Setting up Coil-overs on the '93 Miata

Brad Mackey · **Posted:** Tue Apr 04, 2006 1:12 pm

Karl Shultz wrote:

What spring rates and lengths is the SM suspension? Being that it's not my car, I've got no idea what we're running, but I know it's "not the SM suspension."

Mazda Comp. sells the "SM Package" and lists the springs as Eibach 700 X 6" for the front and 325 X 7" for the rear.

Which is what I bought. Already had the SM Sway Bars from Eibach.

Rich Anderson · **Posted:** Tue Apr 04, 2006 1:22 pm

Bowie Gray Jr wrote:

Rich Anderson wrote:

Where do you measure the ride height? Based on Les's figures of 12.5 and 13, unless he is using the metric system, I assume that it is not the bottom of the rocker panel.

Quote:

Measured he same way you did, from the center of the hub to the top of the fender.

If you measured from the ground to the rockers (or what is left of my rockers, they have led a hard life) the right height is very close to 5" front, a tiny bit more rear. Or at least that is where I used to run them. I have no idea how far from that they are now that I knocked the nose of the car and OPM rebalanced it afterward. I know the car works REALLY well, which is what matters.

Why is this used as the position for measurement? To eliminate the variable of tire size?

Karl Shultz · **Posted:** Tue Apr 04, 2006 1:26 pm

Rich Anderson wrote:

Why is this used as the position for measurement? To eliminate the variable of tire size?

Because it's what the original poster used. Apples to apples.

There's also very little rocker panel left on the underside of Bowie's car. Trust me on this one. When I ask him "where should I jack it up from" the answer invariably comes back "wherever."

Rich Anderson · **Posted:** Tue Apr 04, 2006 1:27 pm

Karl Shultz wrote:

Rich Anderson wrote:

Why is this used as the position for measurement? To eliminate the variable of tire size?

Because it's what the original poster used. Apples to apples.

OK. Sorry, but beyond this specific case, (and split this someone if you want to) why would one choose to measure it there? Obviously someone had to decide that was a good place to do it.

Karl Shultz · **Posted:** Tue Apr 04, 2006 1:36 pm

Rich Anderson wrote:

OK. Sorry, but beyond this specific case, (and split this someone if you want to) why would one choose to measure it there? Obviously someone had to decide that was a good place to do it.

(Edit: apparently I was being "bitchy" before...)

One reason I can think of is that it takes wheel diameter out of the equation. IIRC Brad runs some sort of 13" Diamond Racing wheel on his car. We're on tallish 205-50-15s - big ones, at that.

Rich Anderson · **Posted:** Tue Apr 04, 2006 1:43 pm

Karl Shultz wrote:

Rich Anderson wrote:

OK. Sorry, but beyond this specific case, (and split this someone if you want to) why would one choose to measure it there? Obviously someone had to decide that was a good place to do it.

Any reason not to?

Jeez. I'll think twice before trying to help again.

Take it easy. I am just asking a question. If you don't want to answer then don't. I just have never heard of it being measured this way before and I was curious as to why that would be used versus the (I assume) conventional rocker height method. No need to get bent about it. I wasn't questioning you specifically.

AdamMenges · **Posted:** Tue Apr 04, 2006 1:53 pm

Quote:

I was curious as to why that would be used versus the (I assume) conventional rocker height method.

Probably because 95% of cars over a year old don't have straight rocker panels any more. It only takes one time for someone to jack their car from the wrong spot to crush a pinch-weld, or dent the rocker itself. The hub-to-fender is a bit more constant.

Whats with all the hostility/bickering on the forums lately? Everyone seems extra bitchy this month.. :roll:

Les Davis · **Joined:** Fri Aug 29, 2003 2:04 pm **Posts:** 2059

Rich Anderson wrote:

Karl Shultz wrote:

Rich Anderson wrote:

OK. Sorry, but beyond this specific case, (and split this someone if you want to) why would one choose to measure it there? Obviously someone had to decide that was a good place to do it.

Any reason not to?

Jeez. I'll think twice before trying to help again.

Take it easy. I am just asking a question. If you don't want to answer then don't. I just have never heard of it being measured this way before and I was curious as to why that would be used versus the (I assume) conventional rocker height method. No need to get bent about it. I wasn't questioning you specifically.

Yes, this sort of measurment eliminates differences in tire size. It also measures the most important aspect of ride height to the double wishbones. Seems to make perfect sense to me. This is basically the only measurement I've seen used in the Miata world. Since I've never run coilovers on any other car, I have no experience with how other cars are done.

Ryan Holton · **Posted:** Tue Apr 04, 2006 7:38 pm

Les Davis wrote:

Are you sure about that, lower in the back than front? If so that might explain some of the handling difference I've noticed in the car. Hmmm...

I just rechecked the measurements, and its still dead on with the Gray mobile. Center of hub to fender/rocker.

We be rolling deep in our 1.6's!!!!!

Time to borrow Feinberg's scales, but I wanna do my car too!

Brad Mackey · **Posted:** Tue Apr 04, 2006 8:00 pm

Yep, Les.
That's the way it always is stated in the stuff I've read.
But that's Miata's only. Never addressed it on any other car, but seems just as logical as any other place. It takes tire size, wheel size out of the equasion.

It's used as a "relative" number anyway, when you make changes to the spring perch. Just a very convenient commonly-used datum surface that's repeatable... unless you ball up the car.

Les Davis · **Joined:** Fri Aug 29, 2003 2:04 pm **Posts:** 2059

Ryan Holton wrote:

Les Davis wrote:

Are you sure about that, lower in the back than front? If so that might explain some of the handling difference I've noticed in the car. Hmmm...

I just rechecked the measurements, and its still dead on with the Gray mobile. Center of hub to fender/rocker.

We be rolling deep in our 1.6's!!!!!

Time to borrow Feinberg's scales, but I wanna do my car too!

Very strange considering at stock ride height the back is over an inch higher than the front, so to get the back lower your lowering the back several inches over stock and a couple inches more than the front. Of course since I've always liked the way that car drives better than mine, it certainly makes me curious. It just seems that lower the back that much would be too much of a change in suspension geometry...

Ryan Holton · **Posted:** Wed Apr 05, 2006 11:28 am

Les Davis wrote:

Ryan Holton wrote:

Les Davis wrote:

Are you sure about that, lower in the back than front? If so that might explain some of the handling difference I've noticed in the car. Hmmm...

I just rechecked the measurements, and its still dead on with the Gray mobile. Center of hub to fender/rocker.

We be rolling deep in our 1.6's!!!!!

Time to borrow Feinberg's scales, but I wanna do my car too!

Very strange considering at stock ride height the back is over an inch higher than the front, so to get the back lower your lowering the back several inches over stock and a couple inches more than the front. Of course since I've always liked the way that car drives better than mine, it certainly makes me curious. It just seems that lower the back that much would be too much of a change in suspension geometry...

Dont ask me, as amazing as it sounds, its exactly like Tom set it.

For once I have a car I really dont need to mess with and it bothers me....

Aaron Buckley · **Posted:** Wed Apr 05, 2006 11:45 am

Back when I had my '93 Miata, I was running Spec Miata shocks with the Ground Control coilovers with 375# fronts and 250# rears. I corner balanced the car, starting with the front an inch and half lower and the rear about 2 inches lower (as compared to stock).

After an alignment, the car was neutral to slight oversteer on throttle. I had -3 degrees of camber up front and -2 degrees in the rear with zero toe front and rear. I think a bit of toe in would have made the car less of a handful, but I liked the oversteer. (running 205/50/15 Victoracers) - AB

Vincent Keene · **Posted:** Wed Apr 05, 2006 12:04 pm

Ryan Holton wrote:

For once I have a car I really dont need to mess with and it bothers me....

Yeah...Ryan has something that isn't broke, but he's dying to fix it. :roll:

Man you should have been an engineer.

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

Aaron Buckley wrote:

I had -3 degrees of camber up front and -2 degrees in the rear with zero toe front and rear.

My 95 maxed out at -1.6*on the driver's front. I don't know how you got -3 out of it.

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Setting up Coil-overs on the '93 Miata

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