I been cycling around 3000 miles and recently bought a cheap Schwinn speedometer. I am amazed by how useful this gadget is. Basically it has taught me it is faster if I bike in lower gears. I have a Dahon D7 and always put it in gear 6 and 7 for speed, but the speedometer tells me I get max. efficiency in gears 4 and 5.. I encourage others to make this $9 investment from amazon! I wonder how else I would have figured this out without it?