A standard open differential allows the driving wheels to rotate at different speeds for cornering, but under hard acceleration it directs torque to the wheel with least grip, causing the unloaded inside wheel to spin. A limited slip differential (LSD) limits this difference, transferring drive to the wheel with grip. The result is improved traction out of corners, more stable power delivery, and a real advantage in competition and spirited road use.
How an LSD Helps the Midget
The Midget is a light, short-wheelbase car, and under hard cornering acceleration the inside rear wheel readily loses load and spins. An LSD keeps both wheels driving, allowing earlier and harder application of power on corner exit. For autotest, sprint, hillclimb, and circuit use, the gain in traction and consistency is significant; on the road it provides more confident drive out of junctions and bends, particularly in the wet.
Fitment to the Rear Axle
The LSD unit replaces the open differential within the rear axle. Fitting involves removing the axle, stripping the differential carrier, and setting up the crown wheel and pinion meshing and preload, precise work that is best entrusted to an experienced mechanic, as incorrect set-up leads to noise and premature failure. The unit must be matched to the final drive ratio and crown wheel and pinion fitted to the car.
Ordering Considerations
The Midget rear axle used several final drive ratios across production. The LSD must suit the crown wheel and pinion and the axle type fitted, so the axle and ratio must be identified before ordering. An LSD is a specialist upgrade most appropriate for cars used hard on road or track, and is usually fitted as part of a wider axle overhaul. Setting up the differential correctly is essential to its reliability.