Model A caster adjustment

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daren007

Well-known member
How do you go about changing the front axle caster. My axle is off left to right this means I will have to somehow twist the axle.
 
Are you sure the caster is unequal left to right? One degree of difference will, on a straight axle vehicle, produce a slight pull to the side with the lesser caster. This can also be caused by back bent or unequal spindle offsets.

If you are sure it is the axle only it can be bent (twisted) on the vehicle with very specialized axle clamps and hydraulics. Prior to WWII, when straight axles were common on cars many shops/ dealers had the tools. Truck service shops also have hydraulic on-vehicle axle twist (caster correction) tools, but most are too big to fit tiny A axles.

If you have the axle off the vehicle and stripped then four alignment rods through the spindle (kingpin) and wishbone bores can be used to judge alignment and angle corrections as you arm-strong the axle with a 20 ton press and lo-o-ong levers to twist in the corrections.

Of course, all this becomes moot if your spindles, wishbone, frame, and engine position (attachment for wishbone ball) are bent and off. And with an 87 year old car that has slammed plenty of chuck holes, curbs, railroad tracks and parking lot wheel stops, this is all likely.
 
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I'm wondering if we are confusing caster from camber.

But, regardless, if each side is different then as Mike said, bending is needed.
 
Caster is the tilt of the axle that projects the kingpin centerline forward of the tire contact, as shown below. Moving the wishbone up or down affects BOTH left and right caster equally. If, however, the axle is bent or twisted outward of the wishbone attachment points the left-right caster becomes unequal and the vehicle will always drift/pull to the side with the lesser caster. Only brute force bending/twisting of the axle will correct this.

Camber is the outward tilt of the wheel tops as shown in the adjacent illustration. Unequal camber will have little effect on straight line tracking of the vehicle. It will only create undue and uneven tire wear, and some tire skidding/ creeping/ screeching on tight turns.
0902sr_02_z-science_of_straight_axles-caster.jpg
 
The car has a slight pull to the right. The left king pin hole axle is not in alignment with the other three holes. It is forward. Can someone tell me what the EE on the axle indicates.
 
Just a humble question...Is it possible that your front brakes are slightly out of adjustment. You might try tightening the brake shoe adjustment on the side opposite of the pull and see what happens. This has happened to me over the years and the slight adjustment has worked for me. Good Luck...Ernie
 
It is not the brakes. I have a model T that pulled really hard to the right, Let go of the wheel and you were in the ditch. I checked castor with a level and square and found the left wheel off by over 1/4 inch at the top of the axle kingpin. I fabricated two bending bars with really long pipe handles. My son and I danced on the bars and gradually brought the axle back into alignment. Now it drives straight. The A is a different animal though and I do not think the bars would work without heat.

Daren
 
Go to a Good alignment shop that does trucks. They should the bending bars to get the axle back into the correct angles.

John Poole
 
I have straightened the axles on both of my cars. I removed them from the car stripped them down then used 4 alignment pins made for me by a friend that has a lathe. Found both axles were bent from left to right - straightened them in a 20 ton press. After that they needed very little twisting to finish them off.
 
daren007 said:
The car has a slight pull to the right. The left king pin hole axle is not in alignment with the other three holes. It is forward. Can someone tell me what the EE on the axle indicates.
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The "EE" is a reference to the facility that forged the axle. More common are axles with the embossed "AA" reference, which comes from a different forge and has nothing to do with the 'AA" parts made for the 1.5 ton trucks.
 
Here is what I learned straightening axles:

Axles

The AA and EE refer to the type of steel used to make the axle. At least that is what I recall seeing on the print.
 
daren007 said:
It is not the brakes. I have a model T that pulled really hard to the right, Let go of the wheel and you were in the ditch. I checked castor with a level and square and found the left wheel off by over 1/4 inch at the top of the axle kingpin. I fabricated two bending bars with really long pipe handles. My son and I danced on the bars and gradually brought the axle back into alignment. Now it drives straight. The A is a different animal though and I do not think the bars would work without heat.

Daren
Click to expand...

DO NOT use heat. You will ruin the axle. An annealed axle will be too soft to do its job afterwards.
 
Cooper1661 said:
Assuming you have a straight axel how do you adjust the caster ? I’m a newby!
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Caster is normally not adjustable EXCEPT for a small amount as you might find it by moving the wishbone attachment down using the aftermarket ball retainer on the bell-housing.

That said, it is possible to adjust caster by the wheel straightening advice given above by Kevin in NJ. But this requires a total strip-down of the front axle and possible replacement of those hard to remove spring perches.

If the king-pins and spring perch holes are not "co-planer" (all in alignment) you have a bent axle. My experience has been (5 axles) that ALMOST ALL Model A axles are bent to some degree or another.

The typical damage is hitting something with the passenger car wheel and pushing the axle end to the right of the spring perch UP (reducing camber) and to the rear (increasing caster on that side) Although the actual damage has to be determined.

Repairing caster would require "twisting" the axle from the spring perch outwards one way or the other - an action best done in a press and with the luxury of time. But one respondent above indicates this can be done "in place" with the necessary fulcrums and restraints.

Most repair shops of this area do "frame straightening" of a "global" kind and are not really equipped nor experience capable to dealing with an I-beam axle. (i.e. they would rather not.)

But your area may offer opportunities.

Joe K
 
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