History of Jaguars IRS – RWD – Unit which drove over 500,000 plus Jaguar Cars from 1961 to 1996

The original Jaguar Cars IRS Unit was first used in the E Type Jaguar and was the first production Jaguar to benefit from extensive research development program on independent rear suspension options and designs for Jaguars new prototype E Type.

Anecdotally it was designed by Bob Knight head project engineer for EA 1 & EA 2, all for a £5 bet with Sir William Lyons saying that he couldn’t do it within a month, Bob certainly burnt the midnight candle and won the bet.

For the revolutionary new Jaguar E Type launched in 1961, it was very unusual for a car to have rear independent suspension and was one of the main attributes in the E Types impeccable driving characteristics, this was very much noted by many other motor manufactures at the time.

Bob Knights IRS designed unit carries the rear differential, drive shafts, UJ’s, rear hub’s, rear suspension and inboard rear discs, all housed in a steel cage, which proved to stand the test of time and remained in production until 1996 when the XJS Jaguar ceased production.

The result was greater rigidity and strength to the E Types monocoque with the subframe being attached to the body by four Metalastic mountings, and also to the underside of the floorpan at each side by massive radius arms, via rubber bushes and an anti-roll bar.

In total Bob Knight’s designed IRS unit Jaguar Cars fitted to not only to 72,000 E Types but also 300,000 plus XJ6 and 115,000 plus XJS models which in total, totalled over half a million units, so maybe Sir William Lyons £5 bet with Bob wasn’t a complete waste of money.

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