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GT1 Ultimate Brake Kit

Fitment Guide available Product Installation Services AvailableTraditionally, the 928 owner's brake upgrade choices were limited to upgrading to the brakes found in the next-newer generation of 928's. 928 and 928 S owners upgraded to brakes for a 928 S4 or GT, and S4/GT owners went up to GTS brakes. And there it stopped.

But wheel upgrades haven't stopped as 18" and 19" wheels are now fairly common, and the brakes have not kept up. And if you're a racer - you may have found like many of us that you can over-cook the GTS brakes. But no more.

928 Motorsports LLC® in collaboration with Brembo has developed a new brake kit for the 928, dubbed the "GT1" big brake kit.

Not to be confused with others' "big brake" kits sporting 304 or 322mm rotors, these GT1 brakes are a whopping 355mm rotor with a lightweight two-piece rotor and hat combination.

78-79 all,
80-85 US models
282 mm 108 mm 12.28 lb
80-86 Euro S models 282 mm 110 mm 15.41 lb
87-91 S4 and GT 304 mm 121 mm 18.10 lb
92-95 GTS 322 mm 131 mm 21.00 lb
993 TT 322 mm 131 mm 20.49 lb
928MS GT1 355 mm 150 mm 17.75 lb


ROTOR DIAMETER: the easiest part of the upgrade to see. Larger diameter rotors Increase the thermal mass (decreasing brake fade) and improves stopping power by increasing the effective radius (see below). And they look AWESOME through aftermarket 18" wheels!

EFFECTIVE RADIUS: the benefit received when using a longer wrench to turn a tough bolt. In this case, using a longer wrench to stop the rotor from spinning. The longer the effective radius of the caliper/rotor combination, the more powerful the brakes. Not the same as the radius of the rotor, but the distance from the center of the rotor to the center of the caliper piston.

ROTOR WEIGHT: although increased thermal mass helps decrease brake temps, increased weight means more unsprung weight and higher rotational inertia - both which hurt performance. The answer is a two-piece rotor/hat combination that gives the rotor the thermal mass it needs, but lightens the assembly for less unsprung weight and inertia.

We selected 4-piston calipers for our GT1 kit, and this is why:

There is a common misconception that 6-piston calipers have better stopping power than 4-piston calipers. That isn't true. The increase in stopping power comes from the increase in rotor diameter, effective radius, and the hydraulic gain of the system. Brake pad size and the number of pistons in the caliper have nothing to do with braking effectiveness.

Most 6-piston calipers flex more, cost more, and fit inside fewer wheels - making wheel fitment a challenge. Brake pads for a 6-piston caliper also cost more, and are offered in only a few materials. The only merit they have is that the brake pad on a 6-piston caliper is larger, so they last longer between pad changes - which is a valuable feature if you are endurance racing. But, it also means they cost more at each pad change.

On the other hand, our Brembo 4-piston caliper is stiffer, and requires 10mm less of clearance than the 6-piston model, so it will fit inside virtually all 18" wheels. It has a broad selection of brake pads available for it, and they cost less. Additionally, the 4-piston caliper features the quick release pad design, which is a nice feature for customers tracking their cars.

This kit fits all S4, GT and GTS models. A direct bolt-on fit. This kit also can fit 1978-86 models with a custom steel caliper adapter we manufacture and a set of early spindles.

We specifically designed this kit to perform with the stock 928 master cylinder and brake bias valve, so that pedal force and pedal travel would be the same as stock. (I can hear you saying "how can you do that?" It's done by changing the diameter of the pistons in the calipers so that the mean hydraulic gain remains the same) This also means you can install our kit on the driveway - it took me less than 30 minutes per wheel - and you're done. No need to change the master cylinder or brake bias valve at all.

Although we designed this kit to be compatible with most all 18" and 19" wheels, a paper cut-out of the rotor and caliper is available for download and should always be used before ordering to confirm that your wheels will fit around these brakes. Brembo recommends a minimum of 3mm clearance between the caliper and the wheel spoke or rim.

Brembo uses the highest quality components for everything from brackets to rotors to even the disc assembly hardware. Our parts last longer and these kits do not have the same issues commonly associated with brake kits from other manufacturers. Some brake companies advise to take off their product in the winter, rebuild calipers yearly, safety wire hardware in place, etc.
The resources Brembo has and the testing we do before a kit is released allows us to provide upgrades that do not require our customers to invest additional time babysitting the product.

There are several reasons that a two-piece floating disc assembly is of benefit. First, using an aluminum bell for the hub section of the disc saves a great deal of weight. Since this is both rotating and unsprung, it benefits the acceleration, braking, and handling of the vehicle. Secondly, it is better able to handle the large temperature changes that a brake disc experiences, and provides a better thermal break to reduce wheel bearing temps.

The mounting system is designed to allow a specific amount of float in both radial and axial directions. Brembo has engineered special springs that are used on every other fastener in order to slightly preload the assembly. This has been done to prevent excessive noise from the system during street use.

Brembo supplies a directional curved vane disc in these assemblies. The discs are installed with the vanes running from the inside to the outside diameters in the direction of rotation. Orienting the disc in this manner creates a centrifugal pump. The rotation of the disc causes air to be pumped from the center of the disc, through the vanes, and out through the outside diameter of the disc. This greatly enhances the disc's ability to dissipate heat.

The main advantages of drilled and slotted discs are the same: a continuous refreshing of the brake pad surface, and a exit path for water and out-gassing of the pads.

Drilled discs have the additional advantage of being lighter and running cooler. They continuously clean and refresh the pad surface, shed water and debris, prevent gas build up, and increase pad "bite". There are certain pad materials that should not be used with a drilled disc.

Slotted disc offer increased durability under extreme conditions. They provide higher thermal capacity than a drilled rotor, which makes them a better setup in race like conditions. This is the more appropriate track setup as it constantly refreshes the pad and improves initial bite. You can also run more aggressive track oriented pads without the potential premature cracking seen with most holed discs

  • 355 mm front rotors
  • 328 mm rear rotors
  • new 4-piston calipers (select color)
  • billet aluminum caliper spacers
  • hardened caliper bolts
  • SS braided brake lines with hardware
  • brake pads (select type)
  • Instructions

Multiple Brake Pads Available
Here are all the pads we carry for this kit

Ferodo    Ferodo FM 1000 (Front & Rear)
Ferodo FM 1000 w/ pad sensor (Front & Rear)
Ferodo DS3000 (Front Only)
Hawk    Hawk DTC 30 (Front & Rear)
Hawk DTC 60 (Front Only)
Hawk DTC 70 (Front Only)
Pagid    Pagid Blue 4-2 (HP Street) (Front & Rear)
Pagid Orange 4-4 (Race) (Front & Rear)
Raybestos    Raybestos ST04 (Street) (Front & Rear)
Raybestos ST42 (Race) (Front Only)
Porterfield    Porterfield R4S (Street) (Font & Rear)
Porterfield R4 (Race) (Front & Rear)

All GT1 brake kits are custom built to order, so it is important to verify wheel fitment before placing the order.

Each GT1 kits ships in 2 boxes labeled Left / Right). This makes the installation even easier because customers do not have to determine the correct calipers or rotors for each side.



GT1 Ultimate Brake Kit


Caliper Color

Rotor Type

Brake Pads
















* Domestic US shipping shown. International shipping will be calculated based on location.

Phone: (920) 485-0928
Email: info@928motorsports.com

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Horicon, Wisconsin USA

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