Bike Computer Install - I Just Don't Get It!
03-23-09, 08:52 PM
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Bike Computer Install - I Just Don't Get It!
I found a Vetta VL110 for a great price and it arrived over the weekend. I installed it yesterday. There are so many things to track, I really just played around with it on my first trip out (to the store with the kids). Today, I reset everything before I left and couldn't wait to get to work to see all the data I had collected. While on the way, I had it set to AVG/MAX speed. I couldn't believe how fast I was really going! It just didn't seem like I was moving at +76 mph down that hill! Heck, my average was near 50 mph! Needless to say, I have something set or installed wrong. I just can't figure out what. I took the rim size right off my tire, 700x36C, and I've checked the setting at least a dozen times at this point. For magnet proximity issues, I have the sensor mounted very low on the fork, about 3 inches from the hub. The install instructions (very vague) give direction just to make sure the sensor is mounted 2-4 (or more) cm away from the brakes. Now I took "or more" to mean it really doesn't matter, but to me it has to matter. Logically, a magnet mounted toward the tire end of the spoke is going to pass by the sensor many fewer times than if it were mounted an inch from the hub. But everything I read says it doesn't matter where you mount the thing. If anyone here can give me direction or help me reason this out, I would really appreciate it!
03-23-09, 09:31 PM
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It's physically impossible for one part of a spoke to pass the fork more times than another part of the same spoke... so no, it doesn't matter where on the spoke you mount it.
You've got it calibrated wrong.
The 'size' has to do with the circumference around the tire (How far the bike goes per single revolution of the tire/wheel)
That's the ONLY thing you can really do wrong on the setup (Well... you COULD leave a magnet from an old computer on there and be double counting revolutions.... but that's not really likely)
The other thing to check is that you're set for MPH not KPH....
You've got it calibrated wrong.
The 'size' has to do with the circumference around the tire (How far the bike goes per single revolution of the tire/wheel)
That's the ONLY thing you can really do wrong on the setup (Well... you COULD leave a magnet from an old computer on there and be double counting revolutions.... but that's not really likely)
The other thing to check is that you're set for MPH not KPH....
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"There is no greater wonder than the way the face and character of a woman fit so perfectly in a man's mind, and stay there, and he could never tell you why. It just seems it was the thing he most wanted." Robert Louis Stevenson
03-24-09, 05:50 AM
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OK, in my defense...
Well, I guess I have no defense 
I just couldn't wrap my head around such a simple concept. Even worse, I'm most likely guilty of the solution you say probably wouldn't be the one. I left the magnet from my other computer on the spoke. Actually I meant to leave it on because I was trying to compare the two, just to make sure my new one was matching the old. I thought, because the proximity of the magnet was so close to the sensor, there was no way it would get a signal from the other magnet a couple of inches away. I hope I'm wrong and this solves my problem. Thank you so much!
I just couldn't wrap my head around such a simple concept. Even worse, I'm most likely guilty of the solution you say probably wouldn't be the one. I left the magnet from my other computer on the spoke. Actually I meant to leave it on because I was trying to compare the two, just to make sure my new one was matching the old. I thought, because the proximity of the magnet was so close to the sensor, there was no way it would get a signal from the other magnet a couple of inches away. I hope I'm wrong and this solves my problem. Thank you so much!
