I came across this site and saw this

http://www.instructables.com/id/DIY-Bike-Rollers/

anyways seems like a good idea and also an interesting project. does anyone know any specifics on skate bearings??? id od etc. also i know that there are planty of engineers on here so would just a bolt thru the bearing and the frame be solid enough or would their be to much weight there and require a thru rod??

Anyways any help or ideas would be swell.