Wheels And Hubs

Wheels can make a big difference on a bike. Lightweight wheels are better for climbing and deep rims are better for aero.

Wheels are composed of a rim, hub, spokes, nipples, rim tape, and a valve stem for tubeless tires.

Rims are made in aluminum or carbon fiber. They define the wheel size, rim width, spoke count, and tubless tire compatibility. Standard aluminum rims can use rim brakes, but lightweight aluminum or carbon rims may be disc only due to thinner walls. Eyelets (metal grommets the spokes go in) on nicer rims protect them from tool marks when truing the wheel. 

Spokes are commonly double butted, which means they have a thinner diameter in the middle than in the threads and shoulder. Low end wheels have heaver non butted spokes, and lightweight wheels can have triple or aero/bladed spokes. Cutting edge wheels have carbon fiber or polymer spokes.

Hubs determine the over locknut diameter (OLD), the width of the hub including lock nuts and spacers that will fit within a frame's rear dropouts. Road bikes are typically 130mm, old mountain bikes are 135mm. Thru axels for road are 142mm, and 148mm boost for mountain bikes. Some hubs have adapters that can convert between quick release and thru axel.

Bike wheel sizes