Sigma Sport BC500 Bicycle Speedometer

WHY? Accuracy.  Most of the Harley-Davidson motorcycles I've owned have had fairly accurate speedometers, but it's very common for the import bikes to be off by a considerable margin; the V-Strom is no exception.  Realizing that my speedometer was reading higher than my actual speed, I cranked up my trusty handheld Etrex GPS and found that the stock instrument was off by a consistent 7.7% (when the speedometer reads 70 MPH, actual speed is 64.6 MPH).  I figured that I had four options to deal with the problem:  1) ignore it, 2) watch the speedo and "guesstimate" my actual speed, 3) install an auxiliary speedometer, or 4) install a correction device.

Options 1 and 2 didn't much appeal to me.  Installing an auxiliary speedometer is certainly a viable option, as some bicycle speedometers are very reasonably priced and can be calibrated to function with respectable accuracy.  I was surprised to find a new Sigma Sport BC500 unit on eBay for only $10.95 plus shipping, so I decided to check it out. 

SERVICE. N/A.  The eBay seller shipped promptly.

INSTALLATION. A piece o' cake, and one that could be accomplished by just about any owner.  While the installation instructions are for a bicycle (go figure) it's not difficult to modify them for use on a motorcycle.  The first order of business is to measure the circumference of the front tire and program the results into the unit; the measurement must be precise so that the readings will be accurate.  The unit fits into a base that is easily attached to the handlebars with a rubber O-ring and a lead wire that is attached to a magnetic pickup.  You'll need to find a way to attach it to the lower fork leg; since I only planned to use the unit for a short time I secured it in place with a heavy rubber band.  It also comes with a magnet that's designed to attach to one of the bicycle's spokes.  Since it obviously won't work on the V-Strom's front wheel another magnetic source must be used.  Off to the local Radio Shack to pick up a pair of tiny rare earth super magnets ($1.89/pair, part #64-1895).  These magnets, though very small--about 1/8"--are very powerful.  I fit them into the head of one of the front brake rotor bolts, where magnetic force held them in place nicely.  Here's how things looked;

RESULTS. Pretty darned good.  Because the magnetic pickup detects only one pulse signal per revolution (the V-Strom's speedometer registers about 80 signals per revolution) there is a small lag in displaying the speed but at constant speed it's very accurate.  

Worth the money? Absolutely.  I don't plan to use the unit permanently, but it's an incredibly inexpensive way to provide an accurate speedometer reading.  At less than $20 for the entire setup it's a heckuva deal!