NA/NB Miata Alignment Numbers Again

[jev61]

Lets talk NA/NB Miata alignment numbers again please.

Loren has written about aligning a "stock" Maita with as much negative camber up front as possible with +.5 degree more in the rear. This is what I've run the past three racing seasons with stock springs, a 1 inch front bar and a 11 mm rear bar. Thanks Loren, it has worked well.

Emillo of 949 Racing recommends less negative camber in the rear than the front. Here is a link to his article: http://949racing.com/miata-race-alignment-info.aspx

I'm not asking who is right or who is wrong; rather have you tried it? What where your results?

Thanks, Joe

[Loren]

There's a lot of personal preference, and a lot of "other suspension setup" involved.

No matter what you do, it's best to start with a known baseline and "improve" from there. You said you've run a certain alignment for 3 years. What are the pitfalls of that alignment? Does it oversteer? Understeer? Not give sufficient steering response? Cause tire wear issues for your street tires that you can't cope with?

I generally run more negative camber rear than front, but sometimes only about .2 degrees more negative. I think Brian used to run 2 degrees all around on his Mazdaspeed. You're only talking about a half-degree difference. You can fine-tune the balance of the car by that same amount by messing with spring rates, ride heights (to determine bump stop engagement), bump stop length/stiffness, sway bar adjustments and tire pressures. Depending on how many of those things you are willing to tweak around with, you could set the alignment anywhere you want within reason, and adjust around it to your preference. But, if ALL you have to play with is alignment and tire pressure... then your exact alignment choices become more important.

At stock ride height, a Miata is camber-limited in the front. You'll generally max out somewhere between -1.3 and -1.7. (and I seem to recall that NB's were on the lower end of that spectrum more often than not) I think the "run half a degree more negative in the rear" mantra comes from the stock specs, and people wanting to be sure that they're not recommending a "wild" alignment to the general public. More negative in the back generally helps keep the back end planted, and is safer. Will is induce understeer? That takes us back to driver preference. I prefer to have a setup that will keep the back end stuck (making full use of what little power that a Miata has to ACCELERATE whenever possible) and I will tolerate "slight" understeer (that I can adapt to by simply slowing down a touch more on turn entry and keeping my mind on the front contact patch) to that end.

When you lower the car, then spring rates, bump stop lengths and rates and all that come into play, as well. Since Emilio is talking about "race car" alignment, he's probably not talking about stock suspension. As evidenced by his prefacing that article with the requirement that you must have:
* Either factory sport package Bilsteins, Koni's or high performance aftermarket dampers
* At least 550# front springs
* At least 1" front sway bar
* EHP (<=200UTQG) or R compound tires

That's nowhere near "stock", which sort of makes most of the rest of the article irrelevant to a stock setup.

I did notice this, however:
His recommendation of a -1.4/-1.0 alignment for "dual duty" at 12" (hub to fender) ride height seems pretty awful to me. Consider a mild stock alignment of something like -1.2/-1.6. And consider that the stock ride height is roughly 14.5" and compresses to about 11.5"... 3" of travel. Then consider that the stock suspension gains about 1 degree of negative camber for every inch of suspension compression.

His recommendation at that ride height would give you about -1.9/-1.5 maximum camber at full cornering (because there's only about a half inch of active suspension compression travel left). The stock suspension at stock ride height would yield -3.2/-3.6 maximum camber at full cornering. Sure, body roll fits into that equation... but I'd bet that the stock suspension would have higher cornering ability in this instance.

It's all about compromises. And ultimate purpose (track use, autocrossing, mountain road carving, commuting). And driver preference. There are no easy answers.

[jev61]

Thanks for the detailed response, I was expecting a yes or no with only a few comments.

I went to Miata.net and looked up Emilio's post about his alignment recommendations again. The critical part I missed was the racing springs part. I saw the street driven and dual use portions and became interested in learning more without realizing he was making recommendations for a car with much stiffer than stock springs.

It stands to reason with stock springs and less camber in the rear, the car would be loose.

Thanks again for your input.