Suspension for Auto-X v. Track.... How different?

[mtimney]

I'm posting this here rather than in the suspension section of the forum because I think I'm likely to get better informed opinion. So... excuse me if this does seem to be off topic a little, as well as for my ignorance as I'm new to autocross.

1) How different is a good suspension setup for autocross than for high-speed motor sports?

2) Can you detail some of the specific differences in dampers, spring rates, etc. as they related to the BRZ/FRS?

3) Anything else I should know?

[CSG Mike]

1. AutoX favors fast response over static cornering grip. AutoX drivers want quick response for smaller direction changes to slalom quickly, while tracks typically move larger, more sustained turns that maximize momentum. In other words, AutoX setups push in sweepers, but change direction quickly, while track setups will hold more speed through sweepers and rotate more easily, but are slower to change direction and respond to quick inputs.

Given identical suspension, you'll see more effective spring in the front with an AutoX setup, while track cars will typically balance out the effective spring. Ratios are approximately 1.0 (0.97) in the front and 0.75 in the rear.

2. dampers are identical, spring on the FR-S are closer to balance. Both are set up to understeer at terminal (sweepers) from the factory


Re: #1: We mitigate this on our track setup by using a fairly high spring rate in the front (but stock sway), and bring up the rears to a balancing point. We've tried different setups, but ended up settling on 10k/12k. YMMV.

Based on the questions you're asking, seat time will be the most important factor for you for now.

[GTB/ZR-1]

I use the same basic setup for both, even though it's optimized for the cones (where I actually compete). I adjust rebound & tire pressure for the tracks & that gets me close enough for the HPDE work.

It's a more neutral setup (coilovers, front bar & alignment), as the car was too loose from the factory for me preferences.

[forwallblakmail]

Another big item is tire size.
Ideal track size seems to be 225 (NA power levels)
Autocross ST+ classes you'll probably want a 245+ for maximum low speed grip.