Upper Control Arm Shims Required for a 73 Mach 1 Mustang?

[Fed]

Hello.  I'm currently replacing the front suspension on my 73 Mach 1 and noticed that the current upper control arms were installed using shims.  My understanding was that the '73 did not require the use of shims, is that correct? 

I'm going with a stock non-adjustable replacement upper control arm, and just wanted to be sure before I completed the reassembly.

Thanks for the help. 

 

[cwalker509]

Bump to get this guy some help. I do not recall shims on 71. Fed....take a few minutes and introduce yourself and post a pic of your car please! We have a welcome aboard type page for newbies.

 

[OMS]

I do not recall any shims from the factory on the upper arms. Adjustment was made with the eccentric on the lower arm.

But I can see an alinement shop sticking shims in there to compensate for bent/ worn parts, to get it adjusted and out the door if the customer wanted it done that way.

 

[timachone]

As far as I know shimming the upper control arm was only on the 1965/1966 Mustangs. It was the way to get the camber and caster adjusted. Later Mustangs do not have them and as Don said, on our Mustangs adjustment was made with the bolts and their eccentric washers in front of the inner bolt hole of the lower control arm. 

If there are shims you have probably some more concerns: a) somebody did not know about the eccentric bolts and washers, b) they are totally worn or corroded c) your complete suspension is worn out or d) your car had an accident and the frame isn't as straight as from the factory anymore... 

 

[Hemikiller]

When aligned to stock bias/belted tire factory specs, shims should not be needed, the strut rod and lower control arm eccentric should do the job. However, radial tires don't like bias/belted alignment specs and require more caster, which pulls the tire forward in the wheel opening and may cause oversize tires to hit the front valance. A simple fix for that is to use alignment shims under the front UCA bolt, which increases the available caster. More caster improves steering feel and return to center, as well as reduces the "loose" feeling these cars are known for. 

Opentracker Racing has some street performance alignment specs on their site 

https://opentrackerracing.com/technical/

Personally, I'd add 1/8" ~ 3/16" shim pack behind the front bolt to build in more caster. Give the above specs to your alignment guy and go from there. Do not let them use factory specs. 

 

[Bill73Ragtop]

I can see a shop reverting to shims if they stripped the lower eccentric bolt.   Also, in agree with potential reasons cited by OMS and timacone.

 

[droptop73]

When aligned to stock bias/belted tire factory specs, shims should not be needed, the strut rod and lower control arm eccentric should do the job. However, radial tires don't like bias/belted alignment specs and require more caster, which pulls the tire forward in the wheel opening and may cause oversize tires to hit the front valance. A simple fix for that is to use alignment shims under the front UCA bolt, which increases the available caster. More caster improves steering feel and return to center, as well as reduces the "loose" feeling these cars are known for. 

Opentracker Racing has some street performance alignment specs on their site 

https://opentrackerracing.com/technical/

Personally, I'd add 1/8" ~ 3/16" shim pack behind the front bolt to build in more caster. Give the above specs to your alignment guy and go from there. Do not let them use factory specs. 

I added a thick hardened washer behind the front bolt for exactly this reason. It really helps with directional stability.