I recently bought a HAC4 and its great and all, but I can't get the odometer to work correctly. I did a ride today that should have been around 67-68 miles, and the HAC4 reported 60.
I've measured my whell circumferance several times. I have 700x23 tires and my circumferance measurement is 2097 millimeters.
To add to the confusion, looking at the manual, a 700x20C tire should be 2070 millimeters and a 700x25C tire should be 2090. I coming up 7 millimeters higher than the bigger tire.
I found a web page that has circumferances for diffent tire sizes (http://www.branfordbike.com/computer/comp10.html) and it states 2096 millimeters for a 700x23C tire (2105 for 700x25C;2086 for 700x20C).
Has anyone else seen this problem with the HAC4s? How have you resolved the problem.
Originally posted by chadwickgreen I recently bought a HAC4 and its great and all, but I can't get the odometer to work correctly. I did a ride today that should have been around 67-68 miles, and the HAC4 reported 60.
I've measured my whell circumferance several times. I have 700x23 tires and my circumferance measurement is 2097 millimeters.
To add to the confusion, looking at the manual, a 700x20C tire should be 2070 millimeters and a 700x25C tire should be 2090. I coming up 7 millimeters higher than the bigger tire.
I found a web page that has circumferances for diffent tire sizes (http://www.branfordbike.com/computer/comp10.html) and it states 2096 millimeters for a 700x23C tire (2105 for 700x25C;2086 for 700x20C).
Has anyone else seen this problem with the HAC4s? How have you resolved the problem.
Thanks, Chad
Not sure how you're measuring circumferance, but that's probably the source of the discrepancy. Published tables are just approximations, and measuring without the weight of the rider can make a noticeable difference. Plus, circumferance isn't fixed but varies depending on inflation pressure (and, thus, air temperature, humidity, ...), rider's weight, tires, wheels, etc.. It's doubtful that there's anything wrong with the HAC4. If you really know the exact mileage, just calculate what the circumferance would need to be and enter that value. One technique I've used is to ride with a portable GPS a good distance (25+ miles) and then adjust the circumferance setting to match the GPS mileage.
If you have access to a tape measure, simply stretch the tape measure on the ground, place the edge of wheel next to tape measure, then roll the wheel till it makes a full revolution. Easiest if you have a metric ruler, otherwise simply multipy inches by 2.54.
If you want to be real accurate, pump tires to your favorite pressure and sit on bike while rolling the wheels.
Originally posted by chadwickgreen I recently bought a HAC4 and its great and all, but I can't get the odometer to work correctly. I did a ride today that should have been around 67-68 miles, and the HAC4 reported 60.
I've measured my whell circumferance several times. I have 700x23 tires and my circumferance measurement is 2097 millimeters.
To add to the confusion, looking at the manual, a 700x20C tire should be 2070 millimeters and a 700x25C tire should be 2090. I coming up 7 millimeters higher than the bigger tire.
I found a web page that has circumferances for diffent tire sizes (http://www.branfordbike.com/computer/comp10.html) and it states 2096 millimeters for a 700x23C tire (2105 for 700x25C;2086 for 700x20C).
Has anyone else seen this problem with the HAC4s? How have you resolved the problem.
Thanks, Chad
Hi Chad,
The difference between 2096 and 2070 mm is about 1 %. This can only cause a maximum error of about 0,7 miles during your trip. You lost 7 or 8 miles so you have an other problem!
Check your HAC4 recordings for a constant/correct speed or unexpected losses of speed and dips during your ride. Check the distance between the magnet and the speed sensor. Check the distance between your HAC4 and the speed sensor.
I entered 2096 mm for 700x23 tires into HAC4 and it worked fine from the start.
Check your HAC4 recordings for a constant/correct speed or unexpected losses of speed and dips during your ride. Check the distance between the magnet and the speed sensor. Check the distance between your HAC4 and the speed sensor.
Also, try to mount the magnet as close to the hub as reasonable. The farther away from the hub, the faster (linear speed) the magnet passes the pickup. Especially if the magnet and pickup aren't perfectly aligned, or if the gap between them is large, a fast-moving magnet can zoom past the pickup too quickly to register. You'd notice this problem if the speedometer shows a slower speed when you're really hammering.
