Mazda 6 Forums banner
21 - 38 of 38 Posts

·
Registered
2014 Mazda 6 GT - 6AT
Joined
·
17 Posts
Duh, youre right, but i still wanted to be sure. I dont feel i need more brake cause of the Z23 pads, but its nice to know this is a viable choice later on.
It did open up the EBC OrangeStuff, which I am excited to try out once they get broken in. I could not find that particular compound for the stock calipers, but there are tons of choices for brake pads in general.

Some other things to note about these calipers that came as a bit of a surprise. Pistons are phenolic, no metal options currently available that I have found (stocks M6 calipers do have metal pistons of some variety) One of the two slide pins rides in a rubber grommet / bushing (in the second photo you can see that rubber bushing on the lower left side of the bracket). On the stock calipers both are hard connections, metal to metal. I anticipate having the car out on Road Atlanta later this year and will give some feedback on how this setup does.

Automotive lighting Camera accessory Lens Cameras & optics Optical instrument
Automotive wheel system Font Auto part Rim Metal
 

·
Registered
Joined
·
3,380 Posts
These will clear all the stock rim sizes? (e.g. the 2015 Sport) and fit the existing factory caliper brackets?!

I might be willing to pop for those, although with the Powerstop pads I'm not sure I need anything more in terms of stopping or fade resistance for even very-spirited street use....
 

·
Registered
2014 Mazda 6 GT - 6AT
Joined
·
17 Posts
These will clear all the stock rim sizes? (e.g. the 2015 Sport) and fit the existing factory caliper brackets?!

I might be willing to pop for those, although with the Powerstop pads I'm not sure I need anything more in terms of stopping or fade resistance for even very-spirited street use....
They clear the 19" GT wheels. They clear 17" wheels on the CX-9, but I do not know if they clear the 6's OEM 17s. They do NOT fit the existing brackets. If you are going this route you will want to order the CX-9 calipers with the CX-9 brackets. I also went to CX-9 brake hoses when I did the swap.

What size discs are these. I've been looking to fit something bigger on mine as the standard discs are tiny.
12.6" (versus 11.7" stock)
 
  • Like
Reactions: Raymond

·
Registered
Joined
·
3,380 Posts
I'm gonna have to do some measuring as if those fit.... wow. The brackets bolt up to the knuckle eh? Now that's cool -- IF they clear the wheels....
 

·
Registered
Joined
·
91 Posts
Did you swap the rears too? You probably added a lot of brake bias to the front axle if not. It may feel fine in normal driving but once you get to the traction limit (in an emergency stop) you may find that you lock up the fronts much earlier than normal, so much that total braking capacity is reduced.
 

·
Registered
Joined
·
239 Posts
Very interesting!
Yeah, echoing bdc101 - I'm very very curious how that kind of front brake power increase will affect your brake balance.
Did you upgrade the rear brakes to the CX-9, too?
If I may ask, what did the junkyard parts run you?
 

·
Registered
Joined
·
5,058 Posts
Did you swap the rears too? You probably added a lot of brake bias to the front axle if not. It may feel fine in normal driving but once you get to the traction limit (in an emergency stop) you may find that you lock up the fronts much earlier than normal, so much that total braking capacity is reduced.
Theres no difference across the models, i looked. 70% of the braking is done up front anyways.
 

·
Registered
Joined
·
91 Posts
Theres no difference across the models, i looked. 70% of the braking is done up front anyways.
Then OP would need to replace the brake proportioning valve. If the original bias was 70% then OP just made it something like 85%. For his sakes I hope that ABS will take care of it in a panic stop, but I could not comment on how well it would be able to do that.
 

·
Registered
Joined
·
5,058 Posts
Then OP would need to replace the brake proportioning valve. If the original bias was 70% then OP just made it something like 85%. For his sakes I hope that ABS will take care of it in a panic stop, but I could not comment on how well it would be able to do that.
Show me ONE example of this causing an actual accident. Otherwise, stop spreading misinformation.
 

·
Registered
2014 Mazda 6 GT - 6AT
Joined
·
17 Posts
Did you swap the rears too? You probably added a lot of brake bias to the front axle if not. It may feel fine in normal driving but once you get to the traction limit (in an emergency stop) you may find that you lock up the fronts much earlier than normal, so much that total braking capacity is reduced.
I did not, since I have a manual parking brake (2014) it would take some doing to get the CX-9 rears on there. You are absolutely correct, this will have some impact on the bias. That is something I was a bit worried about when I started on this. After measuring pistons and rotors (and negating pad effect) it looks like the bias shift should be less than 10%. I didn't tear my rear brakes and a CX9s rear brakes apart to get all the numbers for an exact calculation. The CX9s front pistons are ~1.79" vs ~2.25" on the stock 6's single piston. So we are by no means doubling up in the front. The larger diameter rotor gives the brakes more leverage, but on a 0.9" change that impact is fairly small.

I find it interesting you are concerned about this small increase in front caliper piston area when there are BBKs out there fitting very sizable calipers to the front only on these cars. I have not done any math on their total piston area to compare to stock, but I have to assume it is quite large.

Do stock Mazda's have brake proportioning valves at all? If so, would you mind sharing the part number?
 
  • Like
Reactions: Raymond

·
Registered
2014 Mazda 6 GT - 6AT
Joined
·
17 Posts
Very interesting!
Yeah, echoing bdc101 - I'm very very curious how that kind of front brake power increase will affect your brake balance.
Did you upgrade the rear brakes to the CX-9, too?
If I may ask, what did the junkyard parts run you?
I paid ~$165 shipped for the front calipers and brackets. I found those on car-part. Then I got the hoses on rock auto for very inexpensive. Don't forget to factor in the pads and rotors and that's your swap cost. If you are super detailed oriented, I have heard the CX9 brake shields bolt up and they are a better fit for the rotor size. You should also be able to use front shields from a new turbo 6 since they share their rotor with the CX9. I just kept the stock shields for now.
 

·
Registered
Joined
·
91 Posts
I did not, since I have a manual parking brake (2014) it would take some doing to get the CX-9 rears on there. You are absolutely correct, this will have some impact on the bias. That is something I was a bit worried about when I started on this. After measuring pistons and rotors (and negating pad effect) it looks like the bias shift should be less than 10%. I didn't tear my rear brakes and a CX9s rear brakes apart to get all the numbers for an exact calculation. The CX9s front pistons are ~1.79" vs ~2.25" on the stock 6's single piston. So we are by no means doubling up in the front. The larger diameter rotor gives the brakes more leverage, but on a 0.9" change that impact is fairly small.

I find it interesting you are concerned about this small increase in front caliper piston area when there are BBKs out there fitting very sizable calipers to the front only on these cars. I have not done any math on their total piston area to compare to stock, but I have to assume it is quite large.

Do stock Mazda's have brake proportioning valves at all? If so, would you mind sharing the part number?
Thanks for providing the numbers. My math says you increased front brake bias by 37%. That includes 27% more piston area and 8% greater diameter, but I don't know the center of pressure of each caliper, so that is just a guess. Indeed that is not a 2x factor, which is good to know. Hopefully that is within the ABS system's ability to correct, when you reach limit braking. Regardless, you have still added a lot of turn-in understeer when you are driving at the limit, because the front tires will run out of grip sooner than the rears (due to the added braking force). Hopefully you are tuning that out with bars and sticky tires.

I do not know if the brake proportioning valve is replaceable or where it is.
 

·
Registered
2014 Mazda 6 GT - 6AT
Joined
·
17 Posts
Thanks for providing the numbers. My math says you increased front brake bias by 37%. That includes 27% more piston area and 8% greater diameter, but I don't know the center of pressure of each caliper, so that is just a guess. Indeed that is not a 2x factor, which is good to know. Hopefully that is within the ABS system's ability to correct, when you reach limit braking. Regardless, you have still added a lot of turn-in understeer when you are driving at the limit, because the front tires will run out of grip sooner than the rears (due to the added braking force). Hopefully you are tuning that out with bars and sticky tires.

I do not know if the brake proportioning valve is replaceable or where it is.
If you are claiming that a 27% increase in front piston area and an 8% increase in rotor diameter amounts to a 37% increase in front brake bias. As in the car going from 50-50 to 87-13, or even 68.5-31.5, I think your method is oversimplified. Please do elaborate on how your arrived at your figure. I worked a lot with some online calculators. But of course you must have the information on the rear brake system in order to arrive at any actual bias numbers. I had to stick with the default values and hold them constant since I had no actual data on the rear.

Here is one of those calculators: Bias Calculator.

I have messed around even more with this calculator since I originally wrote this post. It looks like using their logic and default values for unknowns the change to the front bias is just under 10% points. A change of ~17%. You have me intrigued and If I find out any more details about rear numbers or how to get the most accurate value of the change to the bias I will post back up. I will also let you guys know if I end up on ice skates at the limit of braking.

I believe, but do not know for certain, that there is no such valve in these cars. Proportioning is handled by the sizing of other components in the system (caliper pistons, rotors).

Edit: added more options of what I think you may mean, trying to get my head around your logic. Also added more figures from my original looking at this.
 

·
Registered
Joined
·
91 Posts
Looks like I mis-spoke. I meant there is a 37% increase in front braking force for a given brake pressure. You have increased your piston area by 26% and the diameter of your rotor by 8%, so that will increase front brake torque by 37% for a given brake pressure. Likewise, for a given rear brake bias you will be braking 37% more on the fronts. This is less than I thought, so I hope that it all works well.

You are right that we would have to know the original brake bias to know what the new brake bias is. I don't know what the factory brake bias is, or how to find it out. It's not something that is usually published.
 

·
Registered
2014 Mazda 6 GT - 6AT
Joined
·
17 Posts
Looks like I mis-spoke. I meant there is a 37% increase in front braking force for a given brake pressure. You have increased your piston area by 26% and the diameter of your rotor by 8%, so that will increase front brake torque by 37% for a given brake pressure. Likewise, for a given rear brake bias you will be braking 37% more on the fronts. This is less than I thought, so I hope that it all works well.

You are right that we would have to know the original brake bias to know what the new brake bias is. I don't know what the factory brake bias is, or how to find it out. It's not something that is usually published.
I think with the same measurements (piston diameter, rotor diameter) off of the rear we could figure it out. I still feel like there are a lot of factors at play that need to be accounted for to get the true value for all of these things. For example, id think pad width or how close to the edge of the rotor the centerline of the pad is would impact brake torque in a meaningful way. That number would vary from caliper to caliper.

Having the actual old bias and new bias would be the easiest way to digest just how significant the change is.

I appreciate you challenging this, it keeps me thinking about all of the possible implications, and how to make the setup the best it can be.
 

·
Registered
Joined
·
5,058 Posts
and how to make the setup the best it can be.
Pads and tires will make more of a difference than anything. You can have all the clamping force in the world, but if you dont have traction on the rotor and the pavement, it wont matter. So, dont focus just on the calipers.
 

·
Registered
2014 Mazda 6 GT - 6AT
Joined
·
17 Posts
Pads and tires will make more of a difference than anything. You can have all the clamping force in the world, but if you dont have traction on the rotor and the pavement, it wont matter. So, dont focus just on the calipers.
That is a good point. I am excited to try out the EBC OrangeStuff which is the I went with for the time being. A second set of wheels/tires is on the list so I can have something a little more sticky for events.
 
  • Like
Reactions: TalonTsi90
21 - 38 of 38 Posts
Top