Wheel alignment spec problems

[71fast]

After doing a search for wheel alignment specs it seems the numbers are all over the place.  After new suspension and steering back in 2016 this is the print out from the shop.  Steering wheel doesn't return after cornering and needs correction after hitting bumps.  I installed QA1 lowering springs and going to take it in for another alignment.  Would you take it to the same place after looking at this printout?  Do I have to tell them what numbers to put in there or should they know?

 

[MKSpeedlab]

Some shops will align it to whats in the book and that doesnt work with new radial tires. The old alignment specs they might be using could still be for old bias ply tires. These are the specs I used when I took mine in to the shop. I printed them out and said this is what I wanted. Opentracker does a ton of Mustang stuff so they know how it should be set up and have some specs for street or a street performance setup. 

https://opentrackerracing.com/technical/

 

[Stanglover]

Well, I'm no expert on this, but I may be able to offer some insight based on my own car. First, the factory specs are useless for Radial tires.

Here's what my car is currently set at, Castor; 3 degrees both sides. Camber; left -.5 deg. right -.8 deg. Toe; left 1/16" right 1/16". The rear numbers don't make a lot of sense to me to be honest. 

I would suggest a bit more camber and toe in. I plan on redoing mine in Spring, but 3 degrees was the max we could get in without shimming, which will be the next step. I would like to add more toe up to 1/8" or somewhere between the two. (after test drives)

What I find with my car that has stock springs at the front, a 1 1/8" antisway bar and KYB G-A-J shocks, is I have slight understeer and the wheel does not center as fast as I would like, i.e. needs more castor.

 

[71fast]

After looking at the printout, do you think they used the stock bias tire specs.  The shop has been around for 50 years, you think they would know all that.  They had laser beams shooting all over the place and put little pin marks on my wheels to attach stuff.  I think I will choose another shop.  Thanks for the info.

 

[Ryunker]

Alignment specs they used are OK, with the exception caster needs to be more like 3+.

This service needs to start with setting the steering box pre-load. Pitman arm disconnected and it set, then do the alignment. This stuff is easy when the entire job is done as it was designed many many years ago.

 

[midlife]

One almost can't have too much caster, which is what results in your steering wheel returning to center. 

You need to find an old-school alignment shop, where the old geezers know how to align these beasts.  I had one in Panama City that was great!  Unfortunately, Hurricane Michael wiped out his shop.

When I lived outside of DC (back circa 1999), I took my 66 fastback to an alignment shop in Manassas, VA.  I walked up to the counter and said I needed an alignment.  He responded with: "well, what do you need?  We can set it up..." and he rattled off 6-7 various scenarios from oval track to open track to back roads to DC-quality roads.  I was blown away. 

The best thing you can do is find a good set of specs and tell your alignment shop to set it up that way.  Opentracker has some good recommendations for alignments.  https://opentrackerracing.com/technical/

 

[Bentworker]

They adjusted it to the specs stored in their alignment machine.  Probably straight from Ford with bias ply tires and 1970’s vehicle “safety” in mind.  Take alignment specifications from Opentracker Racing for the shop to use.
 

I would imagine it being a bit squirrely with negative caster.  Possibly a bit shipping cart like?  It will be a totally different ride if you align it to Opentracker’s suggested specifications.

 

[jspears]

If it's lowered, you need more caster to reduce bump steer. The negative caster is probably why it doesn't return to center and probably why it bump steers. I am running -1 degree camber, 6.5 degrees caster and I started out at 1/8 inch toe measured 6 inches from the ground at front and rear of tires and added slightly more toe in until a thermal camera showed even heat across the tires after a couple miles of highway. You won't get that much caster but the more the better its ok if you can only get 3 degrees positive caster, 3.5 is better and 4 is better still. So my advice is -1 degree camber, as much positive caster as possible and just enough toe to take the darty feeling out. (its possible they used caster setting from manual steering car)

 

[rackerm]

Some shops will align it to whats in the book and that doesnt work with new radial tires. The old alignment specs they might be using could still be for old bias ply tires. These are the specs I used when I took mine in to the shop. I printed them out and said this is what I wanted. Opentracker does a ton of Mustang stuff so they know how it should be set up and have some specs for street or a street performance setup.

https://opentrackerracing.com/technical/

In 1973 you could order a Mustang new with radials, so there must be factory alignment specs for radials if in fact they were different. I gave the attached OpenTracker specs (the PDF attachment below) to my mechanic to use on my unmodified 73 vert with factory-installed radials. On my 70 Mach 1 with Global West Suspension, Modern NItto 17" tires, and the " One Inch Shelby Drop" used the Global West Specs below.

Global West Plus 3 arms have caster built into them so there is now a right and left control arm. The arms allow you to have more positive caster and still keep the
tire in the center of the fender. In the past, you could not get enough caster without the tire hitting the forward portion of the fender.

Alignment Specification for Global West Plus:


Note: Race alignment settings vary somewhat with the application.

Always check the clearance between the control arm and the back of the wheel/tire at
full steering lock. If the tire or wheel hits, you will have to add material to the
steering stops. This situation is fairly rare and occurs mainly with wide wheel widths
on small diameter wheels with extreme offsets.