Suspension Calculations

[mla163]

Nerd alert.

I'm going to try and model the suspension to figure out the Roll Stiffness, Front Roll Couple, etc. Hopefully, this will give a better conceptual picture of the best swaybar and spring setups. I am an engineer and have done this a little bit in the past, but I'm far from an expert.

Dennis Grant has a basic calculator that I was going to use.

There is another one that I have used for Miatas that provides a reasonable results.

I have gathered a decent amount of info - corner weights, spring rates, dimensions, etc. But there are a few things that I can't find. I may need a little help.

This is a tricky one - has anyone calculated the roll centers? Or is there a link to a reputable calc?

Also, I am looking for sway bar sizes. Diameter, length, arm length, etc. I may just get under my car this weekend.

Motion ratios. I am ASSuming 1.0 for the McStrut. I have seen a reference to 0.75 for the rear, but I'm not sure how accurate this is.

[Sccabrz192]

All of my reference material is at home, if you are willing to share some of the data you have already collected I'd be willing to assist. I'll PM you later.

Don't assume 1:1 for MacPherson Strut, its something that can be found fairly easily.

[canu_50]

i know the rear swaybar is 14mm compared to the wrx 17mm.

If i can recall the front is a 20mm but i am not 100% sure on that one!

[Sccabrz192]

I'm not a fan of how Dennis' calculator approaches the ARB calc... it assumes all ARBs are made of the same material and the rate is entirely dependant on bar diameter. It doesn't take into account hollow versus solid, material, hollow bar wall thickness, etc... all things which play a HUGE part in ARB rate. IMO, the end goal is don't run a bar that you don't know the rate of.

[mla163]

I can do the tubular swaybar calcs with another equation if needed. Or I can convert it to an equivalent solid diameter. Physics, bitches.

[soros151]

watching