Originally Posted by
dabac
Whenever you're planning to pursue a less than ordinary solution, consider that there's probably a very good reason why what you're asking for isn't commonly done. Then ask yourself if you and your needs are really that special.
This. Typical mountain bike gearing is usually good enough for any reasonable speed. The problem may be that you're trying to 'mash' too high a gear. Gear down a bit and spin instead. You'll cover the same distance with less effort.