RPMs rating is irrelevant... that increases and decreases with the vehicle's physical speed, not affected AT ALL by the engine speed. It does have a greater resistance to the rotational stresses and dampens shocks better than steel (aluminum is horrible at this). The biggest benefits though are weight (reduced rotational mass) and the fact that if it does fail it just turns into a broom, not a 13LB metal spear coming up through the rear seats or hatch... or the following traffic's windshield.
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