When you break in a new tire, especially a track tire, its tread compound is stretched and some of the weaker points between rubber molecules will be broken. This generates heat. And if the tire gets too hot during this process, some of the stronger rubber bonds will be broken, too—obviously not a good thing. (It can affect grip and wear qualities.) This is why we recommend running every track tire through a heat cycle, instead of attempting to break it in on the track. The results are almost always perfect, which means the risk of a ruined tire is lower. And in reality, a heat cycle can actually make the track tire consistently stronger. (Read more.)
For a small fee of $15/tire, Tire Rack will mount your new track tires between rollers to complete the heat cycle for you—which means they'll be ready to go once you get them.