Alignment theory Mustang II

Hi,
Went in to have the 40 aligned by new shop, Big O tires.
On their computer, they pulled up specs for 1940 Ford and swore
that stock number was the correct thing to do.

Now my 40 lost it's I beam axle and wishbones long ago. Currently I have
a Mustang II front end with the strut arms. So my question: What should I
set Camber, Caster, Toe to? They use a lazier Hunter machine and are
working off the rear wheels for a 4 wheel alignment? Is there a rule of thumb
or a set of workable numbers that I can give them? Advice?

Lots of people have been down this road before, so fill me in.

Answer #1.....
1/2 degree camber on the left 1/8 degree on the right
1 1/4 degree caster on the left 1 1/2 degree on the right
zero toe with radial tires unless you are getting bump steer

Answer #2.....
1 1-2 degrees caster for non-power assist and 3 1/2 degrees for power assist steering.

Answer #3.....
Camber: 1/4 degree negative L and R
Caster: 6 degrees positive L and R
Toe in: 1/16" to 1/8" overall

Answer #4.....
General rules are; lighter cars get more caster, cars needing stability at higher speeds get more caster, if you like a little heavier steering feel with more feedback, give it more caster. Heavy, low-speed cars get less. The "crown" that most road surfaces have for water drainage can cause your tires to wear on the inside a little faster, some positive camber fixes that. If you're out road-racing or something and want ultimate cornering traction, give it some negative camber just for the occasion but you'll obviously wear the tires faster in normal driving.

Answer #5.....
Motors Manual says for 1977 Mustang:
Caster +1/8 to +1 5/8 Degrees with +7/8 Degree desired for right and left.
Camber -1/4 to +1 1/4 Degrees with +1/2 Degree desired for left and right.
Toe in 1/8"

Answer #6.....
I put 4 degrees positive caster, 1/2 degree negative camber, and 1/2 degree toe in.
I started with 2 degree positive caster, too quick steering for highway speeds. I have run this set up with manual and power steering.

Answer #7.....
I have used as much as 7 degrees positive caster with no ill effects.

Answer #8.....
Caster left +2, right +2 1/2
Camber left 1/4, right 1/4-1/2
Toe-in 1/8 - 3/16
.

Wow. Thanks Tech.

Following your general trend, I think I will ask for a bit more caster.
He put in 2.7 on the left front and only - .01 on the right front.
I find it strange that there would be that big of a difference between the two.
I can see some difference due to the crown of the road as you noted, but not that much.

He also had trouble getting the nuts loose on the right front camber, reading
-.04 degrees so will soak with knocker loose and try that one in a couple of days.

Toe appears to be in line with your general numbers.

Reason I took it in was I say it was having wear on the inside of both front tires. Wear about 1/2 inch wide on the inside edges and close to smooth. The car has always tracked well and smooth as silk. Speed has often been held at 100 or over on some of the long empty stretches out west with no problems. Just winging and singing.

Thanks for the advice. Anyone else chime in?

Scooting if it had been me I would have left when they told me they were going to use the stock specs, especially when I looked at what those specs were. The stock 40 Ford Car specs I come up with are:


Alignment Specs 1940 car *

Caster

Max + 9

Min + 4 1/2

Max Variation 1/2

Camber

Max +1

Min +1/4

Max variation 1/4


Toe

Max 1/16”

Min 0

( * Fine for original suspension, dirt roads and skinny bias tires)


Now from what I see they didn’t even come close to matching those specs when they aligned the car anyway. Your right there is way too much difference in the caster readings.

Road crown is compensated for with Camber not Caster…..usually no more than a + ½ degree (on the left) and now days most shops tend to only go +¼ degree.

Wear on the inside of both front tires is usually indicates the wheels are toed out or possibly WAY too much negative camber on both sides.


There are a lot of opinions on aligning modified front ends. What has worked for me is to use the factory specs for the donor car as a starting point……Tech’s answer # 5 77 Mustang II. I would probably shoot for about +1 ½ degree caster and +1 degree camber (just due to my own past experiences).

I’m lucky, I have a very good shop I use….after we set the alignment I drive the car and if necessary we do any fine tuning. That is all included in the alignment cost.

Just my 2 cents, if they let the car go out with the caster specs you have I would not even bother going back there......find a shop that knows what they are doing and will take the time to do it right.



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one thing they never take into account is the way these cars are set up. with the dago of these cars your alignment changes at speed. on average they will be 1 to 2 inches lower at 70+ mph. which will take away toe which in turn will eat the inside of your tire.
i discovered this by bolting a small piece of strap on the front frame horn with about an inch of clearance .. did this on a nice flat stretch of road. the bottom of the strap was bent in an L . ran the road up to about 90 mph. car never bounced but the strap was scraped and bent.
i like the shim alignment so i can fine tune it later .

Several reasons there why I bought an alignment rack to use during the build/mockup-----------
some of the most severe issues are brought on by wheel offset choices--

I think Jerry is alluding to scrub radius.
https://www.youtube.com/watch?v=VbReLNi2JP4

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