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Rotor weight

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  • Rotor weight

    It's meaningless to compare the brake rotor weight w/o relating to the Volumetric Heat Capacity (CP,v , J⋅cm−3⋅K−1) which is the amount heat that must be added to "one unit of mass" of the substance in order to cause an increase of "one unit in temperature". As a substance of an iron therefore, the heavier of a rotor the more of it's heat capacity and conversely the lighter a rotor the less of its heat capacity.

    Only the volume of a rotor can truly represent it's weight, not the dimensions that customary used in expressing a rotor size (eg diameter x thickness - 390x36mm), for example you can make rotors with the same external dimensions but with variable friction plate thickness (A), and annulus (B) to achieve different "volume" and result in various rotor weights and heat capacity.

    Click image for larger version  Name:	2662-390x36.png Views:	0 Size:	221.3 KB ID:	11829

    To make the evaluation more specific and meaningful, the weight comparison shall base on the same material - Iron (not CCM) and construction - 2pc w/aluminum hat and iron disc (not 1pc)

    And here is a filtered result on 390x36mm iron rotors out of our some 700+ two piece rotor kits.

    Click image for larger version  Name:	390x36%20rotor.png Views:	0 Size:	338.2 KB ID:	11828
    These are OE rotor sizes for heavy and fast muscle cars with hundreds of thousands of vehicles, and spans decades of applications, so the data sample shall be sufficient to support my question on how sound for a "same size" of rotor made to 25% lighter, so that consumers (not intended for professional racers or alike) can better evaluate a brake set up (rotor, pad size and heat factor) than just the rotor weight.

    Rotor weight reduction is at the cost of losing its heat capacity and will run hotter at the same ratio, i.e. a 21 lbs rotor runs at 500C vs. a 28 lbs rotor at 400C - It's the fundamental science.
    Attached Files

  • #2
    Anti knock back spring - Is it needed?

    We have a collection of 240+ units of OE & Aftermarket fixed piston calipers including 42 units from Porsche (Brembo), and 6 units from McLaren (AP) and can never find one single caliper that's equipped with such a spring, so I can safely conclude, based on our decades of experience & knowledge in caliper business that this extra spring is not required.

    Anyone (including professional racers or alike) with "knock back" issue can rebuild one's OE calipers with RB components, or replace them to RB calipers and see for yourself if such a spring is ever required.