I have a 38tooth on a 70lb beach cruiser with a 48cc grubee. I have to pedal to about 10mph then the bike will accelerate even up steep overpasses, with a bunch of canned food in the basket. It is not neck snapping fast, is not as fast to speed up as the 44t was, but easily pulls all the groceries I can carry (in milk crate and a backpack!). It was well worth it. I think the bikes only come with the 44t because its cheap for the mfgr and "governs" the speed of the bike to about 25mph for less liability. If you ride off road or at 5-15mph leave your stock cog on.