TB6 - Technical Bulletin 6

Spring Selection

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  The HQ-HZ Holden series used coil springs front and rear.

  The front springs are too long to be reused in the Cheetah.

  Coil springs are often cut down to alter ride heights, sometimes by so much that they become displaced over road bumps, or, in extreme situations fall out altogether.

  Cutting coil springs down to change ride height is illegal.

  With the number of suppliers and cheap options available today, there is no need to cut down the existing springs.

  Cheetah Cars have used King Springs in the Targa car, and in our road cars.

  With the weight bias of the Cheetah near 50/50, we have found that the rear springs of the sedan are too light and also have to be replaced.

  For the Targa car we used KHFL-25 730lb springs at the front and KHRS-04 springs for the rear. These were also used on the Cheetah prototype.

  For Targa use, we found these springs ideal, but getting a trolley jack under the front subframe necessitated using ramps.

  For practical road use we found the front springs to be too low and the ride quality a little hard.

  To raise the front height 25mm, and soften the ride in our road cars, we have used KHFR-02 500lb springs. Note, these cars have cast iron small block Chevrolet engines and Supra W57 gearboxes installed, neither particularly light.

  Before considering purchasing springs, it is best to have all major components fitted and the car weighed at each corner. This is a good starting point to calculate the required spring rates.

  With the large selection of springs available today, an off the shelf set can usually be found to suit most applications.

  As can be seen in the image above of an HQ-HZ front King spring, the top coil has been bent over and flattened so that it fits snuggly into the top of the spring mount. This is done during the manufacturing process, and is another reason to use properly manufactured items.