AUTOCAR - Why limited-slip diffs shouldn't die by CHRIS HARRIS 11 April, 2007

‘As car addicts, we can't allow the Quaife limited-slip differential fitted to Birds' 335i BMW to be ignored'

Occasionally, a component or widget with great significance to the car enthusiast  audience is slow to learn of its arrival.  A thingummy of zero interest to the outside world, but one pertinent to you and me. Why, I still ask myself, did it take four months to learn that Pirelli makes a sticky P Zero Corsa tyre for the Audi RS4?

Similarly. We can't allow the Quaife limited slip differential fitted to Birds' 335i demonstrator to suffer such a fate.

As is always the case around the time BMW is unveiling new M3 prototypes, companies such as Birds,UK begin fettling the fastest 3-series currently available. The car showcases a heap of gear from German tuner Hartge, including a development of the 3.0 litre twin-turbo straight six with 381bhp and 336lb ft of torque.  If the first number poses no threat to the forthcoming M3, then the second one - the one that defines performance potential on the road - should have the M3 peeking into its undergarments with some concern.

Kevin Bird, the man who owns the business of the same name, is a kindred spirit on the subject of the demise of the limited-slip differential in road cars. I harp on about the things because their removal through the increased (and infernal) use of electronics has done more to spoil the way fast cars drive than any other prevailing mechanical development of the past decade.  The real irony is that the dramatic power increases seen in just about every sector should have dictated their universal fitment.

Copyright - David Smith via BMW Car.

It is 10 years since a BMW options list offered a tickable box marked'LSD'. But Birds can rectify that and will soon have units to fit just about every BMW in recent memory.

They are invisible to the naked eye (and the official BMW technician), too.  Anyone tired of that yellow flashing light and impeded acceleration on their 535d should talk to Birds (UK - 01892 810850) immediately.

Hear what Chris Harris says about Birds 3 series and see the car in action at www.autocar.co.uk ( ‘videos'  second page).