Mustang II Alignment Specs

[mrloboy]

I am just finishing a complete build on a '49 Meteor (Ford) sedan. We used a Mustang II based front suspension with tubular control arms and a Manual Rack & Pinion Steering. I am taking the car for an alignment and wondered what caster, camber and toe-in specs I should use. Rick

[Learpilot]

Rick,I put 4 degrees positive caster, 1/2 degree negitive 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.
Rick

[jaybee]

Modern tires seem to want a little less toe in and a lot more caster (4 to 7 degrees) than the tires that most of our hobby cars first came with.  I say that because complaints about darty steering with alignments close to original specs are common and because even new cars come with double or more the caster from "back in the day."

[mrloboy]

Thanks Rick. Good to hear from someone that has experience with the specs. I will follow your lead! Rick

[mrloboy]

Modern tires seem to want a little less toe in and a lot more caster (4 to 7 degrees) than the tires that most of our hobby cars first came with.  I say that because complaints about darty steering with alignments close to original specs are common and because even new cars come with double or more the caster from "back in the day."

Is there a downside to 7 degree caster over 4? I have driven a few cars with Mustang II suspension that do feel very sensitive. If 7 degrees will clear that, it would be a bonus. Thanks, Rick

[enjenjo]

I have used as much as 7 degrees with no ill effects.

[Learpilot]

I have used as much as 7 degrees with no ill effects.

Rick, The thing you may run into with 7 degrees of caster is your slots in the upper hats may be too short. I had to lenghten slots in mine to get 4 degrees, and check for clearance of the upper a-frame. Tubular a-frames offer more clearance than stock a-frames.
Rick

[40cpe]

I have a Heidt's set-up in my '40 frame and for years had a slight intermittent shake in the steering wheel at higher speeds. Increasing the caster to 4.5 inches didn't help, but in the process of checking everything I wound up with a toe-in of 1/16" as opposed the previous 1/8". I decided to try it and now for two road trips of 1200 miles each I haven't experienced it again. I'm now gradually reducing the tow-in by 1/4 turn at at time to see if I can pick up on an optimum setting.

My frame is probably more flexible than yours but I'm convinced that there are so many combinations and variations in different set-ups that no one set of specs is right for every body. You have to experiment a little. It gets a little expensive if you have to go to an alignment shop every time you change something.

[enjenjo]

I wound up with a toe-in of 1/16" as opposed the previous 1/8".

You have to remember that the original Mustang specs were for bias ply tires. Radial tire don't like that much toe in. The reason? Imagine the belts in the tire as a bulldozer track. Onece a direction is set, it wants to continue in that direction. With a lot of toe in, the front tires are trying to turn the car in the direction the belt is headed. Which ever tire has the best traction will push the car in that direction, until the other tire gets better traction, then it will head the other way.

I recently fixed a car that was doing the same thing. The technician doing the alignment insisted it needed 1/8" toe in, and 2 degees caster.  The owner called me, I explained it to the tech, he set it at 1/32" toe in, with 6 degrees caster, and it drives fine now.

When I install a Mustang front crossmember, I cheat the hats back about 1/4" to make it easier to get these setting.

[mrloboy]

I expect I will use 7-8 degrees of caster and 1/32-1/16 toe for the original setting. Unfortunately after the alignment, I ship the car for a few hundred miles and follow up will be difficult. I will advise the customer to keep an eye on tire wear and if handling is not perfect to try and adjust the alignment until it is comfortable. Hopefully he is understanding that it is a trial and error situation.

[40cpe]

can anybody estimate how much (in fractions of an inch) a 1/4 turn of each tie rod will affect the toe? I'm moving mine in increments and don't know if that much is a negligible amount or too big a step at one time? I can't measure it each time I move it, but I'm keeping track of the movements so I can reverse If I go too far.

[enjenjo]

Thread pitch is 9/16" by 18. So one turn would be .055". and one quarter turn would be .0138".

[jaybee]

Good idea to move the hats.  You can do much the same thing on a tri5 Chevy by cutting the spot welds on the forward side of the hats, pushing that side outward, then burning it back into place.

In the days of bias ply tires these sorts of alignment specs just weren't usable.