ESPN's Tim Brewer answers your questions

We know NASCAR fans have a lot of questions from watching Sprint Cup races, so we went to one of our experts for some answers.

ESPN analyst and former championship crew chief Tim Brewer has many years of experience from working on NASCAR teams and has offered to share his knowledge and connections.

ESPN.com's NASCAR Icons gathered some of your questions earlier this week and Brewer obliged with the following answers:

When is it legal to pass on the right during restarts? Do you always have to wait until the start-finish line before passing on the right or can you do it once the green flag has dropped.
Lincoln, Calif.

Brewer: At the start of the race, you have to start across the start-finish line. But on a restart all passing done to the right has to be to the right before the start-finish line.

That's the reason you see, when the leaders at Daytona and Talladega because they are usually low-speed restarts, as soon as the green flag is displayed everybody puts their car right against the wall so nobody can pass on the right side. And that protects their position. But if you see a guy leave enough room on the right side during the race it's legal to pass that guy.

I have noticed a small domed shaped device located just right of center on the rear panel of some of the cars. I noticed at Loudon that Tony Stewart's car had a plate over the opening where the device would be located. Is this only used during practice/testing or during the race? What is its purpose?
Black Mountain, N.C.

Brewer: That would be a camera. You see those fabulous shots from the roof cam, inside the car on the driver ... well, we also have a rear bumper cam. And the rear bumper cam is not on all the cars, but it's on select cars throughout the events. And when Tony had the plate over the rear of the car that just meant that he didn't have an on-board camera that particular day.

Why can't they make the end of the splitter upswept or blunt to prevent a slight bump from cutting a tire on the other car?
Mike Carson,
San Jose, Calif.

Brewer: It's not so much that the splitter cuts the tire as when the splitter goes inside the wheel and actually knocks the valve stem off the wheel. That's what deflates the tire.

When the cars are on Pit Road before a race the teams usually have a box on the ground beside the car and a large box/tool chest behind each car. What purpose do they serve?
Michael Poole,
Jasper, Ga.

Brewer: Well, it's basically a generator on wheels. And we carry some tools on top of it.

But what that generator is for is to make sure that we have adequate oil temperature in the oil tank, the transmission and the rear end so when we pull on the race track we've got optimum oil temperature in all three areas to where a guy can go out an lay down that great qualifying lap right off the bat. Because if you were to pull out there without the motor oil, transmission and rear end being hot, the car probably wouldn't run within 3/10ths of what it would with optimum oil temperature.