Wheelcover for Triathlon

Avery the Guinea Pig dines on some celery in the presence of some fine company, a wheel cover

Though one of the least creatively named weapons in a triathlete's arsenal, the wheel cover is to me one of the most exciting. 

Just as wheels have translational (forward and backward) and rotational momentum, they also create drag in these dimensions. I remember after riding for some time on Ksyrium Elite wheels (with bladed spokes) and then transferring back to my Bontrager Select round-spoked wheels. It felt as though a soft cushion of air was pushing against the front of the bike. As the spokes spin at feverish pace, they create quite a bit of turbulence. Bladed spokes reduce the frontal profile of the spoke and correspondingly decrease drag. Disc wheels and wheelcovers go  one step further and eliminate the spoke, greatly reducing drag derived from the wheel's rotation. Now, instead of the smooth air ahead of you being churned up by a spinning monster more ravenous than Rosie O'Donnell, it is cleanly sliced by the smooth-surfaced scythe of the wheel cover. 

Aerodynamics is a complicated science, so I can't tell you that if you use a wheel cover you'll magically improve your time by X seconds. But it will get you faster for the same power output or let you travel an equal speed with less energy. I also love the aesthetic of having the solid surface in back. 

Wheel cover vs. Disc wheels

Discs are outrageously expensive, difficult to repair if damaged, and barely lighter than the wheel + cover combination. It is also generally accepted that they only perform very slightly if at all better than a wheelcover. Wheelcovers offer the same performance at a dramatically reduced cost and offer the easy maintenance of a spoked wheel. 

Where do I get one?

I have no relationship or invested interest with Wheelbuilder.com beyond having purchased a wheelcover there, but can tell you that I had a great experience and believe them to be the best option available should you choose to purchase and not make one. 

Custom

Wheelcovers also allow an excellent opportunity for customization. Try fully custom vinyl decals available from, for example, Taigraphx.com or Chase Bicycle Products. Or, if you're of the loving parent variety, give your children some markers and rock the resulting decorations out on the race course. 

Some more images:

The frontal profile

The curved non-driveside surface of the wheelcover

The flat driveside surface of the wheelcover

Final Considerations:

-This is very important: note how the logo on the tire is aligned with the wheelbuilder.com decal but not aligned with the KSYRIUM of the wheel. Never make this mistake with your own wheelcover.

-The cassette must be removed during wheelcover installation. This is a very quick and easy procedure, but does require the purchase of a chain whip and Shimano or Campy compatible lockring. Alternatively, you can also take it to the local shop and have them do it for you in 10sec, but this will make you look most lame. It's my belief that a cyclist must do as much self-wrenching as possible, especially with simple tasks. 

-In order to pump up the tube with the disc wheel on, you will need a presta adapter which is commonly referred to as a 'crack pipe.' The L-shaped extenders allow your tube to be inflated when it would otherwise be inaccessible to a pump. The wheel cover has a cutout surrounding the valve on one side. Simply attach the extender to the presta valve, then the pump to the extender and fill with air. It is another hidden cost, though, at around $15-$18. See one here. 

There you have it. For approximately $150 (cover+lockring+chain whip+crack pipe) you can have the performance and aesthetic of a +$1,000 disc wheel and get the added bonus of spoked wheel maintenance.