66 Mustang Custom Suspension Data

[GT408]

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.

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.

Mustang Suspension 1.pdf



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!

[GT408]

Crickets so far...

[mikedc]

The OEMs rarely make steel suspension arms less than 0.100"- 0.120" thick. It's probably good to heed that rule of thumb.

4130 gives you some room to use thinner tubing walls but it's not as much as you might assume. By the time you heat up the 4130 to weld it, the strength (near the welds) gets somewhat reduced.


Tube size . . . Well, bigger diameter = stronger. How much strength (at the expense of weight) do you wanna carry?

The aftermarket is willing to go down pretty small with round tube diameters. 1.00" or so, especially with UCAs. But they also build a lot of stuff that wouldn't stand up to a few weeks of Detroit roads. That's what really beats up suspension arms. It's not the intended stress from acceleration & cornering, it's the everyday potholes and curbs.

The UCA (assuming there is no spring or shock or sway bar mounted on it) mainly feels loading in the horizontal directions. These days you see some pretty flat UCAs from the factories, like on the big pickups. Although that is partly possible because of of the trend towards VERY tall spindles.

The LCA sees a lot more vertical loading because of the spring/shock/sway on it. And the LCA sees more impact forces (potholes, etc) because the lower BJ is nearer to the center of the wheel than the upper BJ.

[GT408]

The OEMs rarely make steel suspension arms less than 0.100"- 0.120" thick. It's probably good to heed that rule of thumb.

4130 gives you some room to use thinner tubing walls but it's not as much as you might assume. By the time you heat up the 4130 to weld it, the strength (near the welds) gets somewhat reduced.


Tube size . . . Well, bigger diameter = stronger. How much strength (at the expense of weight) do you wanna carry?

The aftermarket is willing to go down pretty small with round tube diameters. 1.00" or so, especially with UCAs. But they also build a lot of stuff that wouldn't stand up to a few weeks of Detroit roads. That's what really beats up suspension arms. It's not the intended stress from acceleration & cornering, it's the everyday potholes and curbs.

The UCA (assuming there is no spring or shock or sway bar mounted on it) mainly feels loading in the horizontal directions. These days you see some pretty flat UCAs from the factories, like on the big pickups. Although that is partly possible because of of the trend towards VERY tall spindles.

The LCA sees a lot more vertical loading because of the spring/shock/sway on it. And the LCA sees more impact forces (potholes, etc) because the lower BJ is nearer to the center of the wheel than the upper BJ.

That's what I've gathered mikedc. Done some more reading this week and I've decided to go 1.25" .120 wall for both the UCA and LCA. Also believe I'm going to go with threaded Spohn Del-sphere pivot joints up front. Maybe the same thing in the rear 3-link since they're about the same price as heavy duty rod ends. Still hoping to get some feedback on the geometry I have cooked up. The one part I forgot to change before my trial software ran out was a sway bar rate of 350 lb/in instead of the 70 I think is the stock value. (350 is the rate of the splined bar I was looking at.) If I need to include more info let me know.

[mikedc]

1.25" tube would be good. 1.5" wouldn't hurt for the LCA but I don't know if it's necessary or not. I am most familiar with cars a bit heavier than yours.


My own preference is to keep control arm bushings made of rubber, although lots of people disagree.

(My rant: Show me somebody who complains about the mushy rubber bushings that they replaced with poly. I will probably show you somebody who had 20-30yo rubber ones. Lots of parts get crappy when you run them decades longer than intended.)


I agree on the 17" wheels over 18" especially for a car that size.

[Merritt5]

Check out delrin for the front control arms.

For my rear lca on my fox, i'm going to use something like the ballistic joint you posted. On my rear upper arm, I have regular rod ends.

[GT408]

I can definitely see the validity of your argument for the use of rubber mike, it makes sense. A 20-30 year old anything is going to suck compared to new. I like the del-sphere approach a little more because I can design it to compensate for any small misalignments (and I mean from a purely fitment perspective) during the fabrication process. I'd hate to get everything fabbed up and find that the bolt is a 1/32 of an inch away from making it through the hole.

Thank you for the input Merritt5. Does your rear-end setup work well for you?