an avoidable accident had the rear brakes worked. Since the suspension lift, the breaking had been horrible and in looking for and answer, I learned about the LSPV. I dont know how many out there have had the same problem with bad breaking, but if you have a suspension lift and you are having breaking problems and have not readjusted the LSPV, you need to get on this before something unfortunate happens. If you have an OME suspension and you

This link from another post may help. What to do with my LSPV after OME lift installation?

I can just go with the 2" bracket and move on, but I (maybe just being picky engineer) am interested in finding the exact measurement (and to avoid another accident) I have searched high and low for the measurements, but have not found them.
sorry for being long winded!!!

 

[89BIGBLUE]

Okay,
When I got my 89, the rear leaves were SHOT! The LSPV thought it was loaded down with weight ALL the time, and the rear brakes would lock up in the grocery store parking lot.
After the OME spring install, I did put a 2” spacer under the LSPV. it helped, but I later put a 3” spacer under it. That helped even more.
I don’t have any measurements or pictures to contribute unfortunately.
If it helps, my goal was to make the arm from the valve “close” to parallel with the frame, before it bends up to meet the bracket on the axle. I figured if it was sensing a heavy load when the springs were shot, I would try to put it back near it’s original sensing range after the new springs, with the lift block.
I know this is what you want to do, I don’t have the measurements to help you, just the experience.

 

[89BIGBLUE]

Here’s a few picks of current set up, which seems to work well when loaded or empty:

I found a chunk of UHMW plastic laying around, and used it with some longer bolts and washers.

While not specifically what you asked for, I hope it helps you figure it out!

Sorry about the accident!

 

[cruiserneck]

Okay,
When I got my 89, the rear leaves were SHOT! The LSPV thought it was loaded down with weight ALL the time, and the rear brakes would lock up in the grocery store parking lot.
After the OME spring install, I did put a 2” spacer under the LSPV. it helped, but I later put a 3” spacer under it. That helped even more.
I don’t have any measurements or pictures to contribute unfortunately.
If it helps, my goal was to make the arm from the valve “close” to parallel with the frame, before it bends up to meet the bracket on the axle. I figured if it was sensing a heavy load when the springs were shot, I would try to put it back near it’s original sensing range after the new springs, with the lift block.
I know this is what you want to do, I don’t have the measurements to help you, just the experience.

That is great info. Thanks so much.

 

[cruiserneck]

That is great info. Thanks so much.

Wow, again thanks. UMHW is really good and strong solution and makes it easy to cut to proper size. Parellel with the frame makes great sense to me.
Fortunately the accident was not too bad (could have been worse).

 

[cruiserneck]

The pics are great. Question:. Is the block of UHMW square?? It may be the pic, but it looks a bit angled. Probably tie angle of the pic. Again, THANKS for the pics

 

[89BIGBLUE]

It is the angle of the picture. I cut it square, or, rectangular.
Good to hear that the accident wasn’t too bad.
Fix it up, post pictures, and cruise on!

 

[Cruiserdrew]

I'd like to know if there is a way to set rod position by pressure measurement. For drum or disc brakes.

Here's my dilemma-I installed an 80 rear axle with disc brakes and hooked up the LSPV! But I don't have a way to really calibrate it. I can feel the rear brakes are working well but don't know if they will lock before the fronts. But I've done some hard stops with no issues.

I've considered measuring pressures the way it's described in the 80 series FSM.

Interested to see if any science comes out of this thread.

 

[89BIGBLUE]

I'd like to know if there is a way to set rod position by pressure measurement. For drum or disc brakes.

Here's my dilemma-I installed an 80 rear axle with disc brakes and hooked up the LSPV! But I don't have a way to really calibrate it. I can feel the rear brakes are working well but don't know if they will lock before the fronts. But I've done some hard stops with no issues.

I've considered measuring pressures the way it's described in the 80 series FSM.

Interested to see if any science comes out of this thread.

I wonder if you could put an adjustable proportioning valve in the rear line, so you could tune as needed...

I wonder if you could put an adjustable proportioning valve in the rear line, so you could tune it as needed.

 

[Cruiserdrew]

I wonder if you could put an adjustable proportioning valve in the rear line, so you could tune it as needed.

Sure you could, but how would you tune it? The LSPV is like a smart proportioning valve. It varies the pressure based on load in the rear. That's pretty cool. But what's the unloaded setting? It's hard to gauge but I'm thinking some hard stops on loose dirt might allow a seat of the pants tuning. You want the fronts to lock just before the rears-meaning, you never lock the rears or the rear end swings out.

 

[89BIGBLUE]

Here’s the data from the fj62 FSM.
Immuna stew on it...

 

[Cruiserdrew]

And what about with disc brakes and a different master? LOL. Way too many variables. But I'm thinking there is a relationship. X pressure = y amount of breaking force.

In my FJ62 case, with 80 swap in the rear, the obvious thing is to eliminate the LSPV. I've elected to keep mine, (and it working well now) but I want to find a way to make sure it's calibrated perfectly. Unfortunately, I think that means empiric testing on a loose surface.

In my FJ60, also swapped to 80 rear, the rear brakes are running at full pressure, since it's basically impossible to lock 37s anyway.

 

[Kleatus]

I think on a 30 year old truck that’s been through a few brake jobs, has bigger tires, stiffer non-stock springs, etc. that the “exact” measurements and pressures in the FSM may not really be “perfectly right” anymore.

I like the LSPV, and myself (and many others) have been well served by making a block of some sorts to space the rod up. It’s quick and easy to do, and you could even test it in 1mm increments and post up the spreadsheet of the results to satisfy the “picky engineer” in you .

 

[cruiserneck]

Here’s the data from the fj62 FSM.
Immuna stew on it...

View attachment 1686507

View attachment 1686508

Thanks, that helps as well. BTW, looks like you are in NM!! My wife is from Silver City. I love that state, Beautiful!!!

 

[cruiserneck]

I think on a 30 year old truck that’s been through a few brake jobs, has bigger tires, stiffer non-stock springs, etc. that the “exact” measurements and pressures in the FSM may not really be “perfectly right” anymore.

I like the LSPV, and myself (and many others) have been well served by making a block of some sorts to space the rod up. It’s quick and easy to do, and you could even test it in 1mm increments and post up the spreadsheet of the results to satisfy the “picky engineer” in you .

Great point Kleatus, so many variables have been added to the mix, trial and error tweaking. I like the break pressure formula by Cruiserdrew also. No doubt, I want to keep the LSPV because it was put there for a purpose. THANK