{"product_id":"gt-rassy-jpggt-rassy2-jpggt-rassy3-jpggt-rassy4-jpg-find-a-dealer-need-help-contact-us-ap-racing-j-hook-2-piece-disc-assembled-pair-front-390x34mm-r35-nissan-gt-r","title":"AP Racing J Hook 2-piece Disc Assembled Pair (Front 390x34mm)- R35 Nissan GT-R","description":"\u003cdiv class=\"product-summary\"\u003e\n\u003cp\u003eAP Racing 2-piece J Hook Disc Pair for\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003efront\u003cspan\u003e \u003c\/span\u003e\u003c\/strong\u003eof the 2012+ R35 Nissan GT-R (\u003cstrong\u003eexcept NISMO with 14mm studs\u003c\/strong\u003e):\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eDirect replacement for the OEM 390mm x 34mm discs, 84 vanes\u003c\/li\u003e\n\u003cli\u003eWorks with OEM calipers\u003c\/li\u003e\n\u003cli\u003eHuge increase in airflow, cooling capacity, and durability vs. OEM discs\u003c\/li\u003e\n\u003cli\u003eDesigned for: road, club racing, time trial, autocross, HPDE\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eTwo-piece Floating Design with Aluminum Hat\u003c\/h3\u003e\n\u003cp\u003eAs is the case with most metal, iron brake discs grow substantially when heated. As it is heated, a disc expands radially, increasing in diameter and circumference. One-piece disc designs run into problems when this occurs. Look at the picture below and imagine the disc is being heated on the track. As the disc expands, the outer edges of the disc are pulling away from the center of the disc, but there are no built-in provisions to allow for that expansion. The edges of the disc therefore pull, lift, and distort, which is called coning. Now imagine that disc vertical on the car, running in your caliper. Coning directly impacts the brake pads’ contact with the disc, leading to uneven wear and tapering, and even a long brake pedal.\u003c\/p\u003e\n\u003cp\u003eTwo-piece discs on the other hand, compensate for the expansion of the disc as it heats. This is accomplished by building ‘float’ into either the disc itself, or the disc hat\/bell. In this case, the float is in the hat.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/oem_disc_heat_expansion_web_3.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/disc_heat_expansion_web_3.jpg\"\u003e\u003c\/p\u003e\n\u003ch3\u003eMounting Hardware and Anti-Knockback Spring Clips\u003c\/h3\u003e\n\u003cp\u003eIf you look closely at the mounting hardware we use on our 2-piece discs, you’ll notice a few details that are often overlooked in lesser products. These components are specially made for their intended purpose. These are not the cheap bits found at your local big box store. They are custom made for Essex and AP Racing.\u003c\/p\u003e\n\u003cp\u003eIn order to help control the lateral motion of the disc, which pushes the pistons back into the caliper, we use an anti-knockback spring clip on every disc attachment point. These spring clips help keep the disc hat and iron ring in alignment, while still allowing the disc to expand and float radially. As an added bonus, they prevent the hat and iron disc from rattling and making noise.\u003c\/p\u003e\n\u003ch3\u003eHat Design\u003c\/h3\u003e\n\u003cp\u003eFloating two-piece discs also have the added benefit of reducing heat conduction to the hubs and bearings, decreasing wear and tear on these costly components. The disc hats themselves are manufactured from 6061 heat-treated billet aluminum, with a hard anodized coating. This material was specifically chosen for its strength at high temperatures, as it will be in direct contact with the searing hot iron discs.\u003c\/p\u003e\n\u003ch3\u003eInternal Vane Quantity and Quality\u003c\/h3\u003e\n\u003cp\u003eThe internal vane design on AP J Hook Discs is quite a bit different vs. OEM-style discs and other brands of aftermarket discs. Many OEM discs feature a pillar vane design, which can be thought of as a group of posts or pillars connecting the two disc halves together (see pic below). The pillars are not organized linearly from the outside to the inside of the disc, and turbulence is created as air flows through and among them. Pillar vane discs are therefore not particularly well suited to heat evacuation. The goals of a pillar vane design are disc face stability for low NVH (noise, vibration, harshness), and a low cost of production. Pillar vanes are non-directional, and the same part number is used on both sides of the car (again for cost reduction). Other OEM discs feature a straight, non-directional internal vane. While that type of vane flows more air than a pillar, it does not move nearly as much air as the directional vanes featured in AP Racing's discs. Having directional vanes means that AP Racing discs are handed. There is a unique left disc and a right disc in each pair, and they cannot be swapped from side-to-side on the car. The orientation of the vanes is optimized to spin in a certain direction, pumping the maximum amount of air possible through the disc. The shape of these internal vanes is also optimized to promote smooth airflow.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/left_right%20illustration_3.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/Disc_CutOut_three_quarter_view_WEB.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003eIn addition to having a superior internal vane design, AP Racing discs have far more of them! Most aftermarket discs have 30 to 48 vanes. After extensive CFD and thermal stress analysis, AP designed the Competition J Hook's with a high vane count (typically 60 to 84 depending on application). Having more vanes increases airspeed and heat transfer through the disc, reduces air recirculation between vanes, and reduces deflection at the disc face. Compared to an OEM-style disc or competitor's 48 vane discs, the 60+ vane discs are less prone to coning, distortion, and cracking, while providing less brake fade, reduced judder, more even pad contact, and a longer service life.\u003c\/p\u003e\n\u003cp\u003eBelow is a comparison of a one-piece OEM pillar vane disc and an AP Racing two-piece J Hook. A few things to note in these pictures: The AP Racing disc has a much wider air gap between the disc faces, allowing considerably more airflow into and through the disc. The uniform, directional vane design also contributes heavily to superior airflow.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/OEM_disc_vane_design_WEB_cropped.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/jhook_disc_vane_design_web_cropped_2.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003eMost of the cooling air that enters a brake disc comes from the back side of the discs, particularly if brake ducts are being employed. The top disc is an OEM pillar vane. The second disc is an OEM dual-cast disc (which is technically a two-piece disc). The bottom disc is the AP Racing J Hook. Which of these discs do you think will flow the most air? While the OEM discs have narrow inlet port and\/or obstructions blocking the disc vanes, the AP Racing disc offers a clear path for cooling air to enter and flow through the disc. The result is significantly cooler discs that are less prone to cracking and wear.\u003cbr\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/OEM_disc_vane_design_inlet_WEB_cropped.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/frdiscairgap_dualcast_cropped_2.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/Jhook_disc_vane_design_inlet_WEB_cropped.jpg\"\u003e\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ch3\u003eExclusive AP Racing J Hook Slot Pattern\u003c\/h3\u003e\n\u003cp\u003eWhen you cut a slot or drill a hole in a disc you impact heat transfer. The area around the slot or hole acts as a cool spot when the disc heats up, which is not ideal. Ideally, heat is distributed uniformly around the disc so it can be hit with the cooling air that is pumping through the disc, radiate outwards away from the disc, etc. Cool spots create stress risers and increase the likelihood of the disc cracking. They also cause the face of the disc to distort unevenly, leading to uneven pad deposits, vibration, and judder.\u003c\/p\u003e\n\u003cp\u003eThe OEM discs avoid this problem by simply leaving the face blank. While the risk for NVH goes down, so does the pad bite and feel of the disc through the brake pedal. Competitive aftermarket offerings typically have straight slots, which tend to leave cool spots across the disc face between the slots.\u003cbr\u003e\u003cstrong\u003e\u003cbr\u003e\u003c\/strong\u003eDuring exhaustive R\u0026amp;D testing, AP's J Hook design was found to create a constant pathway of evenly distorted material on the face of the disc. The hooks are spaced out as evenly as possible both around the circumference of the disc, as well as from the inside edge (where the hat attaches) to outer edge, with a slight overlap to promote even heat distribution\/distortion. In addition to reducing cracking, the even heating of the disc also helps provide an even transfer layer of pad material on the disc when you bed them in.\u003cbr\u003e\u003cbr\u003eAdditionally, the J Hook slot pattern produces a greater number of leading edges for the pads to bite into vs. a traditional curved slot pattern, and particularly a plain-faced disc. While this may lead to slightly more whirring or scraping noises from the discs when applying the brakes, the benefits of more even heat distribution, less propensity to crack, cleaner pad material transfer during bed-in, and more bite far outweigh the slight increase in NVH for the serious enthusiast.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/www.essexparts.com\/storage\/wysiwyg\/jhook_two_web_3.jpg\"\u003e\u003c\/p\u003e\n\u003ch3\u003eFeature: Complex Metallurgy Developed Through 50+ Years of Experience\u003c\/h3\u003e\n\u003cp\u003eAP Racing has been designing brake components for more than 50 years. They've had their components on cars that have won more than 750 Formula 1 races! On any given race weekend, AP J Hook discs can be found on 75% or more of the NASCAR Sprint Cup grid. AP has learned from these experiences, and have developed a proprietary iron alloy with extreme durability, designed specifically for what you intend to do with it (flog the hell out of it). The primary objectives with OEM discs are simple: they must be cheap and easy to produce. The design objectives for these two products are vastly different.\u003c\/p\u003e\n\u003cul\u003e\u003c\/ul\u003e\n\u003cul\u003e\u003c\/ul\u003e\n\u003cul\u003e\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c!----\u003e","brand":"AP Racing","offers":[{"title":"Default Title","offer_id":45882499006723,"sku":"20.01.20001","price":2549.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0604\/9264\/4611\/files\/gt-rassy.jpg?v=1724783047","url":"https:\/\/www.elite-performance.com\/products\/gt-rassy-jpggt-rassy2-jpggt-rassy3-jpggt-rassy4-jpg-find-a-dealer-need-help-contact-us-ap-racing-j-hook-2-piece-disc-assembled-pair-front-390x34mm-r35-nissan-gt-r","provider":"Elite Performance","version":"1.0","type":"link"}