We were invited by Jaguar World magazine to attend a test day at Mallory park recently.

The weather was attrocious but the XKR performed exceptionally well and was driven by a professional racing driver who was impressed with the Jaguars improved handling dynamics.

Following on from the very successful implementation of uprated suspension bushes for the Jaguar XKR, we turned our attention to the springs.

We are always careful about our choice of strategic partners, and in this case we were happy to choose Eibach as our prefered supplier of road springs. Eibach are one of the best springs manufacturers in the world with experience at the very highest levels of motorsport.

We wanted to lower the car slightly to provide a lower centre of gravity without compromising the utility for everyday use. The Eibach springs reduce the ride height by approximately 10cm.

This is the difference between the standard and Eibach spring

This is an Eibach spring fitted to a shock absorber.

These are the ride heights before the spring change.

This is the new lower ride height.

Having completed the development of the poly urethane suspension bush upgrade on the XKR, we spent approximately 3 months on performance evaluation and durability testing.

The significant improvement in performance allows the driver to have considerably more confidence in the car now that the input commands and responses are totally predictable and controllable.

We are very pleased with the end results and hope that anyone upgrading their XKR suspension will experience a new level of driving enjoyment.

These suspension components have been released for sale and can be viewed at: http://www.tdi-plc.com/catalog/index.php?cPath=1_788_826_827_832

Having dealt with the deficiencies of the rear subframe, we turned our attention to the front suspension.

To deal with the immediate concern of the excessive compliance inherent in the bushes of the front anti roll bar, upper and lower wish bones and front sub frame, we developed some poly urethane replacements.

These are the uprated front anti roll bar bushes:

These are the upper and lower front suspension arms:

These are pictures of the bushes when installed on the car:

As identified previously, the rear sub frame bushes are a “void” design which allows for an unusual amount of movement, which in turn causes an unacceptable degree of geometry deflection.

We designed and commissioned some poly urethane replacement bushes to correct this issue.

The images above show the difference between the standard bush and the poly urethane bush. None that these are development bushes and that the production models will not be yellow!

Additionally, we installed poly urethane panhod rod bushes to reduce the amount of slip between the axle and the body. The bushes are shown below:

The next area to be considered are the springs and shock absorbers, and the kinematic geometry.

As mentioned previously, the spring rates are exceptionally high, presumably in an attempt to compensate for the poor Dynamic Index. The damping rates seem adequate and have the CATS system incorporated.

The geometry that is recommended by Jaguar seems to suggest that they are aware of the poor DI and have attempted to improve the turn-in by manipulating the geometry, at the expense of tyre life and straight line stability. The additional kinematic geometry induced by unwanted geometry deflection tends to exacerbate this issue.