Designing and building a front suspension using C7 parts

[Qua-Hoon!]

Hi All, I need another set of eyes / others with experience in laying out a near clean sheet suspension design.

I am building a 49 Cadillac with C7 front suspension components. I'm pretty much starting with bare frame rails and intending to graft on the upper and lower control arms. I've done some reading but I'm sure as some of you know that this topic and this path is filled with tons of road blocks and other knowledge required before you ACTUALLY make a decision.

Back story, I'm building a 49 Cadillac and want to make it all wheel drive. The C5,6,7 hub to upright ease of use kind of made the C7 the best choice for me using US manufacture components (also huge Grand Sport / Zo6 brakes for decent money). I have all the parts. I also have a 2006 Yukon AWD front differential (3.73), BW4472 transfer case, C6 T56, an LQ4 engine on the way, and a stupid hellcat supercharger to split that power between front and rear. I need to figure out that cam still, but that can be done later.

I'm trying to design this front suspension to be street drivable but also be good enough to take to autocross events or maybe even a road course once a year. I want it to be safe but provide turning and grip with the tires.

So far I'm intending to use a 245/40/19 tire. If I remember my research this tire size had a lot of options.

I'm using racing aspirations to help me conceptualize this project. So far I think my input in the website for the upright / steering knuckle measurement for KIA / SAI is incorrect for C7 front knuckle.

Overall I'm hoping for another set of eyes at this point. I have more reading to do for sure, but I also need someone to say "don't do that in design, research this part / reason and try this angle / measurement".

Things currently not open for change:



C7 Upright
C7 upper control arm (8" length)
C6 rear lower control arm (used on the front) [17.25" length] {planning on pushrod suspension for front axle shaft clearance}
A rough track width of 59"
Frame width of ~33.5

Things I can change:

Upper control arm mounting point
Lower control arm mounting point
Frame lower width (moving the lower control arms in or out)
Wheels at 19" currently to clear brake system (I think this is the smallest I can go)

Let me know if I should supply other info. Here is my model I've been working on and tiring to decipher if it's a good plan. (sorry for the long link below -also seem to take a minute to load once you load the link) Screen shot attached if link isn't allowed.

http://racingasp.com/pxnz6dst?uX=in&...6.75%22%7D&END

[Screamin_67]

My son and I are doing something similar with my 65 AWD full framed Ford Falcon. All C6/C7 suspension / Nissan diffs / 3.5 Ecoboost / 6R trans / AMG-Chrysler X-case / 315s on all 4 corners / yaddah yaddah yaddah. Feel free to borrow any of my specs that may help you. Nice to meet somebody as bat chit crazy as me and my kid. LOL! Here is the link to my setup, hope it helps. http://racingasp.com/f0dskmlu

[mikedc]

I'm an amateur, but . . .

Is there a reason why you have the control arm mounts so far apart on the chassis, in the vertical sense?

The time-tested "tall spindle" design is to have the ball joints on the spindle be a bit farther apart (vertically) than the upper & lower control arm mounts on the frame. Lower control arms end up sitting in the ballpark of horizontal at ride height. The UCAs are a bit higher at the ball joint end, and they run downhill to their chassis mounts.

If the UCAs are tilted the other way (so the spindle end is closer to the ground) and control arms are farther apart at the chassis end, then it tends to be bad for the roll center & camber.

But I learned on classic muscle-car-type front ends. Those tend to have smaller dimensions of arms & spindles. The modern control arms & spindles are getting so big (in relation to the total suspension travel) that it kinda changes the rules. The arms have much less change in their angles from full bump to full droop.




Also, are you intending to tilt the UCAs for anti-dive? Make sure you understand how that complicates the geometry planning.

This trophy truck UCA is an extreme example of the issue. The chassis mounting point for the UCA is an imaginary point, for geometry purposes. And it's actually outside the two UCA legs.

[dhutton]

My son and I are doing something similar with my 65 AWD full framed Ford Falcon. All C6/C7 suspension / Nissan diffs / 3.5 Ecoboost / 6R trans / AMG-Chrysler X-case / 315s on all 4 corners / yaddah yaddah yaddah. Feel free to borrow any of my specs that may help you. Nice to meet somebody as bat chit crazy as me and my kid. LOL! Here is the link to my setup, hope it helps. http://racingasp.com/f0dskmlu

That is awesome!

[Qua-Hoon!]

Thanks for sharing this and your suspension design on racing aspirations Screamin_67! This helped me troubleshoot some of my own design ideas. I ended up a lot closer to how your build was moving before I found your reply, I guess trial and error pays off. Now I'm trying to figure out how I'm going to mount front shocks / coil overs / pushrod suspension with the C6 lower control arm and additional front CV axle now up front. Maybe I can figure out a bracket of some sort out of steel to clear the CV shaft. Also, what differentials are you using? I think my escalade front diff is a little big for a car this low.

[Vimes]

I realize the OP is pretty far along with his Corvette parts, and I'm using a Corvette suspension myself, but if I'd wanted AWD I'd be using the newer Charger/Challenger setup. They come as AWD cars and as they weigh over 4000lbs, the suspension will handle just about anything they're put under. They handle pretty good too, which can be verified with a test drive. I used to have a 2016 Charger R/T RWD, but it just wasn't what we needed so now we have a Durango R/T RWD. I'd use the suspension, axles, brakes, wheels, the whole bit. The 8HP transmissions are amazing as well, which would also solve the rest of the drivetrain. There are adapters if one didn't want to use the Dodge engine.

[Qua-Hoon!]

I actually considered this route. But I wanted a manual transmission and couldn't figure out a way to adapt to the dodge spline count transferase without an engineering background and / or custom machine shop near by that would help me with re-splining the transmission main shaft or creating some sort of hardened adaptor.

[Larry Callahan]

Oh what a cool project!