The next episode of fixing the sins of the PO. On this installment we are working on the front end The set up: Stock 30 model A frame (and front cross-member), Flathead V8, dropped I-beam axle, reverse eye spring, hairpins, F-1 steering box (with a little play in the steering wheel) 6.00x16 bias ply tires on '40 ford wheels. The problem: Wandering on uneven roads, (I.E. crowns, ruts, pavement transitions), front end shake at speeds above 55-60mph. The current situation: wheel/tires are balanced well, toe is currently set at just under 1/4" total in, Caster is 0 degrees , The Plan: The first order of business is to get some caster in the front end. As taking the car apart to change the angle of the cross member is not an option at this time I have picked up a set of adjustable spring perches that will be going on next week sometime to prevent the spring from binding after I dial in the caster. From what I have found, it appears that 5-7 positive degrees of caster is what I am after. Once this is done I am going to work on the alignment. Here is my question. a couple of builders who's opinion I respect have mentioned that a bit of toe out is good with bias ply's on a set up like mine (maybe an 1/8th total out). What is the group think on this idea? Thanks for the info. Chappy
I was having some wander in my car a couple years ago (dropped I beam, bias ply Firestones on 40 Ford wheels, stock wishbone, rebuilt F-1 steering, 5 degrees caster), so I messed with the toe-in a bit. I finally got it to drive the best with zero toe-in. Go figure. Most guys say 1/1/6 to 1/8 inch toe-in.
I had the same problem 55 years ago with my first A. Small block Chev. reversed Merc wheels with bias tires, and split wishbones. I corrected it by increasing the caster to 7 degrees by pie cutting the wishbones behind the spring. twisting the axle with a 24" pipe wrench and setting the caster with a protractor and a plumb line butted against the rear of the axle. Once I had 7 or 8 degrees I welded up the pie cut. Maybe what you would not do today, but worked with the limited resources of a 19 year old at that time. Then I played with the toe and it finally steered and tracked well with about 3/16 toe out. I know it wasn't what conventional wisdom called for but it solved my problem at that time and made the car drivable.
Do not set to toe-out. That's nuts. The caster is set to work with a lot of variables...like steering "overall" ratio (including pitman arm and steering arm length ratios), engine weight, etc. I won't drive with any play in steering. Since that car wasn't built well in other areas, first check where the play is. Look to see if the pitman shaft outer bushing is worn out, see if the shaft rocks back-forth as somebody moves the steering wheel lightly/slowly in that play zone. One big thing often set wrong is in not "centering" the steering worm before attaching the drag link. Unhook the draglink. Then count turns at steering wheel lock to lock. Go back 1/2 way. Loosen locknut at pitman adjusting screw, then turn the screw in while feeling for contact to the worm. If the worm gear is not worn out at dead-center, then as you tighten the screw a bit more, you should feel a slight drag on steering wheel as you get to true center, (while going a 1/4 turn of the wheel each way past that center high spot). You must be "at" that high spot when you hook up the draglink, and have both wheels dead straight. If the builder never did this, you can never adjust the screw to remove play (at dead straight) if the box/worm is not on that high spot. If you cannot find a high spot after trying this several times, the worm is worn. Sometimes you will feel a slight high spot on either side of true center, caused by shimmying for decades that makes wear as a low spot in the worm gear. If the high spot is still good, but the pitman bushing lets the shaft flop a bit, you'll also never get the play out. Bear in mind the truck boxes, and their steering arm lengths when new, are sort of termed wide ratio to reduce effort at the steering wheel. I try to make them a faster ratio by changing arm lengths as much as possible to reduce total turns at the steering wheel, without loosing full turning radius. If a car has lots more turns at the steering wheel, then any play at all will have you sawing the wheel back and forth to stay straight. They also feel way too light, so then caster is often set higher to get more road feel back. My 32 has only 2.5 turns lock to lock, and I run super low caster (less than 2) to compensate for that super fast ratio and a very heavy Olds motor. It does not wander at all with bias and 1/8 toe in.
My pickup was set up with a 4" dropped axle, split bones & bias ply tires, the caster was set at 7° and the toe was 1/8", if you set it up with toe out you will wear a set of tires out fast. On rough roads bias ply tires will evidently hunt but I never had any shaking problems. HRP
If you haven't already done so, turn the radius rods loose from the mounts, gradually put the load back on the front end and re-check caster using an angle-finder. The PO may have mounted the radius rods in such a way that the "natural" caster has been negated in one way or the other. When I first got my coupester the radius rods were mounted about half way up on the frame rails and the car had almost zero caster. Dropping the rear mounting points of the radius rods fixed the caster problem. Lots of other problems with my car as well, most of which were caused by the original builder and subsequent owners having no idea how to set up a dropped axle / radius rod front end properly. It's not likely that setting your toe to toe-out will improve your situation and will most likely make it worse. The slight toe-in setting on most cars is to allow the wheels to run at close to ZERO toe when all the slop is taken out of the suspension by the forward motion of the car. Setting the toe to toe-out will only make this situation worse and will cause the car to dart and hunt on uneven pavement as the front wheels fight each other for directional control. Too much toe-in usually feels nice and stable but will "feather" the tread and wear the tires out quickly. You can tell when your toe is set correctly for your car when it feels directionally stable and the treads wear flat. You can best check for the feathering by running your hand across the tread. Good luck!
The idea is to get zero toe going down the road. Because the tires are outside the king pins they tend to toe out when driven. There is a little movement in every tie rod end the more ends between the front wheels the more toe in is usally needed.
No, I'm old... and over tired. It is toe'd in 1/8". I will edit that mind slip, thanks for the catch.
Off topic for here, but the reason for that is that the front tires are PULLING, so they tend to toe in instead of out. Goal is still zero toe going down the road. Back when I was racing dirt oval we ran toe out to get the car to turn into the corner better but that's a whole different deal than on the street.
Thanks for all of the helpful information. looks like I have a full weekend ahead. Frank, thanks for the advice on the steering i have checked all the steering parts already and every thing is tight outside the box. I will have it all apart so I will check the centering and adjustment in the box... I loathe that job as the box adjustment screw is basically under the header and it is a bitch to get at...lol Missysdad1, thanks, my rear hairpin mount is an inch or two below the frame rail. I will cut it loose and see what I get putting weight back on the front end as I am taking it apart. It looks like I should just be able to put some turns in the lower hairpin mount a gain some caster after I put in the adjustable perch... probably a bit more complicated than that i know, but... thanks again. I will update with progress...and/or more questions...lol Chappy
All my A's with bias ply tires had 1 /8" toe-in and anywhere from 7-9 degrees positive caster.. They went down the highway straight and were also easy to turn with that much caster... May not be right but worked good on about a dozen model A's I built...
I had severe problems with my '32, being pulled all over the road, and after much searching found I has toe out. Toed it in and the driving was transformed! Strange really as it was a cobbled together POS with horribly mismatched parts and had ridiculous kpi / scrub issues, so it became pretty good for what it was! It's all been replaced however - another 'previous owner' saga! Part of the fixes that made a massive difference too was the adjustable perches. Chris
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