Caster angle

Rancho Deluxe

Rancho Deluxe

Senior Member
FordBarners:
My restoration project is just about done. See picture. In road testing, a minor handling problem turned up and I'm convinced it is the Caster Angle. The car wanders off course. No shimmy, shake, or darting around – just a directional unsteadiness that requires attention and frequent small steering corrections. That’s not the way I remember this car operating. It was always rock-steady and calm in the steering department and it should be again after it’s complete rebuild. So I’ve checked everything twice and homed in on the caster angle. At first it was about 2 degrees as measured by the plumb bob and straight edge method outlined in many places including Les Aspen’s book. I returned a 3/8 spacer that was originally above the radius arm ball. It did not look like a stock item to me so I removed it for standard new parts. Putting it back in lowered the radius arm ball slightly and resulted in some but not full improvement. The new caster angle measures out at just about 3 degrees. Now I’m trying to think of something to get one or two degrees more. So here’s the question: Where the spring perches fit through the front axle, is the perch shaft to the axle hole a tight fit or is there any clearance there to speak of? It might be possible to loosen the perch nut and nudge the axle in the radius rod mount before retightening it and thus get just a bit more caster angle. I don’t want to go through the spring tension release process if the perch-to-axle fit is tight and this has no chance of working. What do you guys think? Thanks all. Rancho
 

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I don't think your problem is caster angle, but, strange things can happen. When you mentioned a 3/8 spacer, just what did you mean ? You didn't mean 3/8" thick did you ? If you think you need a little more caster to bring it up to 5º then Paul made a good suggestion. If everything in the front end is correct and snug, I'd lean toward the toe setting. Excessive toe in will cause wandering and too much toe out will cause hunting. Its hard to tell the difference sometimes, but, you didn't mention where it is set.
 
Yes, Patrick L. It's a thick cast iron block shaped to fit the upper radius ball mount just on the bell housing cover. The mount bolts go thru it and the cup pieces for the ball mount under it. It lowers the whole radius arm by the overall thickness amount (and it prevents mounting of the normal spacers and springs above the mount bolt nuts). It is only marked with a cast in "no.42" and a stamped "$". That's why I called it non-standard. No Idea how it got there but it was on when the car came to me in 1956. Toe in is just at 1/16 inch and everything is snug in the rest of the front end. Thanks, Rancho
 
Sounds like a rubber ball housing, I'd lose it go back to stock configuration and shim if ness. Does sound like Toe in/out could be looked at too.
 
Correct me if I'm wrong, but my calculations say that it would take 1 3/16" change at the ball to make a 2 degree change at the axle. In other words, a 1/8" washer at the ball will change the axle angle 0.2 degrees. Me thinks you need to look elsewhere. Like I said correct me if I'm wrong.
 
Rancho Deluxe said:
FordBarners:
My restoration project is just about done. See picture. In road testing, a minor handling problem turned up and I'm convinced it is the Caster Angle. The car wanders off course. No shimmy, shake, or darting around – just a directional unsteadiness that requires attention and frequent small steering corrections. That’s not the way I remember this car operating. It was always rock-steady and calm in the steering department and it should be again after it’s complete rebuild. So I’ve checked everything twice and homed in on the caster angle. At first it was about 2 degrees as measured by the plumb bob and straight edge method outlined in many places including Les Aspen’s book. I returned a 3/8 spacer that was originally above the radius arm ball. It did not look like a stock item to me so I removed it for standard new parts. Putting it back in lowered the radius arm ball slightly and resulted in some but not full improvement. The new caster angle measures out at just about 3 degrees. Now I’m trying to think of something to get one or two degrees more. So here’s the question: Where the spring perches fit through the front axle, is the perch shaft to the axle hole a tight fit or is there any clearance there to speak of? It might be possible to loosen the perch nut and nudge the axle in the radius rod mount before retightening it and thus get just a bit more caster angle. I don’t want to go through the spring tension release process if the perch-to-axle fit is tight and this has no chance of working. What do you guys think? Thanks all. Rancho
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The perch holes should be a very tight fit.

Sometimes the front ends were aligned by bending or TWISTING the axle on a frame rack.
If you had the axle out and put it back opposite of the original way it was,
you could have a lot less caster than you had.
If you have 3 now, that is marginal.

Check the toe-in also.
 
I think I would start over, get an original type wish-bone ball housing along with a couple of those new fangled cup spacers [ used to use a big *** washer]. Try to make sure the arms aren't 'warped' and the ball stud mount isn't 'bent' or otherwise damaged. Your toe setting sounds right depending on where the measurements were taken [Its probably right, just had to mention it]. I forget exactly how high the measurement should be off the floor, I just use the height of the wish-bone and like 1/32"-1/16". There should be no room for the attach points. If all that is OK, then the tires could be looked at as mentioned. Are they old, hard, or chopped ?
 
I've just found Jim Mason's homemade tool info on http://jmodela.coffeecup.com/. This shows a press tool to get the perch out of the axle because the fit is so tight! So that pretty well kills the idea of using play in the fit to get more caster. But what Pete says is still in play. The two perches could have been reversed, left and right and that could have altered the original caster. Hmmm...Rancho
 
1. If "everything" worked before, good to try to first "think" of what or "if" anything has been "changed" during restoraton.

2. Ususally takes two (2) people to "re-check" for possible loose movement after jack stands are placed under the front axle with one person holding the steering wheel steady while wheels are moved by another; and/or steering wheel moved back & forth while one holds the wheel(s) steady; i.e, check tightness of:

A. Drag link connection to square steering sector.

B. Both ends of adjustable drag link rod ends..

C. Both ends of adjustable tie rod ends.

D. Any other loose movement.

Hopes this helps.
 
Since caster is the tilting back of the king pin (positive caster) to provide the centerline of the spindle to be located in front of the tire. Caster is what helps to return the tires and steering to a straight ahead movement. Caster can vary several degrees without any ill effects. The more positive caster the more for the tendency to track straight ahead. More importantly whatever caster is on right side, left side should match. More than specified caster can also make parking or turning the wheels while not moving more difficult. Without realizing it you are trying to lift the car on one side when you turn the wheel. You don't notice this on the side that is lowering however because of gravity. If you would like me to email you a 64 page book given to Ford mechanics in 1936 explaining Ford's alignment as taught in their schools forward me youer email address to sponge19501924@yahoo.com.
 
Ford specified the minimum caster as 3.5 degrees with a maximum difference (side to side) of 1/2 degree. I think Pete is on the right track but I'll add one other variable. Jon's point is on target as well. The wishbone ball must be moved .602" for each degree of change. Now, if you changed the front spring during restoration you changed the caster. For every 1" you raise the front cross member via the front spring, you raise the wishbone ball .666" which reduces the caster by 1.1 degree.
 
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