Following the advice in several earlier threads, for about one year I’ve been running a Zipp disk with Radio Shack rare earth magnet super glued to a small vinyl sticker on the wheel itself. This is mated to the Cateye double wireless computer. The cadence information (from another magnet on the crank) is bullet proof, but the wheel speed information continues to be squirrely, despite repeated attempts at re-alignment. What seems to happen is that bumps in the road cause the Cateye sensor to splay outward and out of the magnet’s apparent range. All this happens no matter how tightly I screw in the positioning barrel on the sensor. The threads don’t seem to be stripped. At IM this year, I literally lost speed at .27 miles into the course; at a 70.3 two weeks later (after repositioning) it worked for just over 2 miles.
I’m not a slave to the computer, and have raced many times without one, but I’m just about to switch over to a front wheel spoke magnet setup (wireless and without cadence) or a hard-wired setup. Has anyone else encountered this problem with the double wireless speed sensor?
Have you identified exactly what is moving?
I’m not familiar with your specific device, but it would seem that a spoke-style magnet wouldn’t matter…it’s not the magnet moving right?
Same with a wired unit. If the sensor is moving, a wire wouldn’t help would it?
If your sensor is moving away from the magnet due to rotation around the chain stay, then put it in place and drop 1 or 2 drops of super glue at the point where the sensor bracket meets the chain stay.
I have the Cateye double wireless, too, and the sensor moves all the freakin time. I’ll have to try the super glue method.
On a related note, I lost my speed data during my half iron this Saturday. Turned out the spoke magnet had loosened slightly on the rough roads and slid outward when my speed shot up on the downhill. Moral of the story, switching to a spoked magnet doesn’t necessarily solve all problems!
I have two rare earth magnets stacked on top of each other and a cateye double wireless…makes for a close fit when the sensor is in the right place…and when it moves (as it always does) the signal still reaches the sensor…just a thought
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I’ve been doing exactly the same thing (stacking 2 rare earth magnets). What seemed to happen at the last race is that when the sensor shifted it sheared off the top magnet. There was only the one (superglued) magnet left on the wheel after the race. I’ve had problems getting it to work with 1 magnet at all…don’t know if the magnets are individually too weak.
I’m using the V2C with a little round magnet from a science supply store (same size as spoke magnet) stuck to a piece of 3M two sided tape (about the same thickness as the magnet) stuck to my disc surface. It is all covered with black electrical tape for a stealth factor.
I now have three V2Cs (2 mine, 1 the wifes) and the sensors don’t ever move. Are you sure you have your sensors put on the bike so that there is the least chance of movement?
Is the cadence sensor resting on the frame? If it were and tightened down, then the speed sensor adjusted and tightened, you would have one side of the sensor combo anchoring the other. Just my two cents.
It sounds like the tightening mechanism on the sensor is at fault. Is there a way you could secure the sensor to the chainstay with some cable ties? This is the technique that most sensors require as it is the most effective way. Just get 2 cable ties and some cable pullers and snug it up!
I’m going to try a larger diameter magnet like yours. The Radio Shack ones are tiny (1/8 inch, I think), which perhaps makes perfect alignment too critical.
Unfortunately, this unit (which is strapped to the chainstay with 2 cable ties) has two pivot points that are independent of the cable ties. One is for the speed sensing arm, and the other for the cadence arm.