SpitfireS

After reading the "snake-oil" post for a while I see its closed now.
And I was going just to post a drawing of the front suspension parts, with calculated measurements.
Really interresting comments about bumbsteer and roll couple
It made me think twice about lowering the car.
Anyway....
I found a good drawing of the front in-wheel suspension in a S2000 PDF brochure.
I printed it out as big as possible on a A4 and calculated the scale with the diameter of the front disk (= 300mm), doublechecked it with the width (= 25mm) to find the scale was accurate ( 1:3.125). Hopefully the rest is to scale as well.

Here are the calculated lengths.
Angles dont change, when drawn in scale.
I'm not saying there within a millimeter, but taking measurements while the components are still on the car wont be accurate to the millimeter as well.

U = 208mm
L = 291mm
W = 247mm
C = 235mm
S = 524mm
CS = 488mm
Mounting point of shock from W = 75mm
Angle L & C = 80 degrees
Angle L & W = 80 degrees
Angle L & S = 67 degrees

Here's the drawing:

brent_strong

Very cool.

Race Miata

Very nice! Good job! Can we get the rear as well?

From my not-absolutely-accurate measurements on my printout of the pic and perhaps correct maths, I get 0.700 motion ratio, which has always been what I estimate it to be. Does this number sound close to what others have found the front motion ratio? Now if we could get the rear...

Race Miata

The upper and lower arms are much closer to horizontal than I thought, which means the roll-center is already pretty low even stock

Race Miata

I tried to shrink the pic and corner it on my printout but even though I shrank it down to ~1/10th of the length of an A4 paper, I still couldn't join the planes formed by the upper and lower control arms (they're almost parallel). I tried to estimate as accurate as possible and the roll center seems to be like no more than 1" off the ground. If that's the case, it's very nice for a race setup!

SpitfireS

Sorry but that brochure didnt have a drawning of the rear suspension.
Youre half way done
The original "cut&copy" is about 2MB, if anyone wants that or the original PDF brochure let me know.
It looks like the pivot point on the chassis of the upper arm are not horizontal, or not in the same plane as the lower arm. What is the influence of that geometry? Caster change on suspension travel?

Race Miata

Damn! The rear suspension should be more fun.

When I first took the wheel off my S, I noticed the front upper arms tilted rearwards. Yes, it'll increase king pin inclination (and thus castor) as the suspension compresses. Should be a good thing if tuned right. It should also provide a bit of anti-dive-on-braking goemetry, though the effect could be really small.

KeeblerElf

Sorry to bring back an old thread, but I thought this might interest anyone who was also interested in the original drawing. I'll probably get some rough measurements of the rear suspension later and do the same thing with those. If anyone's interested I'll post that graph as well. Enjoy

ESCALVANTE

Hmmm... this is interesting as I am really considering the J's front and rear roll center adjusters.

Can anyone explain how these pieces work?

KeeblerElf

They let you adjust the static camber at each wheel, but they have little effect on camber gain. So you can start from 0 degrees and gain -5 degrees of camber or you can start with -5 degrees and gain -5 degrees.

As for anti-dive, as far as I know inclining the upper control arm won't provide as much anti-dive as tilting the lower control arm up in the rear, but I don't know how much anti-dive is "enough" so maybe just a little bit is perfect.