I sleeved the lego wheels with Brass tube. The tube fit tight in the Lego opening and the bore of the sleeve was 2.38mm. This was a very easy thing to do and it resulted in a really true wheel.
Here are some pictures showing the wheels and how they look with the current McLaren I am working on.



I trued the tires and cleaned them with a citrus cleaner. They offer decent grip. Once this car is finished I will run it against and equally prepared car using Urethanes and I will see how these lego tires compare. Good news is there is a huge supply and they are inexpensive.