This is a very quick description of how I managed to get the cadence sensor from a Garmin Edge mounted on a Cannondale Rush.
The problem with the Rush is that the rear wheel 'hangs' from a swing arm that is higher than most. Definitely higher than the designers of the Garmin sensor intended.
There were two possible options to solve this problem:
- Disassemble the sensor, mount the main body somewhere else, then extend the wiring between it and the wheel sensor and mount that on the rear arm.
- Create some kind of mount that hangs under the rear arm and holds the sensor in the location it was intended.
Although several articles can be found that describe success with the first option, the latter sounded a little easier and less prone to bad mistakes - if you don't get the measurements quiet right you've just ruined 20c worth of aluminium, not a costly sensor.
Making a mount isn't really hard at all, and took me an hour or so. The hardest part was working out where to make cuts in the aluminium angle. Luckily geometry is your friend and the numbers required are shown in the first step here:
Rush Cadence Mount: First Cuts
Submitted by Rob on Sat, 09/06/2007 - 09:11.
Take a piece of angle Aluminium (this was 20x20x1.5 section). 180mm long, and make cuts leaving the following lengths:
29mm, 31mm, 54mm, 36mm, 30mm
Rush Cadence Mount: Bend It
Submitted by Rob on Sat, 09/06/2007 - 09:16.
Make a 90 degree bend at the first cut.
We have to remove the backing from what will become the base of the mount as shown here. This is a bit tricky, so to be honest, it's probably best to remove all the back part of the 'L' shaped section from the first bend through to the third cut.
Rush Cadence Mount: Bend More
Submitted by Rob on Sat, 09/06/2007 - 09:18.
Bend the mount a few more times to complete.
Note that it's not possible to fit the sensor here because:
1. There's no way to get a cable tie round the left end of the base (where my thumb is).
2. The arm for the wheel magnet is blocked by the back of the 'L' on the right.
Rush Cadence Mount: Finished Product
Submitted by Rob on Sat, 09/06/2007 - 09:24.
A few finishing touches:
1. Make a vertical cut to the back of the 'L', right of the base - this means the arm for the wheel magnet can actually be used. Handy 
2. The back of the 'L', left has had a section removed from the bottom. This allows room for the cable tie required to hold the sensor in place. Although as I said earlier, it's probably best to remove this whole piece to be honest.
3. At the extreme left/right make two cuts and small fold in the horizontal part of the mount. These should be measured against the frame - they 'grip' the brake cable routing mounts which stops the whole thing shifting up and down the swingarm.
4. Round off all the sharp corners and stuff of course.
Rush Cadence Mount: In Position
Submitted by Rob on Sat, 09/06/2007 - 09:25.
The final mount positioned on the left, rear swing arm.
The rear cable tie (had to use two connected to get the length) goes through the 'V' shape made top of the arm forward.
Rush Cadence Mount: With Sensor
Submitted by Rob on Sat, 09/06/2007 - 09:28.
Finished product with sensor attached.
There's really not much space between the crank and sensor. As mentioned a couple times, removing the back of the 'L' completely, where the sensor mounts would allow it to be closer to the wheel and give more room here.
Note how the small 'fold' at the end of the mount is pulled tight up against the brake host mount - same deal at the front prevents movement.
Job done - how easy was that? :)
Thanks!!
So this is good stuff. I had just decided that I could cope with only the speed since a long and difficult evening dicking around with the sensor brought me to the conclusion that I would not be too worried about cadence (grapes were sour anyway, right?) and mounted it with cable ties right down at the brake assembly to at least get speed.
Modifications will be made, specially now its such a crappy weekend.