Πολλοί ισχυρίζονται ότι βάζοντας hardtop, αυξάνεται η ακαμψία του αμαξώματος. Είναι αλήθεια? Η σύντομη απάντηση είναι σαφώς όχι. Η αναλυτική -και επιστημονικά τεκμηριωμένη- απάντηση έρχεται από δύο guru του ΜΧ-5:
Lance Schall
I’d like to point out that the hardtop does not stiffen the chassis. If improves NVH by reducing wind noise, dampening windshield header/A-pillar shudder, etc. This can improve the perception of chassis stiffness. The distinction is important as the path to achieve the same experience without the top installed should focus on NVH, not mechanical stiffness. Shock tower bars and FM butterfly have a positive effect on NVH and well as a possible improvement to stiffness. However, you might find that dynomat on the trunk lid and rear deck will have more of the desired effect than hanging every brace you can find on the chassis.
Δηλαδή μιλάμε για placebo effect λόγω της μείωσης του NVH (Noise, Vibration, and Harshness ).
Bob Hall
Like the soft top, the hardtop is an unstressed component. If the hardtop were carrying structural loads, the rear window would pop out of its mountings as the bodystructure flexed by any degree.
The top is able to dampen (slightly) some of the lateral movement of the windscreen header, but the primary reason behind this is that with the top up the visual contrast between header and sky is diminished. With the convertible top raised, the multi-component aspects of the top induce rattles which the single-piece hardtop doesn’t have, thereby creating the impression that the hardtop has stiffened the car vis-a-vis the erected convertible top or with the top down.
The car’s torsional rigidity was measured in all three planes (as a body-in-white as well as a completed car) with the top down, top up and the hardtop on and there were no appreciable differences in the figures.
I don’t question that it may feel stiffer, but this is much more an example of the placebo effect than one actually reducing the bending moment of the car, I’m afraid.
To hardtop λοιπόν είναι unstressed component.
Longitudinal deflection of a complete car (not the body-in-white) fore/aft with the hardtop is reduced 0.010435 percent when the hardtop is in place vis-a-vis the car with the top lowered.
Transverse deflection of a complete car left/right with the hardtop is reduced 0.031004 percent when the hardtop is in place vis-a-vis the car with the top lowered.
Τorsional deformation along the centerline of a complete car is reduced 0.029666 (…repeating decimal) percent when the hardtop is in place vis-a-vis the car with the top lowered. If you said 0.03 percent you’d be fine.
Δεύτερο δεκαδικό… Μιλάμε για φοβερή διαφορά. Και όλα αυτά σε ΝΑ, το οποίο είναι το πλέον “εύκαμπτο” miata.