Any suggestions for an elegant way to mount a magnet on a HED rear disk? I use a Cateye Astrale computer where speed is measured off the rear wheel. I just took a piece of styrofoam about the right thickness, put the magnet on top, and just taped the hell out of it with black electrical tape. I thought it looked OK and not too noticeable, but I did get a comment at my last race (“what the hell is that, a tumor on your disk?”). Any suggestions? The sensor is on the chainstay.
Any reason the speed *has *to be measured from the back wheel? Can’t you just mount everything up front?
I got one of the tiny ‘rare earth’ magnets from Radio Shack, and then used double sided ‘servo’ tape to stick it to the side of my HED Disc. I rotated the Cateye pickup to get it very close to the Disc. Worked like a charm.
I just got a round magnet from Home Depot and stuck it to my Renn disk with some silicone adhesive. Let it cure and put a few pieces of black electrical tape over for added security and to “smooth” the whole thing out aerodynamically 
It doesn’t “have” to be measured at the back wheel, but I prefer it (for use with the trainer) and the sensor is back there (design of Astrale).
Do like efernand, and rotate the pickup sensor…then you can lose the styrofoam build-up. BTW, some people have been successful with mounting the magnet in the valve-stem hole. You have to make sure you screw your presta valve in, and support the magnet so that the centrifugal force doesn’t move it towards the rim…but, it can work there with a little foresight.
I went to the lumberyard they had some foam backed tape , sticky on 2 sides. It has lasted 2 years with no problems. I also got my magnet at the dollar store it was a refrigerater magnet. I just broke the little butterfly off and used the magnet.
Elegant - not sure if you would consider this elegant (or even if they can still be bought), but Spinergy used to make what I would consider an ‘elegant’ computer magnet for the Rev-X’s. It is a circular magnet slightly bigger in diameter/width than a nickel and is encased in plastic with an adhesive strip on the back. Excel Sports used to carry them and Cambria Bike currently has them listed on their website for $7.00!
Michael
Thanks. I will rotate the sensor a bit to get it closer to the disk, and then use a “little” build up to bring the magnet closer to the sensor. The sensor is kind of far from the disk. I may try one of the “rare earth” magnets mentioned…I’m guessing it is stronger (?) so may not need to be as close to the sensor?
The rare earth magnets are very strong, and very small, think head of a nail. You need to rotate the sensor on the chain stay, and point the end towards the disc. You can get it quite close that way.