Caster issue - only 3.5 on left, but 5 on right: what is problem
 

Went to get car aligned.
Its 1993 LE with FCM coilovers.

Goal was most camber on front, most caster, and some intelligent amount of toe.

To my total pleasure, -3 degrees was achieved very quickly at max camber setting, both front sides.
All stock bushings (57K miles, clean Northern California occasional driver).

When adjusting toe, problem: Caster dropped on driver (left side) to 3.5 degrees.
Right side was able to achieve 5 degrees.
He tried to figure out why, adjusting, but no go.

No accident history, nothing is "obvious".

What is your first impulse?
Lower control arm?

I find it strange that such beefy front arm would bend at all?
And I wonder if the bushings on left can degrade to cause this? They are little more stressed in cornering as we always go right (leaning on the left side) on on ramps, off ramps.

Rear camber is 0.3 degrees less. He dialed both sides to 3.5 caster..but I want to fix it to get 5 both sides.

Thank you for suggestions.

Have you ever removed a control arm from a Miata and held it in your hands? "Beefy" is not the adjective which most immediately springs to mind.

They bend. I tweaked one of mine (right lower) on the '90 just by hitting an abnormally deep pothole at low speed.

Replace the lower arm and lower balljoint.

Probably bent upper control arms. You havent put new bushings into the upper arms lately have you? Pretty common to bend them in his direction doing that.

Hey, thank you.
I did everything to Miata (ok...no dirty thoughts here..please..not that kind of everything),
and arms seem pretty beefy, however I have not exactly thought about them in terms of stiffness as it was not a concern when working on suspension, I assumed if it was great for all racers it was good for me.

As you can tell from my question: my own first thought was bent from arm.
I did not replace any bushings on this Mata (although I have poly-bushed another).

So new (to me) front lower arm it is...I'll do that with new Extended Ball Joints so Andrew's suggestion is respected and valued by following it, while bringing even more happiness with more camber.

Thank you.

My money is on bent lower control arm. Don't ask me how I know.

(I bent one so bad this year I had NEGATIVE caster)....and I didn't hit anything.

Skip the extended balljoints. They are unnecessary on a street car.

Andrew,

Thanks. I agree, but wanted to track this one. Although frankly at -3degrees of camber, I am good.

Any reason to replace LE Ball Joints at 57K miles?
It was not tracked or driven hard..not even by me yet.
Or just get new-er lower control arm?

If there is good reason to replace them, than I'll get extended joints to have more flexibility.

Would it be reasonable to wonder what the eccentric bolt settings are to find the 1.5* caster difference left and right? I was able to even out the caster on mine but the eccentrics are not as symmetrical to each other.

On my old NA, the eccentrics were very similar (+/- a few notches on the eccentrics) to get the same camber and caster numbers.

Are the RLCAs as fragile as the fronts?

All eight of the control arms are built pretty much the same way; a couple pieces of thin sheet metal formed into clamshells and spot-welded together. In theory, the front lowers are probably the weakest due to their odd, non-boxed shape, but I wouldn't call any of them "sturdy."