Upside-down forks (USD, inverted)

Upside-down (USD) or inverted forks are telescopic forks mounted the other way round from conventional forks. The larger outer tubes are held in the triple clamps, and the slimmer inner tubes (stanchions) slide in and out of them at the bottom, carrying the axle and brakes.

Advantages: the large-diameter tubes at the clamps make the fork stiffer against bending under braking and cornering, and moving the heavier part upwards reduces unsprung weight. That is why almost all motocross, enduro and sports bikes use them.

Downsides are a higher price and stanchions that sit low, exposed to stone chips and dirt. Fit fork guards off-road, clean the stanchions after muddy rides and fix leaking seals quickly, as oil may run onto the brake caliper.