in­stant ex­pert: ANTI-SQuat

Mountain Biking UK - - SUSPENSION -

What is it?

Just as brak­ing pushes your weight for­wards, ac­cel­er­a­tion pushes it back. Ev­ery pedal stroke causes the sus­pen­sion to squat into its travel and then re-ex­tend. Known as ‘pedal bob’, this wastes ped­alling en­ergy. Savvy de­sign­ers can use chain ten­sion to re­strict this – a force known as ‘anti-squat’.

What af­fects it?

On most de­signs, the main pivot is above the bot­tom bracket. That means the rear axle moves away from the BB slightly as the sus­pen­sion com­presses. This adds to the ten­sion cre­ated in the up­per part of the chain as you pedal, coun­ter­ing the sus­pen­sion’s ten­dency to com­press. The more a link­age moves the axle away from the BB, the more ef­fec­tive this is.

What ef­fects does it have? Anti-squat can be used to re­duce pedal bob sig­nif­i­cantly, but there are draw­backs. Be­cause the axle moves away from the BB when the sus­pen­sion com­presses, the chain can pull on the chain­ring, caus­ing the cranks to ro­tate back­wards. This is known as ‘pedal kick­back’, which can feel harsh through your front foot. All that ten­sion on the chain can also make the sus­pen­sion less able to ab­sorb bumps while ped­alling.

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