Track Day 56+57 -- Thunderhill East (Cyclone) and Thunderhill 5 mile W/ Hooked on Driving (HOD)
While I may have settled in the PNW, it's not my favorite region in the world.
October to December or so are throw away months the vast majority of years. The days get short, cold and generally quite rainy. All track operations pretty much cease, it becomes too wet to mountain bike, but generally not cold enough to snow and bring snowboarding to the mountains. I whitewater kayak as well, but the early season river selection is fickle as without snow pack to stabilize the river levels they often spike aggresively and then fall away just as fast.
What's a guy with a shred itch to do for that scratch?
Well, in my case the option is you head South. Thunderhill is a modest 8 hour drive from me, and so I wrap up my day at a reasoanble hour on Friday and then chug 8 hours on south to sneak in a Thunderhill weekend. There's a modestly priced bearable hotel in the area so I'm comfortable, and generally the track days are clear and quite nice... though more on that bit soon.
(NOTE: Article is in progress, if you get here before I finish it, my apologies!)
Leading Up To The Event
Most of my winter plans for the Corvette focused on reliability or safety, though after this event that will be updated... but I first decided to finally tackle the long overdue accusump install I had planned. Way back when I first installed the oil cooler before event #13, I had purchased an accusump and the general parts I thought I'd need to install it. Unfortunately, I was a bit limited on tools at the time as I hadn't settled into a new location yet, along with I was still a bit newer to modifing cars... so into a box for later it went. Fast forward 3 or so years later, I finally got around to coming up with a workable DIY Accusump setup for the C5 Corvette. I'll spare you the full details here, but feel free to pop over and check out the article!
Other minor modifications came in the form of addressing the rear ride height. I was having rear instabilty issues and it was fairly clear to me I had way too much rake in the car. The oversteer issues were less prominent when I put on the Vitours, so I chalked it up to the ECF's just being a lower potential tire... and settled on pulling out some rake to get the car more neutrally balanced. I'd raise the ride height again if I found the car had now strayed into understeer territory.
Otherwise though... there wasn't anything done to the car. I packed my ECF tires as spares but had my Vitour P01R's on the car, hoping I'd be able to smoke my long ago and rather poorly aged personal best at Thunderhill East of 2:05.
How The Event Went - Day 1 - East 3 Mile
Driving down I5 was a largely uneventful endeavor... until I crossed the last mountain pass and was greeted by... a solid thick ocean of fog. I dropped into the fog, made it to a hotel nearby the track and passed out for the night. Were it summer I'd just camp in my truck tent, but with the days being so short and nighttime temperatures dropping to 37, I figured it was a reasonable time to treat myself.
The day of the event was a very slow start. The fog was so thick that the towers couldn't see each the tower before and after, so they shut the whole track down in the AM. With temperatures heaving in the high 30's... I wasn't about to object. As the fog started to evaporate ever so slightly, it also left behind a ton of moisture... so by the time we went out the track was miserably wet and the entire advanced group went out, formed a miserably slow wagon train, and several people spun out. There was a mandatory meeting afterwards, and I joked out loud "So what are we thinking is the lap time to beat today, sub 3?" everyone chuckled, but it was true... things were pretty bleak.
I switched to my Continental Extreme Contact Force tires. They were in theory better in the wet, and since my Vitour P01R's were also worn down to near slicks (where they supposedly get fast). Sure enough, when I went out they were better... but the track was still miserable. Thins started to dry out though, the lines started to burn in, and times came down in general.
All said and done I was able to run a 2:03.09. That's an improvement of over 2.5 seconds over my previous personal best, but I know the car has more left in it. I constantly had to tip toe around oversteer at entry when initiating the turn from braking, and then as the tires got hotter I'd struggle with avoiding oversteer on exit so I'd heave to avoid getting on the throttle as soon.
I made some adjustments after some conversaton with AI. Adding a click of rebound damping to the rear somehow eased entry a bit, but adding a click of front compression somehow made oversteer worse... or maybe the tires were just getting hotter as the track dried out. I don't know the full story, but it would seem I've got something way wrong wtih my setup resulting in oversteer issues. I'm under the impression that I'm oversprung, and AI agreed, though instead of adjusting spring rate they suggested I go with a softer rear sway bar setting. More on that to come though.
(Picture to come)
Day 2 - Thunderhill 5 Mile (West side bypass)
Full well knowing there was no way in heck the event would be starting on time, I slept in. No regrets there, as when I arrived at the track an hour late nobody had even gone out yet. So no loss there. I quickly found the run group leader, had a chat, got some advice to take it easy on the connectors as I'd yet to run the 5 mile... and that was that.
The early session we went out for was actually not nearly as bad as the previous day. The track was in general dryer and things were going well... though one fellow spun out pretty good in his mustang and destroyed his splitter. Sesssions from there on out quickly got up to full speed. I got more and more comfortable with the connectors, and I already knew the West side quite well so I had an advantage there.
Unfortunately... as I pushed the car over the very long laps, I'd start to overheat the rears and start to combat oversteer on "earlier" laps, though miles wise it was about where I'd normally start to see heat in the tires. As the tires began to overheat, I'd start to run wider on turns than planned as I could feel the limits of my traction decrease... and sure enough... I ran just a hair wide on the pavement shortcut in the bend before 7, smacked hard pavement and I immediately knew I bent a wheel.
Fortunately, I had my wheels with the Vitour P01R's on them and there was a trackside tire vendor, so I just had him move my ECF's over to one of the P01R wheels and I kept sending it.
In the end I set a 3:08 lap time on the 5 mile setup which I'm pretty happy about.
Takeaways from the Event
My new Eastside with cycline best is a 2:03.09. I know I've got more in me, especially with Vitours, but I'll take the win. I can get that coveted sub 2 time with a better setup suspension, I just know it.
My westside best time is 1:05, and my eastside best time is 2:03... put them together that's 3:08, and that isn't factoring in the connectors to get from side to side, so I feel pretty confident I was approaching my theoretical limit. I think if I can dial in the rear oversteer issue to be a bit more planted, I'll be able to push better, especially as I was struggling with temperatures come the tail end of lap 2 (7 miles in, usually lap 3+ most other tracks) and thus I only really had one full speed lap chance in me.
I'm happy with what I accomplished overall, but bummed I left some potential on the table and struggled with a chassis setup issue. I am happy though that I have some direction to take the platform, and I think fixes I make to my setup for running my ECF lapping tires will still pay dividens on my Vitour P01R time attack setup. I think the additional grip of the Vitour let me get away with the setup problem for longer, but it does explain why my rears were visibly wearing at twice the rate.
My plans going forward are:
- Regain sway bar adjustability. I can't use the softer setting currently, and so I've lost a critical tuning lever.
- See about spherical rear lower control arm bushings so I can get full camber out of the rear of my C5 corvette. I'm at max and possibly binding up my rear Delrin bushings so getting max adjustability will be critical.
- Get 700lb rear springs (rear is currently 750) incase I need to pull some more out of the rear of the car.
- Consider a hair of extra rear toe. Spec Corvette calls for 1/8" toe in, I'm 3/32" so just a bit less rear toe, but more rear toe is another tuning option.
Pictures from the Event
(coming soon)