Revised kinematic... ideas

Did some thinking. The scallops were bangin, by the way. I'm tempted to make some ravioli now. (Edit - I'm doin it!)

Anyway. Was thinking, and rambling to Grant about how the hell I'm gonna do this analysis. You can look at any variable vs any variable with a suspension. It's an overload of information. It's ridiculous. It's overwhelming.

There's a school of thought that you can't really do suspension design without tire data. I used to even agree with this myself, but realize now it's at least half bullshit. True, without tire data I'm not gonna know what camber and inflation to keep a tire at mid-corner, for a given load, to generate the most cornering force. But some shit is pretty clear.

Roll-steer, probably particularly front to rear balance of roll-steer, is always going to do the same thing to a car on entry. Over- or under-yaw (though I can think of situations that might be beneficial). Diabolical amounts of bump-camber or bump-steer while at the limit of traction, is going to upset the balance of the car. As such, those two items I can probably work to minimize and then leave static alignment settings for when (if) I do get tire data.

The plan is now as follows. Evaluate a set of metrics at each of the following "snapshots" in time This allows for a few quasi-steady state pictures of what the car is going to do through a corner. It's not the full "movie," it's not just a "picture," but it's at least a couple slices that you can hopefully interpolate between:

• Static (baseline)
• Straight-line braking
• Trail-brake entry
• Pure cornering
• On-throttle exit
• Straight-line acceleration

These are the metrics, to be evaluated at each corner:

• Load
• Inclination angle
• Steer angle
• Bump-steer (linear fit for +/- 0.5" wheel movement.. or some arbitrary amount)
• Bump-camber (linear fit for +/- 0.5" wheel movement.. etc)

At this point you might think that I don't give a damn about roll centers. And you're right! At least in and of themselves. Their effect is wrapped up into "load." Ultimately it all comes down to the tires, and the tires react to loads and angles imposed on them. They don't care about imaginary points and lines in space. If when its all said and done it looks like the setup favors something where the kinematic roll center (KRC) moves around a whole inch or two or three, so be it! I don't care what it does so long as it makes my tires happy. Designing around low KRC migration because some old men said so, is silly. Doing anything just because some old men said so (even Carroll Smith or Claude Rouelle), is silly. Prove it to yourself, and screw anything else. I bet the late Mr. Smith would even support that.

Not to mention supposed KRC's are kind of a load of crap anyway, particularly at high loads, deflections, and compliances. Roll Center Myths and Reality (W.C. Mitchell) is a good read for those interested.