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Old 01-05-2020, 08:31 AM
GT408 GT408 is offline
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Default 66 Mustang Custom Suspension Data

Hey everyone, I think I have spent enough time researching and playing with Performance Trends Suspension Analyzer to have come up with the direction I want to head in with my suspension. Let's get a few basics out of the way. I worked backwards from the pre-loaded data points for the C5 Corvette suspension. I'd like to use the C5/C6 spindles with modified steering arms specific to my application. I kept all data points for the spindle the same, but modified the arms and frame attachment points to fit my car. To give you an update on my car, I custom built full frame rails front-to-rear out of 2x3 1/8" wall steel tubing. I need to update my build thread so that you can see pictures.

This car will not be a dedicated track car. In fact, it will probably be 70% street, 25% roadrace/AutoX, 5% drag. But, I'd like it to be as nimble as possible. Front is a coilover SLA (with C5/C6 spindles). The rear-end will be a coilover 3-link with panhard (not gonna have a back seat). Do I understand that there are systems out there that will meet my goals? Yes. Do I have the money to pay for a kit from DetroitSpeed, SoT, TCP, etc? Not really. I understand that their prices reflect the R&D and education and all that good stuff, but I got student loans that prevent spending that kind of cash right now. I like fabbing my own stuff too, and I'm pretty good at it. I plan on running 17" rims, 18" if only ABSOLUTELY necessary. Engine plans are a 351W base for now. Tranny will be manual 5-speed. All the other info necessary should be in the data sheet I will attach. Weight of the car from what I have researched should be right at 3000# with around a 55%/45% weight distribution from what I have read. I've only ever had the car in a stripped down form so I have no real world exact measurements except those I've found in forums.

So what I need from everyone is to tell me about any holes in my plans. The other thing I'd like some opinion on is what size tubing is necessary for the front arms. 1"? 1.25"? Wall thickness? Mild steel or Chromoly? I know chromoly will be lighter, but I'll have to get a shop to TIG it (don't have TIG yet). Also, what version of connection points do you feel is better? What I've looked at so far are either spherical joints or poly-bushing. I also though about making one attachment point of the arms with a threaded rod so that mild adjustments can be made if necessary, or using an attachment setup similar to the early GM cars (bar between the bushings/bearings). See the pics below.

So tell me what y'all think. If I'm way off my hinges, let me know. Again, not gonna be a pure-bread race car, but I'd like it to be as high-tech as what can be produced out of my garage. I'd like to get to building soon...been researching this stuff waaaay too long without any real-world action being done. Thanks!
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File Type: jpg Ballistic Joint.jpg (14.4 KB, 0 views)
File Type: jpg Threaded Poly Bushing.jpg (16.0 KB, 0 views)
File Type: jpg Roller-Upper-Control-Arm-Kit-1965-1966.jpg (19.3 KB, 0 views)
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File Type: pdf Mustang Suspension 1.pdf (42.8 KB, 0 views)
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Old 01-05-2020, 09:31 PM
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egoman egoman is online now
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https://lateral-g.net/forums/attachm...1&d=1578277721
I chose to use the complete C5-6 front end. If it is too wide shorten the cross member, or fab mounts and shorten the rack. The rest is just drawing and designing.
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Old 01-06-2020, 05:52 PM
GT408 GT408 is offline
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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.
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Old 01-18-2020, 05:39 PM
JMcDonough JMcDonough is offline
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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)
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Old 02-13-2020, 10:52 PM
GT408 GT408 is offline
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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!
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Old 02-15-2020, 06:34 PM
JMcDonough JMcDonough is offline
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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.
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