AE92 GT-S Auto-X Setup Suggestions

Thanks to Bryan Heitkotter for this pic of my car at Round 5 in the SFR series. Check out the inside rear wheel trying to get some air time and the outside front tire deflection. Ouch!

Gary Meissner was nice enough to give me some tips on how to properly set up my AE92 GT-S for SCCA SOLO II racing. He runs a '95 Celica ST in the ES class. The Celica and AE92 are very similar in regards to weight (the Celica is just a tad heavier), drivetrain layout, and weight distribution. He teaches at some driving schools geared for SOLO II participants. He also participates in the Nationals. So now, I pass the wealth of information to you. A majority of the following suggestions are taken from Gary's experience. As such, the majority is also his intellectual property. Thanks, Gary!!!

Just so you know, an '88-'91 Corolla GT-S with my mods runs in the FSP class, at least in the San Francisco Region (SFR). I've heard other regions where the modified GT-S is run in DSP. If you haven't upgraded anything on your car, you're gonna be running in the Stock class, HS (yes, at the bottom of the performance heap); typical mods (suspension mostly) and internally stock engines run in Street Prepared, FSP; anything more (like a fat Sprint Car-type rear wing!) and you're stuck in the Prepared or Modified classes which are pretty hard to compete in. =) You can also run in the Street Touring class which is best if you can't afford race tires. You can either run on street tires or all-out race rubber (best if you only have limited mods that don't fully utilize "SP" rules). If this is your first real auto-x season (you've run only a handful before), you should run in the Rookie or Novice classes. You still run with your open class group (in this case, FSP), but you'll be competing against other rookies in your particular Rookie/Novice class with similarly performing cars.

For a quick explanation of how suspension changes affect handling, check out the West Texas Region SCCA Car Setup/Troubleshooting Guide. That way, you'll know what you're dealing with.

Enough talk... Let's get down to the good stuff, already!

Suspension Setup Tips for the AE92 GT-S:
1. 1/8" - 3/16" Front Toe Out
   Effect: Helps the car want to take a turn and hold a tighter line without pushing. Affects steady-state turning.
2. 2°-2.5° Negative Front Camber
   Effect: Keeps the tire's contact patch as close to horizontal to the surface with little to no deflection--that would rob some precious traction. Affects steady-state turning. Note that most R-compound tires require at the minimum -2.5° as a compromise between street and track. Ideally, you should have 2.5°-3.0° for better performance and extended tire life (outside shoulder blocks in particular).
3. -1.0°-1.5° Negative Rear Camber
   Effect: Same as the front camber, but we definitely don't want nearly as much. Otherwise, the car will understeer like a dog.
4. 0-1/16" Rear Toe Out
   Effect: Helps the car take a tighter line by letting the rear end rotate more towards the outside of the turn. As with the front end, running any toe in will make the car sluggish to turn. Try running one event with the factory spec alignment, then another event with more toe out. The more toe out you run, the more scary the handling gets because the rear end will want to come around. Run 0 toe if this scares you.
5. Tire Pressures
   Effect: Yes, the poor man's setup. =) The general rule of thumb is, the more air a tire has, the more load it can carry, thus, the more traction it will have. Since we have a FWD car that naturally understeers, we want less static traction in the rear. So, run higher pressures in the front and lower pressures in the rear. The closer you get to your suspension's sweet spot setup, the more equal the tire loading will be. You'll find that the rear tire pressure will be only a few psi different than the fronts. Affects steady-state turning.
6. Uprated Spring Rates
   Effect: Depending on how high a spring rate you choose to get, it will affect how the car transfers its weight between the 4 corners. FWD cars will need a high rate (relative to weight distribution and natural frequency) in the back. My suggestion: start around 350 lbs/in up front and 225 lbs/in at the rear. Depending on your driving style, other suspension components, and track conditions, you may need to go harder or softer at either end.
7. Bigger Anti-Sway Bars
   Effect: Stiffening both ends of the car will help keep the weight transfer experienced during transitions more manageable. Again, this is a FWD car that can do with a much stiffer rear end. Case in point: TRD-Japan makes its rear bar 67% stiffer than the stock bar! Don't forget to add a front bar as well--if the inside rear tire is getting more air time than a Boeing 777, you need one as a stiffer rear bar will have no effect. Affects both transient and steady states.
8. Adjustable Strut Settings
   Effect: Tunes the transient response. For Koni 1-way Sport Adjustables which only allow rebound adjustments, stiffen the rear struts by one turn. Stiffen the front struts around 0-1/8 of a turn. Work from there... Stiffening the rebound adjustment limits how fast the car reaches its final roll angle. If you find that the car's still pushing, stiffen the rears a little more. If the car's too loose, stiffen the fronts a little more. Just don't get carried away with how many turns you do! Read the NOTE at the end of this page for a better explanation of adjustable struts/shocks.
9. Driver's Schools and More Seat Time
   Effect: You can mod your car all you want and still be slower than a guy with a totally stock setup--I've seen it happen! Attending drivers schools will not only give you more confidence in yourself and your car, you'll be comfortable enough to push it to its limits run after run after run after run. You should only mod your car when you feel like you can't push it anymore.

Notes on Strut/Shock Settings...

All struts/shocks (strut, from now on) have 2 different "systems" that respond and react to different situations. When you hit a bump on the road, that's the strut's compression stroke. When the suspension comes back down, that's the strut's rebound stroke. If you have 2-way adjustables (compression and rebound), consider yourself lucky, you rich bastard! =) But, for weekend warriors, 1-way adjustables are more than enough. You only get 3-4 runs per event and that doesn't give you enough time to properly sort out the compression/rebound settings (along with tire pressures and adjustable anti-sway bars, if you have 'em). Keep it simple. With that said, here are some tips on finding the optimal settings for 2-way adjustable struts...

1. Begin with compression and rebound settings at full minimum.
2. Drive a few laps to get a feel for how the car reacts to the track surface.
3. Increase compression stiffness by 3 clicks and do more laps.
4. Repeat Step 3 until you feel both ends of the car getting stiff over bumpy areas. One end will naturally get stiffer before the other end because of weight distribution. Just keep stiffening the softer end until it feels as stiff as the harder end. If the car hops around while taking a steady turn, you've stiffened the compression too much!
5. Now that you've found both ends' compression sweet spot, back off the compression setting by 2 clicks.
6. As stated before, the rebound adjustment controls how fast the final roll angle is reached. Drive 2 laps and feel how much the car rolls during transient turn-ins.
7. Increase rebound stiffness by about 1/2 of a turn and do another lap.
8. Repeat Step 8 until the car doesn't exhibit too much lean and enters turns smoothly. As with compression, one end of the car will reach its optimum setting first. Watch for it.
9. If you want your car to be more loose, stiffen the rear rebound a little more. If your car's too loose, stiffen the front rebound a little more. This is where your individual preference comes in.
10. Now do you see why 2-ways are more suitable for track days than auto-x events? =)

Notes on Rebound Settings...

Like I said, before... Don't go nuts when adjusting the rebound settings on adjustable struts. If you have relatively low spring rates (for example, stock springs) and you adjust the rebound setting to its max, the car may experience what's known as "jacking down." Imagine taking a series of bumps in succession... If your rebound setting is high, it won't allow the struts to expand and return back to normal height. Hit enough bumps in a certain period of time and the strut/spring assembly will go all the way up the bump stops and just stay there, effectively preventing the suspension from working. Ever notice how some super-slammed cars that are riding on their bump stops just side-step around corners? Same thing here...