RacingBrake replacements for ACR-X rotor rings

[Longdaddy]

For the past several months, I have worked with Racing Brake to develop an alternative to Brembo’s “Wide Ring” ACR-X rotors. As many of you already know, ACR-X front rotor/pad configuration provides larger friction surface, and accommodates “D1001” shape pad. Brembo caliper, used as OEM on GenVI Vipers, is able to fit both “D968” brake pad (SRT-10/ACR) as well as “D1001” shape pad, so ACR-X setup takes advantage of that by utilizing a wider pad with a differently proportioned ring/hat combo.

I am happy to report that Racing Brake has finalized the development, and is now offering the “ACR-X” rotor ring as a direct replacement to Brembo’s ring. A number of pads are also available (D1001 is a common shape, and nearly any performance brake pad compound can be ordered from a variety of other vendors as well, of course).

The price is more than competitive as well. You can see for yourself here: http://www.racingbrake.com/Rotor-rin...406-10-311.htm

Here is some background on how this came about, as well as details on the setup.
Brembo Motorsports 2-piece rotor unit that is supplied with ACR-X, and can be purchased for non-X cars through vendors dealing in Brembo Motorsports parts, is a good rotor that will stand up to heavy track use, as well as repeated high temperature cycles. It does, however, have some disadvantages, mostly centered around noise/vibration during low speed driving (which increases significantly with track heat cycles), and somewhat abrupt initial torque – especially pronounced when using “cold” pads/rotors at track speeds – something that really surprised a couple of drivers that had a chance to try out my ACR. It also wears front pads very aggressively, likely due to material hardness, as well as “J groove” geometry.

Ever since I got the ACR-X rotor setup from PartsRack, I have been looking for an alternative ring which would retain larger pad, can be used with the Brembo hat which I (and many others) had already, and could be a little “friendlier” to street driving in terms of noise/vibration as well as compatibility with dual use pads. So, when the idea of adapting existing line of RB rotor rings to fit ACR-X hats was brought up by Racing Brake, I thought it would be a perfect way to achieve this. I have used their rings in the past, on several vehicles* and always thought they offered a solid value for my money, unlike, for example, StopTech hardware 
I am happy to report that the latest version of the rotor which I test fitted last week appears to be a perfect fit for the Brembo Motorsports “ACR-X” hat (I believe an alternative hat is under development as well)

One thing I like about Racing Brake rings, is that the hardware is much simpler. Neither a washer, nor locking compound are required for the assembly/rebuild, and you can use “normal” 8mm socket instead of 4mm hex bit. If you have destroyed multiple 4mm hex bits and ran out of thread locking compound while rebuilding your rotors (especially at the track!) – you will understand why this little detail can make a big difference.
I am really looking forward to testing these rotors (as well as Racing Brake pads I have) at the racetrack; I am hoping to get the car out in the first weekend of December. On the street, they have been working great so far.

*Racing Brake offers StopTech ring replacements in ACR/SRT-10 sizes as well – which are superior in every single aspect of both track and street use to StopTech units, in my experience.

RacingBrake (left) vs Brembo rings
BremboVsRB.jpg

Mounted with ACR rim & Hoosier R6
mountedACRrim.jpg

clearance between pad and hat
PadHatClearance.jpg

Hardware comparison (RB on the left)
RBvsBremboHardware.jpg

Comparison with stock rotors and D968 shape pads
RBvsST.jpg

[FLATOUT]

Excellent post! I'll definitely keep these in mind when it's time to replace the stockers!

[XSnake]

Since you said they made Stoptech replacements I'm guessing the RB rotor will work with a Stoptech hat?

[Longdaddy]

Correct. I only see hat+ring listed on the website at this point, but I know for sure they sell just the ring as well (I have been running that ring on the ST hat in the rear). Let me work on getting the direct link to that.

[Longdaddy]

here it is (StopTech replacement):

http://www.racingbrake.com/355x32mm-p/14041-311k-02.htm

[Longdaddy]

I've tried these out on the track (as well as RacingBrake XR5 pads in the D1001 configuration) last Saturday, and they work as advertised. It was a cooler, damp day, so I cannot speak to rotor performance in "maximum stress" conditions. The rotors looked as expected at the end of the first day with a couple of hard cycles, and another couple of easy ones. Some material transfer from new pads, no heat checks/cracks, low wear on rotors, moderate wear on pads (I probably could have bedded in new pads a little better - I just drove on them to work and back prior to taking the car to the track)

In any case, the rotors had same predictable bite/modulation characteristics as earlier versions I tried in the summer, which was really nice on the track with braking zones that still had remains of a major "oil spill" from 2 weeks ago. Actually, braking zones were the only areas where I felt I could really push the limits of the car - everywhere else I was basically tip-toeing around very slick track that already ate up a car earlier in the morning, and nearly bruised mine in the second session out!
So, all in all, I am happy with this product.

http://www.youtube.com/watch?v=unrMYq1ETTU

frontstraight.jpg

[Longdaddy]

I have now done 5 events on these rings, and they had held up admirably - no issues at all. I've driven the car around the block a few times after the last day and I am happy to report that there is no shimmer/vibration at all that I can notice (Brembos would have been a little rough at this point, and StopTechs would have been warped to the point of being unusable). I have been using RB XR7 pads for the last few events. Set my new personal best at 2 tracks while running this setup as well (although these are the tracks I've driven the least with this car in the past few years)

[JonB ~ PartsRack]

LD, Your vid does not show the STEEP elevation drop in the 2-3 Esses! PartsRack is happy to have our decal on your bionic banana, and thanks for your feedback. We DO have a distributorship with Racing Brake since 2010....and PartsRack can provide these products to serious track-rats like you.

[Getnlwr]

So these larger rings and pads fit on ACR hats? As in... bolt on slightly larger brake rotors and still use the oem caliper. Sounds... intriguing.

[Back In Black]

So these larger rings and pads fit on ACR hats? As in... bolt on slightly larger brake rotors and still use the oem caliper. Sounds... intriguing.

No. These are replacement rings for the ACR-X big front Brembo rotor. They will not fit on the street ACR hat.

Yes, you still use the oem caliper with the ACR-X rotor and larger pad.

[Getnlwr]

Gotcha, Need the ACR-X hats to make this work.

[Racingbrake]

RacingBrake joined this community via a new ACR-E owner we met at rennlist who was looking for CCM replacement (CCM or iron conversion), and we are now proud to be an official sponsor of this forum.

Please allow me to clarify about two different rotor set up abobe:

ACR Stoptech two piece uses a shorter pad (D968) with 50mm lining height. ACR-X Brembo uses a taller pad (D1001) w/60mm lining. These traditional two piece rotors are fastened together (disc and hat) with different PCD (pitch circle diameter), so both replacement discs are not interchangeable as the rotor hats are specific.

Stoptech replacement rotor ring: http://www.racingbrake.com/Rotor-rin...04-311k-03.htm

Brembo replacement rotor ring: http://www.racingbrake.com/Rotor-rin...406-10-311.htm

Both of them are in our standard replacement disc program and are in stock.

We are pleased to propose our US patented center mount design two piece rotors which can be accept both brake pads with one hat and one ring.

A very good idea to "Replace" and "Upgrade" at the same time



We also offer a complete 4 corner light weight two piece with bundle price here:
http://www.racingbrake.com/RB-Two-pi...dod-irk-02.htm

These are made for severe track duty similar to what we offer for Corvette Z06, Mustang and CamaroSS stock replacement that are considered to be the most durable and cost effective upgrade to stock set up.

Since we have to make new hats for this set up so there is a leadtime (Pre-orders can be expedited to 6-8 weeks).

http://www.racingbrake.com/Two-Piece...r-A-p/2343.htm

We are also capable of building an upgrade BBK (380 or 390mm rotor kits) with our 6-pot/4pot caliper kits. These front pad will have 65mm lining height (same as Corvette ZR1, or Nissan GTR, or Mustang GT500, depending on the rotor sizes).

We look forward to serving your brake needs.

Thank you.

Warren-RB

[FLATOUT]

Well that sucks I thought these would bolt right onto the stock ACR hats. This just became less appealing lol.

[Getnlwr]

Ya. How much are ACRX hats?

Paging JonB... Paging JonB...

[Back In Black]

ACR-X Brembo rotor and hat on left, ACR Stoptech Aerorotor (ring only) on the right.

[XSnake]

Not a bad price on the replacement X rotors. I just bought a new Brembo pair myself.

[Racingbrake]

Here is the difference of two brake pads:



Top one is for ACR-X, bottom one is for ACR. As you can see the top one ACR-X pad with 60mm has a substantial larger pad area than ACR's 50mm to keep the braking temperature down (lower wear rate) for the same brake force applied, and is more beneficial especially for track application.

BTW, the top one is the same as CamaroSS and Mustang front and ZR1 (CCM rotor) rear, while the bottom one is the same as Brembo F40 and GTR rear calipers.

[Getnlwr]

Sooo, the question I asked in 2013... we can now have the ACR-X sized rotor rings, on a stop tech hat, for better and stronger brakes. . .?

[WDW MKR]

Sooo, the question I asked in 2013... we can now have the ACR-X sized rotor rings, on a stop tech hat, for better and stronger brakes. . .?

Did you read the posts?

...so both replacement discs are not interchangeable as the rotor hats are specific.

[Getnlwr]

Got confused at some point. Damn. If they only made the X ring to fit on the stop tech hats.

[WDW MKR]

You can't... the increase in swept area of the ACR-X rotor is made possible by reducing the hat diameter (219.2mm vs 242mm), thereby reducing outer ring ID. Both rotors are still 355mm OD to fit within the caliper mounting geometry. To gain swept are with the non-X hat, you would have to increase overall OD and move the caliper out.

[Racingbrake]

Well interpreted. Unlike RB's center mount design, traditional surface mount rotors (Brembo, Stoptech etc.) the mounting hardware is above the rotor surface which can interfere with the brake pad, so the hat/disc fastening PCD (Pitch Circle Diameter) must move (inward or outward) according to the pad bottom swiping area.

With RB center mount design, the same hat with same PCD can be assembled to two different discs with different annulus (friction width), but you don't have to swap the disc, just keep this heavy duty disc on, and swap either size of pad - This set up keeps your rotor at 355mm under 18" wheels.

However if you prefer to retain the use of OE hat, we have a disc (380x32) same as for Mustang GT500 that can be assembled to Stoptech hat (for original 355x32x53 disc), you will also need a 12.5mm caliper spacer that we can supply. This would be the same over-sized upgrade we offer for Audi R8 (365-->380) and TTRS (370-->380) - For this 380mm set up you will need 19" wheels.

RB has more brake solutions for your brake upgrades.

[Getnlwr]

Hey! Now we're talking...

I've been wanting to do a wheel upgrade anyways.

[Racingbrake]

Here is a picture comparing two different rotor rings (same diameter 355mm but different annulus) in "Longdaddy" first post.


One the right is for standard ACR with smaller pad, and the left is a rotor ring with wider annulus for larger pad (ACR-X)