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      01-09-2011, 11:58 PM   #1
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Exclamation RacingBrake 2 Piece Rotor Review!

As some of you know, I gave a pair of OEM rotors to a company a while back so they could produce a 2 piece rotor for the 335i. In November I received the 2 piece rotors and have had them on my car since.
What Company did I choose? I chose RacingBrake.

Why RacingBrake?

Becuase I was very impressed with their patented designs (which I talk about below), and I was impressed with their detail to making a quality product.

Every rotor is heat treated and gets put through a hardness test.
They use a hardness tester by applying a 2000kg load on the rotor with a 10mm ball to create an indentation in the rotor. After applying the load, they measure the width of the indentation making sure that the width is between 3.65mm to 3.15mm, which translates to 185-245 respectively on the Brinell hardness scale.







The OEM rotor was about 145 on the Brinell hardness scale and the Stoptech rotor was 171.
The RacingBrake rotors that I tested were 196 and 193.

Here is the Stoptech rotor after indented:



Why 2 Piece Rotors?
There are a couple reasons why 2 piece rotors are better than the standard 1 piece rotor.
First off, 2 piece rotors are made with an aluminum hat and a steel rotor. Since they have an aluminum hat, they are lighter than the single piece rotors and if or when there’s a time for a replacement rotor, you can purchase just the rotor and still use the same aluminum hat.
I weighed the Stoptech rotor (after a couple resurfaces) and compared the weight to the RacingBrake rotor (1 track day of use). The Stoptech rotor was 22.0 pounds (Figure i) and the RacingBrake rotor was 18.0 pounds (Figure ii). (Sorry for the bad pictures but I had to use a different camera for these pics)

Figure i


Figure ii



RacingBrake's Patented Designs

RacingBrake has a few patents and I’d like to talk about a couple of them:

2 Piece Rotors that Mount in the center of the disc

This is one of my favorites because when I saw this, I was very intrigued why other companies haven’t done this in the past. If anyone has seen a Brembo BBK rotor or a Stoptech BBK rotor, you will find that the hat bolts to one side of the rotor disc (Figure A). Most of these rotors have directional vanes so given the fact that they bolt to only one side then they can only be used on one side of the car.

Figure A


Racing Brake hats mount directly in the center of the disc and because of this the hat can be mounted on either side of the disc. This means that the rotor can be used on either side of the car (Figure B). If it is set up for the passenger’s side and you would like to change it over to the Driver’s side then all you would have to do is unbolt the screws, switch the hat over to the other side of the disc and then mount the bolts and you’re done.

Also, with the RacingBrake center attachment design, the air going through the rotors to cool can either come from the outterl side or the inner side where as the other rotors can only pull air from the inner side for cooling.

Figure B


Here are some more pictures that I took to show the way the rotors attach to the hat.




Convergent Vanes

Ever since disc brakes came about, manufacturers have done different things to try to keep the rotors cool. The vanes inside the rotor are important for cooling purposes. Directional curved vanes have been a very good design but RacingBrake noticed an issue with regular curved vanes.
Since the inner diameter is smaller than the outer diameter, vanes on other rotors have a smaller hole at the entry point on the inner diameter and have a larger hole for the air exiting (Figure C). This creates uneven disc temperature which causes warping.

Figure C


Racing Brake came up with convergent vanes, which makes the inner entry point the same size as the exiting point (Figure D). Because of this, the rotor temperature is much more even and there are more vanes which mean better structure. Some companies pride themselves on vane count, but there’s more to the number of vanes. Because of this variable vane count, RacingBrake has 36 inner vanes and 54 outer vanes.

Figure D


Open Slots

Let’s talk about some various rotor designs.
There are drilled rotors that look cool but they crack (Figure E).
There are slotted rotors but the slots build up with debris and clogs the slot.

Figure E




The open slots include the best of both worlds. The slots do a great job to help the hot gases escape and the holes provide a place for the hot gasses and debris to escape.



Testing

I installed my old Stoptech rotor to the passenger side of the car and had the RacingBrake rotor installed on the Driver’s side. I drove around and wanted to see if there was a difference with daily driving. There was no difference with driving around the street but I went through a bedding process and noticed that my car was starting to pull to the left after about the 4th bedding cycle. It got more and more noticeable the hotter the pads started to get.
I believe that having each rotor installed at the same time was ideal because both rotors are being put through the same exact experiences. I first thought of doing the test of both Stoptech rotors first and then installing the RacingBrake rotors afterwards and doing the same test but This leads to more errors since the braking conditions could slightly change between tests.

I also started to think about the heating from side to side so I got home from work one day and took the temperature of both rotors.
The Stoptech rotor had a temperature reading of 134.4 degrees (Figure F).
The RacingBrake rotor had a temperature reading of 105.9 degrees (Figure G).
This also showed me that the RacingBrake rotor stays cooler than the Stoptech rotors.

Figure F


Figure G


Track Testing
I went to Laguna Seca on Dec 31 to put these rotors to the real test. I was so amazed with how easily they cooled between each turn. I was used to braking at certain points in the past and I could have easily braked much later than what I was used to. There were actually times where I braked just before the corkscrew and had to let off of the brakes for a bit and then hit the brakes again. That’s how well these rotors cooled down.

Here is one of my videos from my track day:



Conclusion

So, I think you’ve figured that I am very impressed with these rotors by now. It’s amazing to me with how well they stop and how well they are made.
There’s been a lot of thought and engineering that was put into these rotors and after using and testing them, it’s very noticeable.
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      01-10-2011, 02:26 AM   #2
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NIce review as always Mr. 5!! You ever rememver to ask for me if the rotor fit 335xi with no prob ?
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      01-10-2011, 03:02 AM   #3
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What pads are you running?
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      01-10-2011, 03:47 AM   #4
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Sweet review man... So r you going to buttomwillow on the 29-30 from speedventures, if so I would love to see them in person great vid aswell....
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      01-10-2011, 03:53 AM   #5
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Always good info!!
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      01-10-2011, 05:39 AM   #6
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Have they ever done an FEA Analysis of the slotted areas with the integral thru holes to see anticipated stress and breaking point at the very thin web that is left?

I understand the concept and the reason for this design, but in the case of just slots alone - the slots may be 1/16" deep out of the total 1/4" thich rotor surface, or in the case of thru holes alone, you still have the total 1/4" thickness - weak point would be between the holes.

But with this design, you have the depth of the slots (which looks to be more than 1/16") and then they drill out the web thickness that is leftover even more with the thru holes - resulting in a very thin web that is actually left between the holes at the bottom of the slot.

These areas will be very prone to cracking in the thin web area between the thru holes in the slots. You may get away with it on street only brakes - but I wouldn't use them for continous hard track use without having the results of the FEA prove a safety factor of at least '4'

I also understand the concept behind the centrally located hat mounting tabs - so that you can switch the directional rotors side for side - but why would you want to?

Only reason I can think of is if say you had a damaged right rotor - you could swap over the left rotor and only need to buy (1) replacement rotor - but normal practice is to replace rotors in pairs...

Not tryin to bash their design - just throwin some observations out there.
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      01-10-2011, 10:45 AM   #7
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Quote:
Originally Posted by acnhdernegw View Post
NIce review as always Mr. 5!! You ever rememver to ask for me if the rotor fit 335xi with no prob ?
Sorry, but I guess it slipped my mind.
If the 335i rotor is the size as the 335xi rotor then I don't see an issue.

Quote:
Originally Posted by 1QuikWS6 View Post
Have they ever done an FEA Analysis of the slotted areas with the integral thru holes to see anticipated stress and breaking point at the very thin web that is left?

I understand the concept and the reason for this design, but in the case of just slots alone - the slots may be 1/16" deep out of the total 1/4" thich rotor surface, or in the case of thru holes alone, you still have the total 1/4" thickness - weak point would be between the holes.

But with this design, you have the depth of the slots (which looks to be more than 1/16") and then they drill out the web thickness that is leftover even more with the thru holes - resulting in a very thin web that is actually left between the holes at the bottom of the slot.

These areas will be very prone to cracking in the thin web area between the thru holes in the slots. You may get away with it on street only brakes - but I wouldn't use them for continous hard track use without having the results of the FEA prove a safety factor of at least '4'

I also understand the concept behind the centrally located hat mounting tabs - so that you can switch the directional rotors side for side - but why would you want to?

Only reason I can think of is if say you had a damaged right rotor - you could swap over the left rotor and only need to buy (1) replacement rotor - but normal practice is to replace rotors in pairs...

Not tryin to bash their design - just throwin some observations out there.
I'll talk to them about the FEA analysis, but there hasn't been a cracking issue with this design, but for reference, this picture is after 6k miles of driving and a track day at Laguna Seca (which I believe is pretty hard on the brakes).



Also, you are somewhat correct with the center mounting. If you need to use them on either side then you can, but look at how the air can enter the inner diameter of the rotor. If the hat bolts to one side then usually the air flow (for cooling) can only enter from the inner side of the rotor.
Since RacingBrake mounts in the middle, the air entering the rotor can be drawn from the inner side or outer side.
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      01-10-2011, 11:29 AM   #8
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Very Informative!

Awaiting Mr Hacks response... lol
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      01-10-2011, 12:59 PM   #9
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Quote:
Originally Posted by acnhdernegw View Post
NIce review as always Mr. 5!! You ever rememver to ask for me if the rotor fit 335xi with no prob ?
Coupe, sedan, and AWD versions of the 335i all share the same part number(s) for rotors.

Quote:
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Very Informative!

Awaiting Mr Hacks response... lol
Well...Now you know why I am so passionate about RB products. My experience with their rotors have been far more positive than just about any other brake products I've used in the past.
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      01-10-2011, 01:02 PM   #10
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What pads are you running?
I think he's running the Cool Carbon pads (correct me if I'm wrong though Mr. 5).

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      01-10-2011, 01:25 PM   #11
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Awesome review...i'll most likely go with these once time comes to change...still on OEM rotors but 2nd set of pads
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      01-10-2011, 05:44 PM   #12
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I think he's running the Cool Carbon pads (correct me if I'm wrong though Mr. 5).

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Yep, I'm still using the Cool Carbon brake pads.
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      01-10-2011, 06:33 PM   #13
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you're on fire this week with tests and reviews

Correct me if I'm wrong - aren't these only available for the front at the moment?

Last edited by ciomas; 01-10-2011 at 06:53 PM.
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      01-10-2011, 06:38 PM   #14
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Great review. Now I want them even more, hoping the 135i fitment will be ready by April.
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      01-10-2011, 08:32 PM   #15
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Quote:
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you're on fire this week with tests and reviews

Correct me if I'm wrong - aren't these only available for the front at the moment?
Thanks man!
The rears are being developed as we speak.

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Great review. Now I want them even more, hoping the 135i fitment will be ready by April.
Yep, they picked up the 135 rotors a while back and those are next.
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      01-11-2011, 04:02 PM   #16
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Thanks man!
The rears are being developed as we speak.
great! Ill get a set of 4 once they are all available
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      01-11-2011, 07:47 PM   #17
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Quote:
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you're on fire this week with tests and reviews

Correct me if I'm wrong - aren't these only available for the front at the moment?
Fronts are available and will starting shipping in 3- 4 weeks. RB has agreed to give 20% discount for pre-orders only, once the rotors start to ship, pricing will go back retail pricing only. There is incentives to order them ahead of time.
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      01-11-2011, 08:14 PM   #18
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so your saying the preorder price is 899.94 with 20% off so 719.95 for two front rotor, or is the 899.94 already with the 20% discount applied?
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      01-11-2011, 08:44 PM   #19
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Quote:
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Fronts are available and will starting shipping in 3- 4 weeks. RB has agreed to give 20% discount for pre-orders only, once the rotors start to ship, pricing will go back retail pricing only. There is incentives to order them ahead of time.
Not a bad idea. Bring the price per rotor down to what, around $359? Set of fronts for $~$720?

That's a killer deal. Cost a little bit more than OEM replacement, but you get nearly twice the serviceable life.
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      01-12-2011, 12:24 AM   #20
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Quote:
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so your saying the preorder price is 899.94 with 20% off so 719.95 for two front rotor, or is the 899.94 already with the 20% discount applied?
$899.94 is before the discount. The forum thread and our web store will be updated by tomorrow.
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      01-12-2011, 11:30 PM   #21
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Not a bad idea. Bring the price per rotor down to what, around $359? Set of fronts for $~$720?

That's a killer deal. Cost a little bit more than OEM replacement, but you get nearly twice the serviceable life.
That is a really good deal.
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      01-12-2011, 11:38 PM   #22
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What pads would you guys recommend with these? Harold pm me price shipped to Canada (you should have my address)...my rotors are going very soon, originals with 82,000km on 2nd set of pads since ~47,000km..I'll need rears too so I should probably wait until those are done as well
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