caliper replacement

AP - Chris_B

You may call it what you like, but let's look at the facts (aside from the modest outside diameter difference):

Better rotor construction -- The OE disc has to comply with several conflicting demands, including vibration and noise, which Nissan's engineers require their supplier to solve. AND, they must do this at a suitable production cost. I think most people understand that the Akebono units are now where Brembo used to be due to a better (lower) bid.

1. 2-piece versus 1-piece disc: A properly designed 2-piece disc assembly will be lighter overall, have better thermal management properties and allow for much more uniform thermal expansion and centripetal growth. A 1-piece disc will "cone" at higher speed, especially when hot, by its inherent design. Coning is the out-of-plane dynamic when one side of the rotor is free to expand, but the other is restrained by a very stiff hat section. Rotor growth is necessarily out-of-plane, which is bad news for drivers who like to push their cars.
2. Cooling: The OE disc is made with a straight vane construction, the least effective vented design available from a cooling standpoint. This is done so that both left and right hand rotors come off the same tooling, reducing production costs. The most effective 2-piece rotor will have a curved-vane core with an air gap sized for maximum air flow. Expect cooling improvements of over 30% when moving to this type of construction.
3. Metallurgy and thermal post-processing: Again, low bid wins the day for OE. Most current OE rotors are made from an iron composition referred to as G1800 (or very similar). This is a cheap, relatively soft alloy that is known for good damping qualities -- meaning it is less likely to ring (vibrate) and squeal than some other variants. This is important to the factory as they don't want to keep servicing brake noise complaints under warranty. The downside is that G1800 wears a lot faster when used with aggressive pad compounds than other, more expensive iron choices. Sometimes manufacturers will increase the carbon content (like Brembo's "HC" blanks), which helps even more with damping, but is even further detrimental to wear. G1800 also responds less favorably to thermal post-processing, meaning they don't even bother doing it. The better iron alloys are well-served by post-thermal treatments, which ensure that repeated large thermal cycles are handled with very little, if any, permanent distortion.

If you don't need the extra thermal capacity and stability of a high-quality 2-piece rotor, then great! But then you really aren't asking much of the brake system. Staying the OE calipers, improving cooling (adding ducting) and using better brake fluid is likely enough for your driving style and the tracks you go to -- as well as being a more cost-effective solution. But moving to larger, more expensive calipers without also also substantially improving the rotors is largely an aesthetic exercise, despite the cooling challenges they are currently masking.

P.S. I think this pink background is permanently damaging my eyesight!

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Chris Bernal
www.facebook.com/APRacingBrakes.fb
www.stillen.com