Pumpkin spice..

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J Mack said:
I grew up a Chevy guy and had/built a few. The older Chevy's had longer shackles that ran through the frame in the rear and when you lifted them it wasn't out of the ordinary to have 8° plus of caster and we all drove our stuff hard and fast back then..
Fast forward to my first FJ55 and I was given the advise of "just buy the kit and install it as per instruction and you'll be fine"! Without much thought I did exactly that and it was possibly the scariest car I've ever driven at speed on a road with any crown or truck ruts and that set me on the path of not asking the "Toyota guys" about front end geometry ( every one of them will tell you shims or 3° to 4°) and come up with my own plan. I like the 4° to 6° caster for a everyday driver and believe those are still safe numbers if you're just throwing out internet advice.
I had the OME springs and installed 4° shims and it was better but still sucked to drive at any speed and the short front shackles would invert so hard I was bending the anti inversion bolts in the shackles the way I drove it off road. The plan was make a new front end with more caster and get rid of the short shackles, some quick math will tell you the springs we use need a 6"-7" shackle and on my personal pig I like 6° to 8° of caster (proceed with caution if you step out side of the norm) and I built the stuff to keep the front shackle but go up through the frame. I have taken several here on Mud for a ride and a few have also driven on fast fire roads or at highway speeds and this old $hit box rides better than it should, way better than some of the new Heep or Toyotas I own on the same roads around here.
My point in all this rambling is if we stop all repeating bad (Toyota) information and look at what works outside of Toyota I think a simple leaf spring solution could be found or at the very least we could stop telling new'ish guys that this brand or that brand spring doesn't effect your caster and you wont need shims or cut and turn. IMHO every readily available FJ55 lift kit makes the already lacking front geometry worse.
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I'm no hot rod fabricator, but I've never read of anyone installing a lift kit on a FJ55 and it driving OK without 4* shims. That is common knowledge now and 99% of FJ55 owners will be just fine with shims if running the factory drivetrain. I must have missed where the group was telling a newbie that they DON'T need shims.

Shims should come with any lift kit.

I installed 4* shims with my OME lift and it tracks straight and doesn't wander.....up to 70mph....and that is as fast as it wants to go.

Absoltely no need for anything more agressive than simple shims for most of us. You are dealing with a custom setup.
 
onemanarmy said:
I'm no hot rod fabricator, but I've never read of anyone installing a lift kit on a FJ55 and it driving OK without 4* shims. That is common knowledge now and 99% of FJ55 owners will be just fine with shims if running the factory drivetrain. I must have missed where the group was telling a newbie that they DON'T need shims.
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We will just have to agree to disagree.
We read twice a year "Newbie" was sold a kit without shims and wants to know why it still drives so bad. I'm literally dealing with this right now!
You are also making a blanket statement that 99% are going to be fine with four degrees but do you have any idea what more than 4° drives like?
Like I said I'm not looking for an argument just stating what I've said in the past...
Toyota guys will die on the you don't need more than 4° hill without any real knowledge other than what's been said forever on every Toyota forum.
 
I think we are agreeing......its correct that kits don't come with shims.....but they should

So the 'newbie' installs the kit with all the parts supplied, and then it drives like crap.

Then 'mud tells the newbie to install 4* shims to 'fix' it for the vast majority of 55 owners with stock drivetrains/angles

Kits should come with shims....now with a new drivetrain and strange Tcase angles like you are working on now.....well then a cut/turn may be the fix
 
onemanarmy said:
Then 'mud tells the newbie to install 4* shims to 'fix' it for the vast majority of 55 owners with stock drivetrains/angles
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Except for this part...
I don't think giving the advice of install 4° shim is the right answer for the vast majority.
As @cruisermatt said and I agree you could easily see -2° on some of these kits new and more once they settle and a 4° is not enough, and you are dealing with most that will keep the too short centering pin and blindly slap a 4° shim on top of that and hope for the best hitting off road trails?

​

 
The main disadvantage to a lot of positive caster is that the steering requires a higher amount of input effort to turn the wheel. This is likely why Toyota set things with the smallest positive caster. Remember that these were the days of manual steering, bias-ply tires, and slower highway speeds (55 mph speed limit in 1974.

The stock tire size from the factory was a H78-15 on q 15x5.5” wheel, which is roughly equivalent to a modern 205/75R15 or 215/75R15 tire (27-28” high, 5-6” wide.) Stock caster was 1° positive.

I don’t think Toyota intended the 60s/70s era solid axle trucks to be driven at 70mph or more.

In any case, with power steering and radial tires, increased positive caster is not much of an issue. Nor do I think caster shims are much of an issue below 4°. Above that, they’re a wobbly bearing surface between the axle tube and spring plate. As @samc2447 says, and @J Mack is demonstrating, a “cut and turn” is the only good way to return the trunnion (aka caster) angle to something that handles well, with workable pinion angles.

There is another, but it invokes coil springs and a linked suspension. A lot more money and complexity. 😛

Positive caster also creates or increases a jacking effect when the wheels are turned. The front inside wheel rises and the front outside wheel falls. This transfers weight to the rear outside wheel.

Now someone can crack on about “jacking”.
 
Black paint day .

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gonzopancho said:
a “cut and turn” is the only good way to return the trunnion (aka caster) angle to something that handles well, with workable pinion angles.
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Not only do I agree but I agree wholeheartedly.
Before you head down the path of cut and turn you are likely to have the ability to check angles and you will know what you are starting with not blindly adding a value based on something you read.
This is why I struggle with giving the just add a four degree shim advice myself because I have no way of knowing what the person on the other side of the computer screen is starting with.
 
tucker74 said:
Honestly - I have no idea what’s on there, just not worth selling my soul to old Zuck to see those pics. He knows what in your garage I promise 😆
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Yeah I can’t see most of the re posts as I’m not signed up either.
 
gonzopancho said:
The main disadvantage to a lot of positive caster is that the steering requires a higher amount of input effort to turn the wheel. This is likely why Toyota set things with the smallest positive caster. Remember that these were the days of manual steering, bias-ply tires, and slower highway speeds (55 mph speed limit in 1974.

The stock tire size from the factory was a H78-15 on q 15x5.5” wheel, which is roughly equivalent to a modern 205/75R15 or 215/75R15 tire (27-28” high, 5-6” wide.) Stock caster was 1° positive.

I don’t think Toyota intended the 60s/70s era solid axle trucks to be driven at 70mph or more.

In any case, with power steering and radial tires, increased positive caster is not much of an issue. Nor do I think caster shims are much of an issue below 4°. Above that, they’re a wobbly bearing surface between the axle tube and spring plate. As @samc2447 says, and @J Mack is demonstrating, a “cut and turn” is the only good way to return the trunnion (aka caster) angle to something that handles well, with workable pinion angles.

There is another, but it invokes coil springs and a linked suspension. A lot more money and complexity. 😛

Positive caster also creates or increases a jacking effect when the wheels are turned. The front inside wheel rises and the front outside wheel falls. This transfers weight to the rear outside wheel.

Now someone can crack on about “jacking”.
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Agreed! Only thing I would add is a Spring under Fj55 or Fj40 would require a cut and turn more than a Spring over 1980 through 86 mini truck with the Spring over 😘. I have owned the Mini truck with stock H78-15 bias ply Dunlops and aired down to 10lbs after wheeling and driving to gas station to air up was dangerous with a tiny steering wheel and no power steering ( hence the Bus sized 40 and 55 steering wheels ). My 80 had a 3" spring and no cut and turn because it was a spring over and unnecessary. 12/.5 -33/15s no problems 😘
 
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