I had one of the covers you speak of. In case you hadn't seen one up close, here's what I recall from installing one:
They're made of nylon, have a reinforcement at the center hole and a "sleeve" around the outside with a cord running through it. With each disc came a pair of flexible wire "hoops" and a bunch of spoke clips.
Installation involved:
- removing the freewheel/cassette
- putting the disc on (dork disc over top or removed completely)
- replace the cassette
- place the wire hoop around the edge and trimming to size (it came with a little joint to connect the loose ends
- put the fabric around the hoop and tighten the pull cord so it was snug
- "clip" the disc (now with a rigid edge from the wire hoop) into the little spoke clips
- repeat for side 2 (usually you had to test fit and replace each side at least once before finalizing
I found this link of interest:
http://www.wisil.recumbents.com/wisi...wheeldisks.htm
BTW, I DID ride the disc while out and about and on the wind-trainer. If nothing else, it does keep things from getting tangled in your spokes. I'd install one again in a second on my current bike. I'm kind of sorry I let it go with the bike. :\ In the photo you'll see I have the fabric turned "inside out" - the logo is on the inside part of the disc. Don't remember the name... "Aero disc" maybe?
