The front axle in my truck seems not quite as it should be, and I'd like some expert comment. I was told it was a Mor-Drop, but it looks like a cast aftermarket axle to me (no markings, so not a Superbell). It's 48" long, which I believe is stock (not narrow) for a '34. The front tires are 4.50-4.75-16s on unmodified 16" Kelseys, the spindles are the early square flange type, and the brakes are '40 Ford. The steering is F-100. These are the problems, and their apparent causes: (1) The steering has always been extremely heavy. I've tried a variety of possible solutions including careful rebuild of the steering box, truing the steering column, and lengthening the steering arm, which helped some, but it's still a chore. I've always been told that the kingpin centerline is supposed to point at the center of the tire contact patch, but mine points at a spot inboard of the inner sidewall. The only explanation I can see for this is the small diameter of the front tires -- if they were 2 or 3 inches taller, as they would have been stock, the contact patch would be more distant from the centerline of the spindle, and would converge with the kingpin's projected centerline. (2) The assembly of parts has visible negative camber, and my front tires are wearing unevenly (heavy wear on the innermost rib) as a result. I understand that Ford changed the kingpin inclination at some point in the evolution of the beam axle, so there would be an early and a late correct combination of spindle and axle, and presumably the possibility of incorrect combinations as well -- but I think all my parts are commonly used together, and I'm unaware of others with the same problem. Of course it's possible to bend the axle to correct the negative camber, and I'll do that. But it won't change the relationship of the kingpin and tire contact patch; they'll just move inward a bit. Am I missing anything, either in the combination of parts or their adjustments?
I dont believe they ever changed the king pin angle, (but I could be wrong) they probably tried different degrees of camber. I think I would get the camber back to about one degree positive. Check the toe and check for excessive caster. With a good close up of the end of the axle, I could say what it is. Beautiful V8 ford by the way.
it does look like it has negative caster..meaning the tops of the tires are leaning in i'm not sure how that could be with and aftermaret axle , unless it was made wrong somehow..so i'm guessing it has to be an original axle that was dropped improperly could you take some close up pictures of your axle and post them? and the steering setup? the sugestion of going to positibe camber is correct.....but if it a cast axle that cannot be done..only a forged axle could be rebent do you know what the caster is? when you say you lenghthen the "steering arm"...do you mean the one on the steering box? or the arm on the spindle?
Bruce Lancaster did a lot of research a while (months) back about the king pin angle changes over the years. From memory he found that there were some differences but that in his opinion they would not significantly impact on front end geometry. There have obviously been a vast number of combinations over the years without major drama. Re: the king pin centreline and contact patch relationship, you've obviously realised that this relationship is fixed and only tyre height, width or wheel offset is going to alter that relationship. BTW I am yet to drive an early Ford with I beam axle so forget everything I just wrote. Pete
It was information from Bruce that informed me about the kingpin angle. I don't remember if it changed in 1934, or 1936, or 1941, but it was a change of a degree or two. It's clear that if you assembled parts from before and after the change, a camber change would result, but I haven't found anybody who can speak knowledgeably about this condition and its possible results. As I recall, the caster was like 5° on one side and 7° on the other, or maybe it was 7° and 9°. The guy who measured it is a wheel alignment guy with 50 years of experience, and he said it was within spec. I can't recall if he checked the toe, but I think so. I've been told that it is possible to adjust a cast ductile axle with care. The steering arm that was lengthened was the one at the box, slowing the steering ratio slightly and reducing the effort. We tried multiple lengths and picked the one that reduced the effort a bit but didn't make the steering too slow. The truck isn't at home currently so I can't photograph the axle or steering just now. I may be able to do that in a day or two. Thanks for the comments. Anybody else?
If the caster is 5 degrees on one side and 7 on the other that's hardly in spec and would make funny things happen. If those are camber figures then it may matter a bit less but it's hardly optimum and at the very least they should be the same. Solid axles are not hard to bend with the equipment at big truck shops. Equalize both caster and camber and try to keep the caster less than 7 degrees or so. Lengthening the pitman arm on the steering box normally results in increased effort and faster steering. If you swapped to a longer arm and the steering effort decreased then something else weird is going on.
HI .. If you have an "aftermarket" axle , the CAMBER is probably not your problem .... CASTER , well , are you running a stock & unsplit wishbone ??? If so , Caster is set ... Next move is to check Toe-in / Toe out ... KLAZ
The intersection point business seems really odd. Two things: See if you can do a reasonable measurement of kingpin inclination. If pin has a flat top, perhaps you can get a clinometer on there. Then put a jack under front axle so that axle remains at normal ride height with a wheel off. Drop down a line or carpenter's square to marx ground right under flange where wheel bolts on and lay something straight along kingpin as accurately as possible and see where these meet or don't. What is your front tire diameter? I'm guessing that won't be as far from stock as you think.
As was said, the longer pitman arm will increase effort required to turn the steering wheel. Fwiw, the Vega steering box pitman arm on my 32 is 6" eye to eye, lock to lock turns is about 4 1/2. Steering effort is quite easy. One finger does it as long as the car is rolling, even slowly. My 32 runs 6 degrees positive caster and runs 195/70R-14 radial tires at 30# inflation pressure. Along with the long pitman arm, what is the caster on your car? I know that the later solid axle Fords call for as much as 9 degrees positive (kingpin tops leaning back), but that's too much for your car imo. I was told - by a knowledgeable guy - of a gal who owned a 32 sedan that had 8 degrees positive caster. The car's steering wasn't as easy as she would have liked. They brought the caster back to 5 degrees positive and steering was much improved. Caster is the first place I'd make a change and next would be to go to a shorter pitman arm.
But--the tires are tilted INWARD at the bottom visibly, it doesn't look like there's any radical offset to wheels, and intersection point is waythehelloff... he's got like NASCAR grade scrub radius.
Recalling an article in a Rod magazine qredited to Pete & Jakes, the steering link from the pitman arm to the spindle should be as close to parallel to the wishbone as possible. changing the length of the pitman arm will affect this relationship. Are you running split wishbones or stock ?
I'm in agreement with the fellas above about your caster. That can cause the steering to be a workout if it's too much, even worse if it's different on either side. That might be acceptable on a more modern car with a more sophisticated suspension and power steering. Caster helps keep the wheels straight, and on the flip side makes it harder to steer. Here's a great site that explains it (I like the shopping cart reference) http://www.ozebiz.com.au/racetech/theory/align.html I leave the number of degrees to the professionals, but I'd definitely try to make both sides match up.
I`m sure you meant camber meaning the way the tires lean in at the top. 9 degrees of caster is a massive amount & would take alot of power to turn. Mercedes use 9 to 10 degrees and that`s the most I have ever seen on a car. I would recommened dropping the caster to 2-3 degrees with no more than 1/2 degree difference between the right & left. Camber is a tire wear problem, NOT caster!
A possible horror here: Aftermarket axle made for '53 Chevy spindles bushed to fit Ford...I think that would put us right about here...
Actually, not to start any arguments with ya, but the tops of the tires leaning in would be negative CAMBER, not CASTER. If there was two different caster angles, the axle would have to be twisted. I've got an A axle with '40 spindles and the tops of my tires lean wayyyy out, at least to my eye The joys or mixing parts.... Flatman
And a slow typer as well By the time I'd posted, several people had pointed it out. Didn't mean to heap on ya. Has anyone else seen alot of outward wheel tilt with an A axle and '40 spindles? I'd hate to wear away a good pair of tires when she gets on the road. Flatman
I agree.....the more caster the greater the trail. Trail is effectively the distance from the imaginary point where the kingpin would hit the ground if extended to the centerline of the tire. The greater the kingpin inclination angle (caster) the more trail created. Trail creates a "positive" feeling steering. This is because it makes a "restoring force". Basically it is a force which pushes the wheels back to straight. The force is felt through the steering wheel (greater steering effort required), hence why it is called "positive feeling".
I'm embarassed at having made a couple of errors in my original statement of the problem: 1. It was the Pitman arm that we changed, not the steering arm. 2. We made it shorter, not longer, guided by AV8's description of a similar improvement to his car. And it did result in slightly lighter-but-slower steering, as intended. Darwin and C9 are correct, the longer arm would have the opposite effect. Answering a couple of specific questions asked by y'all: - The wishbone is unsplit. - My front tire diameter is just shy of 25". I think the original tire on the '34 would have been a 5.50-17, with a diameter around 28". - The drag link is not parallel to the wishbone, it angles upward maybe 5° from the Pitman arm to the steering arm. The shorter Pitman arm improved this slightly; there's no room to bend the steering arm down for further improvement. To reiterate a couple of previous statements: - Yes, it has negative camber, maybe 1° or so. This is noticeable, and the tire wear confirms it. - The caster is different side-to-side by 2° -- it probably was 5 and 7. I'm told by the wheel alignment guy that this is within Ford spec; AV8 recommends a similar range. Maybe reducing it, and getting both sides the same, would help. I compared my front end with another early Ford today, one that has 16" disc wheels on the front. On that other truck, the backing plate is in the same plane as the inner sidewall, and his kingpins seem to point within the tire contact patch -- just. My backing plates, on the other hand, extend inward from the inner sidewall by about an inch. This relationship is the same on my roadster, which has the same brakes, wheels, and tires. The Kelseys on both vehicles have the much-discussed spacers between them and the brake drums, but they're only about 1/8" thick. It appears that the Kelseys may have more offset than the disc wheels, which (together with the smaller tires) may account for the goofy intersection point. So where I come out is to straighten up the camber to zero, reduce and equalize the caster to 5-6°, and put up with it. Thanks to everyone for your input. If anything else occurs to you, please let me know.
Here's a couple of items to add to what's already been discussed (and I kinda' breezed through all of it). Did you mention what your steering wheel diameter is? The smaller the wheel, the harder steering efforts will be. The diameter of a stock '40 Ford steeringwheel is about as small as I would want to go. I think that's about 17". Also, increasing tire pressure will help decrease steering efforts. But there's a down side to this. If ya' go too high you'll loose some straight ahead directional (tracking down the road straight) stability, but with 5-7 degrees of caster (this is the correct "c" word) you shouldn't have a problem. The other thing with high pressures is the steering can become too responsive, sometimes called twitchy. That's no good, because then you'll loose road feel and possibly induce a rear sway which many folks interpret as a problem with the rear suspension, but really isn't. Having the correct combination of front/rear tire pressures can solve a host of vehicle problems. Best part of all this is, air is free . How do I know all this stuff? Ask me someday and I'll explain it to ya'. It's very complicated. It's 10 years of my life that's now included in my work resume .
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