Mazdaspeed 6 K Sport Big Brakes Initial Review

      I have a confession to make.  For quite some time I struggled badly with “big brake envy” when driving my Mazdaspeed 6.  Evo’s, STi’s, G37’s, 350Z’s, 370Z’s, the Focus RS, and even the new Civic Type R, all came with big, sexy, and glossy forged fixed brembo calipers.  I’d see these cars and cast a forlorn stare at the drab gray cast metal sliding calipers peering at me behind the 6’s wheels.  I lusted after big exotic Brembo calipers on anything I saw them on.  I lingered longer than I should have at the Brembo display at SEMA…twice.  I endlessly shopped and researched what might possibly fit my own Mazdaspeed 6, and couldn’t shake the fever, I had to have them.  Sure, the boring brakes on the Mazdaspeed 6 are quite good functionally speaking; they tested in numerous magazines boasting of a 70mph-0 stopping distance of around 155ft. This is a solid number even by today’s standards, and in fact rivaled the Evo and STi of the day.  Even in my own experience of many years of driving, I never had any outright failures with the factory brakes, but on a couple of occasions after extended use, I did cook them pretty heavily to the point where pedal pressure was compromised. The typical confident bite on initial brake application, was replaced with a sinking pedal that quickly evaporated my trust when entering a high speed corner.  This was despite several upgrades to the factory equipment in the form of stainless steel braided lines, my ATE super blue brake fluid, Hawk HPS pads and DBA slotted rotors in front. So although they were great, I was curious if they could be improved upon. In terms of performance, I hoped to see a decrease from that 155ft. stopping distance but I was not setting all my expectations to that aspect alone, as I wanted an increase in braking endurance as well. If overall stopping distances were about the same, I might be a bit disappointed, but the brakes maintained that stopping distance under any amount of heat and several hot laps, that would be a win in my book. After researching a few options, I made the call to K Sport, and set about my plan to not only install, but test the results of their big brake kit.

    I have found that big brake upgrades are one of the most maligned modifications you can talk about on the internet forums or Facebook groups.  Raising the topic illicits eye rolling from the internet cynics, and the common refrain was; “tires will do more to stop than brakes”, “get stickier, wider tires”, “you’ll never be fast enough to justify it”, and perhaps the most frightening “you will make the car stop worse than stock”.  Indeed, sticky tires make a huge impact on every aspect of a cars performance, including stopping, but let’s assume I already have the widest and stickiest rubber that I want or I am able to run, and I want to improve brake performance by looking to the brakes themselves.  Whether in terms of stopping distance, repeat-ability (aka eliminating fade/overheating brakes), or even saving some unsprung weight.  I wanted to find out for myself the outcome. Also, let’s not dismiss cosmetics completely, a glossy set of large floating calipers compliments a set of BBS wheels quite nicely, we’ll just consider that a bonus perk.  In this first installment covering my journey down the path of big brakes, we will get into the specs of the kit versus factory, the install of the kit, and the initial driving impression after installing the big brakes in front.

    First, the details of the kits I would be using, and giving my initial impressions of in this article.  I opted for K Sport’s ProComp 8 piston caliper with 13” rotor, to replace my OE front brakes.  Remember that bit about cosmetics?  These brakes look fantastic! I initially wanted to go with K Sports amazing looking titanium finish, but being a special finish it was a bit more expensive and here again I was trying to keep costs down.  I ended up choosing the standard gloss red finish, and my remorse over not getting titanium finish quickly melted away. The calipers are coated in a nice thick layer of quality paint/epoxy, giving a beautiful, wet looking, deep red finish.  It is a durable finish as well, as during install I accidentally knocked it into things a couple of times with no harm done. In addition,as of this writing they have seen several thousand miles on the street including winter months exposed to snow, salt, rain and seem no worse for wear (they clean up easily as well!).  The rotors are a two piece variety, with the option to order as full floating rotors. Just unwrapping the kit, the rotors were obviously a much heftier piece than the OE components. This would seem to bode well for heat dissipation, but I wondered if they would come as a weight penalty.  

    Obviously one does not invest in a brake system like this based on cosmetics alone, you want performance results, and on paper at least, it would seem the K Sport brakes should deliver.  The K Sport rotor diameter is 13” in front, which is just a slight increase over the OE front that measure 12.6” in diameter. (It should be noted K Sport offers several sizes, up to a whopping 16.6″ for this car even!)  Thickness is where it is more significant an increase, the factory front rotors are about 25mm with the new K Sport pieces increasing to 32mm.  While a 7mm increase in thickness may not sound significantly different, in person, the difference makes for bigger venting windows in the KSport brakes than the OE brakes and significantly more metal on either side of those vents.  All this equates to more mass, and hopefully more thermal capacity, brakes are all about absorbing and shedding heat.

    Examining the large 8 piston calipers in this kit, we find where the bigger differences lie.  The individual pistons are small in diameter but with the higher than average number of pistons in this kit (versus the more common 4 pot or 6 pot).  So the pistons individually appear smaller but the total piston area is greater with the K Sport units, than the large single piston on the factory calipers.  The front single piston OE calipers have a total area of 23.76cm2 per caliper.  While the total piston area of the 8 smaller individual pistons of the K Sport caliper, is 35.46cm2 per caliper.  That is approximately a 50% increase, which seems significant enough.  Seeing the two calipers side by side in photos below, the difference is staggering.  There is an added benefit in the form of unsprung weight savings.  The OE caliper and rotor weigh in at about 32lbs, while the KSport caliper and rotor come in at about 26.8lbs, a savings of just over 5lbs per wheel.  This came as a surprise to me, because even though the calipers are feather light, I thought the difference would be more than made up with the larger, thicker rotors.  

    Logically the brake pads follow a similar trend, with factory front pad material providing 49.50cm² of friction surface, while the K Sport pads increase that to 77.01cm².  To this point, on paper at least, the kit seems to be an overall improvement in every aspect; slightly larger diameter rotors, substantially thicker rotors, dramatically more pad surface area, and even a decrease in unsprung weight.  

    Installing the kit was incredibly straightforward.  Essentially it’s replacing your factory brake calipers, brake caliper brackets, rubber (or stainless steel braided in my case) brake lines, and brake rotors, with the parts included with the K Sport kit.  K Sport does include special spacer washers if there is a need to adjust the caliper centering (making sure the rotors pass through exactly in the center), but these were not necessary for me during install.  Also worth noting, the spacers provided really only amount to a millimeter or two of change.  So the tolerances are tight, and very well thought out it appears. To this end, and it is even mentioned in the instructions, you must ensure the mounting surface of the hub is clean…very clean! If you’ve got heavy lumps of corrosion, it must be ground flat. If you’ve got an old rotor screw broken off in the hub, it must be ground completely flat!  This tripped me up momentarily, as just a millimeter of bulge that I did not even detect, ended up making the rotor fitment incorrect and would have caused issues down the road. Luckily I caught it, addressed it, and carried on with the install. In the end, there was no fiddling with adjustments or grinding of any metal, I simply bolted everything up, slid in the new pads (K Sport’s own “street” pad) and bled the brake fluid.  The whole job is not much more difficult than changing a set of pads and rotors.  Of course with larger calipers such as these, brake clearance will be an issue with the factory wheels.  The big K Sport calipers will not come close to fitting the factory wheels as-is. If you are set on keeping the OE wheels for the Mazdaspeed 6, I have confirmed first-hand that 20mm bolt on spacers will allow the needed clearance. However, I use this strictly for winter wheels and I would not necessarily recommend it, as the change in scrub radius does cause the handling to feel a bit off.  Fortunately, I have already equipped my 6 with BBS wheels from the Mitsubishi Evo MR (18×8.5 +38 offset), and these do clear the brakes easily without need for spacers.    If you have any question on whether they would fit under your specific wheels, K Sport will supply handy templates that you can use to check against the actual wheels you run on your car.

      Initial driving impressions are a purely subjective test, but certainly should not be disregarded when it comes to something that sees regular street driving.  In this regard, the K Sport big brakes did not disappoint.  A bit less pedal travel to feel the brakes begin to grab, and a bit more aggressive on the initial bite, but without feeling overly grabby or jerky.  They immediately feel sharper, feel more responsive and feel quicker to slow the car. I have logged a few thousand miles on the street during summer, fall, winter; in traffic, on the highway, and even a few spirited canyon runs in Colorado. I have not encountered any squealing or ugly noises from the brakes, nor any drop in performance, nor any other inconsistencies throughout.  They did just fine handling snow as well, in low grip situations the ABS triggered as it normally would and it stopped the car with at least equal amount of confidence as it did stock. In single digit temps, the pedal feel remained solid, albeit a bit stiffer as tends to happen in those conditions, but they performed just as well and predictably as ever.  To my great pleasure, subjectively the brakes felt better in every regard during street use.

    All told, I am quite happy with the K Sport front brake kit so far, at least in driving feel it seems to have improved the performance of the car, and seeing the beautiful calipers peering out from behind my wheels never gets old.  All this though, is admittedly subjective, and for the next installment in this series, I am going to get into some real performance testing and attempt to get some objective results and usable numbers for comparison, stay tuned!

– photos and writing: Robert Sixto 

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