Anyone running Z17 or Z18 Brembo BBK Kit? Thoughts?

[mrgizmo04]

YMMV, but I would bet most prepped E46s could benefit from moving the bias back slightly. Track suspensions don't allow nearly as much dive, leaving more traction in the rear to take advantage of.

Of note, rotor diameter is not a big factor in bias.

I'm not aware of pad tapering being an issue on this platform, and I talk to a lot of 991 GT3 owners who track their cars.

On the 3 points above.

The problem with options being discussed in this thread on the latest Brembo donor car discoveries is that they move the bias forward. I'm with you on slight rearward adjustment. I'm actually quite enjoying 996 kit even after dropping weight at the rear of the car.

Rotor diameter is not a negligible contributor. While it does contribute at 1/2 the diameter increase and piston contributes a square term, it can not be disregarded. If CSL didn't increase front rotor to 345, bias would drop ~2% to close to 62%. A lot of variables at play, which inclides rotor, piston bores, pad mu, etc.

GT3 guys got smarter over time and learned that pads that can take proper heat are a must upgrade. Rolling off the dealership floor and going straight to the track resulted in tapering when the street pads on their cars melted and tapered. Their caliper and attachment is super sturdy and their entire systems were designed for the car. Have you seen those washers/spacers that get included with the brackets to mount whatever Brembo calipers on our cars? I would not say that is a sturdy design for when you really need your braking system. These retrofits are a concern, but as I said before, just doing street driving might be ok.

Haven't heard of AP issues with taper, as I don't follow them too closely, but interesting. They are seen as the creme of the crop, so that must be annoying.

Sent from my SM-G950U using Tapatalk

[heinzboehmer]

Yes there is unsprung mass to be removed. You can get a few lbs per corner doing wheels / brakes. But depends on what options you go with and whether the net result will be loss of mass or not. Larger rotor increases mass and could be offset with lighter caliper. Sometimes it's a wash, sometimes it net increases mass. For example, 996 rear caliper with bracket and pads is around 6.8 lbs, while stock cast iron is 9 lbs, while Stoptech 355 bbk rear caliper/bracket/pads was around 11 lbs.

To add, moment of inertia of a cylinder goes up linearly with mass but quadratically with radius. So even a lighter rotor with a larger radius will not necessarily result in more response at the wheels. Not to mention that most larger rotors are heavier.

But yeah totally agree with you, moving to a BBK is not necessarily going to change unsprung mass/rotational characteristics at the wheels in a favorable direction. Lots of factors that need to be considered.

[crow4213]

Can we see the rears as well? I want to see what a 360mm front rotor and 328mm rear rotor look like together.

Here is a crappy cellphone pic of the back and front together.

[Lee_Enfield]

So, what are the overall thoughts on the F80 swap then?

How about the db9 fronts with 996 rears?

Honestly this is a fun build car so not track oriented for me.

[maupineda]

E82 6 pots work fine with 996 rears. But both calipers clamp less. About 15% less, but keep bias in check, they actually shift it back a few %, and you can still trigger ABS. I think the best are the megane 4 pots as clamping force is not reduced, and pair them with CSL rear calipers.

[EthanolTurbo]

Buildjournal has some of the older options, yes. Ok, DB9 has different pistons. YAY!

I tie out to their bias calculations +/- 0.1%. DB9 places more bias forward and important point I forgot to mention in my previous long post, although I alluded to it with "understeer", is that most folks like CSL or other staggered wheels and placing more forward bias on skinny front tires will overload them further, resulting in plowing.

I will not comment on Buildjournal in general, they are selling "stuff", but it is scary to me that they crown Megane calipers as "best" upgrade. I guess it depends, best for what. Their primary point is bias. Ok good start.

I want to make sure folks understand tapering pad and what that results in from same size pistons. Leading piston effectively overpowers the trailing piston because the trailing piston gets additional gases/material to overcome, which it can't. The leading half (approx) of the pad starts wearing faster, tapering the pad. That starts placing the pad in the caliper at an angle and jamming it in the caliper because it no longer sits square. From a piston point of view, the backing plate also starts putting pressure on a single point of the piston instead of sitting flush against the circumference face of the piston. This also jams the pistons in their bores. The net result of this is you have a jammed piston and pad when you need your brakes. It is somewhat similar to pad knockback, yet very different, as pad knockback has several solutions like pumping the brakes a few times or adding piston springs. This tapering becomes scary as it changes the geometry and you basically experience jammed brakes.

Again, can be mostly disregarded if street driving.

Sent from my SM-G950U using Tapatalk

BuildJournal recommends what makes them the most money. Most of their data and expertise is plagiarized from those who pioneered it way before. I don't know why anyone listens to them, the owner is just using his profits to fund his track cars.

[EthanolTurbo]

So, what are the overall thoughts on the F80 swap then?

How about the db9 fronts with 996 rears?

Honestly this is a fun build car so not track oriented for me.

F80 swap increases unsprung weight so overall the car will be slower in every way. They are much heavier than stock from what I can see.

[mrgizmo04]

BuildJournal recommends what makes them the most money. Most of their data and expertise is plagiarized from those who pioneered it way before. I don't know why anyone listens to them, the owner is just using his profits to fund his track cars.

Ding ding ding

Sent from my SM-G950U using Tapatalk

[mrgizmo04]

DB9 I believe is meant for a 32mm rotor, while ours are 28mm. See discussion above on issues that can create especially on street cars that don't check pad wear frequently.

To make DB9 bias a bit more inline with stock, I would keep stock caliper there. Pairing with 996 rear will run around 69%.

F8x are heavy. For street/show you can throw them on, but as said, a lot of added unsprung weight. For track, that is also unnecessary amount of added meat.
Some comparison figures:
-Front calipers: 10.78 lbs
-Front rotors 380x30: 24.89 lbs
-Rear calipers: 7.94 lbs
-Rear rotors 370x28: 20.39 lbs

Compare to say 996:
-996 front calipers: 6.4 lbs
-M3 CSL 345mm front rotors: 19.1lbs
-996 rear calipers: 5.2 lbs
-M3 CSL 328mm rear rotors: 14.5 lbs

Sent from my SM-G950U using Tapatalk

[Epsilon]

The DB9 also works with the stock 325mm rotors and pairing it with the 996 rear brings it closer to the CSL front and rear brake bias. This setup does not require expensive 345mm rotors and brings the bias closer to the factory CSL. yay or nay?

[EthanolTurbo]

DB9 I believe is meant for a 32mm rotor, while ours are 28mm. See discussion above on issues that can create especially on street cars that don't check pad wear frequently.

To make DB9 bias a bit more inline with stock, I would keep stock caliper there. Pairing with 996 rear will run around 69%.

F8x are heavy. For street/show you can throw them on, but as said, a lot of added unsprung weight. For track, that is also unnecessary amount of added meat.
Some comparison figures:
-Front calipers: 10.78 lbs
-Front rotors 380x30: 24.89 lbs
-Rear calipers: 7.94 lbs
-Rear rotors 370x28: 20.39 lbs

Compare to say 996:
-996 front calipers: 6.4 lbs
-M3 CSL 345mm front rotors: 19.1lbs
-996 rear calipers: 5.2 lbs
-M3 CSL 328mm rear rotors: 14.5 lbs

Sent from my SM-G950U using Tapatalk

Based on those weights, an F80 brake kit would increase unsprung weight by 37ish lbs vs a 996 setup with no advantages.

[mrgizmo04]

The DB9 also works with the stock 325mm rotors and pairing it with the 996 rear brings it closer to the CSL front and rear brake bias. This setup does not require expensive 345mm rotors and brings the bias closer to the factory CSL. yay or nay?

Depends what you are going for. Just a big red caliper? I keep coming back to those plastic caliper covers I saw on Ebay that say "Brembo" on them for like $20 .

Read above on your take about our rotor thickness vs what the caliper was designed for on donor car and how you feel about it.

DB9 on 325 paired with 996 rear is around 67.5%, not CSL front/rear which is closer to 64%.

Sent from my SM-G950U using Tapatalk

[mrgizmo04]

Based on those weights, an F80 brake kit would increase unsprung weight by 37ish lbs vs a 996 setup with no advantages.

Depends what you are going for. Endurance racing on a full weight E46 and a quick driver could benefit from it. Remember you have to convert [1/2 * m * v^2] (m here is mass of car/driver/etc) to heat via [m * material heat coefficient * delta T] (m here is mass of rotor/pad available to absorb/dissipate heat) of the braking system capacity.

Sent from my SM-G950U using Tapatalk

[Lee_Enfield]

Interesting, lots of good info.

Might just go with the 996 options, I suppose its the most popular retrofit for a reason. Whats the going rate for a set of the calipers these days? Seems about 1000 CAD for a set is the going rate.

Also apologies to the OP for a minor thread Hijack.

[oceansize]

I think I'm going with some stick-on Brembo bling after all this lol...