A swing arm linkage for a mid-wheel drive wheelchair , comprising: a first swing arm having a first swing arm pivot point and a linkage member first mounting point , a second swing arm having a second swing arm pivot point and a linkage member second mounting point , wherein the first swing arm is a rear swing arm and the second swing arm is a front swing arm, or the first swing arm is a front swing arm and the second swing arm is a rear swing arm, a linkage member configured to be connected to the linkage member first mounting point and to the linkage member second mounting point , to enable force transfer between the second swing arm and the first swing arm , wherein the linkage member has an elongated shape defining a linkage axis (A) extending between the linkage member first mounting point and the linkage member second mounting point , a first straight line being formed between the first swing arm pivot point and the linkage member first mounting point , and a second straight line being formed between the second swing arm pivot point and the linkage member second mounting point , wherein the linkage member first mounting point and the linkage member second mounting point are so arranged relative to each other that the sum of an angle (α) between the linkage axis (A) and a line perpendicular to the first straight line and extending from the linkage member first mounting point and an angle (β) between the linkage axis (A) and a line perpendicular to the second straight line and extending from the linkage member second mounting point is constant or increasing with increasing ditch angle (γ), the ditch angle (γ) being defined as the acute angle between two planes (P1, P2), a first plane (P1) that is tangent to both the front caster wheel contact point to the ground and a ground contact point of the drive wheel (D), and a second plane (P2) that is tangent to the rear caster wheel ground contact point and a drive wheel ground contact point. a first swing arm having a first swing arm pivot point and a linkage member first mounting point , a second swing arm having a second swing arm pivot point and a linkage member second mounting point , wherein the first swing arm is a rear swing arm and the second swing arm is a front swing arm, or the first swing arm is a front swing arm and the second swing arm is a rear swing arm, a linkage member configured to be connected to the linkage member first mounting point and to the linkage member second mounting point , to enable force transfer between the second swing arm and the first swing arm , wherein the linkage member has an elongated shape defining a linkage axis (A) extending between the linkage member first mounting point and the linkage member second mounting point , a first straight line being formed between the first swing arm pivot point and the linkage member first mounting point , and a second straight line being formed between the second swing arm pivot point and the linkage member second mounting point , wherein the linkage member first mounting point and the linkage member second mounting point are so arranged relative to each other that the sum of an angle (α) between the linkage axis (A) and a line perpendicular to the first straight line and extending from the linkage member first mounting point and an angle (β) between the linkage axis (A) and a line perpendicular to the second straight line and extending from the linkage member second mounting point is constant or increasing with increasing ditch angle (γ), the ditch angle (γ) being defined as the acute angle between two planes (P1, P2), a first plane (P1) that is tangent to both the front caster wheel contact point to the ground and a ground contact point of the drive wheel (D), and a second plane (P2) that is tangent to the rear caster wheel ground contact point and a drive wheel ground contact point. <EOS>