The Stovebolt Site Forums The Shop Area General Truck Talk Where can I find caster shims?

I have a 51 3100 that I have added power steering and front disc brakes, and have a somewhat low profile tire (235 60's on 15 inch rims)
I think this has changed the caster alignment; the steering wheel doesn't want to return on its own. I checked with several allignment shops, and can't find anyone who does this kind of alignment anymore. I did several searches trying to find shims on my own, but have not had any luck finding 1.75 inch wide shims. (NAPA stopped stocking them )
I've managed to learn just enough to get myself really confused, so here are all of the questions I have so far;
1 Where can I find shims?
2 What size shims do I need? I've seen recomendations for evrything from 1/2 degree to 9 degrees! The shim that is on now is about 1/4 inch, which I calculated to maybe 3 degrees.
3 How hard is it to remove the bottom leaf on the leaf springs? I don't have much thread left on the u-bolts, and removing one leaf might give me the room I need to add a thicker shim.

Thanks for any help!

Which side of the axle is the thick part of the shim on? You'll want it to the rear of the axle to give you the positive caster. I don't think that they make the narrow shims anymore, only the 2 1/2 and 3". I don't have the Northstar catalog handy, it's at the shop, but I can check.
As to a spec, I'd say about 3 1/2 to 4 degrees, anything deeper than that will make the steering effort much higher.
I also would sugest that you not remove the bottom leaf. Maybe the one above it would be ok.
One question, are all 4 tires the same size? Going to a smaller diameter tire shouldn't have changed the caster that much, unless you have a much taller tire on the rear.
I will make one suggestion if you have no luck finding shims; try a shop that does alignments on semi trucks. They should have the proper equipment an possibly the shims needed to get the caster in where it needs to be. I'd also suggest longer U bolts instead of removing leaves.

Have you tried a shop that specializes in big truck suspension? Lots of I beam axles out there on newer trucks and RVs. A good shop should be able to fix you up.

I would look at a shop that does front end alignment on I-beam type axles, they either have the shims, or have a suppler and can get the size you need. They may even have some advice.

I found the caster shims I needed on my milling machine.
http://rides.webshots.com/photo/1484200068080251109FlXuOW

Grigg

Is your truck still sitting fairly level? If so, you haven't changed the caster angle, and I would think the shims you have in there now are correct. But, if you need more shims, any spring shop should have them. You can cut down a wider shim with a cutoff wheel, just cut a little off both sides so the alignment hole stays in the middle.

The only reason I can see for needing more caster is if the truck has a rake, or a nose-down stance.

NAPA sells them, I bought a set a few years back. I can't find them on line, but the in store catalogs have them. Mine were 1.5 degree and the part number was #264-4113 in the NCP line. Any store should be able to get them. Joe

Thanks for all of the quick replys!
Longbox: The wide part of the shim is in the back. All 4 tires are the same size, I used to have taller tires in the back. It seems to me that the caster should have increased, but it doesn't feel that way.
Grigg: You might have to go into business making those shims! They look pretty thick, what degree are they?

I'll try NAPA again in person. Hopefully they still can get them, or I'll try the special size order place dave posted. Does anyone know what size bolt hole I should get? Can I stack shims, or do I need to get one the correct thickness?

The shims I made were really for pinion angle adjustment, 6.5 degree and about 3/4" on the thick end and 1/4" on the thin. They also adapted a spring center bolt head diameter of 1/2" to the 3/4" hole in the spring perches.

Shims, like lift blocks, should not be stacked.
Be sure you have enough of the spring center bolt head in the axle to hold it in place.

Grigg

I agree with Grigg make'm your self. If you don't have a milling machine they can be cut on a band saw. You can cut them to the exact size so there would be no need to stack them.

I believe NAPA's were from 1 degree up 5 in 1/2 degree steps. I wish they had there whole catalogs on line. A good alignment shop should also be able to get what you need. The other guys have a good point about the center pin, make sure it still does it job in the axle. The ones I bought, had a slot in the center so any center pin up to about 5/8 would work. Joe

So does the shim slide over the bolt that holds the springs together, or does it get bolted to the springs? If it just fits over the bolt, do you think the bolt is long enough to still work with a a shim that is maybe 1/8 inch thicker in the middle?

The hole in the shim is larger than the bolt-head so it just fits around it. Before you bolt it down, just take a look in there and see how much of the bolt sticks out below the shim. You should be good to go if the shim is only 1/8" thick in the center.

These guys have them in there paper catalog for $5 each (1/2 to 4 degree).
http://www.espo.com/

Thanks Joe, I'll call them first thing monday morning.

I checked with NorthStar, they only make shims in 2 1/2" and wider, from 1/4 degree up to 4 degrees.

A milling machine, bandsaw, jigsaw, or a hacksaw will fix that... if aluminum even the tablesaw will cut it.

Grigg

They make them in 2 materials, aluminum and magnese-bronze.

Either should be fine, the bronze should last longer.
Both can be easily trimmed to the proper width.

Grigg

Some like the NAPA ones or universal and have a slot where you can cut for narrow spring width. It would be really easy to narrow one up. Joe

So if the shims I now have are around 3 degrees and the steering wheel doesn't try to center itself at all, what size shim would you all recommend? I was thinking 5 or 6 degrees, but I'm just guessing.

4 degrees is about as far as you can go, and I wouldn;'t suggest going any further, as other problems may develop. particularly, hopping during sharp turns (I've seen this happen with more than 5 degrees caster). You might check the steering gear too make sure everything is tight, particularly the steering box itself. 3 degrees should be plenty to make the wheel re-center.

The question is what is your actual caster angle right now, forget what the shims are, what is the amount the king pins lean forward from vertical?

If you know what you have, and what the max allowable is, you can decide what you want yours to be. Then take that and the knowledge you have about your old shims, and order the correct new ones.

Grigg

An easy way to do this would be to have the truck on a level surface, then use an angle finder to determine what tangle the alxe is at, preferrably checking on the spindle itself.

Allright, I'll see what the angle is now. but it doesn't fit into my motto "There's never time to do it right, but there's always time to do it over"