The Mazda MX-5 Roadster Coupe | Part Six

Body & Chassis - Not a Gram too Much

The soft top version of the Mazda MX-5 owes its unusually agile and linear handling characteristics to a strict gram strategy applied during the development of the third- generation version. One of the main goals in developing the new Roadster Coupe version was to keep the unavoidable gain in weight as low as possible. Only by delivering this, could MX-5’s famous Jinba Ittai driving dynamics be assured for the hard top version as well.

The Roadster Coupe version is just 37 kg heavier than the soft top model. Of this weight, 30.2 kg were needed for the roof itself, the rear deck cover and other small related parts; 3 kg for the steel (rather than aluminium) boot lid, 1.6 kg for the complex wiring harness switches, 0.3 kg for additional material at the aero board and for trim configuration modifications and 1.4 kg for the additional body reinforce- ments and sound insulation features.

Because the Roadster Coupe’s body opening for stowing the hard top is 45 mm wider and 82 mm longer than that of the soft top model’s, local reinforcements had to be employed to compensate for a slight loss in body stiffness. These include:

  • A 1.8 mm thick reinforcing bracket at both corners of the rear deck opening
  • Increasing the thickness of the front surface of the rear deck from 0.7 mm of the soft top model to 1.8 mm for the Roadster Coupe model
  • Strengthening the sides of the rear deck opening by inclusion of a closed-section structure that extends through the front surface of the rear deck.

These local reinforcements make body shell stiffness of the MX-5 Roadster Coupe comparable to the soft top model. Here as well, developers kept the weight gain as low as possible, limited to 820 grams.

While body shell stiffness of the soft top model is nearly the same whether the top is open or closed, with the MX-5 Roadster Coupe, body shell stiffness is slightly higher with the top up than when it is down. To compensate for this slight difference, developers attempted to keep the difference in perceived handling feel as minimal as possible.

Larger Front Stabilizers and Optimized rear Springs and Dampers Settings

Because there is slightly more weight at the back of the Roadster Coupe when the hard top is stowed behind the seats, engineers optimally tuned the rear springs and dampers. At the same time, a larger front stabilizer is introduced (increased in diameter from 21 to 22.2 mm) along with new settings for the front dampers.

These features give the Mazda MX-5 Roadster Coupe handling characteristics that provide further refinements compared to the agile and nimble handling characteristics of the soft top. This slight difference is ideally suited to the new model and meets the premium quality demands of its target customer.

continues... | Part Seven
Published 6 September 2006 Melanie Carter

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