Jim, my curent front tires are 25.88 in. dia. The OEM 16:00 x 16 tires were 28.89 in. dia. So far, so good regarding handling and wear.
if you use your rim to set your toe in, wont that be a lot more toe at tire dia.? i have 26'' dia. and 29'' dia. tires on diff cars and set all @ 1/8'' in on both tire dia., run good for years.
I always scribe a line on the tread 'center'. Doesn't necessarily agree w/the molded tread. Have used 1/16 - 3/32" toe in.
Re: Caster, camber, and toe. For toe, we use 2 pcs. of square particle board the same size as the diameter of the tires. Prop or hold them against outside of each tire and measure across front and rear corners. With a 14 qt. dropped oil pan it's the only way to simulate 3 and 9 on o'l 5. We put lean- in camber on R.F. with a torch and a 16 pound mall till it looked right. For caster, we borrowed my uncles magnetic cas. and cam. gauge.Really slick. Hang the mag. end on the hub. Went something like turn steering right,set bubble vial, turn left, set a vial, turn to straight, Read caster. Unfortunately uncle is gone and so is gauge. Fireball 5
Too many people seem to way over think and over do the method of setting toe in. I've done the same exact thing that Pitman said he did; to quote I always scribe a line on the tread 'center'. Doesn't necessarily agree w/the moulded tread. Have used 1/16 - 3/32" toe in. Jack up the car use something to steady your hand while you hold a pencil to the tread, slowly spin the tire to put a mark around the center of the tread (on both tires) let the car down bounce it a few times to settle the suspension out and with the wheels aimed staight ahead measure from line to line at the back and from line to line at the front equally high on each side and figure the difference. That is the most accurate way without special equipment. laying boards beside the tire as some wags suggest won't come close to being accurate as will going from tire tread to tire tread (that works somewhat on the side of the road when you are alone though) . The trammel thing is accurate an does work if you are alone but you still have to put the lines on the center of the tire tread to be accurate with that. That may be the only way a guy working at home by himself can get it real accurate. We don't always have a helper (or a willing helper) available when we need them.
spin the tire, use silver spray can on center of tire, set jack stand with awl vise gripped to it, spin tire and move awl slowly into tire, making a mark around center of tire, in fresh paint. Now ya got yer mark, let car down off jack, bounce a couple times, have helper hold tape on one inch mark, front and back, 1/8 toe in on Fords.
After I check the toe, and make any adjustments, always roll the vehicle back at least 20 feet, then roll forward and recheck. That way the tires will take a set, and will be tracking correctly.
A couple of other factors for toe are scrub radius and FWD. In FWD the torque of the drive axles tend to create a toe in force. Negative scrub radius (the KPI line hits the pavement outside of the tire center line) creates a toe in force. Positive scrub radius ( the KPI line hits the pavement inside of the tire center line) creates a toe out force. The greater the scrub radius, the greater the force. RWD usually have positive scrub radius. Changing wheel offset or tire diameter will change scrub radius. I know when we were racing the generally accepted theory was a little toe out helped turn in on corners. On the street excess toe out makes a car squirrely.
I have read that with 1/8" of toe in the rolling resistance of tires and the general compliance of the suspension results in both tires running parallel which seems ideal per no scrub.
Here is a photo of my home made jig for setting toe. There is one of these for each side of the vehicle. I bent two pieces of aluminum, added a strip of wood so the jig would index on the sidewall and not the bottom tire bulge. I use two tape measures so that you do not need to go back and forth, front to back, to measure. Be sure to center the jig on the wheel. I copied my stuff from a set that I borrowed from another race team at Bonneville. It worked accurate enough to go in excess of 250 mph at Bonneville. John
Too much toe either in or out will cause darting.. We have some good techs in this area (Pittsburgh) that know what they are doing. One guy is 26, he has a Hunter Hawk eye rack he gets a car perfect! So if you have it put on a rack, don't let the techs age stop you..
John View attachment 4092154 [/QUOTE] That's exactly what the Longacre device looks like. We set the tires on 2 aluminum plates with grease between the plates. Once a measurement is complete bounce the car up and down and check it again.
Funny story; when I finished my Mysterion clone I forgot to address wheel alignment. Granted, it doesn't matter much with the car sitting on display 99.999% of the time but you occasionally need to push it around, onto trailers, etc. I just screwed the tie rods together by eye-ball and called it good not realizing it still had an inch or so of toe-in. The thing pushed like it had the brakes locked up and the front tires squealed like a banshee of fire! I am pretty sharp so I figured the problem out after several months using 2 men and a boy to shove that thing around!
Don't know if this is generally true or not but when I got my '53 Chevy pickup with stock beam axle it had bias ply tires. No matter how I set the toe, that thing followed every groove in the road and was not a pleasant drive. Then I changed to radials and the thing steered like a dream. In my observation, tires make a HUGE difference, radials cover a myriad of sins.
This is exactly the way I have been setting toe on my racecars and hot rods with a homemade setup (four 4" x 4x4 and two 2x4's x height of tire with a slot in the ends)for 50 years. It is repeatable. I can set it, drive it and recheck. Numbers are the same. It works. No one can tell you what your toe should be exactly. Every car will like something slightly different. I like to use a paint marker to put dots at 90 degrees apart on the tie rod tube. Look where those dots are when you get it set to 1/8" in. Then see how much the tube needs to be turned to achieve 0 toe. Go out and drive it. Take a wrench with you. I can accurately adjust the toe while pulled over to the side of the road on my hot rods. If you play with it you will find that sweet spot.
Another old dirt racer's trick. Before we had all the fancy equipment we set caster and camber with a level. Set it up plumb in front (or back) of ball joints or kingpin and measure top and bottom. The difference is your caster in inches. Set it beside and measure to the wheel top and bottom. The difference is your camber in inches. Now you have something you can adjust from and return to. Every car will have it's own sweet spot. I'll bet you I can align my cars and all the fancy lasers in the world can't get it any closer.
My old trick. A tape measure and measuring from 3 and 9 o'clock on the front wheels. It isn't rocket science.
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