Adding castor to the axle

[jimTN]

Anyone have a good tried and proven home method of adding castor to the front axle?

[Joe K]

Looks like adding blocks between the wishbone ball mount and the transmission might do it.

Alternatively heat & bend the wishbone arms.

There are those who say using the aftermarket wishbone ball seats adds caster - but the amount added is negligible, and I can verify that the car drives NO different between the OEM design and the cast iron adder.

Joe K

[duke36]

You can try shimming the top of the ball with the vendor's cup washer tacked to the upper clamp plate. Some say it doesn't add much increase in angle. I saw a photo ( but can't place it) where a shim plate was added between the housing flange face and the upper clamp plate moving the assembly downward. The thickness would vary on how much added caster is needed. The bolts may have to be lengthened to allow for springs and clamping movement. I can't recall if the rubber ball assembly bolts are longer.

[Synchro909]

I did a quick calculation and arrived at one degree of extra caster required the ball to be lowered by 5/8" so it is easy to see why those who say the washer makes no difference were right.
I lowered the ball by about 1/2" and didn't notice any real improvement on the driving but I did find that the extra load put on the bolts that hold it all together meant they worked loose in the housing. That created quite a bit of work to rectify.
IMO, it's not worth it - just maintain things in good order and drive it.

[Tacoma Bob]

There was a very good article in the restorer a year or two ago on what it takes. Big job but do-able.

[Bill G]

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Just curious. Are you trying to add caster to the original design or get lost caster back?

[Wick]

New front leaf spring and shackles,along with good spring perchs will make a difference.
Make sure cross member is not cracked or broken.

[jimTN]

I did not build this car originally, I do know everything appears new and tight but it sure does wander. I have an original axle tool but you would have to be in a pit under the car with a long bar to do any good.

[Patrick L.]

Why do you think you need 'more' caster ?
Ford built them with 5º+ caster which is plenty. Anything from 4º-5º is just fine.
I tend to prefer the 4º, steering wheel returns better.

I would think that a car that wanders has a different problem.

[Jack Shaft]

Olds hotrodder trick,increasing king pin inclination reduces steering effort..also leads to wheel 'flop',the car loses its ability to self correct to straight.Dont think its what your fighting however.

[Dana Barlow]

Much of the time,wonder is not caster*,but sloopy things,like steering box adjustment,or play in other parts. Sometimes it is mods done wrong for lower look or tire rim combo that dose not belong.

[desotoguy]

jimTN, are you working on a hot rod that someone built or is all the front suspension original?

[1931 flamingo]

How old are your tires?? Is the axle visibly bent??
Paul in CT

[David R.]

Service bulletin for November 1929 shows new production longer radius rod wishbone for AA trucks to add 3 degrees.

[Joe K]

Originally Posted by 1931 flamingo

How old are your tires?? Is the axle visibly bent??
Paul in CT

Classic bent axle for the Model A front is right king-pin "pushed back" from co-linear with the other kingpin/spring perch/spring perch. Its what happens when you hit a pot-hole at the right side of the road (most common location/side.)

Difficult to correct (and keep the king-pins mirror image tilt and "planar") while on the car. Best is to remove the axle, disassemble completely, and "straighten" the axle in a press.

I have about five front axles hanging around here. ALL of them show this defect in varying degrees.

The correction best done under the guidance of "alignment rods" - which were made by KR Wilson back in the day but which can be "cobbled together" from parts and a lathe. Below shows the alignment rods applied to a Model T axle - but the A axle is the same.




There was an article in the Restorer last year about someone who went through the entire process (including checking king-pin camber)

Joe K

[Tinbasher]

I think the first step is to find out why. 1/16' is close to one degree. So find out what you have. You can use a bubble level on the face of the axle to check this. and then see what out of square. worn parts, bend frame at the cowl (rear engine mount) etc. If there is a heavy truck alignment shop in your area they'll have the tools to bend the axle if it's needed. JP

[jimTN]

Tires are near new, car is restored car, not a hot rod. It apparently was never driven much after it was built. My books show 5 degrees required by Ford for cars and my experience has been 6to 7 degrees work best. There is little play in the steering gear and all rod ends are excellent.

[CWPASADENA]

I would first tighten up the tie rod ends and the drag link ends. Often when people put together these cars, they do not get enough preload on the tie rod and drag link ends.


After athat, check the toe. Set to about 1/8 in. toe in and see if that helps.


Also, be sure the steering box mountings are tight and also the steering box itself is properly adjusted.


That is what I would do first.


Chris W.

[Jim Brierley]

Years ago some company made a 'shim', about 1/2" thick, to add caster. 4 or 5 degrees should be enough. The shim I speak of was placed over the ball on the wishbone.

[johnny]

A tip you Jim just gave :car was restored ,some time back. suggest you look to see that the axle is not in backward ,look to find the casting Numbers should be on the boss part of the axle on the right front some say there was no front side when new but maybe through it's life it had been bent to increase caster, and then installed backward ,so if it is in backward it would be really low on needed caster. One more thing .look closely at the crossmember spring saddle .My understanding is that the crossmembers were originally installed with a 4 degree angle if there is wear showing or cracks suggest a shin could be fitted to the saddle between it and the spring ,thick side to the back .