Originally Posted by
racerjon1
So, I really think there is a lot of speculation based on feelings, that just may not play out the way some folks feel it will..
I autocrossed a C-Modified 1983 Van Diemen on Toyo R888s a month ago on what might have started as the poorest initially setup FF I've ever driven. (When I climbed in it, it had 0 Camber f/r, 1/2" toe out front and 1/4 toe out rear.) The owners/drivers of the car had put 12 runs on the tires at an event the month before (they still looked brand new).
During the 2-day event (autocross "school" + two 6-run events) we ran, we put 66 runs between four drivers. We ended up at -1.5f and -1r with 1/8th toe out front and 1/16th toe-in rear while I incrementally dropped the ride height. It does still need work as the ride heights need more adjustment along with alignment. With a "school" that morning and an event the month before, these were runs 17-82 on this set of tires.
At the end of the weekend, the 3 relatively inexperienced formula car drivers they were MUCH happier (and faster compared to other consistent drivers) than they had been on Hoosiers with less than 50 runs total, and much happier with grip and breakaway characteristics of the 888R overall.
The two primary drivers commented, "up until now we were not sure if we wanted to keep running it, now this car feels like people told us it would." They didn't miss the slicks, and have benefited a great deal from the consistent performance delivered over 80+ runs - with plenty left.
I drove the car for a total of 12 runs, including the cold-tire/first runs on day 2, and here is my report on that experience: As a bit of data comparison, most recently I drove the Clement's 1994 Van Diemen at the SCCA National Tour in Charlotte on the R20/R25.
- Building heat: While the car wasn't perfect, the delta of performance between cold and warm tire runs was so much smaller than on slicks. On the R20/R25 there is a massive difference between the cold and warm runs, especially in cooler ambient temps. On the 888R, the balance of the car between ambient and warm tires was roughly the same, with far less adjustment needed to driving style, braking points, etc.
There will be far less of a necessity to have a "tire warmer" and when there are two drivers in the car, both will have a better opportunity to be competitive on the 888R.
- Grip Levels: Sure. It's not as much as the R20/R25. Data bears that out. But while max G on the 888s and max G on the slicks is different, Once I got the 83 dialed in closer, the "max grip" wasn't what I really noticed, it was the balance difference between the two.
We can discuss what grip we WANT to have for eons I'm sure, but honestly, when people talk about grip, IMO they are talking about balance. Mark Donohue's famous quote was "If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough horsepower" can easily be adjusted to say, "if you have to slow for a corner, you don't have enough grip." So - until they build a tire we can't overdrive (they won't) then none of these tires have "enough" grip: we're all chasing balance. I trust that no one here is running an autocross course without lifting or braking.
If ultimate grip on any given surface in an autocross environment is really a necessity; BM and AM are classes with slicks AND wings and those are great options if that's what you're chasing.
- Tire Feel/Responsiveness: Breakaway, controlability and feedback are not that different. Holding the car at a constant angle in a slide was probably EASIER on the 888 than the slick. I was still easily able to differentiate what parts of the corner the car was breaking away in on the 888R, and feel the adjustments I was making to tire pressure, toe and ride-height between runs.
- Heat Retention/Overheating: There is some worry about not building up heat with a street tire/the 888R, but I saw no evidence of this, and the handling characteristics stayed very consistent throughout the runs, and temperature stayed pretty steady - as a test I sprayed the tires to cool them off to make sure we were not overheating them, and we were not. Thermal imaging stayed consistent and characteristics stayed the same.
Running these as an autocross tire in larger sedans, overheating is a problem. One thing that people often forget when it comes to evaluating a tire for autocross is the lack of straights that cools a tire down in a road race environment, and the buildup of surface vs core temp when it comes to tires. While I certainly want (and plan) to do more testing, I actually feel like these tires were VERY well suited to the autocross environment considering the cold/warm tire delta, and how they built and retained heat leading to a consistent tire behavior to set the car up with.
- Power down/Braking: Andy Howe and I theorized that a lack of forward bite from the 888R would create more power-on oversteer in the FF - effectively making it feel more like the rain or like the car had more horsepower. This DID NOT bear out in my testing.
In fact, I fought more power-on oversteer from Eric's 94 on the R20/R25 than I did in the 83 on the 888Rs. Maybe it's the weight of the 888Rs, or the fact that the 83 was a carbureted Ford and I roll the throttle slower to avoid "dumping" the float bowl, but I didn't notice much if any difference in longitudinal inputs with the throttle or brakes. As with other items more testing is needed - especially with the variations in surface and throttle application between the two engines.
- Subjectively: The 888s were just as fun as the R20/R25. I felt like I could do every bit as much pedal-dance balance with each set of tires. I didn't miss the grip, or more accurately think "oh man this grip is fun" when I got to Eric's car. My brain was still just working to find the right set of inputs to get each car and tires to do what I wanted. My bank account is certain;y happier when I think about tires with 80+ runs still offering "like new" performance compared to the slicks.[/LIST]
What's Next?
- More testing: I know we need a "same surface same car" type test as we get closer to maybe making a choice. I would have brought a set of 888Rs to the Tour if I could have gotten them when I realized I could attend, but Tire Rack is out of them.
- more tires: I want to try one of the vintage tires and see what they feel like. I want to get a set of the A048s (which I found them for <$600/set in Europe, but shipping is $250+ per set.)
- Inviting others: Eric and I want to mount these up on some wheels and have them sitting at the practice course at Solo Nationals. So if folks want to come try them, they can. Sure cars won't be optimized for them, but right now it's all speculation, and working together as a class to gather and compare data will go a lot further than, "I thinks" and, "Someone saids."
News From Hoosier Re: C Mod Tires
