66 Mustang Custom Suspension Data

[GT408]

While I appreciate the suggestion egoman, the drawing and designing is the part I was hoping to get some feedback on. The fabrication is the fun, and fairly simple, part. It's the attachment locations and how it affects roll center, camber gain, motion ratios and my prelimanary selection of spring rates that I want to be evaluated before I start putting everything together. I haven't spent as much time researching materials as I have suspension theory, and am sure I can find that info with more time...I was just hoping someone might inform me while they were already here critiquing my schematics.

[JMcDonough]

I took a similar approach to egoman, but stopped short of using the C5/C6 subframe or steering rack. C5/C6 arms are strong, light, and have enough clearance to run a coilover through the middle of the upper arm. In the back I used a Ford 8.8 with a 3 link. As you mentioned, unless you get the engine really far back, you have to modify the C5/C6 steering arm to get the rack down under the front of the engine.

Only a handful of auto-x events and about 1,000 mi of street driving on my setup, but it has performed well for how little tuning I've done so far. Drives nicely, but will be stiffening things up for next season (currently has too much body roll due to soft springs).

A few thoughts on some your numbers:

- 12deg is quite a bit more caster than I'd run. I'm at ~6deg. For road courses, ~9deg seems acceptable, but I didn't want large amounts of camber difference in tight vs open auto-x turns.
- Bake in ability to run up to -3.5 deg of camber. Even stiffly sprung double A arm auto-x cars will run that or more for best performance.
- Front roll center height is reasonable. I'm at 2".
- I targeted +0.5" scrub radius, steering feels good to me (S197 power steering rack).
- Due to packaging, I traded off ackerman for better bumpsteer characteristics. With the track width, cg height, and grip wide 200tw street tires create, the front inside tires is very lightly loaded. I couldn't justify trying to keep it happier with caster and ackerman at the expense of the loaded tire.
- Rear anti-squat is in line with what I target, but didn't quite achieve. Again, some adjustability here is a good idea.
- Rear upper length is good and better than what I could package on a 2nd gen camaro (while keeping the back seats)
- Make sure to design in enough travel. I targeted 2.5" bump, 3" droop front and rear.
- Get the rear springs and shocks as far outboard as you can. I compromised some here due to packaging and now need more rear bar to compensate for the springs not doing as much work in roll.
- If you plan to route the exhaust over the axle - make sure to leave room for that.

Other thoughts:
- Tire selection in wide sizes is much better with 18" wheels. Not many options wider than 255mm in the sticky ~200tw tires at 17".
- Since you aren't buying off the shelf, package as much front wheel width as possible. It'll have more grip and better tire life. Bonus if you can fit as wide as you want to run in the back for a square setup you can rotate front to rear.
- Used corvette wheels are cheap and plentiful. I designed around using a square set of 19x12 C6 Z06 rear wheels with an 18mm spacer up front to get the scrub radius I wanted. Lots of 18x10.5's out there from C5 Z06s.
- A&A mfg is a great place to order chassis brackets/tabs/mounts/etc. Very reasonable prices too.
- Plan some budget to fine tune things (springs, bars, shock valving)

[GT408]

Wow! Thank you so much JM! You have provided me with more insight than I have gotten from other sources. It's nice to hear that my numbers are in the ballpark for what I'm trying to achieve. I see what you mean by the caster needing to be lower...honestly cannot remember why I had it that high. What I understood was a couple degrees more than the KPI/SAI is a good place to be. I could get the springs and bars out back a little wider, but I feel like I will have defeated my purpose of running parallel rear frame rails out to get bigger tires in a less radical body panel. Hate to have done all that work for nothing lol. Thank's again for your help!

[JMcDonough]

Getting the springs/shock out wider is nice, but IMO tire clearance comes first (especially if you are running wide tires with stock-ish fenders).

Happy to provide more data on my design if you'd like. I used an old copy of WinGeo3. For the most part it worked well, but a few things didn't quite add up in it (ex: rear axle anti-squat, front axle anti-dive), but those were easy enough to calc with a spreadsheet.

[frojoe]

This is awesome, and the exact thread I've been hoping to see pop up here for years.. I plan to do essentially the same for my Nova. Subscribed for infos!