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You've read all the "quick-fix guides". You've read all the canonical texts on car physics. Now you sit behind the wheel of your favorite racing simulator staring at the chassis setup screen. OK, so where do you start? What should you do first? After that, then what? Maybe you just use the default setups that come with the simulator. But after hours, days or even weeks of tweaking on the chassis, you're still a half second off the pace of the leaders and the chassis is just a different kind of junk than the junk it started as. Sound familiar?
In this article, Blackhole Motorsports chassis pro Julian Data mentors "greenhorn" sim racer Timothy Bennett in the "ins and outs" of setting up a chassis from A to Z.
Here, Julian not only shares his wealth of knowledge regarding car physics, but we get a chance to "peek" inside his head and witness his approach to setting up a chassis. We'll be using the Nascar Heat racing simulator by Hasbro Interactive. The track is the North Carolina Speedway. At just over a mile in length, speeds at the ends of the front and back stretches approach 170mph. You've got to break at both ends of the track, and the two corners are just different enough to cause many sim racers to scratch their heads.
Timothy Bennett >>
I'll run 30 laps tonight using Heat's Advanced setup as a starting place. What data do you look at/record after running your first 30 laps on a setup? What kind of data are looking at during the run? What mental notes are you taking during the run?
Julian Data >>
Here's what I look for:
- Lap times at the start, middle and at the end of the run and the mean and deviated averages between them.
- Tire temps on all four through the run: 1/4 of run, 1/2 and at the end of the run.
- Rate of wear - what tire goes first then which is next? Green, light green, yellow, orange/red What lap do they go? How did the car change as the each tire wore.
- How the does the car feel during the start, middle and at the end of the run.
Timothy Bennett >>
Julian, here's the results of my first 30 lap run in Hardcore mode. What do you think?
Lap Times (sec)
Best Worst Average Std Dev Variance
start (laps 1-10) 23.899 24.863 24.229 0.317 0.100
middle (laps 11-20) 23.964 24.237 24.096 0.099 0.010
end (laps 21-30) 23.937 24.559 24.218 0.208 0.043
total (laps 1-30) 24.181 0.233 0.050
1/4 Run - The car feels tight all through the turn. Having a hard time getting it to stick on the bottom of track. Have to let off the gas early to avoid braking hard, which locks the brakes and causes the rear to kick out. Also, can't get into the throttle too soon as the car doesn't want to turn while exiting the turn. All four corners are still green.
1/2 Run - Feathering the gas exiting the corners to keep from hitting the wall. The wear indicator for all four corners seems to have turned a lighter shade of green.
End of Run - In the latter half of the run, the car "loosened" up a bit. It became easier to get into the turn and keep the car on the bottom of the track. Also, I didn't have to feather the gas, but could drive off the bottom of the corner real well.
- lap 19, the RF wear indicator turned yellowish-green.
- lap 24, the RR wear indicator turned yellowish-green.
- lap 25, the LR wear indicator turned yellowish-green.
- lap 30, the RF wear indicator turned orangish-red and the LF wear indicator turned yellowish-green.
Tire Temperatures (°F)
LF RF
Lap O M I I M O
7 190 185 184 211 206 204
15 193 189 186 225 223 217
30 193 189 185 226 223 217
LR RR
Lap O M I I M O
7 193 187 179 202 193 187
15 193 188 180 199 191 185
30 192 186 179 198 190 183
Note: All tire temperature readings were taken at about the 1/3 distance mark of the backstretch.
My Thoughts: Looking at the lap times, I know that I need to trim at least 1/2 second off. So that's my goal. The car is a handful the first 10 laps or so. It's really tight, and it doesn't loosened up until about lap 25. I can't drive hard into the corners, because braking hard is dangerous it moves you from a tight condition to a very loose condition almost instantaneously. I feel like if I could drive a little harder into the corners (or drive out of the corner a little sooner), I could improve my times. I definitely would like the car to stick on the bottom of the track. The lap times didn't really drop off too much at the end of the run, and the tire temps (with the exception of the RF) were mostly stable throughout the run. I didn't really expect that. What do you see? What's our first move? Maybe a sway bar adjustment to help loosen it through the whole turn?
Julian Data >>
The RF is heavily loaded by looking at the tire temps. The setup really falls after the 30 lap mark, a known trend since you are close to half tank. Need to balance the tire temps a bit more. First adjustment: Increase the Rear ARB, increase Rear Weigh.t It's going to be a bit free in the middle of the corner for the first 30 laps and it will most likely get looser these laps.
 
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