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Using Brembo 2-Piece 380mm Type 3 Rotor w OEM '13-'14 GT500 Caliper

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cholmes1

400lb Gorilla
350
216
Denver, CO
I am going down a rabbit hole with the Type 3 Brembo 2-piece rotors 380x32 for my 2013 GT500 caliper swap on my 2013 Boss 302 LS and am hoping for a greater explanation of why I have been repeatedly told that Brembo Type 3 rotors/rings cannot utilize custom hats and work with the OEM '13-'14 GT500 calipers?


For example, if you purchase the rotor rings separately and make custom aluminum hats, I see no reason why this would not work; that said, I am not an engineer and not nearly as skilled with brakes as many on this forum

If the OEM ’13-’14 GT500 rotor is 14.96"x1.26" or 380mmx32mm

Rotor Outside Diameter (in.): 14.96" = 380mm
Brake Rotor Bolt Pattern (in.): 5x 4.50"
Brake Rotor Bolt Pattern (mm): 5x114.30mm or 5x4.50"
Nominal Thickness (in.): 1.260" = 32mm

and the Brembo Type 3 rotor/ring is also 380mmx32mm or 14.96"x1.26"

Why would you not be able to take a custom hat CNC cut to the same/similar specifications as the OEM replacement hat sold by Baer for their 2013-2014 GT500 Eradispeed OEM rotor swap but use the bolt pattern from the Brembos (10 in ring circle as opposed to 12)? Especially given multiple Brembo race setups utilize the 380mm rotor. Even if a larger width ring was selected, like 34mm, you could adjust the pads, and it would fit.

Baer Eradispeed Hat Specifications
Wheel Bolt pattern 1: 5 x 4.50" or 114.3mm
Wheel Bolt Hole Diameter: .625"
Baer Rotor Bolt Circle: 12 x 8.500" (Cut to match Brembo Type 3)
Rotor Bolt Hole Diameter: .257" Through hole (Cut to match Brembo Type 3)
Hat Center Bore: 2.796"
Hat Depth: 0.235" (Likely a further adjustment point - but maybe not)
Hat Face Thickness: .300"
Mount Style: Fixed or Floating (Custom McClaren Hardware)
Material: 6061 T6 Aluminum

Has anyone made custom hats? I know they are more common in the kit market (Factory Five, etc.) ,but hoping someone has insights or some glaring aspect I am overlooking.


I like the Girodisc rotors, and having spoken with them yesterday, I know some very nice developments are coming this summer for all S197s (especially 2013-2014 GT500s) to enjoy. However, I still am confused why the multiple vendors I contacted stated custom hats of the Brembo Type 3 rotor could not be done with the OEM caliper.


I could understand vendors saying Type 3's are ‘not recommended for primarily street,’ a ‘waste of my time or money to make it work,' or even ‘possible but look, we sell XYZ, which is easier/better' but to say ‘it cannot be done' is confusing if the only limitation I can see for fitment is making certain the hat is perfectly aligned to the OEM '13-'14 GT500 caliper.

Any and all help/guidance is appreciated.
 
Last edited:
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1,240
In the V6L
It's probably a brake pad problem, not a rotor problem. The "depth" of the friction face of a brake pad, measured from outside edge to inside edge (furthest from the hub to closest to the hub), has to match the width of the face of the friction ring (the "annulus") of the rotor. OEM rotors tend to have a wide annulus while a lot of the "GT" type BBK's use a narrow annulus rotor. To make it all work, the pad has to match the rotor diameter and annulus and the caliper has to accept the pad. I'm guessing that the OEM caliper takes a wide annulus pad and the rotors you are trying to install will only work with narrow annulus pads.
 
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Thank you for that insight @JAJ

I will look and report back with more information. That is something I had not considered
You might want to check this out: https://www.racetechnologies.com/products/brakekits/2013/ford/mustang-boss-302-0?vehicle=8335

Race Technologies is the "Brembo Racing" factory rep in the USA. The kits on the site are "factory Brembo" sets for the professional market and they show up with a bill of materials, a QA checklist and no instructions. I had a set on my 2014 GT500 and they were absolutely bulletproof.
 

cholmes1

400lb Gorilla
350
216
Denver, CO
You might want to check this out: https://www.racetechnologies.com/products/brakekits/2013/ford/mustang-boss-302-0?vehicle=8335

Race Technologies is the "Brembo Racing" factory rep in the USA. The kits on the site are "factory Brembo" sets for the professional market and they show up with a bill of materials, a QA checklist and no instructions. I had a set on my 2014 GT500 and they were absolutely bulletproof.
Thank you. I am very familiar with Race Technologies. They have been a great resource for many of my projects and were consulted on this question.

Unfortunately, in this instance they could not or would not go into specifics for why the 380mm Type III would not work with the OEM caliper with a custom hat. They simply pushed me towards there race specific applications which are not appropriate for this project.

I will certainly research the pad and disc surface area (annulus) to see if that is a factor of concern.
 
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In the V6L
Thank you. I am very familiar with Race Technologies. They have been a great resource for many of my projects and were consulted on this question.

Unfortunately, in this instance they could not or would not go into specifics for why the 380mm Type III would not work with the OEM caliper with a custom hat. They simply pushed me towards there race specific applications which are not appropriate for this project.

I will certainly research the pad and disc surface area (annulus) to see if that is a factor of concern.
I thought this was an interesting question, so I did some digging and figured it out. It's a bit circuitous to get to the answer, but here goes:

1. What is the annulus on the Brembo GT rotor? Well, I went to Zeckhausen Racing - I trust Dave Z for technical information on brakes - and found a Stoptech direct replacement for the 380mm Brembo GT rotor. Specs are here: https://www.zeckhausen.com/catalog/index.php?cPath=82_1516_1518

According to the specs on the top of the page, the annulus is 51.5 mm. That was, until recently, a common size for racing rotors - anywhere from 48 to 52 was "normal".

2. So, what about the OEM 2013/14 GT500 pad? What's the pad depth? Once again, Zeck to the rescue. A pad outline for a pad that fits the 2013/14 GT500 OEM brake setup: https://www.zeckhausen.com/catalog/index.php?cPath=7426_7431_8024

You can confirm this if you go through his "find parts for your car" workflow, you'll find that pad is selected for the 2013/14 GT500. Depth is 55 mm, which is too wide for the Brembo rotor at 51.5 mm.

So, if you want a Brembo racing rotor that will work with OEM GT350 calipers and pads, this one looks like it'll work - 380x32, 65mm annulus: https://porterfield-brakes.com/product/racing-rotors/brembo-racing-rotors/380mm/xa29132/ The XA29133 is the other side. You might need a custom hat.
 
I am going down a rabbit hole with the Type 3 Brembo 2-piece rotors 380x32 (#1M39031A) for my 2013 GT500 caliper swap on my 2013 Boss 302 LS and am hoping for a greater explanation of why I have been repeatedly told that Brembo Type 3 rotors/rings cannot utilize custom hats and work with the OEM '13-'14 GT500 calipers?


For example, if you purchase the rotor rings separately and make custom aluminum hats, I see no reason why this would not work; that said, I am not an engineer and not nearly as skilled with brakes as many on this forum

If the OEM ’13-’14 GT500 rotor is 14.96"x1.26" or 380mmx32mm

Rotor Outside Diameter (in.): 14.96" = 380mm
Brake Rotor Bolt Pattern (in.): 5x 4.50"
Brake Rotor Bolt Pattern (mm): 5x114.30mm or 5x4.50"
Nominal Thickness (in.): 1.260" = 32mm

and the Brembo Type 3 rotor/ring is also 380mmx32mm or 14.96"x1.26"

Why would you not be able to take a custom hat CNC cut to the same/similar specifications as the OEM replacement hat sold by Baer for their 2013-2014 GT500 Eradispeed OEM rotor swap but use the bolt pattern from the Brembos (10 in ring circle as opposed to 12)? Especially given multiple Brembo race setups utilize the 380mm rotor. Even if a larger width ring was selected, like 34mm, you could adjust the pads, and it would fit.

Baer Eradispeed Hat Specifications
Wheel Bolt pattern 1: 5 x 4.50" or 114.3mm
Wheel Bolt Hole Diameter: .625"
Baer Rotor Bolt Circle: 12 x 8.500" (Cut to match Brembo Type 3)
Rotor Bolt Hole Diameter: .257" Through hole (Cut to match Brembo Type 3)
Hat Center Bore: 2.796"
Hat Depth: 0.235" (Likely a further adjustment point - but maybe not)
Hat Face Thickness: .300"
Mount Style: Fixed or Floating (Custom McClaren Hardware)
Material: 6061 T6 Aluminum

Has anyone made custom hats? I know they are more common in the kit market (Factory Five, etc.) ,but hoping someone has insights or some glaring aspect I am overlooking.


I like the Girodisc rotors, and having spoken with them yesterday, I know some very nice developments are coming this summer for all S197s (especially 2013-2014 GT500s) to enjoy. However, I still am confused why the multiple vendors I contacted stated custom hats of the Brembo Type 3 rotor could not be done with the OEM caliper.


I could understand vendors saying Type 3's are ‘not recommended for primarily street,’ a ‘waste of my time or money to make it work,' or even ‘possible but look, we sell XYZ, which is easier/better' but to say ‘it cannot be done' is confusing if the only limitation I can see for fitment is making certain the hat is perfectly aligned to the OEM '13-'14 GT500 caliper.

Any and all help/guidance is appreciated.
I don't understand why you would go through all of this? Not just purchase the GT500 rotors from Girodisc that fit the application?
 

cholmes1

400lb Gorilla
350
216
Denver, CO
I don't understand why you would go through all of this? Not just purchase the GT500 rotors from Girodisc that fit the application?

This a valid question and one I welcome. The Griodisc setup is excellent, and what they are releasing this summer is exciting and will be what I purchase. That said, when I initially began my search, the Brembo Type III rotor was my desired option, and to be told repeatedly that it could not be done served as motivation to find out why. Many thanks to @JAJ for going down the research path with me.

Similar to my Cortex rear axle posting that caused similar confusion, and even my current efforts to see if different hardware will work with the '13-'14 GT500 calipers, they are ways to explore options. The '13-'14 GT500 caliper and 15" S197 rotor are not very well supported in the aftermarket, so having more possible options for repairs, upgrades, and so forth only serves to help the community.

I liken this effort to steveespo findings on the S550 caliper working on the S197; we never know until we try.

All that said, Girodisc will certainly be what I go with but rest assured, I will certainly be trying this project out as well, and we will see what happens. If it works, we all benefit, and if it does not, my wallet and time were the only casualties.
 

cholmes1

400lb Gorilla
350
216
Denver, CO
Final Update - Thread can be closed if needed/deemed appropriate

I finally connected with US Brembo engineer Dani via George at Race Technologies to discuss a variety of Brembo rings, and the annulus and/or air gap are the deciding factors for why a Brembo 2-piece rotor ring cannot be used with the '13-'14 GT500 caliper. If one was correct, the other was way out of balance.

Girodisc really is the best player in this game for a race-spec 2-piece rotor for the '13-'14 GT500 caliper. While Baer and FullTiltBoogie offer 380x32 2-piece setups, they lack the thermal capacity to be effective in anything beyond street driving, though they are very lightweight. StopTech offers their 380x32 2-piece AeroRotor, which may be a bit more robust but still not on par with the Girodisc option.

The closest Brembo option to OEM was disc 09.A009.22 at 380x32 with a 65mm annulus, but the air gap is 20mm v OEM 12mm. Essentially, the disc is the same thickness as OEM (32mm), but the rotor wall is 8mm thinner, greatly diminishing thermal capacity.

Disappointingly, the rabbit hole I fell into came to an end without any positive results for the community. Thanks again to @JAJ for his insights. As I closed with previously, "If it works, we all benefit, and if it does not, my wallet and time were the only casualties." Fortunately, my wallet was spared, and my time learning the nuances of brake rotor construction and caliper pairing was worthwhile. I eagerly await the Girodisc releases this summer.
 

cholmes1

400lb Gorilla
350
216
Denver, CO
Any details on what Girodisc has in the works, or are you sworn to secrecy?
Not sworn to anything. Girodisc will happily confirm if you call them. Everything below is planned for launch this summer. No firm month given.

1) They are changing the grooves on the rotor face to improve cooling. I have not seen the design but they described them as ‘curved’

2) They are changing from the pale blue hats to black.

3) Most exciting for most, they are finalizing the production of a rear 2-piece rotor in the ‘13-‘14 GT500 size. This will allow those on 15” fronts to have a matched set in the rear.

They are guys at Girodisc (and Bellingham, WA) are great.
 
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2,111
Exp. Type
Time Attack
Exp. Level
5-10 Years
SoCal
3) Most exciting for most, they are finalizing the production of a rear 2-piece rotor in the ‘13-‘14 GT500 size. This will allow those on 15” fronts to have a matched set in the rear.
This is what I was hoping to see!! I talked to them a couple years ago and they didn’t feel there was enough demand to justify the tooling cost. I reminded them not to base their estimates solely on the 13-14 GT500 VIO numbers. The much bigger market is S197 track cars that have converted to the bigger rotors to keep heat off the axle seal and bearing. Thanks for sharing.
 

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