No, you’re not reading a typographical error in the title, but I thought it would be a good idea to slip in another Test Session report before the race season starts in anger.
This time it was slightly different. My little beauty would be shod with different wheels and different tyres. Instead of the JEC championship Vredestein tyres run on 15” chrome wires, I have bought some Dunlop Racing ‘L’ Section Cross Ply tyres and fitted to the latest MWS 16 inch, 5.5 inch, 72 spoke competition wheels. (Details below).
I wanted to test this configuration in preparation for FIA Appendix ‘K’ races that will be on the race calendar this year. In addition, this will be an ideal combination of wheel and tyre to be used at Spa-Francorchamps which is a long-lap circuit (Approx. 4.5 Miles).
In addition, I have recalibrated the speedometer to be in line with this 16 inch wheel’s rolling radius. This happens to be the calibration of the original Jaguar car as it was originally manufactured with 16” wheels and cross-ply tyres in the 1950’s.
The difference between 15 inch and 16 inch wheels will give me potentially a higher top speed, e.g. going down the Lavant straight at Goodwood or on the Kemmel straight at Spa.
I hadn’t raced on Dunlops for some seven years, so it took me some laps to get my brain into gear and remember that these tyres have a lot less grip but, they are very predictable and progressive in terms of side-slipping and therefore ‘Drifting’ the car into and out of corners.
In between sessions, Keith, from Keith Martin Classic Cars, popped over to check my wheel alignments, as I thought I was scuffing too much outside edges from the front tyres. His checks were fine and I was back on track and my learning curve.
I was very pleasantly surprised that at Lavant Corner, which is a double apex corner and, when you get it right, it’s a ‘Constant-radius’ turn, which means that if your entry to Lavant is correct, you won’t need to adjust the steering wheel, only to start unwinding the lock on the exit.
With these tyres, which as I mentioned do slide and, by the end of the day the car was happily four-wheel drifting through Lavant and all I had to do was to ‘Turn-on-the-Throttle’ for a perfect exit.
A further assessment of the car’s performance was the terminal velocity I could achieve on the Lavant Straight, which was 132 mph at 6200 RPM, without using the overdrive. This was an excellent result from a 3.4 Litre engine and just 2 X 2” SU carburettors.
NOTE: Just before taking the car to Goodwood, I borrowed a ‘Corner Weighting System’ from my good friend Jeremy Rogers, the Proprietor of Surrey Sports and Classics, based in Ripley, Surrey.
The car showed that the overall weight was slightly over for the JEC Regulations and, the corner weighting was almost perfect, with only a slight addition of the rear near-side weight to make it perfect with me in the drivers seat. This was a very interesting result form a very front-end heavy car weighing 1390 Kgs.
WHEELS – The New XK Alloy
In summary, the car performed extremely well at Goodwood together with the new wheels from MWS, which can be seen in a close-up of one of the pictures of the car outside the MWS Offices. This wheel looks very like the Borranis I know of old.
5½” x 16” Polished Aluminium Rim
Highly Polished Stainless Steel XK-style Centre
60 or 72 Highly Polished Stainless Steel Spokes & Nipples
Compared to my ‘Dunlop’ Racing 15” wheels they are 3 Kgs lighter per corner. So if you are racing and weight is important, then they will save you another 12 Kgs on the car.
Please call MWS and enquire about pricing.
John D Roberts