Technical Model A toe-in and stability

The RPU in my avatar had an old set of 21” whitewalls all around. When I rebuilt the front end I replaced the tie rod because the old crusty one on the car was bent. (This vehicle came to me from a previous owner who decided it was too much work for him. He said it had previously been used as a work machine on a large orchard in the area.) When I reassembled the front end I wasn’t able to achieve the recommended 1/16” toe in because I ran out of threads. I think I measured a bit under 3/8” toe in, but not sure. Anyway, when I first drove it it seemed to go down the road pretty straight and steady.

Last week I put on new tires and wheels. 5.50-16s up front, 6.50-16s out back. Now it seems more susceptible to wander going down the road. So I carefully rechecked toe this morning and measured 1/4” toe-in. It seems logical to adjust the toe closer to specs, but that will require finding a machine shop to turn down a short section of the new tie rod because the diameter is just a bit too large to merely run a die to extend the existing threads, and my lathe is too small to handle it. I think I will first increase the toe in a bit to see if that makes the situation better or worse.

Searching the web seems to suggest that more toe in increases straight line stability, while neutral to toe-out decreases it. But I suppose too much toe in could have the same effect as the tires fight over which one will determine the vehicle’s path. Any experience-based comments?

 

Yes, I did a whole back and forth adjustment with my car years ago and found too much is as bad as too little. Do whatever you need to to get close to 1/8” or 1/16”.

 

Probably a '32 or later tie rod? I think they are a bit longer. Are the threads bottoming out inside the ends? If so trim a little off each end?

Dave

 

Instead of turning down the tie rod end, you could just shorten the tie rod on one side (pick the side that has the right hand thread if that's the tap you have) and then tap the internal thread deeper. Can easily be done at home.

 

As alchemy mentions, Model A Ford's like about 1/16" tow in, 1/4" is a bit much.

 

There is no thread showing outside the tie rod ends-it looks like the ends are bumping the shoulder of the tie rod. It should be for a Model A since I bought it from Snyder’s.

The good news is that it just fits in my lathe, so I’m gonna attempt it myself, just doing the right hand thread end about 1/2.”

 

I run zero toe-in. So wheels are parallel. Absolutley no wander, steers fine.

On 16" wheels all round stock suspension and steering.

 

Is your aftermarket tie rod a tube with open ends? If it is like a stock tie rod with solid ends attached to center a tube; a half inch beyond the last thread would be in the area where the two pieces join.

 

The toe needs to be correct for sure but I'd suggest that your wheel / tire swap with a nice rubber rake has reduced whatever caster you had, possibly to an insufficient amount, and this could easily explain your symptoms. What caster do you now have? You're looking for 5 or more degrees.

Chris