What is a Quaife ATB limited-slip differential?

The Quaife ATB (Automatic Torque Biasing) differential is a unique type of limited-slip diff that substantially improves traction for powerful vehicles using only gear mechanisms. This clever design revolutionised the differential market - offering a superior level of performance and warranties compared to its competitors.

Quaife is now the world leader in differential technology. Successfully used in all forms of motorsport including F1, rallying, circuit racing, rallycross and drifting, they are also ideally suited to high-performance road cars. Quaife even supply FORD as original equipment for their Focus RS range.


Why do you need a limited slip differential?

All standard BMW and Mercedes cars come from the factory fitted with the basic "open differential" - a simple device that allows the driving wheels to turn at different speeds (enabling the car to navigate around corners). The problem with the open diff is that it can only ever apply the same amount of torque to both driving wheels, so when a wheel slips, it will only put through the amount of torque it requires to power that spinning wheel (very little!). The car spins away power in these instances.

Additionally, BMW and Mercedes use various electronic traction systems that "curb" power to the drive wheels during traction loss (indicated by the flashing traction light on your dashboard). The Dynamic Stability Control system (DSC) is designed to "curb the engine output and stop slip on the wheels", a good feature in theory, but is still in its early stages of development and is way too intrusive, often frustrating the driver when trying to push on. If you accelerate hard from slow speeds, or try to power out of turns (especially in slippery conditions), the loss of traction will make the engine sap power away from the wheels. Turbo-charged rear-wheel drive cars with high torque outputs suffer the most, such as BMW's M135i, and conditions are worsened by the fact they are equipped with run-flat tyres and stiff suspensions. Of course if you are lucky enough to have sufficiently deep pockets, all BMW M-Powers come from the factory with a mechanical limited-slip differential, demonstrating that even BMW themselves know that powerful cars need these important devices.

Fortunately, there are clever differentials out there on the aftermarket that will transfer torque to the wheel with more traction rather than take it away... 

How does a Quaife ATB differential improve performance?

The Quaife unit uses sets of floating helical cut gear pinions that run in pockets and mesh during normal driving, acting as an open diff. Should one of the driving wheels start to spin however, the helical gears start to generate a torque bias thanks to the axial and radial thrust of the helical gear pinions in their pockets. The result is an instantaneous and progressive transfer of torque away from the spinning wheel to the one with more traction, always varying accordingly and automatically.

With the DSC and traction systems switched off during traction loss, you will feel the Quaife transferring the power to the wheel with more grip in a smooth and predictable manner. Any movement at the rear end is controlled and intuitive for the driver. With the traction systems switched on, you will rarely ever see the light flicker on your dashboard as the Quaife allows you to power through any loss of traction, working in perfect harmony with all of the BMW's standard equipment.

The car ultimately becomes easier to control and is able to apply its power to the tarmac with maximum effect. Acceleration, cornering speeds, handling, steering, and overall dynamics of the car are dramatically improved! The Quaife is capable of varying the torque split from 0-80%, and does this quietly and smoothly in operation. It does not affect any of the traction systems on the car, and does not affect the manufacturer's warranty. All backed by its own worldwide lifetime guarantee.

Chris Harris of AUTOCAR Magazine demonstrates the Quaife's abilities in our 335i demo:



Why is the Quaife superior over others?

Quaife ATB BMW Limited Slip Differential Conversions

Quaife ATB Mercedes Limited Slip Differential Conversions

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