Fitment: This ACT performance street sprung disc fits 2004 - 2021 Subaru STI and 2007 - 2009 Subaru Legacy GT Spec B. It's a replacement for ACT SB4 part numbers. Features: If your ACT Performance Street Sprung Replacement Disc for the Subaru STI (3000503) is worn out and you don't want to buy a whole new clutch kit, this replacement is a great choice. The disc uses premium organic materials with high copper content, which enhances heat transfer. It allows for quick shifting and smooth engagement. With a reduced marcel, it enables faster shift action to match ACT pressure plates. The spring - centered assemblies use bushings and cone springs like factory clutch discs, creating frictional dampening that improves clutch life and reduces noise. It offers quiet operation, increased strength, and reliability. Feel: It provides smooth engagement, quicker shifts, and has mild gear rattle similar to OE. Recommended Use: Ideal for both street and race use. ACT Difference: It has steel - backed linings for higher burst strength and a reduced marcel for quicker shifts. Manufacturer Warranty: Comes with a Limited Retail Warranty. Installation Instructions: Follow ACT's General Installation Instructions. FAQ: Can an ACT Race puck - style disc be used for daily driving? ACT's race discs are too aggressive with harsh engagement. They can cause judder and noise when starting from a stop. They're only for professional race settings, not the street. ACT recommends organic discs for street use for smoother engagement and long - lasting performance. When should a clutch disc be replaced? Most new discs are 0.312 - 0.315 inches (7.93 - 8.00 mm) thick. They should be replaced when they're 0.275 inches (7.00 mm) or less. Some Audi and BMW applications start at 0.332 - 0.335 inches (8.43 - 8.50 mm) and should be replaced below 0.295 inches (7.50 mm). Measure with a micrometer. For organic street discs, compress the engagement cushion (marcel) between the linings. If the lining rivets touch the flywheel or pressure plate, replace the disc. Using a disc outside the pressure plate's designed working range can lead to poor results.
Using this ACT street sprung disc is straightforward. First, make sure your vehicle is the right fit - it's for 2004 - 2021 Subaru STI and 2007 - 2009 Subaru Legacy GT Spec B. When installing, follow ACT's general installation instructions carefully. For normal use, you'll enjoy smooth and quick shifts, whether you're on the street or at the race track. But remember, if you've got an ACT race puck - style disc, don't use it for daily driving. It's too aggressive and will make your driving uncomfortable. To know when to replace the clutch disc, measure its thickness regularly with a micrometer. For most cases, replace it when it gets too thin. Also, check if the lining rivets are touching the flywheel or pressure plate. If so, it's time for a new disc. For maintenance, keep the disc clean and free from debris. If you notice any unusual noise or a change in shifting performance, it's a good idea to have it checked out. With proper use and care, this disc will serve you well for a long time.
