Doog, and if I may McKay, we're really getting into my area of expertise. The tires in all current modern Nascar Kits, AMT or Revell Monogram, are molded with this seam in the middle of the tire. There are two things you can do with regard to it.
Most common, you just sand the surface which gives the tire the used or scuffed looked. This can be achevied by placeing the tire on a wheel and chucking it into a drill or dremel tool and hold a piece of sandpaper up against it. You also, as I do, can just take a piece of sandpaper in one hand, tire in your other hand and have at it. Either way, be careful not to sand up on the sidewall.
The other is to leave it as is to achieve the look of a sticker tire. This is one which has not been run at all and still has its label on it identifying its size, intended use, manufacturer and etc. Its a new tire. So all the flash and little knobs even on the 1/1 tire would still be there and this is the look we have on McKay's Intrepid. You would do almost no, or absolutely no sanding to a sticker tire but do want to put a sticker on it such as come in the AMT kits or on various aftermarket sheets. There is one label on the tread face of each tire (even though its a slick and technically has no tread).
You should either sand the tire thouroughly or put a sticker on an untreated or new tire, otherwise it will look like you didn't know what you were doing or were lazy since its one of the easiest things to accomplish as a stock car modeler. Sand or put on a decal.
Hope this helps both of you achieve a simple thing which one way or the other adds a ton of visual pop and realism to any roundy round car. And yes! McKAy!, this is indeed one nice model!
Dave B.