yes another "toe-in' question: bias vs radial .0 or 1/8" and stock shackles

[slickrock]

I am trying to track down a specific cause of death wobble. My questions only pertains to shackle angle and specific toe in, not all the other issues that can cause it since I never had it until the following changes were made. My bearings are good.

I have a 73 FJ40 with 35" BFG muds / just switched from 35" Coopers, front flipped springs, 4" SUA with 1" shackles, and 60 series steering.

I wanted to level my rig out (rear is SOA) and I took out the 1" shackles and put the stock ones back. I had a bit of steering wobble, but nothing that was concerning but I did need to adjust my toe in a bit.

Before I could adjust my alignment I changed from 35 Coopers to 35 BFGs (A bit taller and a lot heaver) The 40 mile drive there I had a little wobble. We balanced the tires with a friend’s electronic balancer at an auto repair shop but only did the inside of the wheel balancing. On the 40 mile drive back, I had pretty good wobble at slower speeds and thought that the balancing wasn't good on the tires (had about 1,000 miles on them before I got them). Monday morning, I adjusted my toe and took the tires in to a tire only shop and the tires took a lot of weight. On the way home, more wobble and one bumpy road, it went to bad wobble. I watched them zero out the tires when balancing so I know they are good.

I checked to see if my previous adjustment was off and I messed up someplace and my toe was a little under 1/2" less in front. Too much and I think this is why the wobble was worse.

I readjusted toe last night and my toe is at 1/8" less in front. I haven't driven since. Figure it I all good until I saw a few posts talking about how the FSM is for bias tires and that a radial should be set at 0"s. What are thoughts on this?

Second question: With a 4” SUA lift, should I have longer shackles than stock to correct my axle angle? My shackle angle is not perfect, but they are angled forward and not straight up and down. Would a stock shackle with this lift cause DW?

 

[John Smith]

1/2" toe in is way too much. I have always had good luck with 1/8" toe in be they radial or bias tires. I have never heard about different toe settings for bias vs radial tires but I am no tire guru either.

 

[Maros N Bagos]

What is your caster angle?

 

[slickrock]

I set it agian at 1/8". I think that my round retainers may be the culprit. I think they can no longer hold the tie rod in place and they back out casuing my toe to be about 1/2 after about 45 miles. Need to get new retainers.

 

[dgangle]

I set it agian at 1/8". I think that my round retainers may be the culprit. I think they can no longer hold the tie rod in place and they back out casuing my toe to be about 1/2 after about 45 miles. Need to get new retainers.

What is a 'round retainer'? Tie rod ends?

X2 on the caster question.

 

[slickrock]

retainer is the clamps that hold the rod from turning. Caster sholud have never changed since it was fine before. After driving it for a while, my toe goes form 1/8 to about 1/2".

I have no idea what the castor is. Haven't checked it in a while and I do not have an angle finder. shortening the shackels 1/2" should not have totally blown the castor out of wack. I drove it 40 miles today and it all seemed good but I cranked down on the tie rod clamps and put some red lock tight on it.

I never had shims in it since it always tracked straight and true with no DW. Maybe with the heaver tires it might be time to look into that and the castor angle. I can see why weight would make somethig that I never noticed before miht have made the little thing into a big issue. I'll check after I have time to get an angle finder.

If it is my castor angle, what angle shim should I get for a 4" spring that is probably a bit saggy now? would I need a 4 or 6 degree?

 

[dgangle]

You have some serious problems and should either write a book, go to church or both if the clamps on your tie rod are loosening while driving causing your toe-in measurement to change. That is just plain absurd and honestly I don't think you know what you are talking about. If this is correct you are probably the first person in written history to ever have this problem. The only way the toe could change with your reasoning is if the threads on the tie-rod or tie-rod ends themselves were stripped or if your tie rod is mysteriously rotating, thus changing the adjustment while you drive. Normally these adjustments are rarely ever made and rust pretty much solid making them only adjustable after applying generous amounts of the blue-tipped wrench and a big pipe wrench.

Second, the questions about your caster angle are an honest attempt at people wanting to help you understand your steering geometry as to help answer your original question about death wobble. It does no good to say you don't know and then reason it shouldn't have changed. If you have non-standard springs, shackles, or flipped springs, it very well does matter and I'll bet money it's ain't what you think. Buy a $12 angle finder at Home Cheapo and determine what it is yourself in 5 minutes. Or pay a tire flunky $60 to tell you.

One can only determine what angle shim to use only after they measure what you have and where you wanna go.

If this isn't due to compromised steering components, then dimes to dollars the prelaod on your trunion bearings is inadequate. I don't put a lot of faith that you are confindent in their condition or adjustment.

 

[Poser]

You have some serious problems and should either write a book, go to church or both if the clamps on your tie rod are loosening while driving causing your toe-in measurement to change. That is just plain absurd and honestly I don't think you know what you are talking about. If this is correct you are probably the first person in written history to ever have this problem. The only way the toe could change with your reasoning is if the threads on the tie-rod or tie-rod ends themselves were stripped or if your tie rod is mysteriously rotating, thus changing the adjustment while you drive. Normally these adjustments are rarely ever made and rust pretty much solid making them only adjustable after applying generous amounts of the blue-tipped wrench and a big pipe wrench.

Second, the questions about your caster angle are an honest attempt at people wanting to help you understand your steering geometry as to help answer your original question about death wobble. It does no good to say you don't know and then reason it shouldn't have changed. If you have non-standard springs, shackles, or flipped springs, it very well does matter and I'll bet money it's ain't what you think. Buy a $12 angle finder at Home Cheapo and determine what it is yourself in 5 minutes. Or pay a tire flunky $60 to tell you.

One can only determine what angle shim to use only after they measure what you have and where you wanna go.

If this isn't due to compromised steering components, then dimes to dollars the prelaod on your trunion bearings is inadequate. I don't put a lot of faith that you are confindent in their condition or adjustment.

Saved.

 

[werd]

I have a 73 FJ40 with 35" BFG muds / just switched from 35" Coopers, front flipped springs, 4" SUA with 1" shackles, and 60 series steering.

I wanted to level my rig out (rear is SOA) and I took out the 1" shackles and put the stock ones back. I had a bit of steering wobble, but nothing that was concerning but I did need to adjust my toe in a bit.

Second question: With a 4” SUA lift, should I have longer shackles than stock to correct my axle angle? My shackle angle is not perfect, but they are angled forward and not straight up and down. Would a stock shackle with this lift cause DW?

I never had shims in it since it always tracked straight and true with no DW. Maybe with the heaver tires it might be time to look into that and the castor angle.

Shackle length doesn't matter. You need to check your castor. It sounds like you seriously need shims. I am a little confused that you didn't have shims with the longer shackles and it handled fine. However, this seems to have arisen when you put on the shorter stock shackles that would normally call for less of a shim.

Did you have wobble before you flipped your front springs or did this occur after you flipped them?

I can see where changing shackles (without shims) would cause this, but not heavier tires.

Get an angle finder, check castor, and shim. Good Luck!

 

[Poser]

I am trying to track down a specific cause of death wobble. My questions only pertains to shackle angle and specific toe in, not all the other issues that can cause it since I never had it until the following changes were made.

There are SO MANY THINGS that effect what people perceive as DEATH WOBBLE, and to arbitrarily write-off certain things because you do not want to address the issue by a methodical problem-solving system, but rather, a throw-s***-at-it-and-see-what-sticks system is only going to confuse you further and create animosity with the people you are trying to get help from.



Castor plays a huge roll in this issue, as does:




Worn steering gears, arms, tie rod/drag link ends, spring bushings, shackle pins/bolts, steering knuckle pre-load, loose u-bolts, broken spring pins, cracked frames/broken leaf spring anchor points, and the list goes on and on.




Just because it did not happen with one size tire on the truck, and then you switch to a larger diameter, heavier tire and wheel assembly does not mean that the system was not originally taxed to the max with the previous size tire and wheel and you have strained EVERYTHING with this subtle change in tire/wheel combination.






Your best method of attack to this issue would be to make a chart of known possibilities and check them off as you and someone else who knows these vehicles inspects and verifies the serviceability of the components in question.

My bearings are good.

According to who?

 

[Poser]

Shackle length doesn't matter.

It does for eveyone else...Longer shackles on the front axle of a conventional suspension configuration, ie no shackle reversal, will lessen the caster angle, every time.

 

[werd]

It does for eveyone else...Longer shackles on the front axle of a conventional suspension configuration, ie no shackle reversal, will lessen the caster angle, every time.

You're the bus driver...you just took me to school.

 

[slickrock]

It does for eveyone else...Longer shackles on the front axle of a conventional suspension configuration, ie no shackle reversal, will lessen the caster angle, every time.

Well on my drive home from work (40 miles) yesterday, I got the wobble back. I double checked my toe and it was right at 1/8".This all started when I put the stock shackles back on. I needed some time away from the every day issues with family life last night and took an hour to swap my extended shackles back on and reset the toe to 1/8". The shackles probably gave about 1/2" lift.

I hope that since I don't have shims with 4" lift, the longer shackles bring the castor back closer to stock.

I also think the tires play a part in this. The BFGs took a LOT of weight to balance. I am going to get 4 8oz bags of innovative off-rod beads for the tires as a stocking stuffer from the wife. That should help keep the tires at a better balance.

I will stop by the hardware store on the way home and get an angle finder.
Is there a link for checking castor?

 

[bustanutley]

fix castor, check knuckle preload, install hydro assist with big TREs, no more wobble.

 

[slickrock]

hydro is on list, preload is great, castor check on the way

 

[slickrock]

OK Guys, I just checked my Castor. With the angle finder on the passenger side pinion fin (the large level one in front of the pinion flange) I am showing 2 maybe 3 degree pointing to the front of the cruiser. so + caster?

Is this the correct way to check? positive caster is towards the front and negative is towards the rear?

From what I have read +1 is good for stock setups and 2 - 3+ caster is good for larger tires.