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Old 01-08-2016, 12:43 PM   #1
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Default RacingBrake rotors vs AP Racing J hooks

Originally posted by Corvette Forum member here:
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Old 01-08-2016, 01:02 PM   #2
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Default Vane Count

Statement from JRitt@essex: “Vane Count – AP Racing C7 Z51 J Hook discs have 72 vanes, vs. what appear to be 24-48 on the RB discs. More vanes increases airflow and disc face stability.”

Our response:

Vane count for most brake manufacturers (including AP) is based on single count (ie. 48, 52, 72 etc.), however RB’s cooling vanes are variable between the inner and outer rotor edge (typically 36 inner and 54 outer) to optimize the cooling effect. The traditional single vane count is certainly not the primary factor for rotor cooling; the design of how to effectively cool the disc is what really "counts".

Convergent vane: RB's patented design USPO#7,568,560

RB’s convergent vane design utilizes wide inlets and narrow outlets. Velocity of airflow increases as it enters through wide inlets, and exits through narrow outlets. Wider inlet can maximize the airflow at lower pressure, while its velocity decrease through (more) cooling vanes to absorb more heat from the disc before exiting to the outlet.

Conventional or competitions' "single vane count" design has a flaw in which due to the rotor outer diameter is larger than inner, so it ends up being "Divergent" vane which is opposite to optimizing the air flow for effective cooling per Bernoulli's principle illustrated below.

Benefits of the convergent vane design can be supported and better understood with review of Bernoulli’s convergent duct principle.

Bernoulli's theorem states: "When a gas or fluid is flowing through a convergent duct (as in nozzle stator vanes or venturi), its speed will increase and its temperature and pressure will decrease.


Heat removal = (t2 - t1) * air flow
t1 = Inlet air temperature
t2 = Outlet air temperature
Assume the air flow and inlet air temperature are constant, we want the outlet air temperature to be as high as possible to maximize the cooling effect.

RB's convergent vanes optimize the cooling effect not only can remove more heat and keep the disc cooler but result a more uniform disc temperature across the braking surface which is essential to keep the rotor from warping and cracking.

Real rotor casting:

Learn more on various vane design here:

The Convergent vane benefit was observed by the competition (Alcon):

Typical competitions' design - Stoptech's Aero Vane:

The advantage of RB two piece rotors last more than 20 track days and run 100-125 deg F cooler was officially recognized and reported by an NSX track racer in 2006.

2 piece nsx rotors for oem calipers
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Old 01-08-2016, 01:43 PM   #3
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Default Air Gap

Statement #2 from JRitt@essex: “Air Gap- AP J Hooks have an open path for the air to flow through the vanes. If you look at the RB discs, their hat attachment points block a considerably portion of the disc. The flanges on the iron rings cross over the area where air enters the internal vanes, blocking airflow. The only places where the air isn't at least partially obstructed is in between hat attachment points, which is less than 50% of the disc (there are 9 gaps between the 10 hardware attachment points).”

To be more precise, this comparison of “air gap” here is referring to the difference of how a disc is attached to the rotor hat and how it impacts the air flow.

There are two types:

Conventional/Competitions' Surface Mount:
  • Air circulation is limited as this type of mount admits no cold air from outboard* (spoke side) while the inboard is usually blocked by dust shield. (inboard).
  • Stress load is unbalanced as the load center is on the outer friction surface where the hardware connects.
  • Heat load to hat is solely from outboard disc surface and is unbalanced.
  • Heat transfer is directly from outer disc surface to rotor hat which heats up rotor hat more rapidly.
RacingBrake Center Mount: (RacingBrake’s Patented design)
  1. More efficient air circulation – Center mount provides air inlets from both inboard and outboard sides.
  2. Heat load on rotor hat is balanced from both sides of friction surfaces.
  3. Heat transfer from disc surface to rotor hat is greatly reduced due to longer distance of mounting tab to travel.
  4. Stress load is balanced due to the mounting surface being at the center plane of the disc.
  5. RB disc can be assembled to either left or right by flipping the hat, without having to identify whether left or right like surface mount. This can save your inventory cost and head-ache and avoid mix-up in assembly. Uni-directional disc is a truly remarkable design that tuning shop and track enthusiasts appreciate.
  6. Change of disc thickness will not affect the offset (unlike surface mt which the offset will change according to disc thickness), so same hat can be used for different duty discs (eg. 34mm for track and 30mm for street).

* Stoptech has a directional hat design to improve the air flow. This design requires 4 P/N for a set of rotor (2 for disc, 2 for hat), while RB only needs 2 P/N (1 ea for disc and 1 ea for hat).

Other manufacturer also has the similar idea with unique hat design to achieve the same purpose (allowing more air to flow from outboard side of rotor):

But the problem is the air doesn't travel in angle so the ventilation effect is very limited.

The benefit of Center Mount design was observed by Brembo's when they started shipping this "Dual Cast" rotors for CTS-V although their discs are not replaceable, and many other applications since (BMW, Corvette, MB, Porsche etc.)

RB’s Center mount two piece rotor is still the best design in the performance industry.

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Old 01-08-2016, 01:52 PM   #4
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Default Slot Design

Statement #3 from JRitt@essex: “Slot Design- AP's J Hook slot pattern distributes heat far more evenly around the disc than a conventional slot pattern, which leaves cold spots between slots. The J Hook reduces stress across the disc face when heated, and also promotes more even pad distribution.”

It's up to AP to substantiate their claim of benefit on their "J Hook" or may be they can comment on some of the draw backs stated below on surface slots.

RB uses “OPEN SLOT" design, Open slot is also a pattern design bu RB far from conventional slot pattern and offers the following benefits:[/b]
  • It combines the advantages of both drilled & slotted rotors, but our slots never disapper like the competitions' surface slots as the discs wear down.
  • Allows the disc to expand and contract via those oblong thru slots and minimize the disc from warping and cracking during heat cycles.
  • Increase cooling area (vertical wall of slots) while retains more friction surface.
  • Slots relieves thermal stress.
  • Slots are self cleaning and avoid pad debris build up as seen on conventional surface slots not it will clog those drilled holes and keep the disc surface clean all the time.
  • The brake dust can exhaust via those open slots to wheel barrel instead bouncing to spokes and keep your wheels cleaner.
  • Reduces brake pad dust buildup and keeps the wheel clean through vacuum effect.

Surface slots with debris build-up, or slots disappear:

Drilled holes cracks and clogged:

Our disc finish design merits are explainable, easy to understand and above all importantly they work.

Related info: slot.jpg
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Old 03-02-2016, 09:18 AM   #5
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Old 03-02-2016, 03:43 PM   #6
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Default Best 2 pc light weight rotor for grand sport...

Best 2 pc light weight rotor for grand sport...

We just replied to this thread here which related to this discussion:
Racing Brake rotors vs AP Racing J hooks

Since AP representative presented AP rotor design and had some critics about RB design which not only doesn't hold the ground but can be misleading. So we like to present our design principle* and why they work better, and leave it to members' judgement.

We expect to post two more replies for this topic, so for those who are interested in learning more please follow above thread.

We appreciate the support and confidence that Corvette track racers placed on us since our release of two piece rotors for Z06 in 2006.

Thank you.


*Discussion is focused on design theory only than some brake incidents noted here.
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Old 04-05-2016, 09:47 AM   #7
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I simply replied to JR's comment about his comment on the design feature of AP rotors vs RB rotors
, although I wasn't sure if that's what AP really wants to engage into discussion.

It was anticipated that someone (especially from JR who initiated this comparison) can further question or extend the discussion on design feature after our 1st response (w/two more to post), so we stay on objective discussion in "DESIGN differences" and learn from it, than as if anyone was questioning how popular AP rotors were in professional racing teams, because it was not what the thread title was suggesting.

I although believe Corvette community is for weekend warriors, who spent their own money for the best value of their brakes, than those racing team drivers.

We can only speak for what our brakes are made for (aftermarket stock replacement) with the following facts:

RB offers the first aftermarket light weight two piece rotors for Z06 since 2006 (including other American muscle cars like Camaro, Mustang, Viper etc.)
RB two piece replacement rotors (including Z51) has the longest running history on Corvette community than any other competition.
RB makes more two piece replacement rotors (from Acura to VW) than all the competition combined.
RB and AP (represented by Stillen) co-exists in Nissan GTR community, as two top serious track racers' choice on brake rotors.
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