Hi;

so I spent several years here in the S197 world... and we had this thread of all the various spring rates as measured by Grant 302.

Do we have such a list here on this side of the forum?

At minimum, I'd like to know what came in my Ecoboost High Performance Pack. I think they're the same springs as a PP1?

I haven't seen one on here, but I've been researching S550 springs for comparison to S197 springs and this is one of the better lists I've found. Lifted from Mustang6G.

I noticed that the S550 rates are similar to the S197, slightly stiffer across the board, which makes sense. I think they realized everyone wants it a bit stiffer. The stiffest OEM S197 front springs would be the Boss springs which are 148 lb/in. Curious about the rear though. Is the huge spring rate mostly because of the weight of the IRS? Or does it have more to do with different geometry?

This is what AI says. Sounds like it makes sense.

The S550's rear springs are positioned further inboard on the control arms compared to the S197's shock/spring location. This configuration changes the motion ratio (the relationship between wheel travel and spring compression), meaning a softer spring is needed at the wheel position to achieve the required stiffness at the chassis. To compensate for this mechanical disadvantage and achieve the desired overall stiffness for performance handling, a much higher nominal spring rate is required for the physical spring component itself.

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Duane Black said:

Hi;

so I spent several years here in the S197 world... and we had this thread of all the various spring rates as measured by Grant 302.

Do we have such a list here on this side of the forum?

At minimum, I'd like to know what came in my Ecoboost High Performance Pack. I think they're the same springs as a PP1?

Click to expand...

Ya, combo same as PP1. Interestingly, the last "Premium" Mustang Ford put out (Mach 1) had the least split front-to-rear.

Not a reasonable combo in the lot, IMO. Of them all, the Swift is the least bad. I consider about 300#/in front to be the floor for front spring, but that would be a street rate. No lower than 400 if you want to get the front to work reasonably on a track. The rear rate is "salt-to-taste" to some extent. I prefer softer; others prefer stiffer.

There seems to be this idea that a stiffer rear spring automatically means lower lap times. That's not a thing. Generally speaking, the faster a driver is, the more understeer he *wants* in the car in terms of roll-couple and spring platform. Slower drivers don't load the car correctly at corner entry and don't induce the necessary rotation in the car.

The S197 guys have on-track wheel rates much better sorted than the S550 guys. The fastest S197 out there (Phoenix) seems to be running chewing gum for springs on the rear of their car and not much, if any, rear bar. It probably takes some disciple to drive, but it's got traction like no one else.

There's a lot more to a setup than just rear spring, but it's clearly a fundamental component of theirs. (FWIW, I have no idea what that rate is, but I know a car that sticks when I see it.)

Check out this thread,

GAR944 said:

Check out this thread,

coil over spring rate help

2020 mustang gt limited to 390 hp and 380 trq, stock mt82-d4 trans, 3525# w driver, triple adjustable coilovers, sphericals everywhere on stock arms, giken diff, pp2 package aero (front splitter and wing - so not any real heavy aero forces) hoosier r7's, and ford performance sway bars (35.5mm...

trackmustangsonline.com

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Ya I wrote a lot in that one.

It's funny, on one of my posts about the snap-oversteer YouTube video thread I wrote something like, "Your whole video is about 'snap oversteer', but your example is 'trailing throttle oversteer'. You're not talking about the right thing."

I don't think that comment went well, but I got 1 like. The one like was from "Jon Fogarty". Then he follow with the note, "I liked this message before I saw who wrote it."

He was a former driver of mine. Any questions...Google him...spoiler: he's not the guy in the band.

Side note, one of the guys in the video connected with me on LinkedIn just enough to stalk me and then left. Honestly, I'd help them out if they'd ask. They have a ton of views and something like 2M subs, but their information is just not right.

TeeLew said:

Ya I wrote a lot in that one.

It's funny, on one of my posts about the snap-oversteer YouTube video thread I wrote something like, "Your whole video is about 'snap oversteer', but your example is 'trailing throttle oversteer'. You're not talking about the right thing."

I don't think that comment went well, but I got 1 like. The one like was from "Jon Fogarty". Then he follow with the note, "I liked this message before I saw who wrote it."

He was a former driver of mine. Any questions...Google him...spoiler: he's not the guy in the band.

Side note, one of the guys in the video connected with me on LinkedIn just enough to stalk me and then left. Honestly, I'd help them out if they'd ask. They have a ton of views and something like 2M subs, but their information is just not right.

Click to expand...

And a great read it was, just went through it all again.
Back to a small tight track this weekend and want to try find this oversteer everyone complains about. Will make some changes from your comments and see how we go.
The only snap oversteer i've experienced was from forgetting i trailered the car there and tyres need more than half a lap to get some heat into them. Grass seeds all over the front spoiler in all the photos is my reminder of my lapse of judgement.

GAR944 said:

And a great read it was, just went through it all again.
Back to a small tight track this weekend and want to try find this oversteer everyone complains about..

Click to expand...

Thanks!

It all starts with braking hard enough & carrying enough entry speed. If you underachieve a bit on entry and don't actually need to trail into the corner to make the apex, you won't find it. When you're not inducing enough entry rotation, then you'll have understeer with a possible snap loose on exit. In that scenario, the snap is related to the mid-corner U/S which is a product of not getting the car turned early enough in the corner.

A short, tight track is the perfect place to practice.

This is from the mustang 6G forum but is a public spreadsheet with all the springs in them.

BackInBlack said:

I noticed that the S550 rates are similar to the S197, slightly stiffer across the board, which makes sense. I think they realized everyone wants it a bit stiffer. The stiffest OEM S197 front springs would be the Boss springs which are 148 lb/in. Curious about the rear though. Is the huge spring rate mostly because of the weight of the IRS? Or does it have more to do with different geometry?

Click to expand...

Because the rear springs are located about half way along the lower suspension arm on the IRS, the wheel rate (rate at the wheel) is about half the spring rate because of leverage.

The wheel-to-spring motion ratio is 0.52.

Spring rate @ wheel= spring rate * mr^2

It's a lot closer to 1/4 the rate, not 1/2.