Question about tires.....

I've been a race fan for many years. There is one thing I've never been able to figure out.Currently, race tires are slick, no tread on the surface. When they are changed during a pit stop, they are worn, but still slick.So, my question is, what makes them lose their grip? Maybe someone here can help me.I know they lose their grip. Just can't put it together in my head as to why, since they are slick on, slick off.
updated by @edwin-sibley: 12/05/16 04:04:08PM

There are several things that can happen. Tires normally get harder as they go through heat cycles. Depending upon the track conditions, we used to either cycle (scuff) our tires or run stickers (fresh ones). The main thing is that as they wear...again depending upon the track and the set up...they don't always wear evenly. There's only so much rubber there to wear, so many times it's a matter of changing them rather than wearing them into the chord. If you notice the pit guys checking tire temps across the tire while practicing, they are determining if the complete tire patch is making contact with the racing surface. If one sie of a tire is getting hotter than the other...adjustments are made to event out the contact patch. If the center is hotter thatn the outer...chances are that theres too much pressure....and the opposite applies...if the outer is hotter than the center...there is probably not enough pressure to ensure that the complete tire surface is making an even contact with the racing sureface. During a race it's is common for pressures to build causing an uneven wear situation....and a tire that increases in size on a particular corner will affect the set up. Many times teams will take this into consideration when determining the starting pressures. the two toughest pressures to regulate are the right front and the right rear on most short tracks. Most all levels of racing now use nitrogen rather than air to decrease the amaount of expansion. Hope this helps...that's about the limit of my knowledge on the subject. There are some current and past crew chiefs on here who can do a better job if they will respond to your question.Jeff


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Founder/Creator - RacersReunion®

Thank you Jeff. That was an outstanding reply. Very informative.

Thank you Robbie for the generous information. I have seen NASCAR racing slicks, and cut away's. So I understand what you are talking about. When they are new, there is not that much rubber there, and to say they charge so much for them. I think you said the price would choke a dog, or something like that.Anyway, its great to have a place where you can talk to drivers and get good info. So thank you again.Checkered Flags,Edwin