Downhill Mountain Bike Wheels and Rims
The speed and impact durability of a downhill mountain bike places a lot of responsibility on the wheels and rims. The size and design of a wheel, as well as the absorptive shock capacity of the rims, is essential for a downhill mountain bike competitor trying to descend a mountain in as little time, with as much flair, as possible. Rims need to be able to absorb the shock from huge jumps and collisions without bending or snapping, while wheels need to maintain their tru (tru is a term used to describe the constant, equal tension between downhill mountain bike spokes. If a wheel is out of tru, it rotates unevenly, rubbing against the brakes or even the fork of a bicycle, causing too much friction and resistance and slowing down the overall ride) and thus their speed, to perform at their peak.
While any bike shop will be able to tru a wheel back into position, very few mountain bike stores and mechanics set up shop in the middle of the woods where your single track moutnain bike train is likely to be. So, purchasing wheels and rims of the highest quality is essential. Some of the cheapest rims, like certain models made by Mavic, run at a pricey $350! Other wheels and rims, made by companies such as Ritchey and Shimano, cost more. Downhill mountain bike rims should be between 26" and 24", depending on the size of your mountain bike frame and the speed withi which you wish to travel.
Cromoly (steel), aluminium, and titanium are all materials used for downhill mountain bike rims - as with frames, and pedals, the price increases with the quality of the material, with steel and aluminium wheels running at the lowest proces, adn titanium wheels being the most expensive. Also, make sure that your rim is wide enough to accomodate a thick, durable tire - a rim that is too small runs the risk of increasing the likelihood of pinch flats, or flat tires that occur when the tubing of a mountain bike tire tire is caught between a rim and a tire.