Homestead April 17, 2005

Fools Run Autocross


April Fool's Day was late this year. It arrive April 17th at the Homestead Autocross track. At least for me...

I thought we were going to have an easy race. The last run we finished a good 2.488 seconds faster than our nearest competitor. This time we would have new tires designed for autocross. And maybe I would get a full four runs to set my fast time.

Ha! April Fools.

I drive the Imp to the track and the crew bolts on the race wheels with our brand new Hoosier 205/55Z14 A3S04 compound tires. As the car comes off the jack someone asks, "What is that hissing?"
As the rear of the car sinks lower, the answer is obvious.
"Heh, I just filled those!"

The two rear tires were leaking so badly that air is leaking out faster than we could put it in.

We have ten minutes before our first run. The crew flies into action.

The car goes back up on the jack. The rear wheels come off and are driven to the nearest gas station. It is just a convenience store and even it's air machine is broken.

At the next service station the air compressor is working. The tires are over pressured and then bounced like basketballs to try and force the bead to seal to the rim.

Unbeknownst to the crew, some rubber scraps left from the tire mold, have folded between the rim and the tire bead. This prevents a seal. It will require the tires to be dismounted and the scraps removed before the tire could ever seal. After much valiant effort, the crew returns with the tires still leaking.

We have missed our first two runs and it is almost time for our last two runs. We decide to run our street tires and do the best that we can.
The street tires have a couple of big disadvantages. They use a very hard compound. This is great for going 30,000 miles but not too handy for turning a fast time on the track. They are also taller tires.

This raises the car up higher hurting handling and the tires barely fits in the wheel wells. This turns out to be the biggest problem.

Run 1

I get the go and I am gone.

As I take the first turn, the body rubs on the top of the front tire. This makes an oddly musical sound and a little rubber smoke. It also upsets the car slightly as the body repeatedly slams onto the tire and rebounds the other direction. I ignore it.

Full throttle until the first 180 degree turn. Brake from 60 MPH and turn the car around. Finding my way, I lift a little on the way back. Brake, turn 180 degrees. Brake again as the road tightens. Brake and pivot the car for the first 90 degree turn. Back on the throttle. Brake and pivot the car.

I am doing a good job using the brakes to pivot the car through the second 90 degree turn when I notice that the exit is tighter than I thought. If I bang on the throttle to stop the car pivoting, I will hit the cone. If I don't, I will,…opps...Spin.

I make my spin into a circle and finish the course. My time of 56.810 seconds will win no prizes.

View Run #1 Video (10.74 MB)

Run 2

I review the video while the crew checks the tires. They seem OK. The top inside of the tire is rubbing on the bottom of the wheel well. The hit is quick and does little damage. If I can smooth out my driving, the car will rub less and handle better. I review the course again.

I brake later for the first 180 turn but still carry the same speed through the corner. Big gain.

Late brake the next 180. Another big gain. More speed through the wiggles and no spin in the 90s. Biggest gain!

46.641 isn't bad. We have to wait and see what the other cars turn.

47.524! We have pulled out a win.

View Run #2 Video (9.67 MB)

Compare Time chart 041705 Autocross
Sum up

There is always something to make the overconfident look foolish in racing.

We made three mistakes.
- We should have checked the tire pressures again an hour after they were mounted. If they leak more than 3 PSI an hour, they need to be fixed.
- We should have taken the time to raise the spring seats before we made our runs. We knew rubbing might be a problem.
- Finally, after the first run, we could have quickly adjusted our anti sway bar to full stiff. This might not be the optimum handling set up but it would have minimized body roll and the tire rub.

All wheel drive and excellent power from our Kokam batteries and Siemens motors set up saved the day.

autocross 1st place trophy

Three autocrosses this year.

Three victories.

We are half way to a Championship.

Let's see if we can make it the rest of the way.

Fools Run



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May 15, 2005


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