How are baseline ride frequencies set?

[vinuneuro]

Assuming non-aero vehicle and passive dampers (though maybe that isn't as relevant at this stage?):

I've always wondered how are baseline ride frequencies set? And what proportion of roll stiffness is set between springs and roll bars? And what ride frequencies front vs. rear? Does it go, my CoG's are at _ and _ , vertical tire stiffness is _ and chassis frequency is _ , so we should start at _ ride frequencies?

What kind of ratios does an engineer shoot for, tire stiffness vs. chassis stiffness vs. roll stiffness?

Apologies for asking such a broad question, but where does the engineer start with a new vehicle? I'm guessing baseline setup is done entirely through simulation.

I'm guessing large teams have models of everything, and the good teams will have accurate models. Given this, how much work is done through optimization through say nonlinear programming in simulation?

[Greg Locock]

Do you mean for a road vehicle (passenger car) or a circuit car? I'd guess for the latter the approach is quite different.

[vinuneuro]

Hi Greg, yes circuit car.

[Greg Locock]

Never done it. I don't think ride frequencies or their ratio are a high priority

[vinuneuro]

How is it done with road cars?

Thanks in advance.

[Greg Locock]

RWD- select front wheel frequency depending on vehicle class. Decide on optimum flat ride cruising speed (Olley's criterion). That gives the rear axle frequency. Work out the two mode shapes, check that you like the node positions (not something I have any feel for). So now you've set the wheel rates in bounce. Now decide on a desired roll gain. Add enough sta bar to get that. Check the understeer budget, adjust front to rear sta bar proportion to get what you want there. Start all over again.

FWD - like RWD except you can't use much front bar and you probably won't meet your target front to rear frequency ratio