Kevin
Because you can't measure acceleration, brakes, handling or downforce in the same way as you can measure FE and TE I don't believe anyone other than the developers can give you a definitive answer on this.
I've been playing this game for five and a half years and in all that time if I've learnt one thing, it is that the devs are understandably very reluctant to give away details of game mechanics.
I've always assumed that all of the design characteristics use a similar curve but I wouldn't go as far as to state it as a fact, it is pure speculation on my part.
Sorry I can't be more help.
Experience managers' opinion/guess is all I need, I haven't been around for long enough to know everything, or at least I didn't pay enough attention. Thanks.