Yet another expensive, electronic bike computer fizzled out on me. This last one lasted a whole 500 miles, then stopped registering my speed and mileage. Magnet alignment looks fine, plenty of battery left. It just stopped working. Another $39 down the electronic rathole.
Looking for a replacement on Amazon.com, I found ye olde-schoole analog-mechanical speedometer for $15. One week later, here it is gracing the dashboard of Discovery 7. Had to mount it in that low-slung mode because the cable was exactly one inch too short for the regular above-the-handlebar position.
Seems to work just fine, for now. [Update 4/3/10 - it lasted 50 miles.]
And it looks like something that would have been at home on my 1970-vintage Schwinn Stingray with the green vinyl banana seat and patented Nutcracker(R) five-speed shift knob. Heh. I loved that bike, he said in a really high voice.