No announcement yet.

Direction of rotation

This is a sticky topic.
  • Filter
  • Time
  • Show
Clear All
new posts

  • Direction of rotation

    I recently fitted a Goodwin Big Brake Kit V3 to my Miata. Can you confirm that the pink slip showing rotation direction is correct, as every other slotted rotor I've seen (on Mercs, Porsches and in Fred Puhn's Brake Handbook pg28 & 145) shows the opposite direction, ie outer edge of slot is trailing. Thanks

  • #2
    For high performance applications the slots and vanes (if curved) should always angle to the rear. The curved vanes must sweep rearwards to evacuate heat from the rotor, likewise the slots must angle rearward to evacuate brake pad dust.


    • #3
      That's what I thought. So why do your pink instruction slips show the opposite?
      Thanks Ian


      • #4
        Here is the source of reference:
        HP Books, Brake Systems - OEM & Racing Brake Technology by Mike Mavrigian & Larry Carley (1998) Page 141 (quoting from AP Racing)


        • #5
          The description in the image above makes sense: "Angled vanes must sweep rearwards to evacuate heat from the rotor, and slots must angle rearward to evacuate brake pad dust." Therefore both the vanes and the slots must angle in the same direction - rearwards - for the rotor to work most efficiently.

          However, the image shows the vanes and the slots angled in opposite directions, which seems to be a mistake in the drawing. More importantly to me, the RB two-piece rotors I just bought and am about to install in my Acura NSX also have vanes and slots angled in opposite directions.

          Honda's NSX-R came from the factory with the slots in the brake discs angled rearward (like the vanes in the drawing above), I assume to better evacuate the brake dust. I plan on installing my RB rotors the other way around, with the slots angled forward (therefore the vanes angled rearward) so that the cooling of the discs functions properly.

          It seems that if I mount the discs one way the cooling will be optimized and if I mount them the other way, the brake dust will be evacuated properly. Since the vanes and slots are angled in opposite directions, I can't have both. Do I understand this correctly?


          • #6
            Understand OE (Honda) or stock (aftermarket) rotors are all non-directional meaning with straight vanes, but RB upgrades and makes the rotors to directional (curved) vanes even for one piece rotor. Don?t know if you purchased one piece or two-piece rotors. However we all know the 'vane' direction is what important than 'slot' direction which is more cosmetic than any significance of performance and every mfgr / user are entitled to have their own opinion.
            As we stated in our previous answer if the rotors are non-directional or ?straight? vane you may install whatever you feel right but since RB rotors have curved vanes so you must install them as recommended.


            • #7
              Thanks for your quick answer. I'll install the discs for proper vane direction.

              In your New Development forum, I just had a closer look at the rotors you are going to use in your NSX Big Brake Kit (shown here). The CAD drawing has the vanes and slots angled in the same direction, not in opposite directions as they are in the two-piece rotors I just bought. Based on what was stated previously regarding brake dust evacuation, it looks like an improvement in the design.

              Are you making this change with all your curved vane rotors? Maybe I just bought some old stock.


              • #8
                Thank you for your query. The slot direction showing on the CAD dwg was incorrect and shall be corrected. The BBK slot direction will be made the same as yours ? Same way we have been making.


                • #9
                  The diagram on the RB website is also confusing. It is not obvious that the lines shown on the sketches are the external slots or internal vanes. They are curved, suggesting vanes, but I believe the rotation is wrong for them.

         of Rotation


                  • #10
                    We have just edited our web page to make it more clear.

                    For optimal performance follow these instructions:

                    DIRECTION OF ROTATION

                    - Ready to install. Final precision grinding and balance are done at factory.
                    - Clean friction surfaces with brake cleaner.
                    - Torque lug nuts to O.E. specifications. (Never over torque.)
                    - Follow break-in procedures if new pads are installed.

                    Note: The above direction of rotation is to show the surface slotting and/or drilling direction of straight vane rotors.

                    If the rotors are curved (directional) vanes the cooling vanes were made in opposite direction to these slottings for optimum performance as illustrated below:


                    • #11
                      I just received a set of your rotors which do not have curved vanes. They are not for a car listed in your curved application list, and from visual inspection, they sure look straight. As far as I can tell, the only directional characteristic of these rotors is the slots milled into the friction surfaces.

                      Is there another directional characteristic of these rotors that I have overlooked?

                      If not, then why does it matter which rotation direction they are installed with?

                      I am very curious about this, because it just looks wrong to have the slots oriented as recommended, and unless there's going to be a significant performance difference, I'd much rather install them in an orientation that doesn't look completely wrong and cause random people to ask if I installed them backward by mistake. I take my car to a few shows every year and I expect that I'm going to get tired of explaining this.

                      And if there is a rotation-dependent characteristic of these brakes, I'd really like to know what it is, so I can have an answer ready for the hordes who are sure to inquire.



                      • #12
                        The surface slots are made with an intention so that the rotors are installed in the same direction of rotation regardless it's a curved or straight vane.

                        It's just a recommendation so you can do whatever you feel is better. If someone ask you the same question you can give him the same answer.

                        Thank you for choosing RB products and good lucks with your shows.