We used a pair of these from Northern Tool in 2005:
http://www.northerntool.com/webapp/w...9624_200199624 after using the KOP wheels in 2004. These are 8" solid rubber, and they have a 12" penumatic version also. We've experimented with the pneumatic wheels, and found it was too hard to keep the pressure exactly right to keep them both the same diameter, and also if they are not inflated enough the rolling resistance gets too high.
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Team 5148 - 2014 Wisconsin Regional Rookie All-Stars!!
Mentor: 1379: 2004-2008 / 2530: 2008-2013 / 2861: 2009 / 5148: 2014-??
Lead Robot Inspector: 10,000 Lakes '09 - '11 / Lake Superior '11-'12 / Northern Lights '13, '15 - '16 / Championship '09 - '12, '14 - '15
Attending/Inspecting 2017: TBD, Wisconsin, STL Championship
"Sometimes the questions are complicated and the answers are simple" -Dr. Seuss