Dropped my car off at a very "reputable" race shop. Previously the alignment was -2.4 degrees all around and i was pretty satisfied with it. I asked them for 1/8" total toe out in front, 1/8" total toe in rear. And max the camber out front. They called me and told me my car was done but they could only evenly pull 1.5 degrees total neg camber in front .. 99 miata Im on xidas and 15x10 ul's with 245 a6's... What ride height should i be at to pull around 3 degrees neg camber up front? or do i need offset bushings? any info would be great.. thanks guys

 

The two alignment cams on the front both adjust both camber and caster, and in some cases you have to trade one for the other. Did you ask the shop to prioritize caster over camber?

Max static camber varies with ride height, IIRC with some cars it's possible to get 3 degrees if it's running very low. Offset upper bushings should give you 3 degrees easily, but there are other compromises involved in using them (you might need spacers to get your tire clearance back, for example).

--Ian

 

Yeah, but think about it, MAX caster (reasonable) is the max camber setting. Though I found on my car that the MIN caster setting resulted in even more camber. You should be able to get 3° in the front with about 4" pinch weld heights. On the NB subframe with minimum caster I was over 3° at 4.375 pinch weld. and with like 4something° of caster I am at like 2.8° of camber. But something is funky in the front of my car.

 

The upper arm has no adjustments so to increase caster the front and back inner mounting points for the lower control arm must be adjusted. One moves inward and the other outward to rotate the spindle to give you more caster. The by-product is that they both are not then fully adjusted outward, which would be the way to get max camber. If either setting is maxed out, then the other, by definition, isn't maxed out. The best thing to have is a happy medium, a balance of your needs.

I'm just a grease monkey, but it's really good to know how this crap is interrelated if you are going to be screwing with it.

 

Moving one of the adjustor acts to rotate the arm around the center of the other adjustor. Since the lower balljoint is pretty close to being lined up with the front adjustor (in the left/right axis), moving the rear one moves the balljoint mostly forwards or backwards. Forwards gives you more caster, backwards gives you less. Since it's an arc, however, you'll also move the balljoint inwards or outwards by a little bit, which changes camber.

Moving the front adjustor, OTOH, will rotate it around the rear one. Since the rear one *isn't* lined up with the balljoint (in the fore/aft axis) it's at a different place on the arc , which means you get proportionally more fore/aft (caster) motion even though you're mainly interested in left/right (camber). Max negative camber means moving that adjustor all the way out, which is also going to be as far rearwards as the front adjustor can make it. So max camber is pretty much always going to be less caster than you could get if you didn't care about camber.

Of course, the factory adjustors also move the arms up and down slightly (because you're rotating the eccentric bolt inside a circle defined on the subframe), which is going to have the effect of lengthening or shortening the arm as measured in a plane parallel to the ground.

Double A-arms work well, but the downside is that everything is interconnected and changing any single arm length or pickup point will change every alignment spec by at least a small amount.

If you're ever replacing the bushings (and thus need to completely realign the car anyway), spend a few minutes turning the bolts and watching how stuff moves.

--Ian

 

Not exactly guys.

On a performance alignment the front adjuster is pretty much going to be all the way out on a car that isnt bent. If you set the rear to all the way out you get a decent amount of camber and caster. If you move the rear one all the way in, you are in minimum caster mode by you'll actually have more camber than what you would think was max camber mode because the lower ball joint moves in an arc. You can get even more caster than both adjusters out of course but that would just be silly and would make a massive hit to your camber.

The eccentric bolt doesnt move the arms up and down significantly because the bolt is constrained into a slot, that is why there are only half circles on the subframe

 

Just remember that more caster results in more dynamic camber gain in a corner. Those of you chasing max static camber and giving up caster to do so are wearing your tires more in a straight line and not gaining as much as you think in the corner. Temping your tires tells the only truth, not following the sheep.

 

Depends. Again, my car might be all bent up, but. In a typical turn when static with my current alignment, my outside tire gains about 1° of camber while the inside tire goes almost to zero camber. So most of my caster number is coming from the inside wheel when I do the caster math. And the difference between ALL the camber and minimum caster and my current setup is that in a turn I end up with less camber on the outside wheel compared to the max camber minimum caster setup.