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GiroDisc Two-Piece Rotor Upgrades Make You Think Twice About Big Brake Kits
BY Mike Maravilla //
May 21, 2024
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Photography: Mike Maravilla
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  • GiroDisc is a motorsport-trusted manufacturer dedicated to designing two-piece brake rotor upgrades for enthusiast platforms.
  • These direct replacement rotors crucially reduce unsprung weight, heat retention, and replacement costs versus their one-piece counterparts.
  • GiroDisc’s well-engineered solutions maximize the factory brake system’s capabilities, often negating the need for pricier, more complex big brake kit upgrades.
  • We installed a full set of GiroDisc two-piece rotors on a street/track 997.1 GT3 ahead of the upcoming car season at our preferred local speed shop: R/T Tuning.

If someone gave you the choice between fitting new rotors or a big brake kit, which would you choose? Most would likely choose the latter, but that answer—at least in modern-day context—isn’t nearly as clear-cut as you think. Admittedly, I’ve been in this camp many times before. I thought that big brake kits were the only way I’d confidently extract the performance I needed out of my brakes—especially on the track.

The preclusion toward big brake kits comes from two things: history and showmanship. Not too long ago, single-piston calipers were all we had. They fell short in virtually every measure; single-piston calipers didn’t look very good nor provided adequate braking performance (clamping force) when you needed it most. It was no mystery that an aftermarket big brake kit—with multi-piston calipers, bigger rotors, and better pad compounds—became the commonplace enthusiast upgrade for decades. The second camp didn’t care much about performance but valued the considerable visual upgrade that larger, painted aftermarket calipers offered, often with flashier rotors to match.

But as I alluded to above, OEM brake technology has come a long way in both departments. What you want versus what you need is very different in 2024 than in 1994, and companies like GiroDisc have taken full advantage to fill a gaping void in the aftermarket world.

WHY JUST ROTORS?

While OEM caliper technology has closed the cap on aftermarket offerings, rotors were still lightyears behind. “Traditional one-piece brake rotors are heavy and retain heat, diminishing their effectiveness and adding unsprung weight that adversely affects handling,” GiroDisc said. The Washington-based manufacturer is strategically focused on designing and manufacturing two-piece, fully-floating brake rotors for enthusiast platforms. Its goal is to create engineering solutions that maximize the capabilities of the factory brake system rather than dismiss years of development work. GiroDisc has proven itself quickly within this space; it’s almost impossible to go to a track day and not see handfuls of cars running these rotors. Part of that is down to price. Its rotors are a fraction of the cost of reputable big brake kits, which means your money can go into seat time instead of your unnecessary equipment overhead.

In the case of a 997.1 GT3, 6/4-piston monoblock calipers come standard on both steel and optional PCCB stoppers. Swapping these for aftermarket versions (effectively the same configuration) is relatively fruitless. Porsche’s robust factory calipers have made a perfect case for GiroDisc’s rotor solutions and it’s no secret why it’s one of the most devoted marques to the brand.

WHY TWO-PIECE?

Speaking of overhead, one of the biggest advantages of floating, two-piece rotors is long-term cost savings. The first time around, the 997.1 GT3 front (A1-019) and rear (A2-032) direct replacement rotor sets have bigger upfront costs than their OEM alternatives, but that quickly changes thereafter. The replacement disc—front (D1-032) and rear (D2-032) respectively—are much friendlier expenses and you’ll never look back to anything in the OEM Porsche catalog again. The GiroDisc two-piece rotors are much lighter—roughly a 4lb/corner diet—thanks to a 6061-T6 aircraft aluminum center section (“hat”). The hat material also helps reduce heat transfer between the rotor and sensitive moving parts like the wheel bearings and hub carriers. The discs (“rings”) themselves are born of GiroDisc’s proprietary cast iron material which is poured and machined in its in-house facility.

The rotor assembly will bolt directly to the car and work with OE calipers perfectly. By upgrading your brakes with lightweight high-performance replacements as opposed to a big brake kit, both your factory bias and ABS efficiency are maintained.

WHY SLOTTED?

The factory 997 GT3 rotors are cross-drilled, which on street cars, have tangible benefits to manage heat transfer. But their strengths can turn into weaknesses in more demanding driving conditions—they can develop small cracks over time, which shorten their lifespan dramatically. Slotted rotors are the superior choice in these competitive environments; they offer better pad bite and also evacuate gas and dust with more proficiency than their cross-drilled counterparts. This means more uniform contact can be achieved between the pad and rotor surface. Ultimately, better contact means more friction, which equals better stopping power.

You’ll see plenty of slotted rotor patterns nowadays (i.e. bi-directional, j-hook, straight cut, and sinusoid curved), all of which offer unique benefits. GiroDisc’s curved slots inherently have better initial bite and a good balance between overall braking power and wear.

MADE IN USA

A “Made in USA” claim still means a lot in 2024 and GiroDisc is proud to run its entire operations—ideation, manufacturing, and order fulfillment—from its Bellingham, Washington headquarters. When you’re fully committed at the last brake marker before a corner, trust in your equipment is everything. GiroDisc’s commitment to producing motorsport-grade components in the United States cements that confidence when it matters most.

GIRODISC DIFFERENCE

This being my second attempt at a 997.1 GT3, I wanted every possible upgrade—from the coilovers to the cooling system and the exhaust—to be top-tier. Brakes were no exception. Now, this isn’t the only two-piece rotor on the market, but I believe GiroDisc is easily one of the best available. GiroDisc’s rotors utilize a motorsport-derived, curved, 32-vane design, which acts like a centrifugal pump to force cool air through the disc.

GiroDisc has also put exhaustive thought into its floating mount system. Its version utilizes 12 high-strength steel alloy, cadmium-plated drive pins of GiroDisc’s own specifications. The pins are secured with 12.9-class cap screws and hardened washers. The company has crucially engineered around one of floating rotors’ biggest side effects: they often rattle when cold. There are small, but significant anti-noise spring washers on each of the 12 pins. The resulting space allows the rotor to grow with heat expansion but eliminates the incessant rattle that floating rotors typically have. This float also allows the rotor to self-center between the pads.

THE INSTALLATION

As ever, we trusted this GiroDisc install to our favorite local speed shop: R/T Tuning. As straightforward as a brake job can be, unknowns can always arise; having a shop that can pivot around those unforeseen circumstances makes all the difference.

Thankfully, it was smooth sailing; we set the factory calipers aside and made quick work of the GiroDisc rotor swap—fully plug-and-play as promised. While the calipers were out, it was easy to service the pads. Full disclosure, GiroDisc does make brake pads too—front (GP40-0991.18) and rear (GP40-1300.18)—but they are full endurance track pads through and through. If you’re spending more time on the street than on the circuit (like me), I’d highly recommend looking at another brake compound. GiroDisc recommended trying Endless MX-72s, but were out of stock when I’d scheduled the install. In the interim, I put in a set of Pagid RSL29s which have been my go-to track pad for years.

FIRST IMPRESSIONS

The first order of business was performing GiroDisc’s recommended bed-in procedure. The street version is different than the full motorsport guide I wrote about before, so bear in mind your usage case. Since street bedding is rather gentle, I haven’t had the opportunity to really lay into these brakes yet, but my baseline trust for what I’ll get out of that middle pedal is a few notches higher, and that means a lot. Akin to most track-focused aftermarket upgrades, GiroDisc’s two-piece rotors will give me more confidence at the limit, just as much as any big brake kit I’ve had in the past. That’s a big statement and a huge testament to what GiroDisc has achieved with a much more reasonable price point. I’m excited to put these through their paces soon.


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