I for one always carried a spare unless the course was very short and I had good pit support!
In the last 12 races I only had 3 flats! 2 we were able to make it to an out pit to get them changed without losing any time. the 3rd we were leading a race on the last lap by 7 minutes! got a rear flat at the bottom of a big hill with only 10 miles left to go! with no pit help or chase vehical in site. I got out changed the tire with the jack we also carried, got back in and still won the race by less than 2 minutes.
The tire was mounted on the roof just behind the cockpit and I found out the hard way that it also served as a crush point when gravity failed me and I rolled or flipped the car! The tire would take all the force and the car would just pivet off the tire and we could just drive away! had to replace tire mount both times but the damage to the car was very minimal. My 2 cents worth! Rob S. #975