I have noticed that all the Nascar tires are not 90 degrees and looks like it is slanted. Does that mean they get more grip or something? And why does the pit crew put tape on the new tires?
The slant portion of your question has been answered but for the second portion concerning the tape. The tape is used to line up the wheel with the lugs to change the tire, if you would notice the fender you will see a mark on it. The guy carrying the tire just matches up the tape on the tire with the line so the tire changer can tighten up the lug nuts quicker. The same thing applies to the jack. You can see a piece of tape on the car where the jack is supposed to go also.
Well if the tires were set up in an exactly vertical position then when the cars go through the turns the tires would fold under and ride on the side and wear the tires out plus not get very good grip. To eliminate that they lean the tires in so now when they go around the corner the tire folds in a little and rides flat. More tire rides flat on the track and the car turns better because the tire gets better grip.
The tires are slanted because of something called camber. This is where the tire touches the track, or how much of the tire is touching the track at any given point. On the straightaways, the tire is only touching the track with the inside portion, but in the corners, the whole surface is touching the track. I've never heard of them putting tape on the tires, unless you are referring to stickers, which just means they are brand new tires, they've never seen track conditions, and the pit crew just put them on the car.
