The component that connects a bicycle wheel's hub to its rim is a spoke.
A bicycle spoke is a slender rod running between the wheel's central hub and its outer rim. In most modern bicycle wheels, spokes are made from steel or stainless steel and work primarily in tension. Their combined tension keeps the rim accurately positioned around the hub while distributing loads from the rider and road.
At the hub end, a spoke commonly has a bent head that fits through a flange hole, although straight-pull designs are also used. At the rim end, it screws into a small threaded fitting called a nipple. Turning the nipple changes spoke tension and lets a wheel builder true the rim.
The hub contains the axle and bearings, while the rim supports the tire; neither part alone is the spoke. A common mix-up is calling the nipple the connector, but the nipple joins the spoke to the rim and adjusts tension. Some modern aerodynamic wheels use composite spokes or molded structures, yet their functional role remains the same.