Some will glue side walls to scrub some side bit while keeping the tire larger, so it last longer..

If you are buying a new 12th scale, I would recommned the BMI DB12.
It is probably the best fit and finish of any car I have ever built. And has already proved it is great on carpet and asphalt so you don't need two chassis's or cars.
It may seem a little expencive to you but you get the best of all things 12th scale IMHO.

YOu can go back a few pages, I posted my pics of it.

You will have lots questions but there are plenty of people here ready to help.
-Shookie <><