Autocross #2 for TSSCC is over, and it was definitely an interesting one. I got my butt handed to me by someone co-driving my nemesis Chris’s BRZ (who was also called Chris!) 2nd place will have to do! I’ve learned to completely despise the Lake County Fairgrounds surface, because it brings out all of the weak points of my current suspension setup (street-oriented vs. autocross-oriented) which makes it difficult for me to be competitive. Of course, I also need to improve on my driver skills quite a bit, as becomes obvious when you compare video of my run to that of the man who beat me (more on that below), Of all the surfaces I run on, though, this is where my car is the most disadvantaged. I need to find a different setup for this location, rather than using the same setup I run at Route 66, which doesn’t work well here at all.
Date: Sunday, May 07, 2017
SCCA Chapter: n/a (TSSCC is unaffiliated)
Location: Lake County Fairgrounds, Grayslake, IL
Weather: Clear, 45-50 degrees F, 10 MPH winds.
Car: 2015 Subaru BRZ
Class: 345 STX
Wheels/Tires: 949 Racing 6UL (17×9)/Bridgestone Potenza RE-71R (245/40R17)
Brakes: AP Racing Factory 4-Piston Front BBK w/ APF404 Pads (Hawk 5.0 Rear Pads)
Suspension: KW V3 coilovers, Raceseng Cas/Cam plates, Velox LCAs
Exhaust: Fujitsubo Authorize R Catback
Raw: 48.704 (2nd of 5 in Class)
PAX: 40.034 (29th of 80 Overall)
I have a much longer post coming regarding my AP Racing brakes, so I’m not going to go into too much detail here, but yes, I did have a new front BBK installed for this event. The brakes are not yet optimized though for two reasons. First, the pedal is pretty soft, which is because I think I still have air in the lines somewhere. I only did a quick bleed on the fronts because I didn’t have enough fluid to do everything, so more fluid is en route and I will be doing a complete flush of everything in the very near future. If the pedal is still soft afterwards, I might take it somewhere to have it professionally done. When I replaced the brake fluid two years ago, I think I might have introduced some air into the lines somewhere, so this might be a holdover from that, as the pedal was never super firm afterwards, but it wasn’t bad enough for me to bother doing it again. Now that I have a power bleeder that makes things easy, and now that I have these fancy brakes, I want everything working correctly.
The second reason they aren’t optimized yet is because I’m still running Hawk 5.0 pads in the rear. I figured they would be a decent match for the Fedoro DS2500 pads I’m now running up front, as they are both street-oriented performance pads, from what I understand, however the Fedoros seem to have quite a lot of bite when warm, so I might have a front-heavy brake bias going on right now. I’ll have to clean up the air in the lines and do some more experimenting before I reach any definitive conclusions. Needless to say, the brakes worked quite fine this event, and the pedal feels more linear than it did before, so that’s good, but I won’t comment further until I get everything working properly, and then I’ll post my official AP Racing BBK review 🙂
Rough Surface vs. Street-Oriented Setup
So I mentioned that I really dislike Lake County Fairgrounds as an autocross surface. First off, there is a LOT of loose gravel there. Tons of it. Normally the way autocross works is that the first few runs of the day are disadvantaged due to the gravel on the course, but then it all gets cleaned up and the rest of the day the surface is relatively clean. Not so at Lake County Fairgrounds. The surface starts covered in gravel, and ends covered in gravel. Sure, in a way that’s good as it equalizes all of the runs, but it sucks because it makes it more difficult to push the car, and also makes it a bit scarier to do so. Last year, someone lost it in a slalom, and spun out, but since there is gravel everywhere, they slid across the rest of the lot, into the grass, and through a fence and into another car. The damage was pretty minor, but the point is that the gravel is bad enough when you stay on the racing line, and even worse when you come off of that line. The end result is that I’m still a bit wary of pushing the car too hard here, because I don’t want to wind up out of control, careening across a gravel-covered surface towards something that would be less-than-ideal to run into.
The second reason I dislike this surface, is that it is very uneven, and this is where my street-oriented setup hurts me. I have a pretty soft spring rate on my coilovers (~270 LBS) which is great when it comes to offering a compliant and comfortable ride in daily driving on rough roads. However, it’s obviously not ideal for autocross. Typically, I help offset the soft springs by bumping up the compression and rebound at all four corners to a much higher setting during events. This does nothing to reduce how much the car will lean in a longer corner, but it helps limit how quickly the car does so in fast transitions. In other words, my suspension itself behaves like silly putty. The high compression and rebound resists quick motions (jamming your finger through silly putty doesn’t work well), but the soft springs mean the car can’t cope with sustained cornering (pushing your finger through silly putty slowly is easy.) This setup works well enough on smoother surfaces, but on a rough surface such as this one, all those quick bumps fight against suspension that is now TOO stiff, so rather than absorbing them, the car simply skitters across the surface. This makes it difficult to control, but more importantly makes it hard to put the power down, or brake as effectively, or even corner as well because the tires are hopping around too much.
The obvious solution to this is higher spring rates, but I’m not willing to compromise daily driver comfort just for autocross, so it’s something I have to live with for now. I might try reducing how high I pump those settings up next time, and seeing if that helps. Might be better to trade some initial stiffness for better compliance across such a rough surface, which will make the car more manageable.
So I still managed to be quick enough to outpace my usual competition, but there was a new contender today who really trounced me (by more than a second!) He was co-driving my competitor’s BRZ – the one that is somewhat well-prepared, and he has been autocrossing much longer than I have, and simply knows a lot more than I do. His line was better, he could get on the power sooner, turn in earlier… all the things I’m still working on… and all while driving a much better prepared car than I have. So the end results were pretty predictable. For fun, I created this link which plays both of our runs side-by-side so that I could compare the differences in our lines. There are quite a few areas of improvement I need to make as a driver, but one thing that really stood out was also how much more aggressively his car accelerates compared to mine. This is most obvious right at the beginning since we start at the same point, and his car reaches the first and second cones noticeably quicker than mine. We both launch at about the same RPM, and we both have the same amount of wheelspin, but you can tell that the other car simply pulls much more strongly. I guess a header and tune really should be higher up on my list of future modifications!
Anyway, below is the video of just my run. I got closer to a lot of cones, but there still was room for improvement in my line. I also really need to keep focusing on getting onto the throttle sooner. It’s something I continue to struggle with for some reason, so that’s my #1 goal for things to improve upon this season.