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I purchased a used car with brand name urethane tires. Although I have cut and trued many rubber tires on my tire razor this was my first attempt at doing the same with Urethane tires. To make a long story short I was amazed at how quick these tires true, but I was also amazed that they lost much of their traction quality during the process. My question or questions would be did I perhaps cut them too fast or does the urethane tire have a sticky outer surface but a less sticky inner property. The person who I purchased the car from stated that he made a mistake by leaving his slot box in the trunk of his car on a particular hot day and wondered if the heat could have dried the tires out?

Heat could have harmed them. But using 1000 grit or even finer at low voltage will give you a very clean and smooth tire.

I typically use 300 then 600 then dry or wet sand at 1000.

Bruce

To get the best grip urethane tires must be polished after they have been trued. We normally polish urethane tires by running them around a slid pad. I built a polishing jig with 1500 grit paper, but that did not work well. I have a skid pad made up of Ninco track and 30-60 minutes of running in both directions gets the job done.

Video?? It seems that Ninco would put you right back where you started.

Bruce

This is like the motor break in thread, find what works for you and go with it. :auto-layrubber:

Not having a truer I usually use sandpaper. Sometimes I'll take one down a long ways with a file just to make them fit something else but I've never noticed any change in the compound as I go. There are different urethane compounds that we may switch to seasonally for some of the garage tracks. Often the perfect tire in December is too soft and grippy in July.

As Harry mentioned too fast on rmoving urethane or to kuch pressure actually overheats or in my terminology cooks the tire. It really has a negative impact on the grip. Also i always glue the tire to the wheel before truing to avoid any slippage.
Take your time and do it for as long as it takes withiut overheating the rubber.
Without a machine be very cautious of the pressure applied and do both tires at the same time.
If it takes an hour to get it right ,
it may gain you 10ths on track, do it in a rush and gain nothing
Bob

Like others have stated 1500 -2000 grit sandpaper and water to wet sand them works the best for me. I built my own setup and have a spray bottle beside it that I just spray onto the paper as I am sanding to keep it wet.

I also am learning through proxy racing not to neglect the front tires if you are looking for that super smooth car that drives easy.