More Toe In conundrums

[johnbuckley]

These were posted by The Master Cylinder and Phil Brown recently.
Do you know the thread per inch on the tie rods, how far the tie rod end moves per turn? So I guess one turn of the tie rod equals two times the threads?"
"I believe there 24 threads per inch so .042 each side for one turn of the tie rod, or .082 of change total .....at the point of tie rod attachment on the spindle, not where you check toe- in"
Yes, I reckon 24 tpi also.
So dear Ford Barners, Do you think I have got my following sums about right? 1 full turn changes the tie rod approx 0.08 inch in total. Tie rod is about half way from wheel axis to where we measure toe in so it changes them measuring location at the front of the wheel c 2x 0.08inch= 0.16inch , but it also changes the back of the wheel as much, thus one full turn changes the toe in
2x2x0.08=0.32 inch (or approx 8 millimetres this side of the Atlantic)

 

[nkaminar]

Both wheels are changed. Front and back are both changed. Wheel thread is twice distance to tie rod. So for one full turn:

C = 1/TPI X 2 X 2 X 2. Same formula you got.

For one full turn with TPI = 24, toe-in changes by 0.333 inch. For 1/16 inch change in toe-in the tie rod will have to turn 67.4 degrees.

 

[stevemclark]

Here is a complete description of the tie rod if it helps,from Bratton's.The 44" rod that connects the two spindle arms with left hand threads on one end and right hand threads on the other. Threads are 11/16-24. Solid steel rod.This link shows grease fitting type for correct year.https://www.brattons.com/Images/4530_2.jpg

 

[Phil Brown]

I think you're overthinking this, forget all of the geometry, angles, and how much things move per one turn of the tie rod. A set of toe plates, two tape measures (can read both at the same time but not necessary) and a helper can probably reset your toe in before you do all of that figuring
Again dont overthink it it's the most simplistic car on the road

 

[gwillford]

As an engineer.... I agree. Doing it is faster and easier than calculating! FYI, make sure you have the tie rod ends tightened enough. Too loose and there will be movement because of the springs in each end. You can change from toe in to toe out by grabbing the wheel and pushing and pulling on it. Makes for a loose feeling on the road. Not a great design.

 

[Phil Brown]

gwillford, good point on the springs. Being too weak could also allow toe changes going down the road. I also suspect a lot of "death wobble" could be from this for some.

 

[old31]

Keep it simple.

I am not to sure why you need to know (unless you are inquisitive) the engineering aspects and turns for toein.

Just install your toein bar and turn the tie rod. the toe in bar will tell you if you turned it the right way or not.

 

[Synchro909]

When I am adjusting the toe in on any of my cars, I often speculate to myself about these numbers but by the time I decide to do anything about it, the job is done.
There is one important thing to do when adjusting toe in that hasn't been mentioned here yet. The measurements should be taken after the car has been rolled forward.
My method is very simple and works well. I have made a steel gauge consisting of a piece of scrap angle iron laying on the ground and at each end, a vertical piece, the top end of which is pointed and stands half the height of the wheel off the ground. The distance between the two vertical pieces is from the middle of one tyre to the middle of the other (ish). I put a piece of masking tape with a fine vertical line on it on the tread of one tyre and align one pointer with it, then, I put a similar piece of tape on the other tyre in line with the other pointer. I do that at the front of the wheels for ease.
Now roll the car the car back at least one turn of the wheels, then forward again till the tape is at axle height, only at the back of the wheel. That is, half a turn from where it was before. Using the same gauge, it check from the line on one piece of tape to the other and adjust, repeat and check till I have about 3-4 mm less at the front than at the back.
Works every time!

 

[johnbuckley]

I am not to sure why you need to know (unless you are inquisitive)....

... Got me in one !! but also when measuring the toe-in, if it needs adjusting it gives me a clue as to how much to turn the tie rod before rolling the car forward yet again, getting up and down is no longer much fun these days. ( and all I was after in OP was getting my mathematic checked! - thanks nkaminar and the rest of the team)