[4banger]

Originally Posted by antonch

Overall spring rate reduces when you put 2 springs in series right?

Yes, it does.

[stretch]

Originally Posted by antonch

Stretch-
Can we add tire spring rate to the resonant frequency calculator?

In short: not easily.

I believe I've figured out how to calculate tire rates with reasonable accuracy, but the rates are variable (very progressive) and my spreadsheet is too simple to deal with that. I'd like to change the equations, but it's going to require quite a bit of work and rethinking. I've got a long list of stuff I'd like to add to that original spreadsheet, but I diverted my time towards creating a virtual 4-post shaker rig. Ultimately I think this new spreadsheet I've been working on will completely replace the original since it is much more powerful (but you better have a high-spec computer, it's very inefficient).

Unfortunately, I have been too busy to work on anything car-related for the last two months or so.

[williaty]

Stretch, is there any way to tell your spreadsheet that I've installed the Whiteline Roll Center Adjusters (KCA313) and switched from wagon to sedan control arms?

[stretch]

Yes, the Whiteline RCA's raise your roll center about an inch up front (and only up front). The control arms aren't going to be too relevant to the calculations I do.

[Web_Foot_STi]

If you are looking a weight transfer numbers you might want to adjust the track too. There will be a change. I have an '04 and there is a change in the rear. (Motion ratio change isn't noticable.)

[williaty]

Stretch, is there a way to calculate base roll center height before the addition of the Whiteline RCA? The reason that I ask is that I'm trying to model a 05RS wagon on STi springs right now. I know the ride height, so I was wondering if you could somehow derive the starting roll center height and then I could add the 1" adjustment from the RCA to it. It didn't occur to me until just now that I have a different roll center than an STi.

Ride Height:
-FR: 15-3/8"
-FL: 15-1/4"
-RR: 14-3/4"
-RL: 14-11/16"

[stretch]

I don't have the software to calculate that, no, but even if I did those wouldn't be nearly enough measurements! I bet your car has pretty similar roll centers to an STI, though. Having struts in all four corners pretty much guarantees a roll center barely above ground.

To see what measurements I came up with a year ago (I no longer have the software or measurements), see this thread:
http://www.iwsti.com/forums/suspensi...-analysis.html

[4banger]

I would recommend that you go on the whiteline board and ask if they have any info. The whiteline guys there are usually very helpful.

Originally Posted by williaty

Stretch, is there a way to calculate base roll center height before the addition of the Whiteline RCA? The reason that I ask is that I'm trying to model a 05RS wagon on STi springs right now. I know the ride height, so I was wondering if you could somehow derive the starting roll center height and then I could add the 1" adjustment from the RCA to it. It didn't occur to me until just now that I have a different roll center than an STi.

Ride Height:
-FR: 15-3/8"
-FL: 15-1/4"
-RR: 14-3/4"
-RL: 14-11/16"