BBK Brake Bias - What's up with some of these off the shelf kits?

[Bimma360]

I run these brake bias calculations on most of my cars, as I am always curious about different BBK options. I actually have the Maserati calipers on hand, but truth be told I am not really interested in going the DIY BBK route. At least for these calipers paired with the e9X M3 front rotors (pad doesn't cover entire rotor swept area).

I really like the idea of the more budget oriented Paragon BBK (it's still just under $6K for F&R). Mostly b/c I really want nickel plated calipers and the fact they are owned by Alcon. I don't plan on much track use with this car, so I think these should b a great option. But the rear calipers in this kit have really small piston diameters, and the brake bias for a ZCP car shifts forward a good 6.7% on the 355mm F&R kit. What am I missing here? A 6.7% front increase in static bias is a lot in my eyes. Curious on other people's thoughts, and maybe a second pair of eyes here.

On the flip side, doing the Paragon fronts only and keeping the stock rear yields a -1.9% drop in front bias.


The following are the calculations I came up with for various DIY and off the shelf options to see how they relate to the factory brake bias. (Color coded Brake Pad Heights, represent some level of uncertainty)

**Take note, that these bias %'s are not meant to be real world accurate, but instead a comparison to the calculated factory bias as certain variables are changed (rotor size and caliper piston size). In other words, the goal is to see how and to what extent certain rotor and caliper changes deviate from the calculated factory number.

This is the calculator used:

https://brakepower.com

A note about "Effective Radius of Brake Rotors," which can cause some confusion:

"The effective radius of a brake rotor is measured from center of brake pad to center of brake rotor. In other words, it is the distance from rotor-center to halfway the swept area of the rotor.

More accurately but less easy to measure: it's the distance from rotor-center-line to center line of caliper piston(s)."

Edit: Added the None ZCP factory brakes to the table, and also an additional % Change column for reference. B/c there are other braking related variables between the two factory E46 M3 cars not taken into account, you can't compare the Static Brake Bias between the two cars directly. For example, you can't conclude that the non ZCP E46 is more front biased than the ZCP car directly from these numbers.

		Rotor Information			Caliper Information
Brake Setup or BBK	Location	Rotor Diameter mm	Brake Pad Height mm	Effective Rotor (Radius) mm	Caliper Piston 1 (Diameter) mm	Caliper Piston 2 (Diameter) mm	Caliper Piston 3 (Diameter) mm	Caliper Piston 4 (Diameter) mm	Caliper Piston Area (Total) mm^2	CoF (µ) Brake Pad	Static Brake Bias (% Front)	% Change in Bias (ZCP M3)	% Change in Bias (none ZCP M3)
Factory e46 M3 ZCP	Front	345	64.2	140.4	60				2826	0.4	64.0%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
Factory e46 M3	Front	325	64.2	130.4	60				2826	0.4	66.4%
Factory e46 M3	Rear	328	59.2	134.4	42				1385	0.4
996 Brembo	Front	345	59.4	142.8	40	36			2273	0.4	64.3%	0.5%	-3.2%
996 Brembo	Rear	328	54.9	136.6	28	30			1322	0.4
AM 4 pot Front / CSL Rotor	Front	345	59.4	142.8	40	44			2776	0.4	64.0%	0	-3.6%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
Megane RS275 Brembo Front / CSL Rotor	Front	345	70	137.5	40	40			2512	0.4	65.7%	2.7%	-1.1%
996 Brembo	Rear	328	54.9	136.6	28	30			1322	0.4
w/ 360mm (e9X M3) front rotor	Front	360	70	145	40	40			2512	0.4	66.9%	4.5%	0.8%
Maserati QP 2013+ BMB64 6 pot front / E9X M3 Rotor	Front	360	63	148.5	30	34	38		2748	0.4	69.3%	8.3%	4.4%
996 Brembo	Rear	328	54.9	136.6	28	30			1322	0.4
Maserati QP 2013+ BMB64 6 pot front / E9X M3 Rotor	Front	360	63	148.5	30	34	38		2748	0.4	64.6%	0.9%	-2.7%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
E55 AMG W211,etc. (03-06) BMB-81 8 pot front / E9X M3 Rotor	Front	360	79	140.5	28	32	28	32	2839	0.4	68.8%	7.5%	3.6%
996 Brembo	Rear	328	54.9	136.6	28	30			1322	0.4
Maserati QP 2013+ BMB64 6 pot front / F8X M3 Rotor	Front	380	63	158.5	30	34	38		2748	0.4	67.6%	5.6%	1.8%
996 Brembo / F8X M3 Rotor	Rear	370	54.9	157.6	28	30			1322	0.4
Maserati QP 2013+ BMB64 6 pot front / E9X M3 Rotor	Front	360	63	148.5	30	34	38		2748	0.4	64.9%	1.4%	-2.3%
996 Brembo	Rear	328	54.9	136.6	30	34			1614	0.4
Maserati QP 2013+ BMB64 6 pot front / E9X M3 Rotor	Front	360	63	148.5	30	34	38		2748	0.4	63.6%	-0.6%	-4.2%
Alfa QV 4 pot / E9X M3 Rotor	Rear	350	60	145	30	34			1614	0.4
Maserati QP 2013+ BMB64 6 pot front / F8X M3 Rotor	Front	380	63	158.5	30	34	38		2748	0.4	65.0%	1.6%	-2.1%
Alfa QV 4 pot / E9X M3 Rotor	Rear	350	60	145	30	34			1614	0.4
Maserati QP 2013+ BMB64 6 pot front / F8X M3 Rotor	Front	380	63	158.5	30	34	38		2748	0.4	65.1%	1.7%	-2.0%
Factory F8X M3	Rear	370	63	153.5	44				1520	0.4
Paragon PA015 / PA035 6 pot front	Front	378	54	162	27	31.8	38.1		2506	0.4	64.5%	0.8%	-2.9%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
Paragon PA015 / PA035 6 pot front	Front	370	54	158	27	31.8	38.1		2506	0.4	63.9%	-0.2%	-3.8%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
Paragon PA015 / PA035 6 pot front	Front	355	54	150.5	27	31.8	38.1		2506	0.4	62.8%	-1.9%	-5.4%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
Paragon PA015 / PA035 6 pot front	Front	355	54	150.5	27	31.8	38.1		2506	0.4	67.0%	4.7%	0.9%
Factory e46 M3	Rear	328	59.2	134.4	42				1385	0.4
Paragon PA015 / PA035 6 pot front	Front	355	54	150.5	27	31.8	38.1		2506	0.4	68.3%	6.7%	2.9%
Paragon PA025 4 pot rear	Rear	355	49	153	27	27			1145	0.4
Paragon PA015 / PA035 6 pot front	Front	378	54	162	27	31.8	38.1		2506	0.4	69.9%	9.2%	5.3%
Paragon PA025 4 pot rear	Rear	355	49	153	27	27			1145	0.4
Paragon PA015 / PA035 6 pot front	Front	370	54	158	27	31.8	38.1		2506	0.4	69.3%	8.3%	4.4%
Paragon PA025 4 pot rear	Rear	355	49	153	27	27			1145	0.4
Paragon PA015 / PA035 6 pot front	Front	378	54	162	27	31.8	38.1		2506	0.4	68.2%	6.6%	2.7%
Paragon PA025 4 pot rear	Rear	380	49	165.5	27	27			1145	0.4
Paragon PA015 / PA035 6 pot front	Front	355	54	150.5	27	31.8	38.1		2506	0.4	67.6%	5.6%	1.8%
996 Brembo	Rear	328	54.9	136.6	28	30			1322	0.4
Paragon PA015 / PA035 6 pot front	Front	378	54	162	27	31.8	38.1		2506	0.4	63.5%	-0.8%	-4.4%
Factory F8X M3	Rear	370	63	153.5	44				1520	0.4
EBC Apollo 4 pot BC4104	Front	355	50.3	152.3	38.1	41.2			2472	0.4	62.8%	-1.9%	-5.4%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
EBC Apollo 6 pot	Front	355	50.3	152.3	28.6	31.8	38.1		2575	0.4	63.7%	-0.5%	-4.1%
Factory e46 M3 ZCP	Rear	328	59.2	134.4	46				1661	0.4
Factory F8X M3 4 pot	Front	380	71	154.5	40	40			2512	0.4	61.6%	-3.8%	-7.2%
Factory F8X M3 2 Pot	Rear	370	51	159.5	44				1520	0.4

[9kracing]

Thanks! Can you add the regular ol' Brembo GT kit on there as well? I think a lot of us run that.

[Bimma360]

Thanks! Can you add the regular ol' Brembo GT kit on there as well? I think a lot of us run that.

I just need to know the specs. I think I read somewhere that the front GT caliper piston sizes are the same as those from the AM (Aston Martin). I don't know anything about the rear Brembo BBK though. Also keep in mind this whole table compares against a Comp pack e46 M3.

[xansabi]

What about F8X all around?

[Bimma360]

What about F8X all around?

Turns out adding rows to the table above is not as straightforward. I had AI build the table in BBCode from an excel spreadsheet. So I just replaced one of the crapy combo's, with unfortunately, another crappy combo haha. I do remember doing these calculations before, but never added them to the table b/c it wasn't that good.

Looks like the F8X M3 calipers and rotors reduce front bias by 3.8%. I am not super certain on the Brake Pad Height though, so that could change the numbers. I looked it up using AI, so if anyone knows I can update. But regardless, I think this setup will shift the bias to the rear by some margin.

Edit: I actually just did the F8X M3 CCB's (not worth adding to the table above), and they reduce the front bias even more by 5.9%.

[digger]

IMO going from 64% to 69% absolute is not that much to worry about and IMO is better place to be

[moproblems]

So the zcp bias is already pretty forward compared to the non zcp stuff... What about the paragon 6 pot 355 with the 42mm piston rear caliper? Iirc the difference between the two rears with a zcp front is about 2%

Also, what is the "AM 4 pot" kit referencing? I'd be interested in that based on the calculations.

[zzyzx85]

So the zcp bias is already pretty forward compared to the non zcp stuff... What about the paragon 6 pot 355 with the 42mm piston rear caliper? Iirc the difference between the two rears with a zcp front is about 2%

Also, what is the "AM 4 pot" kit referencing? I'd be interested in that based on the calculations.

It's most likely this: https://thebuildjournal.com/reviews/...e46-m3-review/

[Cronenberged]

How does the rotor affect bias, I thought it was just the piston sizes? Also, Paragon offers a 343x23 rotor

[Bimma360]

I added the None ZCP factory brakes to the table, and also an additional % Change column for reference. B/c there are other braking related variables between the two factory E46 M3 cars not taken into account, you can't compare the Static Brake Bias between the two cars directly. FYI. Also keep in mind this is still a ZCP centered spreadsheet so it will not answer all questions for the none ZCP car, but at least it gives a little more insight.

[Bimma360]

IMO going from 64% to 69% absolute is not that much to worry about and IMO is better place to be

Yeah you might be right, I honestly don't know. This is anecdotal and not apples for apples, but on the e36 M3 the Porsche Brembo F/R DIY BBK reduces the front bias by -6.7%, and that difference is definitely felt. Then I think about how the ABS systems in these cars are designed around the braking system as a whole, and it just makes me wonder ya know.

Also, these % calculations are all relative. If a 64% | 36% F/R change to 68.3% | 31.7% F/R is a front increase of 6.7% front bias, it's also a decrease of 12% in rear bias. I just don't know.

But I am inclined to agree with you I think. Increasing front bias 4 or 5 points, as long it's at 70% or less is probably not the big of a deal.

[Bimma360]

So the zcp bias is already pretty forward compared to the non zcp stuff... What about the paragon 6 pot 355 with the 42mm piston rear caliper? Iirc the difference between the two rears with a zcp front is about 2%

Also, what is the "AM 4 pot" kit referencing? I'd be interested in that based on the calculations.

Sorry, yeah Aston Martin (AM). If retaining your factory rear calipers, it really is ideal. I don't have the non ZCP rear caliper in the calculations, but on the non ZCP car it's probably pretty close to a 0% change too.

I added the non ZCP rear caliper with the Paragon fronts to the spread sheet above. Piston size makes a pretty big impact. We went from a -1.9% reduction to an increase of 4.7% in front bias.

[Bimma360]

How does the rotor affect bias, I thought it was just the piston sizes? Also, Paragon offers a 343x23 rotor

Probably not the best way to put it, I am not an expert on this stuff haha, but I think about it as "stopping power" front and rear.

There are a bunch of variables that can increase stopping power at each end of the car. Some of which are:

Wheel/Tire Diameter
Tire CoF
Rotor Diameter
Caliper Piston Area
Brake Pad CoF - This actually has a very dramatic effect in these calculations. So much so, that I completely stopped trying to play with different pads front and rear.

Imagine having old / bald tires in the front and brand new sticky performance tires in the rear. It makes sense that your braking bias is going to shift to the rear, as your front tire CoF (coefficient of friction) is a lot lower than that of the rear.

[moproblems]

Sorry, yeah Aston Martin (AM). If retaining your factory rear calipers, it really is ideal. I don't have the non ZCP rear caliper in the calculations, but on the non ZCP car it's probably pretty close to a 0% change too.

I added the non ZCP rear caliper with the Paragon fronts to the spread sheet above. Piston size makes a pretty big impact. We went from a -1.9% reduction to an increase of 4.7% in front bias.

I'm looking into it, pricing is good too. Might be the way I go. Just went to zcp stuff so I can resell the front brackets and just keep the bigger piston rears.