Plunging down out of Turn 9
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Photo by UniqueAngle Photography
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James Garvey, who leads the class in his Porsche 944 Turbo S, borrowed some rain tires and took second. Record holder Leos Kubec won in his mighty 911 Turbo. I think I've convinced Nate that we need some rain tires!
Although it rained on Saturday and during the time trials on Sunday afternoon, it was dry on Friday and on Sunday morning. James told me he couldn't get below 1:21 in the dry, and both Nate and I were in the 1:20's in the dry (actually Nate did a 1:19.9 on Friday), so I think we would have had a shot at beating James if it hadn't rained.
I clocked Leos in the low 1:20's in the dry on Sunday morning, so maybe we'd have had a shot at him too.
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I had planned to relocate the upper shock mounts to allow me to get more camber, but found I couldn't do this very readily due to a clearance issue at the bottom of the shock unit.
However, I found an error which had caused us to have even less camber than we thought we did. When I installed the new SN95 spindles and PBR brakes last winter, I had used some Grade 8 bolts, but these kept loosening up. Also, when I checked the front camber after the September event, I discovered that each front wheel had lost about 3/4 degree of camber!
I decided to get some of the correct bolts from Ford. To my surprise, these turned out to be metric. They were only slightly larger than the SAE bolts I was using, but the small size difference had allowed movement, causing the change in camber and the tendency to loosen.
I also made a change which stiffened the front anti-roll bar mounts a little.
Last but not least, I ordered a new, stiffer rear anti-roll bar from Speedway Engineering, because in September we had ended up on the stiffest hole in our stiffest bar, and I wanted the option of going stiffer in case the camber correction didn't cure the understeer we had in Turn 3 in September.
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In fact, for the first time, the balance was good enough that we could detect a difference between the grip of a new front tire and a partially worn front tire. I had replaced the right rear with a new tire before the event, since the rears had nearly 800 racing miles on them and were getting pretty worn. But I kept the left rear, which still had a bit of groove showing.
The right front only had 250 miles on it, and the left front, although it also had almost 800 on it, looked ok. But on Friday, I asked another driver to try our car, and he flat-spotted the left front, so we put our new spare on the left front.
This gave us new front tires on left front and right rear, with a pretty old tire on the left rear and a middle-aged tire on the right front.
The car had been fairly neutral in left-hand turns but pushed in Turn 3, a slow right-hander. I decided to put a new, stiffer rear anti-roll bar in the rear, so we could go up a notch on rear roll stiffness to maybe cure the understeer in 3. Unfortunately, the new bar, though ostensibly identical to the old one in the bushing area, did not fit into the collars we had, so I couldn't install it.
However, with the new left front tire, the car now turned into Turn 3 like a tiger. In fact, on Sunday morning, Nate spun twice in Turn 3, and I got the car sideways twice there. After inspecting the tires, we decided to swap the front tires left to right.
Now the car was fairly well balanced in left-handers, and understeered mildly in Turn 3. It actually turned in better than it ever had into the left-hand Turn 6.
It looks like the somewhat used front tire (abused by running with negative Ackermann and not enough camber) had already gone off, despite its relatively low mileage.
We'll be getting two new tires for the left side before Lime Rock!
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Nate found that he really liked teaching, and that it really helped his confidence. He also enjoyed the opportunity to drive some really nice cars, including a turbocharged Lotus Esprit ... and his student in the Esprit won his class in the time trial! Nate was delighted.
I gave each of my students a ride in our Cobra, and both were thrilled. It's certainly an exciting ride! Compared to even a very good street car, its performance levels are quite high, and the sounds and physical sensations are much more "raw", as one student put it. After the ride, he was talking about ditching his new BMW 330i in favor of building an FFR Cobra!
We had two very experienced drivers drive our car, while I rode along, and I also rode with Nate for a few laps. This was extremely educational, both about our car's current state of setup and about our driving techniques.
Although one of the drivers was critical of the car's transitional behavior, it was apparent that his particular driving style did not mesh well with the Cobra's handling characteristics. He favors a very rapid turn-in, but while this works well in his Mustang, it unsettles the Cobra. I had experimented with this technique earlier in the day, but found that a slightly slower turn-in was far more effective.
The other driver, the very fast and experienced David Foote, was quite complimentary about the car. He said the car was consistent and predictable, and that it communicated very well. His only criticisms were that the steering was heavy (compared to his Busch North car, which has power steering) and the brakes exhibited some directional instability.
Nate was remarkably smooth and precise. My strongest impression after riding with him was of how efficiently he used the car; he drove aggressively, and took the car to the limit in several places where I tend to leave a little bit of margin. Yet he rarely overstepped the car's limits. He also seemed to have found a more efficient line in several places.
During the weekend, Ed Givler observed us carefully and made some extremely helpful suggestions, particularly on how to deal with Turns 10 and 11. Thanks, Ed!
We also had the opportunity to try out a new type of data logger called a DL90 (see also Race Technology and CB Racing) kindly loaned to us by Michael Carr. This clever gadget combines accelerometer data and GPS data to plot acceleration, speed, and many other parameters. It can even generate track maps, and given appropriate sensors it can capture input from the car, such as RPM, wheel speed, and even things like throttle position or brake pressure.
Unfortunately we didn't have the right cable to collect GPS data, but we were able to capture some accelerometer data. The software still needs some work, but this unit looks like it might have excellent potential for low-cost data collection and analysis. It's on our wish list!
Also high on the wish list is a new set of wheels, with rain tires. Nate didn't practice at all in the wet, and I can't blame him; with no top, the Cobra can be mighty unpleasant in the rain. Even though I did practice a little bit in the wet on Saturday, I felt I was just getting up to speed in the rainy time trial on Sunday afternoon.
We discovered on Saturday afternoon that we are allowed to run the convertible top on our Cobra, so we brought it with us (it was at home in my garage) on Sunday morning. With that in place, the car was a lot more pleasant to drive in the rain!
With the top on, a bit more practice, and a set of good rain tires, I think we could have given Leos a very good run for the win.