From the real world to my world.
"These build journal entries are part of a special series on the development of the e9X M3 Custom AP Racing Big Brake Kits by HaimusRacing and written in collaboration with Antonio and his engineering team.
In this journal entry, I provide my personal, subjective review on the kit. After a few months of driving, the braking performance undeniably feels better with surprising subjective benefits of the rear bias engineering."
The previously discussed use change ended up being a positive to test the Clubsport BBK.
I pilled up over 4,000 kms with the BBK during the Fall and got to put it through its paces in weather ranging from 0C up to +30C: rain or shine, the M3 was getting driven.
I feel confident in my assessments of day-to-day driving impressions.
The rotors pop [...]
I did most of my high performance testing in the evenings: it would get cold fast. This would lead to furthering temperature deltas of the glowing discs and ambiant air.
Coming up to a stop, I heard a somewhat loud pop coming from the front.
The bolts holding the rotor to the bells created this noise as the iron and aluminum have different thermal expansion properties.
No harm done - it's a quirk of higher performance 2 piece rotors in the cold.
but the pads don't squeal.
My main concern coming in were squealing noises in cool or cold operating temperatures.
This was compounded by the fact my kit was delivered with APF404 pad material. AP describes it as their most track suitable pads that can be used on the street.
It hasn't squealed once. I was genuinely surprised.
[...] yet they do dust
This is a given with a high friction pad, and there's no way to work around it. It's one of the main benefits to CCBs fitted on the F8x M3 & M4.
It was made worse by the fact the OE+ M359 wheel set I had at the time was finished in OE Hypersilver.
I curb rashed the wheels over the Summer and was planning on spraying them to GTS-like Satin Black. This accelerated my plans.
The wheels were sanded down to metal before being repaired and resprayed.
The byproduct of brake dust is also corrosion. You can see the pad compound reside by the hub created a section that falls victim to surface rust.
There's no structural concern, it is another quirk of higher performance brakes.
[...] and they bite!
I filed this comment under the Street-ability part of my impressions as initial bite is both a plus and a minus for the street.
The OEM brakes always felt soft on initial touch, requiring a lot of effort to get going. Once you passed that initial threshold, they felt like an on/off switch.
You want more than OE, but not too much as to make the brakes too grabby. Your passengers would hate you.
The pad behaves like AP Racing described it: it's their most suitable street pad for the track.
It shows: they bite just right on initial touch.
Subjective performance impressions.
As I've stated on a previous entry, my Stripper E92 M3 is not a track car.
It has barely seen the track - and it barely will. Valuations have gone crazy and the unfortunate truth is I can't flush that value down the toilet.
As such, what matters to me isn't lap time, it's feel. The best feeling a Big Brake Kit can provide you with is a sense of confidence that the car will behave the way you expect it to.
"The TL;DR : the Clubsport kit gives you confidence."
The Stripper is my most confidence inspiring M car. It devours pavement and makes you want to push. The Clubsport kit is a critical component to the recipe.
They have progressive modulation.
"Brake modulation is the ability to precisely and accurately control the amount of clamp force on a rotor with a given amount of lever input."
A stronger initial bite usually reduces the progressive feeling of the brake pedal and your ability to modulate pressure.
The Clubsport kit feels more progressive.
[...] because they clamp harder, and further.
It's actually counterintuitive at first as you don't expect to have further clamping power under your foot if you have experience hitting the ABS thresholds of the OE brakes.
Yet you do have more power and better modulation.
I say better modulation as ultimately a braking system is most efficient as it avoids ABS intervention.
The Clubsport BBK gives your M3 greater initial bite over OE, and higher performance thresholds.
I was able to make use of the extra clamping power with the wider 265 PS4S I run on the front 19x10 wheels
This is a visual representation showing it feels. The range indicates modulation: the top is initial bite while the depth indicates threshold performance.
This range still applies, albeit less, if you are running similar tire grip to the OEM 245/35/19 Continental SportContact or equivalent Michelin PSS or PS4.
The AP caliper selected by Haimus is still able to transfer it its clamping power more efficiently to the rotor over OEM.
They feel solid.
This is arguably the most important subjective, behavioural improvement.
Solidity is a component of confidence. Confidence is everything.
The OE brakes always felt soft.
If you visualize solidity of brake pedal feel as a range between a circle and a square, guess which one is the circle and which is the square.
Blue is OE. Green is Clubsport.
They didn't fade for my use.
The main performance benefits to a well engineered BBK are increased thermal dissipation capacity.
In short: how far can you push it until it fades?
This is inherently dependent on how, when and where you drive your M3 and the always-present tire variable.
My personal fade test happens on mountain roads I've driven on home for the better part of 15 years.
The remote stretch of freshly paved road covers 15 kilometers +: it's the closest thing to the Crest or the Dragon you'll find in Quebec.
I won't say where, but this is where it ends. This is a picture from Spring 2021.
The A to B uphill section is a power test and an opportunity to test the brake modulation. Too much bite and your loss of speed is compounded by gravity.
The Clubsport behaved well: the improved modulation allowed increased precision in pressure applications.
The most important test of fade was B to A: downhill.
My previous runs with OE brakes with 255 and 265 PS4S had me experience fade on some occasions in dry & warm conditions where I felt comfortable pushing to limits of the traction circle.
Most critically, other occasions provoked complete loss of confidence even without fade.
This is where Clubsport BBK shined.
It was a diametrically opposed experience.
More clamping power, the solid feel and initial bite meant I was confident to carry more speed into braking zones.
This meant more heat to dissipate.
Dissipate it did: I didn't experience fade.
Like anything, it has its limits.
This kit will have its limits, I couldn't find them on the street using PS4S 265 front tires.
Stepping up to a CUP2 or similar and going out for sustained sessions in a controlled track environment would have you discover those limits at some point.
This is what Clubsport design philosophy is all about: a compromise.
The icing on on the cake: less unsprung weight.
This aspect of the kit has been my not-so-subtle Ace in the hole ever since I reviewed the blueprint of this BBK with Antonio. The kit removes an impressive 24.2 lbs of unsprung weight at the front.
Alternative unsprung weight reduction options.
The only equivalent reduction in weight could theoretically come from lightweight forged wheels. The OEM M359s 19x9 weight about 26 lbs at the front.
The technical savvy owners will know you wouldn't need to find 24.2 lbs in total considering how rotational inertia works.
Lightweight forged wheels are still an expensive and relatively low bang for your buck modification relative to this Clubsport kit when considering the unsprung weight reduction accompanied with drastically improved braking performance & feel.
The most noticeable feel improvement.
The improved deceleration and acceleration commonly associated with reduced unsprung weight couldn't subjectively by discerned when fitting the BBK. It gets blended into the clamping power increases of the kit.
My usage rarely led to emergency braking scenarios. I had to voluntarily create those scenarios to review the kit and push harder on the occasional mountain runs.
For my usage, the most noticeable performance improvement was the front end steering response.
Every steering input felt faster.
Pardon the condensation. Fall gets cold up here.
Discerning improvements in response.
The stock E9x M3 front end is nothing to write home about in comparaison to my E46 M3 and E60 M5.
I have been progressively fine tuning the front end of my E92 M3 by incorporating upgrades on a per parts basis while maintaining the OEM brake system. The Clubsport BBK has been my latest upgrade.
In a chronological order, I added the following:
- Monoball front thrust arms by Turner
- Bilstein B16 Damptronic coilovers with Turner hybrid plates
- 265/30/19 by Michelin PS4S
- Adjustable, solid end links by Turner
- PU front sway bar bushings by PurpleFlex
- Custom AP Clubsport kit by Haimus
Elevating the front end to GOAT tier.
Starting from a stock M3 and making my way up this modifications list has allowed me to discern the subtle changes.
I can confidently say thhe Clubsport BBK has elevated my E92 M3 in the realm of the best analog front ends BMW M have ever created.
It also succeeds in carving out its own signature feel against the two: it's fast, solid and confidence inspiring.
As closing thoughts, this has been an immersive learning experience.
Antonio's insights and my research led me down rabbit holes learning about engineering brake systems and their historical evolution.
Brake systems are complex.
They are a mission-critical safety and performance component to our M3s.
They need to look good too.
It's a product where you want it all, and want to pay the least.
My recommendation is to save a little more, and do it right.
Remember the bicycle tips?
You owe it to your dad.
Do it for the kids.