Crew chief Alan Gustafson answers your questions
NASCAR Icons readers had a number of technical questions that only someone like Hendrick Motorsports crew chief Alan Gustafson could answer.
ESPN.com's NASCAR Icons took some readers' questions and went to Hendrick Motorsports' Sprint Cup series crew chief Alan Gustafson for the answers.
Blake Keithley Gustafson: Downforce is a major contributing factor to how much grip our tires can generate. Downforce will add a vertical load [which the tires like] without the penalty of the lateral load [which tires don't like]. The higher roll center really taxes the right side tires. The higher roll center of the Impala SS will transfer a lot of weight to the right side tire and, in some extreme situations, the right side tires will handle almost all of the load. That's why you saw only right side tire issues in Indianapolis. That also allowed two tires stops there because the left side tires were so lightly used. As far as the bump stops are concerned, they are an advantage over coil bind where grip and tuning are concerned. They allow you more adjustability and are easier to adjust. The issue with the Impala SS is more so the lack of available front travel. Our old Monte Carlos would have the ability to get 3.5 inches to 4 inches of right front shock travel, where our Impalas are only capable of getting 2 inches. That is more the issue than bump stops or coil binding. What is your favorite or least favorite part of the pre-race spectacle as you get ready for the green flag?
Austin, Texas Gustafson: My favorite part of the pre-race routine is the prayer. It is a great time to reflect and focus on the day and the opportunities it presents. The quiet and calm during this time is very important to me. I really don't have a least favorite time. The only thing I could say that really bothers me is when someone does not know the words to our national anthem. That is tough to deal with.
How much vacuum are the Cup guys pulling in the crankcase now and how much would they be pulling if NASCAR had not put a limit on the length of the dry sump pump? What is the actual reason for the increased horsepower? Is the vacuum acting like a reverse supercharger and actually pulling a bigger charge into the cylinder on the intake stroke?
Don Scott Gustafson: Front end setups and rear end alignment are the two biggest factors that determine our wheelbase. Caster is the biggest factor in the front end that will affect our wheelbase. Positive caster is how much we lean the top of our spindle back. When we do this it creates an aligning torque in our tire much like the wheels on a shopping cart at your local grocery store or the front tire on a motorcycle. The rear axle is a solid rear axle. So as you adjust the fore-aft alignment of the housing it affects the wheelbase. The reason for the misalignment is to adjust how the car tracks, which is evident in the straightaway shots of the cars on TV.