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Old 09-14-2020, 07:09 AM   #1
johnbuckley
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Default how many tie rod turns equates to 1/16 inch toe in change ?

To save my brain ... has any one done the math (or even a guesstimate) as to how many full turns of the the tie rod equates to a 1/16 inch change of toe in?
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Old 09-14-2020, 07:51 AM   #2
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

I don't know the math but it doesn't take much of a turn to get a big result. I am guessing 1/4 turn would give you at least 1/16 change in toe.
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Old 09-14-2020, 08:04 AM   #3
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

The tie rod threads are 24TPI so that equates to .042" per 1 turn of the screw. You would double that for the tie rod since it has opposite threads on each end so that would be .084" per turn of the tie rod.



So, you'd need ~3/4 of a turn to change the tie rod by 1/16".

Last edited by ryanheacox; 09-14-2020 at 09:34 AM. Reason: change toe to tie rod for clarity
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Old 09-14-2020, 09:18 AM   #4
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

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Originally Posted by ryanheacox View Post
The tie rod threads are 24TPI so that equates to .042" per 1 turn of the screw. You would double that for the tie rod since it has opposite threads on each end so that would be .084" per turn of the tie rod.



So, you'd need ~3/4 of a turn to change the toe by 1/16".
But that would be at the tie rod ends. The effect on the tire would be much greater. Or am I missing something.
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Old 09-14-2020, 09:33 AM   #5
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

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Originally Posted by wmws View Post
But that would be at the tie rod ends. The effect on the tire would be much greater. Or am I missing something.

Good point. My gut says you're absolutely right. The easiest way to figure that turn to distance ratio would probably be empirical testing. A rough guess is that whatever distance you change the tie rod, the toe will change by around double.
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Old 09-14-2020, 10:50 AM   #6
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

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The 1/16th is not measured at the very front to very rear. Only about 4".
How far is the tie rod behind the axle?
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Old 09-14-2020, 01:57 PM   #7
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

Interesting question, but it is not the correct one if you are looking for the correct method to adjust toe-in/toe-out. Depending on the actual toe-in/toe-out on the car, you need to rotate the tie rod until you achieve the correct toe-in measurement. I start with aligning the tires dead straight (by measurement), then adjust the tie rod until I get 1/16 - 18 inch. The number of turns needed is not material.
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Old 09-14-2020, 01:58 PM   #8
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

Hotrodart you must have a much more sophisticated measuring stick than my shower rod! ...It is the math that intrigues me .... when I see that the toe in is say 1/4 inch I ask myself ( and Barners) approx how many turns do I need to get the approx correct result!
quick rough measurement.. . axle to tie rod is 6 inches. Axle to centre of tirewall is 13 inches. axle to tread perimter of tire 15 inches. ( Ford Service manuals seem to use centre of sidewalls as the locus).

Last edited by johnbuckley; 09-14-2020 at 02:48 PM.
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Old 09-14-2020, 02:21 PM   #9
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

Quote:
Originally Posted by ryanheacox View Post
The tie rod threads are 24TPI so that equates to .042" per 1 turn of the screw. You would double that for the tie rod since it has opposite threads on each end so that would be .084" per turn of the tie rod.



So, you'd need ~3/4 of a turn to change the tie rod by 1/16".
obviously a very intelligent Barner!
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Old 09-14-2020, 02:38 PM   #10
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

axle to tie rod is 6 inches. Axle to centre of tirewall is 13 inches. axle to tread perimter of tire 15 inches
Soooo.... have I got this right..????
One full turn of tie rod extends it 0.084 inches.
This equates to c 0.084 x13/6 =0.182 inches [approx 3/16inch] at the side wall
and equates to c 0.084x 15/6 =0.21 inches at the tire perimeter

Last edited by johnbuckley; 09-14-2020 at 02:47 PM.
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Old 09-14-2020, 02:46 PM   #11
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

Does caster matter?
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Old 09-14-2020, 02:51 PM   #12
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

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The 1/16th is not measured at the very front to very rear. Only about 4".
How far is the tie rod behind the axle?
. . . Educate me on this please.

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Old 09-14-2020, 02:51 PM   #13
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

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Originally Posted by Curtis in MA View Post
Does caster matter?
Aaaaargh !! I wondered about that meself! It's all a very rough estimate and everyone estimates seem pretty damn close! Perhaps someone can measure it all in situ if nothing better to do..... ZZzz time for bed over here. zzzzz
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Old 09-14-2020, 02:58 PM   #14
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

Hi Brent,
I thought I remembered something about measuring at a point on the rim 6" from the ground, then rotating the tire until that spot was 6" from the ground behind the axle.
Maybe I'm just confused these days!
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Old 09-14-2020, 03:17 PM   #15
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

Donít forget to make sure steering balls are round and have no play before adjusting toe in.
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Old 09-14-2020, 05:55 PM   #16
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

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Originally Posted by ryanheacox View Post
The tie rod threads are 24TPI so that equates to .042" per 1 turn of the screw. You would double that for the tie rod since it has opposite threads on each end so that would be .084" per turn of the tie rod.



So, you'd need ~3/4 of a turn to change the tie rod by 1/16".
Wait, there's more...

When the tie rod turns, it changes the spacing between the rear portion of the wheels, and it is also changing the spacing at the front part of the wheels by the same amount. So I think you really only need to turn it ~3/8 turn to get the 1/16" toe-in change that you desire.

I am not 100% sure of this.

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Old 09-14-2020, 06:18 PM   #17
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

I could never get a consistent reading with the curtain rod. I went and got a real measuring stick and now I do get consistency. So my take on the curtain rod is that it is probably close, but not something to give peace of mind that you aren't grinding away precious rubber from expensive tires. Dang, those white walls are spendy.
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Old 09-14-2020, 06:20 PM   #18
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

I set the toe in by putting a piece of masking tape with a vertical line (fine ball point pen) on the front of the tyre tread of one wheel. The gauge and tape are at axle height. Then the pointer on one side of the gauge in place on the line, I put another on the tread of the other wheel. Now, I roll the car forward till the tape is again at axle height and check the distance between the lines with the gauge. If it is off, I repeat till I get a difference of about 2 - 3 mm front to back. I never measure anything. Perfect.
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Old 09-15-2020, 03:05 AM   #19
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

Yes Brent in Oh C post #12... the Ford manauls indicate measuring and gives toe for, a couple of inches from the perimeter, and Jim/GApost #16-the same thought came to me over night ...I agree.. so recalculating post #10...ONE full turn equates to 3/8 inch change of toe in measured at side walls.
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Old 09-15-2020, 07:20 AM   #20
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Default Re: how many tie rod turns equates to 1/16 inch toe in change ?

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Originally Posted by johnbuckley View Post
Yes Brent in Oh C post #12... the Ford manuals indicate measuring and gives toe for, a couple of inches from the perimeter, and Jim/GApost #16-the same thought came to me over night ...I agree.. so recalculating post #10...ONE full turn equates to 3/8 inch change of toe in measured at side walls.
No, I meant 3/8 turn gives 1/16" change in toe-in, because that was the question you first asked.

And I'm not 100% sure of that because I did not calculate it myself. I took Ryan's answer and divided by 2.

I know from experience of setting toe-in on many Model A's over the years that it is a very sensitive adjustment. It is easy to overshoot where you wanted to end up.

You need to find 2 different references in the Service Bulletins about setting toe-in. The first (earlier) one has the diagram and instructions on HOW to measure it (where, and how many inches up from the ground). But the actual toe-in spec given there is replaced in a later bulletin with the 1/16"+/-1/32" spec that we try to get.
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