[Japper]

I noticed that there is a couple different roller types available for the mecanum wheels. One is gray and the other is like a black rubber. Which would be better for driving on the slippery bridge? Can these be mixed (alternated) to use both types on each wheel?

Also can these rollers be roughed up with sand paper for better traction on the bridge or are there any other tricks for improving bridge traction with the mecanum wheels like adding weight directly over them?

Any tips are appreciated...

Thanks