MTB Front Suspension Lab

SPRING MODE

Rider Mass 72.6 kg (160 lb)

Front Weight 42 %

Unsprung Mass 2.5 kg

Fork Travel 160 mm

Quarter-Car Schematic

Coil Air MTD Wheel t=0 → first contact

Displacement Time-Histories

Axle, fork & tire travel — the study's core comparison plot. Overshoot, ring-down and sag all respond to parameter changes.

≈ STUDY Fig. 9

Cockpit Acceleration (rider comfort)

Vertical g felt at the handlebar. Lower peaks & faster settling = less harsh.

COMFORT

Fork Spring Force vs Travel (linearity)

Coil is linear; air ramps up progressively. Volume spacers steepen the ramp.

SPRING RATE

MTD Transfer Function (why & when it works)

Steady-state amplification swept across frequency. The absorber splits one tall resonant peak into two shorter ones — the classic Den Hartog result.

MTD THEORY

Governing Equations

m_s ẍ_s = m_sg − F_fork(coil/air) − c_f(ẋ_s−ẋ_u)
m_u ẍ_u = m_ug + F_fork − F_tire [contact only] − F_abs [if MTD]
F_tire = k_t·δ + c_t·δ̇ δ=(x_u−x_road)>0 (Kelvin–Voigt)
F_coil = k_c·s | F_air = p₀A[(L/(L−s))^n − 1] (A calibrated once at 75 psi/28% sag ref)
f_opt=f_hop/(1+µ) ζ_opt=√(3µ/(8(1+µ)³)) · Integrated RK4, dt=80 µs