Hello all, I have been looking to do this write-up for a bit of time now but have been busy.
Let's get started with the goods... here is a picture of my 2018 Mazda 3 with EPB, featuring the rear calipers off a CX-9 and rotors of a CX-5. Please excuse the poor framing/general shot, but these are fully functional. (The rotors are black zinc coated, NOT painted... that comes off after first usage
)
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Parts Used
TLDR Executive Summary
How did I get here? Well, I already have a CorkSport BBK up-front, and while I love the look of their rear BBK, I could not justify that pricepoint. I decided to look into other OEM+ options, and discovered through scouring a bunch of forums (mostly this one!) that any rear brake upgrades with the EPB are basically non-existent in terms of documentation.. or at best you find some comments that theorize a potential compatibility.
A common OEM+ rear brake upgrade for NON-EPB users is to slap CX-5 rear brakes in, but I wanted to go even larger to better match the front BBK and so this is what I found.
Mazda 3 Rear Rotor Diameter: 265mm
Mazda CX-5 Rear Rotor Diameter: 302.6mm
Mazda CX-9 Rear Rotor Diameter: 324.8mm
No one has officially documented the CX-5 or CX-9 brakes working with EPB, so I figured if I am already heading into uncharted waters we may as well go big.
The Mazda 3 uses a different EPB motor than the CX-5 & CX-9, which share the part and feature a different connector than the one found on our harnesses. I was able to find a set of OEM CX-9 rear calipers WITH the EPB included off a wrecked 2019 that only had 17k on the clock, for $70 each. The only thing these did not come with is the connector, as where I purchased them from would not cut anything off a harness. I was able to find a local CX-5 and snip the connectors off myself, paid $5.
I mocked up the CX-9 caliper bracket on my hub before sending them out for powdercoat, but made a mistake of not testing with a CX-9 rotor as well. Once I received my powdercoated calipers back, I went to mount up everything and found that the CX-9 rotor was making contact with the CX-9 caliper.
The CX-9 rotor does NOT work with the CX-9 caliper when used on our cars!
This is due to differences in the mounting location for the caliper on the hub between the Mazda 3 and the CX-9. On the Mazda 3, the OEM rotors are quite small so the mounting location is fairly close to the center of the hub... whereas on the CX-9 they are pushed out further to accommodate the larger diameter. This was a bit of a bummer as I originally wanted the largest rear rotors possible, but not the end of the world. What I ended up trying next was a CX-5 rear rotor, which funnily enough worked PERFECTLY and ended up utilizing 100% of the available rotor surface area. I have previously helped a friend with a manual parking brake 3 do a full CX-5 caliper & rotor upgrade, and we found that it is not even utilizing 100% of the rotor surface area. This is not the case when you pair the CX-9 caliper with the CX-5 rotor. It does not run off the edge at all, or encroach too far inward onto the top hat - the pad fits perfectly in the CX-5 rotor area. (Image below of initial test-fitting CX-5 rotor, see pad placement)
![Image]()
The photo above was still a mock-up at this point, in order to fully mount the caliper bracket the hub's OEM bolt passthroughs need to be drilled out larger to accommodate the larger CX-9 caliper bracket bolts. I do not have a picture of this unfortunately - but the metal is quite soft and can be drilled with a single drill bit in one-go as long as you use cutting oil.
Once you can mount the caliper bracket, all that is really left is to swap your existing EPB connector for the CX-5/CX-9 connector. You can choose to either de-pin it or cut and splice. It is only 2 wires, power and ground. I did not have a de-pinning tool so I just cut it off and wired the new one up.
From here, everything is just like normal! You can still enter and exit maintenance mode as you normally would, utilize the parking brake as normal, etc... as mentioned prior the EPB is just a simple power and ground - They know when to stop based on when they feel something in the way.
I chose to get fresh hardware including bolts, stainless braided lines, etc... the only bolts I could NOT freshen up were the CX-9 caliper bracket bolts. They are a very odd bolt, being quite large but also extremely fine thread. I ended up re-using those, everything else was replaced.
I really enjoy the improvement that this upgrade brings, both visually and functionally. The rotors are much larger and closer in size to the front BBK I have which looks great! Functionally, I can feel the car "squat" more evenly under hard braking rather than nose-diving toward the front, and I will be less likely to experience brake fade in the rear thanks to more mass available to dissipate heat through. The only real downside I suppose would be a slight increase in weight, but it is really not much more and so the benefits outweigh this cost.
Mazda CX-5/CX-9 Rear EPB and Connector View
![Image]()
![Image]()
Mazda 3 Rear EPB and Connector View
![Image]()
![Image]()
Let's get started with the goods... here is a picture of my 2018 Mazda 3 with EPB, featuring the rear calipers off a CX-9 and rotors of a CX-5. Please excuse the poor framing/general shot, but these are fully functional. (The rotors are black zinc coated, NOT painted... that comes off after first usage
)Parts Used
- 2019 Mazda CX-9 Calipers & Caliper Brackets (Any from 2016-2023)
- 2018 Mazda CX-5 Rear Rotors (Purchased mine from BrakePerformance)
- 2019 Mazda CX-9 Rear Brake Pads (Utilized Bosch QuietCast BC1934)
- CorkSport Stainless Steel Braided Rear Brake Lines (Can re-use OEM lines if you wish)
- CX-5/CX-9 EPB Motors
- CX-5/CX-9 EPB Connectors
TLDR Executive Summary
- CX-9 Rear Calipers with EPB are a confirmed fitment on the Mazda 3
- To utilize CX-9 rear calipers, you will need to use a CX-5 rear rotor - CX-9 rear rotor will NOT fit without a custom bracket (not worth it imo)
- Will need to drill out the OE passthrough on hub for the caliper bracket to accommodate the CX-9's larger bracket bolts
- Will need to utilize CX-9/CX-5 EPB motor AND their connectors (The connector can be de-pinned or cut and spliced, it is just power and ground)
- With this in mind and testing I have done, CX-5 rear calipers will ALSO work however they are smaller, and will NOT utilize 100% of the rotor surface area. Basically, the CX-9 rear caliper paired with a CX-5 rear rotor is the best combination
How did I get here? Well, I already have a CorkSport BBK up-front, and while I love the look of their rear BBK, I could not justify that pricepoint. I decided to look into other OEM+ options, and discovered through scouring a bunch of forums (mostly this one!) that any rear brake upgrades with the EPB are basically non-existent in terms of documentation.. or at best you find some comments that theorize a potential compatibility.
A common OEM+ rear brake upgrade for NON-EPB users is to slap CX-5 rear brakes in, but I wanted to go even larger to better match the front BBK and so this is what I found.
Mazda 3 Rear Rotor Diameter: 265mm
Mazda CX-5 Rear Rotor Diameter: 302.6mm
Mazda CX-9 Rear Rotor Diameter: 324.8mm
No one has officially documented the CX-5 or CX-9 brakes working with EPB, so I figured if I am already heading into uncharted waters we may as well go big.
The Mazda 3 uses a different EPB motor than the CX-5 & CX-9, which share the part and feature a different connector than the one found on our harnesses. I was able to find a set of OEM CX-9 rear calipers WITH the EPB included off a wrecked 2019 that only had 17k on the clock, for $70 each. The only thing these did not come with is the connector, as where I purchased them from would not cut anything off a harness. I was able to find a local CX-5 and snip the connectors off myself, paid $5.
I mocked up the CX-9 caliper bracket on my hub before sending them out for powdercoat, but made a mistake of not testing with a CX-9 rotor as well. Once I received my powdercoated calipers back, I went to mount up everything and found that the CX-9 rotor was making contact with the CX-9 caliper.
The CX-9 rotor does NOT work with the CX-9 caliper when used on our cars!
This is due to differences in the mounting location for the caliper on the hub between the Mazda 3 and the CX-9. On the Mazda 3, the OEM rotors are quite small so the mounting location is fairly close to the center of the hub... whereas on the CX-9 they are pushed out further to accommodate the larger diameter. This was a bit of a bummer as I originally wanted the largest rear rotors possible, but not the end of the world. What I ended up trying next was a CX-5 rear rotor, which funnily enough worked PERFECTLY and ended up utilizing 100% of the available rotor surface area. I have previously helped a friend with a manual parking brake 3 do a full CX-5 caliper & rotor upgrade, and we found that it is not even utilizing 100% of the rotor surface area. This is not the case when you pair the CX-9 caliper with the CX-5 rotor. It does not run off the edge at all, or encroach too far inward onto the top hat - the pad fits perfectly in the CX-5 rotor area. (Image below of initial test-fitting CX-5 rotor, see pad placement)
The photo above was still a mock-up at this point, in order to fully mount the caliper bracket the hub's OEM bolt passthroughs need to be drilled out larger to accommodate the larger CX-9 caliper bracket bolts. I do not have a picture of this unfortunately - but the metal is quite soft and can be drilled with a single drill bit in one-go as long as you use cutting oil.
Once you can mount the caliper bracket, all that is really left is to swap your existing EPB connector for the CX-5/CX-9 connector. You can choose to either de-pin it or cut and splice. It is only 2 wires, power and ground. I did not have a de-pinning tool so I just cut it off and wired the new one up.
From here, everything is just like normal! You can still enter and exit maintenance mode as you normally would, utilize the parking brake as normal, etc... as mentioned prior the EPB is just a simple power and ground - They know when to stop based on when they feel something in the way.
I chose to get fresh hardware including bolts, stainless braided lines, etc... the only bolts I could NOT freshen up were the CX-9 caliper bracket bolts. They are a very odd bolt, being quite large but also extremely fine thread. I ended up re-using those, everything else was replaced.
I really enjoy the improvement that this upgrade brings, both visually and functionally. The rotors are much larger and closer in size to the front BBK I have which looks great! Functionally, I can feel the car "squat" more evenly under hard braking rather than nose-diving toward the front, and I will be less likely to experience brake fade in the rear thanks to more mass available to dissipate heat through. The only real downside I suppose would be a slight increase in weight, but it is really not much more and so the benefits outweigh this cost.
Mazda CX-5/CX-9 Rear EPB and Connector View
Mazda 3 Rear EPB and Connector View
