era specific alignment

[10yearsgone 15]

So thanks to other postings I was able to get the actual alignment specs (1/4 positive caster, 3/4 positive camber, 3/16 toe in). I went by a sears automotive shop the other day to discuss alignment with them, While their system works on degrees is was accurate to the specs I listed. Here is the question:

 

The tech told me this was "era specific" and not what is common in today's world even given the stock steering, suspension, etc. present on my vehicle. I don't profess any knowledge in this area (or many areas for that matter), but the response seemed a bit odd to me. I would think the specs are the specs and unless you are tailoring the handling to a specific purpose, it wouldn't change.

 

Any wisdom here? I don't plan to emulate Fast and Furious, just a cruiser and maybe lite strip with my Cleveland power train.

[1969_Mach1 333]

It's been a long time since I've done alignments at a GM dealership.  But todays cars typically have different alignment specs.  More positive caster, closer to 0 degrees camber and closer to 0 toe in.  Maybe somebody will chime in with more suitable specs for your Mustang.

 

I'll try briefly to recall the definition of the terms.  If I miss something, hopefully somebody else will chime in.

 

Caster:  Forward and backward angular measurement of a centerline through the upper and lower ball joints.  Positive caster indicates the upper ball joint is behind the lower ball joint.  Negative caster indicates the upper ball joint is in front of the lower ball joint.  Zero caster indicates the centerline passing through the upper and lower ball joints is vertical.  Positive caster causes the tire to turn inward while driving forward and increases stability of the car.  For stability while driving, larger cars and pick-ups need more positive caster than smaller cars.  Also, the right (passenger) side very often has slightly more positive caster than the left (drivers) side.  This helps compensate for the crown in most roads helping the car go straight.

 

Camber:  Inward and outward angle measurement of the centerline through the upper and lower ball joints and hence, of the tire.  Positive camber is top of the tire leans outward and negative camber is top of the tire leans inward.  Again, zero indicates a vertical condition.  it can be tricky to find a balance between camber angle and tire wear.  Some positive or negative camber helps stability.  Zero is ideal for tire wear.  Road race people tend to like more negative camber. 

 

Toe:  Toe-in indicates the front of the tires point inward.  Toe-out indicates the front of the tires point outward.  Ideally for minimum tire wear you want zero toe-in.  But, on rear wheel drive cars the front tires want to toe-out when driving forward so some initial toe-in is needed to compensate for very slight looseness in the steering linkage components.  On front wheel drive cars the front tires want to toe-in when driving forward so some initial toe-out is needed for the same reasons.  On rack and pinion steering cars, like most modern cars, there are fewer parts in the steering linkage, thus, fewer places for slight looseness in the steering linkage permitting toe to be set closer to zero. 

 

Hope this helps some.

[shaun071 62]

I think what the tech is trying to say is those alignment specs are more applicable to tires available in the 60's. Todays tires, even ones that are classic sizes/profiles would require different settings compared to the originals due to different construction and rubber compounds etc.

[1969_Mach1 333]

Tires technology didn't cross my mind.  I was focused on different suspension types, rack and pinion steering and strut suspensions allowing closer to zero toe and camber settings.

[shaun071 62]

There can be very different alignments needed for crossply vs radial tires. Also standard vs heavy duty suspension etc.

[10yearsgone 15]

Thank you both for the detail and thoughts. I'm curious to see the percentage change from the original specs.