eage8

iTrader: (9)

yeah, it does look very long....

if you're mounting it to the stock wheel well sheet metal it looks like you'll have pretty positive camber all the time also.

abeomid

I am guessing he is going through the wheel-well and putting brackets on top of the stock frame which might get mighty close to the steering linkages!

88rx7racer

What kingpin inclination angle are you running? Also did you put the control arm pickup points/lengths/balljoint loactions into any suspension software to check roll center at normal ride height and various other heights as well as the camber gain curve?

peejay

Fairly sure it was a Chevy 2.8 or VG30 engined car.

I remember seeing it, and thinking "Bad Idea." when I saw how he put the springs and shocks on the lower arms. I don't think the FC ball joint would handle tension loads very well, usually suspensions that load the control arm like that will have ball joints at least twice as large.

Travis R

Where did you go Chops? We need more details! ;-)

ChopsMcgraw

Sorry, still trying to get caught up after the El Toro Pro, trying to tune an FRS for STX this season. As suspected, it would appear we have an upper arm length issue, working on a fix, will post pics when we figure it out

ChopsMcgraw

What you said. Not too worried about steering linkage, thats easy to move, more worried about motor.

As for geometry, looking for -7 caster, with the aforementioned camber gain profile. Shortness of the arm is going to make that tricky, although I had a discussion this weekend with a top flight STC driver who goes from -6 to -11 in 2 inches up front, so maybe it will work ok-

Travis R

I estimated that 2" of bump/droop at the tire is about 5 degrees of chassis roll. Feel free to double check my numbers though.

ChopsMcgraw

Need some dimensions, pulled the motor before I decided on this route. Can anyone provide a rough dimension of the distance from the frame-rail to the engine? Bonus points if you can provide the dimension from the firewall to the spark plug locations and the amount of intrusion the plugs have-

Cam_Ron

iTrader: (3)

PM sent

ChopsMcgraw

Movement again, but no pics yet. Strut tower is getting cut out, and a a tubular coilover/upper arm pickup structure is being attached to the frame rail. The thought of just cutting the front of the car off has crossed my mind...

cone_crushr

iTrader: (18)

If you still need some dimensions and cam_ron didn't supply them, PM me since I have a CAD model of the front chassis with turbo engine installed. Presumably you don't have a turbo to worry about.

23Racer

Interesting you say this. The first time I sawa a double A arm setup on the front of an FC was on an RX7 out of Quebec about 10 years ago. They had cut everything off above the lowest frame channels and built up the whole front of the car like a Late Model Stock Car with a half tubular front end. The car worked well, but they told me that they had issues with cracking welds on the firewall and they were thinking of tieing everything together with the 8 point cage. To my way of thinking, this was way to much work and almost like building a tube frame car inside of an FC shell.

Eric

abeomid

That's what I ended up doing. 2x2 frame rails to the front and cage the front tower and tied it into the rest of the chassis. One of the main reasons behind this was the future double a-arms that I had planned which might happen earlier!

You can see it in the following pictures:

abeomid

Sorry for the second post: let me warn you that if you continue on this path, you will wish you just did a tube-chassis and put an FC body on it. All that is left of my car is 1/4 of the original firewall and the roof... haha

ChopsMcgraw

So, this is moving slow. Project is active again, pics pending. Got the drivers side tacked on, pic to be posted shortly.

Rethinking the FP thoughts as I'be been spoiled by 5.0 coyote power in ESP this year, debating whether or not to go with a renesis or get killed by Fred with a turbo 13b or LSX.

ChopsMcgraw

Tacked up to check geometry

BLUE TII

iTrader: (9)

I was looking at a Miata being scrapped out and saw that their front subframe holds both upper/lower arms and steering rack.

Seems like Miata would be good candidate for double wishbone conversion.



Looks like you would have to chop the FC front unibody to clear the upper arm mounts.

j9fd3s

iTrader: (3)

the miata subframe doesn't hold the rotary that well either, maybe FC subframe, and miata arms/hubs/etc?

Travis R

Chops, how are you attaching the coilover on the bottom? Hopefully not to the lower control arm, like before.

ChopsMcgraw

Lol, why yes we are. We think it will be strong enough. If it bends we'll have to rethink the mount, mebbe build a mount structure off of the spindle adapter, which means shortening the shocks. Could build lower arms as well I suppose.

eage8

iTrader: (9)

It looks really similar to how the stock miata suspension is laid out above... the aluminum arms were already built with withstand the sway bar forces at that point, I don't think it should be a problem.... (but I'm not a mechanical engineer)

Josh18_2k

iTrader: (3)

No way will the FC's lower ball joint handle all suspension loads, you'll definately want to rethink that joint. Its a section of ~1/2"x1.5" flat bar... Relatively low resistance to bending. If anything, you'll want to weld a vertical web lengthwise along the ball joint, or something like that.

Switching to a tubular arm with (larger) ball joint would make more sense. Good 'ole circle track parts ;-)

Travis R

I'm not worried about bending the ball joint holder, where it connects to the lower control arm. I'm worried about the ball joint stud connection to the spindle. It only held in place by a small amount of clamping force from a single bolt... what maybe a 10-24 bolt? The only vertical forces it has to withstand in the stock configuration is from the sway bar. But now you're running ALL vertical spring/damping forces through a joint that's meant to handle mainly lateral forces. I'd put money on the ball joint pulling out of the bottom of the spindle.

eage8

iTrader: (9)

That's easily fixed