The Stovebolt Site Forums The Shop Area Driveline ft end wandering - '49 Burb

I put this here instead of in the Burb section because my question applies to AD 1/2t trucks in general.

The ft end wanders, requiring constant attention to maintain a straight line. The entire running gear, front end, and steering have been gone thru and completely reconditioned, so it's not a matter of wear. My thought is that the caster requires attention (being analogous to rake on a bike). If this could be corrected it would really improve the pleasure of driving it.

I solicit the opinions of the informed commentariat on this forum.

Thanks to all,

Stryder

You're on the right track. Caster adjustment is important, and also toe-in (the only 2 adjustments you have, practically speaking). Also check your tires. Not one thing about the AD truck front end was designed for short wide tires and that can and will cause varying degrees of problems. Taller and thinner is better. One other thing to keep in mind...if you have taller tires on the rear and shorter ones on the front, your caster is instantly off. Manuals will tell you your caster ought to be around 2 degrees (1 3/4 plus or minus 1/2 degree), but I've learned over the years that a simple 3 degrees will keep your front wheels in a straight line better. If you get to 4, you're going to need strength or power steering. BIG HAIRY IMPORTANT NOTE: There are locating pins on the bottom of your leaf springs. These make certain the front axle remains locked in place. It is imperative that the locking pins do not get shrouded nor hidden by the caster shims. You want shims that have smaller holes and which are designed so that the pins (you will replace them when you change the angled shims) sit on the bottom of the shims and connect completely with those pins. In other words, your new shims become part of the spring leaf assembly. I've seen a couple of situations over the last 50+ years where people ignored this, and if bumps are hit, if brakes are put on harshly, if the U bolts work loose or weren't tightened properly...that front axle can become what causes a terrible wreck. Good luck.

Add a couple more degrees of caster, most stock trucks use 2 degree. The wedge has the thickest part towards the rear of the truck. Any change to the stance of the truck will change caster angles, big and little tires, higher rear springs, etc..... I run 4 degrees in my '37 due to the front end being lower then the rear. It doesn't take much change to change the caster.

Turn the steering wheel lock to lock, if the truck doesn't raise and lower as you turn the wheel, you need more caster. It should be raise up as you past center. The raising up is the steering geometry lifting the weight of the truck, this weight lifting is what returns the steering back to center after going around a corner. To much caster makes you lift more weight each turn putting stress on you and the steering linkage. If you can't find
1 3/4" wide caster shims, buy wider ones and cut them down, the thing to watch is the leaf spring center bolt head length. The head of the bolt should pass through the wedge and locate itself in the axle.

You didn't mention rear suspension.

A one minute search on the Internet:

REAR STEER
A solid rear axle with worn spring bushings, or broken center bolts or trailing arm bushings
and axle mounts, will also allow the axle to change its centerline of thrust as the vehicle
travels over the road. This, in turn, causes the steering gear to travel off-center and cause
steering wander.

WOW!! Thank you all.
The whole steering and suspension have been rebuilt, so wear probably isn't part of the issue.
All 4 tires are the same: 235/75R15 and it sits level.
Based on what I see here I will contact the resto shop I trust and see about having them do the alignment.

I suspect that the 235/75R15 tires may be the problem. They are not stock. You may be able to make them behave with more toe in.
I run 215/85R16 tires on my trucks. They are not stock either, but they are skinny like the original bias ply tires. They run very true as long as every part of the suspension is maintained and set up correctly.
When you come out of a turn, does the steering come back towards the straight ahead position on its own? If so, your caster is likely correct. Proper toe in (or additional toe in for non-stock tires) will prevent wandering.

What psi are you inflating them?

This is a lot of most useful information. I will try the suggested ways to check on the caster.

Inflation pressure: It looks like I don't really know what the correct pressure for these tires should be in this application.
I have the same make of tires (Wild Country Radial XLT M+S) on 16" rims on a '03 F-250 which calls for 55psi ft and 70 psi rear.
I realize that it's probably not the same.
What is the correct pressure for this application?

Probably 30 to 32 psi, but I would just use 30 as a starting point. Ideally you want the contact patch to be just right and here is a good way to know if your tires are inflated properly: Get some sidewalk chalk...the kind the kids use. Now find a place where there is smooth concrete and long enough that you can drive far enough to make your tire go through at least 1 rotation. Draw a wide line (use the rear end of the chalk and not the pointed end) straight across one of your front tires from one side to the other (across the tread). Now drive far enough that your tires rotate at least once and then stop and go look at the chalk mark your tire made. If you see a nice straight line with chalk evenly distributed all the way across, you know that is the proper pressure and you can use it for both front tires. If you only see chalk in the center, you know you're overinflated. If you only see chalk on the sides, you're underinflated...and you may be able to tell the difference by seeing weak chalk and more generous chalk. In other words if you have 32 psi in that tire and you should have 30 psi, you may see the edges not as absent of chalk but showing only a faint bit of chalk where the center shows notably more. And then do the same test for your rear tires. Note: if you're actually using your AD as a pickup and not just driving around like a passenger car, then put something in your bed (2 or 3 people maybe) to do that test. You'll find you need more psi if you're hauling "stuff" around and only as much as the pressure used in your front tires if you aren't. Using a great deal more pressure in your rear tires when nothing is being hauled can cause your wheels to hop, bounce, etc...especially during hard braking and too much pressure will reduce the contact patch of your rear tires (which isn't good during braking nor for cornering...especially in rain).

I tried to find the specs and info on the Wild Country Radial XLT M+S.

One website said 50 psi maximum inflation pressure however the tire has the max. pressure molded into the tire.
If your like me, get out your glasses and stoop down to see if you can find it.
One website comparison tested these tires at 44 psi.
TBC Brands North America is the USA dealer/rep for these tires and they are owned by TBC Wholesale Corporation.
TBC Brands lists Wild Country under the Multi-Mile model (http://www.multimiletires.com).
Multi-Mile says to inflate to the Original Equipment Manufacturers specification on the door plate or sticker.
In a nutshell the tires are made to satisfy the requirement of today's truck manufacturers.
I buy my tires from a trusted local tire shop and I ask them what inflation pressure I should use on my old truck.

Jon gave you some excellent advice. I can only add a chart from a 54 dealers' data book as an example.
There is an optimum inflation. Above and below that negatively affects tire wear.

Here's a resource for tire inflation. It may contain your tire size, although may not be entirely valid if you've mounted the tires on skinnier rims than the size calls for. It involves weighing each axle, then inflating to the required load. Modern tires on an AD truck would typically have much higher load capacity than needed. Note that this is a Toyo document, but that doesn't matter, as the tire size is what dictates.
Toyo Load/Inflation tables