Positive Camber Impossible?

[dartslantsix]

Wanted to chime in on this. My 67 has the offset bushings and they could only get me 1 degree of positive caster and camber was at zero. Really frustrating. I am saving up for aftermarket upper arms.

My car follows ruts in the road really bad, so more caster is needed. I read that late model Mustangs use 3 degrees caster, so that is what I am shooting for.

 

[ir3333]

could wear and tear on 50 year old lower A arms be a contributing factor?
i have seen some bent and some pretty sloppy when removed.

 

[72bluNblu]

Wanted to chime in on this. My 67 has the offset bushings and they could only get me 1 degree of positive caster and camber was at zero. Really frustrating. I am saving up for aftermarket upper arms.

My car follows ruts in the road really bad, so more caster is needed. I read that late model Mustangs use 3 degrees caster, so that is what I am shooting for.

Depends on the year of the late model mustang. '93-2004 called for +3.6* caster +/- .75, so as much as 4.35*. '05-'13 calls for +7.1* caster +/- .75, so, you could have as much as +7.85* on one of those.

Some folks have gotten away with telling their alignment guys to use '93-'04 mustang specs from the computer, and that wouldn't be bad if you can get them. +3* caster isn't too bad for manual steering, although the more you dial in the more the car will resist turning and with a manual box that will be noticeable as steering effort. If you have power steering, try to get as much as you can. I think Peter Bergman (GmachineDartGT) runs like +7* on his '71 Dart GT. Won't hurt if you've got power steering. But he has adjustable tubular control arms on his car.

could wear and tear on 50 year old lower A arms be a contributing factor?
i have seen some bent and some pretty sloppy when removed.

Certainly could, but that wouldn't be the only effect.

 

[cudak888]

Every time you change the ride height of the front of the car with respect to the rear of the car the caster changes. In your case, if you lower the back of the car with respect to the front, you've added positive caster. Caster is just the tilt on the spindle. Positive caster means the top of the spindle is leaned toward the back of the car. So lowering the back of the car adds positive caster (assuming nothing else changed).

A 215/75/14 is 26.7" tall. A 185/70/13 is 23.2" tall. If your +1.5* of caster was with 185/70/13's all the way around, and you then added the 215/75/14's to the front only, you added a VERY significant amount of positive caster. It's not 1.5* anymore with that set up, regardless of you not changing your alignment. That's a 1.75" rubber rake to the back. Instant positive caster. Nothing in the front suspension changed, so, the camber, toe, everything else is the same. But the caster changed because the angle of the spindle changed with the rear drop.

Makes me wish that I wasn't limited to two tires for that test. Had only three rims to play with anyway, so it wouldn't have happened either way.

When you lowered the front you changed all of your alignment specs. Everything. Caster, camber, toe, all of it. If you just consider the drop in ride height in the front compared to the rear you should have lost caster, but, because the suspension geometry itself changed the caster change isn't just based on the change in rake. You probably made some of the numbers better, which is why the handling feels better. But any significant change in ride height with the front adjusters requires a new alignment.

]

I figured as much, though it helps to hear this from someone who knows what they're talking about. Less things to leave to educated/semi-educated guesses as I sort it out.

And then there's the pulling to the right. This could be a ton of things too, most of them mean your alignment shop isn't great. It could mean that they actually set the alignment specs exactly the same on both sides, which would cause the car to track slightly to the right since most roads have some crown to them. Typically, cars are actually set up so they're specs aren't the same left and right, they dial in a little pull to the left to counter the effect of road crowning. Racers of all kinds don't like this and set their alignments up the same side to side, but out on the public streets that means they tend to pull a little to the right because of road crown. Or it could just mean your alignment was never right to begin with.

I have a suspicion they couldn't get the caster dialed in exactly the same on each side, and I'm feeling the results, especially due to the lack of caster.

I can't seem to wrap my head around why this is such a PITA issue even with the offset upper bushings though. I'm going to wind up getting some degree plates and one of those caster/camber tools to do it myself, but I have a suspicion that not even the offset LCA bushings are giving enough benefit.

It would be nice - if only due to cost - not to have to throw tubular UCA's on these cars just to get good caster in a reasonably repeatable manner. And I don't mean the fully-adjustable ones either.

-Kurt

 

[72bluNblu]

I have a suspicion they couldn't get the caster dialed in exactly the same on each side, and I'm feeling the results, especially due to the lack of caster.

A general lack of caster won't cause it to consistently pull one direction. That's just an incorrect alignment.

I can't seem to wrap my head around why this is such a PITA issue even with the offset upper bushings though. I'm going to wind up getting some degree plates and one of those caster/camber tools to do it myself, but I have a suspicion that not even the offset LCA bushings are giving enough benefit.

It would be nice - if only due to cost - not to have to throw tubular UCA's on these cars just to get good caster in a reasonably repeatable manner. And I don't mean the fully-adjustable ones either.

-Kurt

There are a couple of things going on here. One, the original suspension was designed for bias plys and the alignment that goes with them, which is the opposite of what you need for radials. That's why the offset UCA bushings come into play, and why you need tubular UCA's to get a good amount of caster. The stock UCA's were never intended to get more than +1.5* of caster. In fact, as you can see in the factory specs, manual steering cars were supposed to have negative camber from the factory. Bias plys. Given the advances in technology, it's pretty amazing the stock suspension components can be used at all with modern tires with just a bushing change. (but they can!!!).

The second thing is that the suspension geometry changes with the ride height. This is true for ALL suspension systems. But, because the ride height on these cars is easily adjustable, it means the suspension geometry is easily changed too. This is a good thing, because it makes it easy to lower the car and adjust the geometry to work with radial tires. The camber curves, bump steer, roll centers of these cars can be adjusted to work very well. But it has to be done RIGHT. Otherwise that adjustability just makes it easy to screw up the geometry to a point where you can't get decent alignment numbers.

Offset UCA bushings work great (to a point), and you should be able to get as much as +3* of caster with them. But that does depends on where the ride height is set, which means that it's not necessarily repeatable from one car to the next unless the ride height is the same between the two cars.

Before you condemn your stock UCA's and offset bushings, you need to set your ride height where you want it and have the car aligned again. It sounds to me like the alignment shop you used had no clue how to deal with your car. Which is pretty common, and pretty sad because these cars are SIMPLE to align. As of right now, because of the ride height change, none of your numbers are what they were when it was aligned. A 2" drop with the torsion bar adjusters significantly alters the geometry.