Originally Posted by plodderslusk
...any links to good websites ?
www.google.com 
Seriously, though - check out this site:
http://www.mybikesite.com/shops/shop...=no&loc=hawaii
This listing covers all the islands. The 3 in Hilo are on the big island for sure.
Also, as I am in Oahu, I can tell you to be prepared to get wet in January.
That's the end of our winter rainy season and the start of our spring rainy season.
This year we had almost 2 months straight of pouring rain in Feb/Mar.
I'm planning a tour of the big island by bike, but am looking at doing it after the rains.
Maybe April/May. It's still cool, not quite tourist season, everything is green... etc.