ACT 2004 Mazda RX-8 Flywheel Kit Prolite w/CW03
RX-8 owners who want the Renesis to rev the way a rotary should, or who are building a track or rally car, usually end up looking at a lightweight flywheel. ACT 600140-03 is ACT's Prolite XACT flywheel kit for the RX-8, and it comes with the CW03 counterweight that the rotary needs to stay balanced. At 15.8 lb it is ACT's lightest flywheel option for this car.
The flywheel gives the clutch its friction surface and carries the ring gear the starter engages. On the rotary, the flywheel side also plays a part in balancing the eccentric shaft, which is why ACT states that its flywheel requires a counterweight on RX-7 and RX-8 rotary applications. This kit includes the CW03 counterweight, the flywheel bolts (M10-1.25 x 20 mm) and the counterweight bolts (M8-1.0 x 20 mm). ACT describes the flywheel as externally balanced to match the manual-shift engine using the OE front counterweight.
The Prolite is forged from chromoly steel, CNC machined and computer balanced, with an induction-hardened ring gear of 125 teeth and a 240 mm (9.4 in) friction surface. ACT certifies it to SFI 1.1. Less rotating mass means the engine picks up and drops rpm faster, which ACT says dramatically improves response and acceleration. The trade is drivability: ACT lists mild to moderate gear rattle and recommends the Prolite especially for road racing and rally. If the car is mostly driven on the street, the heavier 600145-03 Streetlite kit is the easier choice.
Most flywheel problems show up once the transmission is out, so inspect the friction face for heat checks, hard spots and cracks, and check the ring gear. If the car is slipping, find out whether the clutch disc, the hydraulics or an oil leak is to blame before ordering parts. Our slipping diagnosis guide covers how to separate a worn clutch from other causes, and flare vs slip helps if you are unsure what you are feeling.
Our listing names the 2004 Mazda RX-8. ACT's own fitment table for 600140-03 runs from the 2004 RX-8 through 2011, including Base, Shinka, GS, GT, Sport, Touring, Grand Touring, R3 and 40th Anniversary models with the 1.3L rotary. ACT clutch kits for the RX-8 note that the ACT counterweight must be used with the ACT flywheel, so this kit is the complete flywheel side of the job. If your car has an engine swap or non-factory transmission, send us your year and VIN so we can check it.
| Brand | ACT |
| Part number | 600140-03 |
| Fits | ACT 2004 Mazda RX-8 Flywheel Kit Prolite w/CW03 |
| Vehicle fitment | Mazda Rx-8 (2004) |
| Type | Flywheels |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
ACT's fitment table lists the RX-8 from 2004 through 2011 with the 1.3L rotary, across all trims. Send us your VIN if the car has a swap.
Yes. The kit is the 600140 Prolite flywheel plus the CW03 counterweight, with flywheel bolts and counterweight bolts included.
ACT lists the Prolite flywheel at 15.8 lb. It is ACT's lightest flywheel offering for this application.
ACT says Prolite gives the best throttle response but reduced drivability and mild to moderate gear rattle. For a daily driver the 600145-03 Streetlite kit is the gentler option.
Yes. ACT says XACT flywheels resurface like stock ones; remove only enough to clean up the face and no more than 0.040 in.
An ACT RX-8 clutch kit such as ZM8-HDSS for street use or ZM8-HDG6 for track use. ACT notes its RX-8 kits must use the ACT counterweight with an ACT flywheel.
