Okay, we finally got an event under our belt with the new AST shocks and stiffer springs. I have good news, but first, let me give a quick run-down of myself and the car.
I started autocrossing in my 1993 Mazda Miata at the beginning of the 2006 season. Since we have five clubs in Dallas/Fort Worth hosting AX events, I was able to get a lot of seat time. I raced in a local tire class (based on E-stock) for 2006 and 2007, switched to R-comps (and regular ES) in 2008, and decided to give STS (formerly STS2) a try for 2009.
I started with an SCCA stock-classed Miata and made the following changes in the off-season in order to prepare for my assault on STS: Racing Beat front sway bar and end links (replaced FM sway bar with stock end links), Borla cat-back exhaust (replaced cheapie exhaust), Sutton Spec Miata Straight 1.6 Intake, K&N filter, aluminum underdrive pulley, Raceland 4-2-1 header, TDR heat shield, HP+ pads in the rear, HPS pads in the front, timing bumped 4 degrees, and most importantly, AST 4100 shocks and coil-over springs. We are currently running Toyo R1R tires on 15x7.5 Rota Slipsteam wheels (the tires came on the wheels), but we plan to switch to Bridgestone RE11 tires before the Houston National Tour.
One of my rules for converting the car to STS2 was that I had to keep it drivable on the street. Not only do I drive this car to events several hundred miles away, but my future fiancé and I enjoy occasional day-trips in the car and I can't upset her! So, I could not make any modification that would compromise this rule. With that in mind, we originally went with 550 lb springs in the front and 350 lb in the rear when we initially installed the AST shocks. Based on my experience with my previous Koni Sport shocks (great shocks, for the price), I was concerned that even this would compromise my ride. However, I was floored by the ride with the new setup. Even with the stiffer springs, the AST shocks made the ride better than stock!
We used the autocross school hosted by the Texas A&M Sports Car Club on Saturday and Sunday’s autocross event to test the car on a course for the first time. After testing on Saturday, we decided that moving to 700/450 springs would yield an even bigger improvement for Sunday’s event. Again, I was very apprehensive about the ride quality, but I again turned my car over to Terry and Brian’s capable hands on Saturday night to make the changes before Sunday. When switching to the new springs, Vorshlag also revalved my shocks so I only needed to run them at the half-stiffness level for competition. (I will let Terry or Brian speak to that, since I would only look foolish.) I could tell right away that the stiffer springs and revalved shocks did not hurt my ride quality on the street. It was the same, if not better. Again, was just ecstatic that I could run such stiff springs with the AST setup and still have a great ride on the street. There is no way that I could have accomplished this with my old Konis.
The car was incredible at the event on Sunday. While my normal co-driver, Thomas, was not able to make the event, I was able to pick up an abnormal co-driver (Brad) that morning. Watching Brad’s first run, I could not believe how flat the car was! Once behind the wheel, I was impressed by how responsive the car was and the sharpness through corners. It just felt so right and it was so much more fun to drive than my old “stock” setup, even on street tires versus my old R-comps. We won our class (I was less than a tenth faster than Brad), and I had so many people tell me how great the car looked on the course, so it was not just overzealous impressions of my own.
The drive home (200 miles) was very comfortable and I have no regrets about my change to AST shocks and the heavier springs. At this point, I highly recommend the revalved (Jerrett-valving?) AST shocks with 700/450 springs on any NA Miata used in STS autocross competition. Just incredible, and I can only imagine how much better it will get with additional testing and seat time.