Suspension fork

Key facts

Introduced

1989

Typical travel

100–200 mm

Standard

Boost 110 × 15 mm axle

Service interval

lowers every 50 h, full service every 100–200 h

How it works

Two stanchions slide inside the lowers. A spring — a chamber of air or a steel coil — holds the bike up, and a damper, oil pushed through small ports, controls how fast the fork compresses and comes back. The spring decides how much it moves; the damper decides how it feels.

What you can adjust

• Air pressure sets the sag — how far the fork sinks under your weight.
• Rebound sets how fast it extends after a hit: too fast bucks you, too slow packs down on repeated bumps.
• Compression firms the fork against brake dive and pedal bob; many forks split it into low and high speed.
• Volume spacers make the end of the travel more progressive, so big hits do not bottom out.

How much travel

Around 100 mm on cross-country bikes, 130–160 mm on trail and enduro bikes, 180–200 mm on downhill forks with two crowns. More travel takes bigger hits but weighs more and changes the bike's geometry.

Care

Wipe the stanchions after every muddy ride and check the pressure every week or two. The lowers need fresh oil and seals roughly every 50 hours of riding — it takes half an hour and keeps the fork smooth for years.

Related articles

• RockShox — An American suspension brand founded in 1989 by Paul Turner. Its first fork, the RS-1, brought front suspension to mountain biking; since 2002 the brand has been part of SRAM.
• Hardtail — A mountain bike with a suspension fork and a rigid rear end: light, simple, cheap to keep running — and the bike that teaches you to ride well.
• FOX — An American suspension maker founded in 1974 by Bob Fox. Its forks and shocks — recognisable by the gold Kashima Coat — are fitted to mountain bikes of every discipline.
• Rear shock — The spring and damper that control the rear wheel of a full-suspension bike. Its tune and setup decide whether the back of the bike grips, pedals and lands well.
• Suspension setup — Half an hour with a shock pump makes a bigger difference than most upgrades. Set the air pressure by sag, then rebound, then compression — one change at a time.
• Sag — How far the suspension compresses under the rider's own weight, standing in the riding position — given as a percentage of travel. The first number to set on any suspension.
• Suspension travel — How far a wheel can move on its suspension, in millimetres — the first number in any mountain bike's description. More travel absorbs bigger hits; less travel pedals and weighs less.
• Boost — The hub-width standard of most modern mountain bikes: 110 × 15 mm at the front and 148 × 12 mm at the rear. Wider hubs make stiffer wheels and leave more room for tyres.