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 .

[Kevin in NJ]

Is the axle straight?

I made up a set of rods and checked the few axles I have. I found they were all bent at the perch point outward. Some had twist.

The 2 'good' axles I have came back into alignment when I corrected the bend rearward. That is the twist came out at the same time.
Based on some of the axles I have seen posted on the boards mine were pretty lightly bent.

It is interesting to note that an axles heated at the perch point bent VERY easy. I would do like 8 pumps of my press, get a big bend in the axle and it would spring back with like 1/16" of change. An axle that was heated was very soft the same 10 pumps did like 1/2" of correction.
My conclusion is a heated axle is not something to be used on a car that you will drive.

Before anyone speaks. Yes I know a lot of people have a dropped axle and they all say they are fine. It is interesting no one has driving an axle hard and check to see if it actually was still inline. I like evidence.

[Kevin in NJ]

Is the axle straight?

I made up a set of rods and checked the few axles I have. I found they were all bent at the perch point outward. Some had twist.

The 2 'good' axles I have came back into alignment when I corrected the bend rearward. That is the twist came out at the same time.
Based on some of the axles I have seen posted on the boards mine were pretty lightly bent.

It is interesting to note that an axles heated at the perch point bent VERY easy. I would do like 8 pumps of my press, get a big bend in the axle and it would spring back with like 1/16" of change. An axle that was heated was very soft the same 10 pumps did like 1/2" of correction.
My conclusion is a heated axle is not something to be used on a car that you will drive.

Before anyone speaks. Yes I know a lot of people have a dropped axle and they all say they are fine. It is interesting no one has driving an axle hard and check to see if it actually was still inline. I like evidence.

[Jack Shaft]

all ford forgings should be straightened cold..hot axle drops have been done for years,doesn't mean they are safe,just one more in the list of reasons 'why hotrodders die'..

[rotorwrench]

Proper precautions have to be taken to not heat the forgings too hot and they should not be pulled like taffy to make up for the drop. A heavy I-beam forging like the Ford straight axles were, still have plenty of ductility if properly dropped. It also has a tendency to stress relieve and old fatigued forging if properly done. They will be as safe as they were from the factory.

Ed & Bob Stewart dropped a lot of axles in their two generations long careers. Here is a good history on them from the HAMB. https://www.jalopyjournal.com/?p=3972

A well dropped Ford axle is stronger than a lot of the aftermarket crap that has been available over the years.

To do a small amount of correction, cold bending is a lot safer for those that have no metallurgic knowledge but for a really bent one, heating is a good idea if not for the stress relief alone but it makes it a lot easier to straighten one back out too.

[Dodge]

Seeing as Bill Williamson isn't on here right now I'm going to say neuter it and it won't
wander so much...

[Jack Shaft]

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I guess Ford had no metallurgical knowledge..but those that do know heating ford forgings hardens them and will lead to failure..

[Jack Shaft]

But hey,anything is possible,maybe ford was wrong...so I checked with Bear..nope they dont use heat either..

[katy]

Ford's illustration as to the ruggedness of their axles:

[rotorwrench]

I've not heard too many tales about broken Ford front I-beam axles on ones that were dropped unless they hit a bridge rail or something like that. I've not heard of one breaking in the modern era. These things were so overbuilt that it would be a rare thing to happen outside of an accident that causes a front wheel to strike something. Folks are still dropping them to this day. Now the guys that drill big lightning holes through the web are definitely weakening them. Anyone that drills them outboard of the perch mount needs their head examined.

Now rear axle shafts are a different story. I've seen a lot of them break.

[wensum]

The chassis on our speedster was assembled by a hot rodding business and without my asking they cut and re-welded the radius arms to give 6-7degrees castor. This enables the car to be driven at 60mph down a motorway, tracking perfectly and needing only a very light touch on the steering wheel. However on very tight corners, it does appear to load up more than might be expected? I have noticed in the past, a very heavy load in the rear of a standard Model A can alter the castor and result in the car wandering more than normal

[rotorwrench]

Some rodders cut a narrow pie section from the wishbone arms on each side then bend the arm to close the gap and reweld. Others split them with rod ends added and adjust the castor by where they weld the brackets to the frame. The last poster noticed how hard they can get to turn off center. Shimming to to where it works best overall is usually the best bet since it can be changed further till a happy medium is felt. A person can lock it in after that but what if they change to different type tires or wheels?

[Chuck Sea/Tac]

I bought a pos aftermarket front spring about twenty years ago. It was way thicker and the curvature was higher. My car drove horribly. I barely drove around the block before I pulled it out.

[duke36]

Just researching how to add 2 to 3 degrees caster on a car where all the spring, axle and other components are to specs, including mounts, u bolts and engine slope. It seems that the angle when measured as close as possible to the spindles indicates a twist from the perches to the spindles. This is same exact condition on both sides indicating no damage to the axle or frame. Any way to add a couple of degrees without disturbing the set up? No wandering is noticeable so perhaps the concern is unfounded?

[nkaminar]

A few comments:


The wishbone for the later AA trucks was a different part than the old one and was done to reduce caster to make the trucks easier to steer.

I saw a Craigslist ad for a modified car, I think it was some sort of speedster, that had the wishbone bent to increase caster. They had a very noticeable bend in the center.

I fixed the caster on my Model T, on one side so the axle was twisted, by using a 6 foot pipe wrench and a floor jack. I wrapped 1/4-inch thick aluminum around the axle to protect it. The front end of the car actually lifted off the ground so there was a lot of torque on the axle. Now, a Model T axle is more easily bent than a Model A axle so it may take a 12 foot pipe wrench for a Model A. I have seen adjusters for the Model T that are cut out of thick steel and fit over the axle.

An iPhone with an angle application can be used to measure the caster.

Fix and tighten everything before you start changing the caster. And adjust the toe-in afterwords.

[duke36]

So how would one hold the perch areas and just twist the king pin holes without removing and clamping the axle in a large vise? I suppose one could remove the axle with the perches and spindles intact and try that?

[burner31]

Just sitting in the garage, not going anywhere, how much movement do you have in the steering wheel?

[GeneBob]

Have you checked the toe-in? I have found that wander can be caused by insufficient toe-in. Toe-out leads to wander, Too much toe-in makes the steering twitchy.

[BRENT in 10-uh-C]

Originally Posted by nkaminar

The wishbone for the later AA trucks was a different part than the old one and was done to reduce caster to make the trucks easier to steer.

Neil, that is interesting as I had not seen that on my prints. If anything when you compare the perch end of the 'wishbone' it appears it even has more caster than what the 1928/29 'wishbone' had. I will make a note to look at that the next time I go back to the archives and see if it is mentioned in the Engineering Information notes.

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[nkaminar]

Brent, see the Service Bulletins, page 392, "New Truck Front Radius Rods."

[katy]

Originally Posted by duke36

Just researching how to add 2 to 3 degrees caster on a car where all the spring, axle and other components are to specs, including mounts, u bolts and engine slope. It seems that the angle when measured as close as possible to the spindles indicates a twist from the perches to the spindles. This is same exact condition on both sides indicating no damage to the axle or frame. Any way to add a couple of degrees without disturbing the set up? No wandering is noticeable so perhaps the concern is unfounded?

If both sides are the same angle, the car drives and handles w/no issues, the tires don't wear abnormally just drive it as is. "If it ain't broke, don't fix it"

[BRENT in 10-uh-C]

Originally Posted by nkaminar

Brent, see the Service Bulletins, page 392, "New Truck Front Radius Rods."

Well, this is yet another mystery (-and likely yet another misprint) in the Service Bulletin info.

My Ford engineering print is dated 10/07/31 and does not signify the use of the AA marking on the Foot, -and the length measurement on my print (38¾") is a different dimensional number than the number (34⅜") listed in the Service Bulletins. (That's a pretty significant discrepancy! )

Adding to the confusion, on my copy of the print it specifies an AA-3412-B Foot to be used, ....however if you look at the 'AA-3412' predecessors that were designed, you will see that the AA-3412-A design was introduced in 10/01/29 however almost immediately obsoleted on 11/2/29. The prior part number for the Foot was an AA-3412 which on November 02 of 1929 was changed to AA-3412-AR.

Since this "change" was printed in the November 1929 copy of the S/B, my initial guess is someone 'jumped the gun' on printing that on Page 392 assuming the AA-3412-A was going to be used, -when in actuality, that AA Radius Rod listed in the S/B never truly went into production and that design was scrubbed. The reason it would have been issued an 'A' suffix is because Engineering did make a few prototypes for testing purposes and so they had to be able to track it. This however, does not mean this prototype ever went into production.

Again, I will research this by reading thru the EIs whenever the Benson Library re-opens however, like I have stated here before, the S/B is not without errors. Just because it is printed in the S/B does not mean we should assume it is 'gospel' until it has been researched thoroughly.

[jayvee34]

Being an old Hot Rodder I heated and bent the wishbone as close to the axle as possible
to get the 5 degree positive castor that I needed in my A.