I've been searching Google and the bike forums for information on this and I've found a webpage (http://www.recumbents.com/mars/pages/proj/tetz/other/Crr.html) that suggests Crr is higher with three wheeled 'bents compared to two wheeled versions. I was thinking this is probably because most three wheeled bents have two smaller wheels, which increase the impact of bearing friction (the ratio of outside/inside diameter), and the additional wheel serves as an extra source of bearing drag. I was wondering if anyone here had experimented with synthetic grease and found any difference between it and the usual bearing grease? I figure the synthetic grease may have lower viscosity, but more importantly, it's viscosity will remain consistent compared to regular grease as the temperature drops.

Air resistance is by far the largest factor in bike rolling. Bearing friction is going to be swamped by air resistance. Grease viscosity and the amount of grease in a bearing certainly contribute to rolling resistance.
The lowest resistance will be in a dry bearing (use ceramic balls), next will be oil lubed bearings. But all of this is idle speculation against the contribution of air resistance, which is really why trikes fare so poorly. Their wide cross section is the real problem, not the tiny wheels.
Steve

trikes have resistance that otehr bikes don't have. I guess the way they track and steer has a fair amount of drag. usually people can go faster on a 2 weeled bent even though the trike is a better areo setup.

I'm thinking about designing a faired trike for daily use since three wheels allow for better stability, naturally minimizing aero is a priority, but I'd also like to minimize Crr. Along these lines I was thinking that having smaller wheels in the back would minimize reference area, but there would be an increase in Crr due to the extra wheel and smaller wheel to bearing difference in diameter. Hopefully I can minimize Crr by using a low RR tire and synthetic grease, but the only way I'll know is to find out. :)