VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1938 Master Caster Shims

When I had front axle off my 38 Master three years ago, I noticed that there were no caster wedges. Now I want to install some. I am wondering where to go to buy them. I also don't know how many degrees they were but I am guessing 1 1/2.

Not sure on the degrees but you should be able to get the shims at most any GOOD spring shop.

X2 Any spring & axle shop should be able to fix you up. If you don't have any close by look for shops that work on big trucks.

Shops that work on School Buss or UPS Trucks also have them.

. The first question I ask alignment shops is if they have caster shims.
If I get a dumbfounded reply, I'll call another shop.
The more caster you have, the better it will self center, but the harder it is to steer.
I have gone to heavy truck supply stores when I know the size I need.
I'll purchase one twice as wide, cut it in half and drill a hole for the alignment pin in the spring.
1-3/4" wide is not a common size.
. The correct caster for your car is 2-1/4 degree plus or minus a half degree.
Replace your ball joints, spring shackles, king pins, wheel bearings and rebuild your steering box to remove play and then your alignment shop can accurately adjust your steering. Get it done properly to prevent "Death Wobble".
. Lou .

My 38 has a straight axle and does not have any of the above problems. My one complaint though is that it gets pushed around by wind. I was reading an old GM technical document in which they said that caster helps fight the problem of side winds pushing the vehicle around. I believe the caster specification for my 38 is 1 1/2 to 2 deg. At the moment I have no caster shims on it.

You might want to determine what caster you have now and confirm that your king pin angle and camber are the same. Then you can determine what to do next.

Fred, not sure if my 38 has Caster Wedges. There is a very short "leaf spring" between the main stack of springs and the axle. I suppose this could be the wedge though a taper of a couple degrees would be hard to see with the gunge on the springs. The thickness looks about the same as the other leaves and it's about 7-8" long. The picture makes it look tapered but it's just the camera angle.

Picture attached.

Hi Tim,

It looks like there are no wedges on your car. The leading end is very noticeable due to the thickness. The length of the wedge is about the same as the front to rear dimension of the seat on the axle.

My car has them. I will try to get some pictures tomorrow.

Interesting. I wonder if the Caster is within spec without shims or were they a definite must have?
Haven't had time to check the parts books. The Canadian cars have some front end differences: Different front shackles - a big kick shackle on drivers side with springs in it, extra leaves I recall, sway bar and tube shocks so maybe there is some caster angle cast into the axle or a different length shackle or spring arch could also set the caster angle in theory.
Hmmm...

Yes the shims on my 51 1 Ton are about the same length as the seat. In the parts book it has a part number for the shim on the 38 and it says except for "kick shackle jobs". Mine is a kick shackle job but I am going to try shims anyways. They may have had a special spring and maybe mine has the normal spring, I don't know.

This makes sense as the kick shackle is adjustable but things have moved and settled in 80 years so shimming may be necessary at this point. I'm glad I heard about these so I'm ready with a variety of shims when I hit the alignment shop.

Let us know your before and after readings when/if you get an alignment done. Curious to see if moving towards the max spec angle you notice an improvement.

The caster could well be set in the positioning of the spring shackles and shaping of the springs. Get the current setting checked before adjusting anything. Most shops that o big truck front end alignment will know what you mean by caster shim/plate and most likely be able to check the setting.
Tony

Just took a picture showing the shim on my '37. This is a view from the front so you are looking at the thicker end of the shim. It is so thin at the rear that you almost cannot see it.

Thanks Rusty,
Being only axle width it would have to be a very noticeable taper. Have you ever had your alignment checked?

Tim,
do you have the kick shackle?

Hi Tim,

You make a good point! I do need to check caster. The way those shims are installed would decrease it. I have removed the axle from the springs twice and thought I had the shims re-installed the way I took them out.

I know that camber and toe are good. Those are easy to check. I need to make one of the templates with the angle marks to put under the front wheels to check caster. It would be nice to know where things are.

The car steers and tracks well and does not wander. I am not seeing any unusual wear patterns on the tires.

Yes, my car has the kick shackle. Never really messed with it or looked close enough to sort out adjustments. It seems to simply be a floating shackle so if a huge pothole is hit with the drivers wheel, it allows the kick shackle to absorb the impact rather than the spring and steering column taking the impact directly.

Many years ago I read some Canadian literature about the 38 kick shackle and it sounded like cars with this actually got a heavier duty suspension and shared springs with the trucks. The roads were more like dirt trails back then so maybe the alignment specs were a bit crude on our cars as their focus was on essentially off road driving, not highway driving. Have to find the documentation about the heavier springs sometime.

I'm glad I've read about these shims. Many shops liked to bend things back in the day as it was easier. I rebuilt the rear end and suspension in my vette 35 years ago (surprise surprise) and it was hard to find a shop that would shim the rear trailing arms and most wanted to bend the arms (yuch). When I took my car to the best shop I could find, all hardware was new, I'd replaced original shims with stainless and I handed them a box of shims, cotter pins and explained where they went.

How many front leaves do you have Rusty?

1935 and 1936 U.S. Master Deluxe models with leaf front springs also had a kick shackle.
The kick-shackle has nothing to do with ride, etc, but rather eleminating road shock in the steering.

Rusty I think your shim is in the wrong way round, in your situation you are reducing the caster.
Tony

Hi Tony,

I agree that things appear to be wrong.

I want to measure the caster before I make a change. It might be that all I need to do is remove the shim. Reversing it might create too much caster. Based on what I have read the shim changes caster about 2 degrees.

One interesting question. The '37 shop manual states that caster is checked with the wheels turned 25 degrees each direction. The 1941 shop manual states that caster is checked with wheels turned 20 degrees.

Any ideas about why that changed?

Note that a 1937 passenger car has a completely different suspension then a 1941.
The 1939 parts books lists 7 different shims for various 1929-1939 models.
I would have a professional alignment shop detrmine is shimming is necessary and have them complete the job.

Hi Gene,

That seems to be the difference. The 25 degrees spec is used with the straight axle cars. In the 1937 shop manual there is a fixture used to check caster directly on knee action cars so no turn spec is given.

I agree I might need to take it to a shop. I will check things in my shop first.

It's not that difficult to do alignment with a few simple tools. We did it all the time on the Miata when we were racing. You do have to understand the principles and math behind the process.

The steering axis (king pin) should point just in front of the tire centre on the road (like a shopping trolley only not so noticeable), may only be by 1/2".
Tony

I am wondering if part of my problem in the wind is that I have radial tires. The sidewalls are not stiff at all but very compliant.