Should I upgrade the sway bar end links and bushings?

You don't have enough? Upgrading just the front bar will give you more understeer. I recommend replacing both bars as a matched set, and getting a good performance alignment. The FM bars are a good choice.

They are worthwhile to eliminate swaybar preload, but unless you're an accomplished autocrosser you'll probably never notice. My OEM swaybar endlinks and bushings are still OK after 142k miles and 13 years.

I don't know if the OP has an NA or an NB but on the NB I'd have to disagree with you Lanny on the front bar upgrade (going heftier) causing understeer. The bigger front bar changes the car much more toward oversteer (in my experience and others I've talked to). I did the matched set from JR (this is a poorly designed front bar, look elsewhere. fitment issues) and the car went from mild understeer to strong oversteer. I've had to use shocks and tire pressures to 'dial it back' so-to-speak. Recently was recommended (by a very fast NB auto-x'r) to go back to the stock rear bar to get rid of some of the oversteer tendencies. We'll see what happens. Of course, YMMV as they say.

Chris

99BBB

Think about what you experienced, Chris. You got oversteer because the REAR bar was too large--i.e., the set was poorly matched. Not because the front bar was too large. JR has a reputation for that on the NB.

IIRC, the OP has a '96. The standard FM set for a 1.8 NA is 1" front,

5/8" rear. The result will probably be mild understeer, depending on the alignment. My older FM bars are 7/8" front, 5/8" rear, and with a 0.5-degree rear camber bias it was neutral, on the edge of being loose. I increased the camber bias to 0.55 degree to make the car a bit less fussy to drive. Perfect (for me).

Since the FM bars are adjustable, I was hoping that I can soften the front up a bit. Both setting are probably stiffer than stock, so I'm barking up the wrong tree. I didn't plan to get a rear bar cause that puts me into a higher class in autocross. I can probably live with that if the car is more fun to drive. I'm getting killed in the stock class anyways since they allow R compounds which I don't have.

Sounds like I'm better off spending the $160 on a rear bar or some track time.

My front camber is -.9 and my rear is -1.5. I guess this could explain why I'm getting understeer, the rear tracks better in turns. The tech who did the alignment and other autoXers suggested -2 camber on both front and rear, but my NA can't do that on stock suspension and wheels. I think I had to lower the car for the front get be able to get -2. My autoX time has gotten a bit more competitive with this setting despite the slight understeer. I'm told that the tires will wear pretty evenly as long as I don't add any toe.

I do not understand that. Theory says stiffening up the front should produce understeer. Hard to see how it would not. Are you running a weird tire pressure? You had this theory here earlier to go below Mazda specs on tire pressure to increase traction. (It might well be true after you have managed to get the car to corner steadily in a circle at a constant speed, I guess.)

If you did a matched set, you have no basis to make a judgment about what the front bar does.

Like Lanny says, the issue is likely that the rear bar is too stiff. It is well known that this sort of sets tend to have overly thick rear bars to produce a "sporty" feel on the street, and a tricky car. See Randy Stoker's page somewhere on miata.net about this and what are well matched sets.

I had Brainstorm's set on Bozo which was a sporty set like that. To get it back to a non tricky behavior, I had to thicken the front bar further to 1 inch equivalent (I put in the Racing Beat hollow front bar.) That most definitely reduced the oversteer again to manageable levels.

Leon

Correct. AFAIK, no aftermarket bar is softer than stock. All are much stiffer--remember, stiffness of a torsion bar increases as the fourth power of diameter.

A competitive autocross Miata will not be fun (or perhaps even safe) to drive on the street. The handling balance will be all wrong, because the vehicle dynamics are so different. Unless you plan on making the car a dedicated autocrosser, you're probably better off to use the sport to improve your control of the familiar Miata you drive every day. Leave the top places to the guys with trailers and deep pockets.

Just a follow up. My FM bars came in yesterday and I installed them this morning with the FM suggested configuration. I took it out for a test drive and it felt really solid. Much less roll in the slalom and when the rear broke, it was much easier to recovery. The car responded much quicker to steering inputs. I took a friend along and he thought the car rolled much less than the last time he rode with me at an autocross event.

My next autocross is Sunday morning, so I'll really be able to test these bars out. Hopefully, I'll gain a little ground on the top Miata drivers, though we won't be in the same class anymore now that I upgraded the rear roll bars.