Is our suspension setup correctly by aftermarket strut MFR's? Is the bias correct?

[2fnloud]

I would be totally willing to loan out my new in box struts if we had a dyno available

[J. Fast]

I'm sure Nascar shops are a dime a dozen in the Northeast. Anything close to you? I've been working with AMS trying to figure out what's going to work best for me if I want to go down the JRZ rabbit hole. It's looking like 14k rear and 11K fronts. If I throw a huge splitter on possibly 14K/14K (front/rear)?

[2fnloud]

nothing with in a 2 hour drive of my city

[KeithMac]

Are you trying to promote oversteer, neutralise understeer with the stiffer rear springs?.

[J. Fast]

Are you trying to promote oversteer, neutralise understeer with the stiffer rear springs?.

No, I'm trying to set the spring rate.

....Unlike the front strut which is pretty much mounted at the hub, a 5k spring rate in the rear does not mean a 5k rate at the wheel. Essentially the suspension arm is a moment arm....placing the spring inwards towards the pivot point means it needs to be stiffer. Sometimes you'll see people mention the "motion ratio." For the front EVO with the strut based suspension, it's close to 1 (almost). For the rear, it's somewhere between .6 to .9.

To get the "wheel" rate, you multiply the spring rate by the square of the motion ratio.

What he said here is... When the pickup point for the bottom of a rear strut is inboard from the rear hub assembly there's a pivot/moment arm which reduces the actual sprung weight at the wheel. You have to multiply the spring rate by the moment calculation in order to realize the actual rate. I would suspect that number is somewhere between .7 and .8 on a 3/S with Supercar Suspension Adapters. So a 12K rear spring actually behaves like a 9K in the rear once the moment reduction is realized.

In english... If you want 600lbs of spring at the rear tire you need like 800lbs of spring on the rear strut.

[J. Fast]

Contined... Since the front strut is inline with the hub and not offset... and the ratio is 1 to 1 then if you want 600lbs of spring at the wheel then you need 600lbs of spring. I believe that's the correct interpretation? Is that how that read guys?

[2fnloud]

That is how I would pick it up, but doesn't that same truth apply to the rear?

[DK77]

That's how I understood what you posted...

[J. Fast]

That is how I would pick it up, but doesn't that same truth apply to the rear?

No, it doesn't apply to the rear because the rear strut doesn't terminate at the hub. It's offset. The offset difference is a lever arm.

Think of it like a teeter todder. Say there's a 600lb weight on one end and a 300lb weight on the other. You can balance out both by moving the fulcrum. In an illustrative way the reduction is the distance moved from body center.

[2fnloud]

OK I thought it was really close to hub, my bad
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