ACT 1991 Mazda Miata HD/Race Sprung 4 Pad Clutch Kit
Miata owners who autocross, run time attack or have added a turbo or supercharger to the NA or NB car often need a clutch that will not fade or glaze when it gets hot. ACT ZM2-HDG4 puts ACT's Heavy Duty pressure plate together with a 4-pad, spring-centered ceramic race disc. It holds 310 ft-lb, shifts quickly and keeps the pedal manageable, at the cost of a harsher, more on-off engagement than a street disc.
In the Miata the clutch sits between the flywheel on the four-cylinder and the rear-drive five- or six-speed gearbox. ACT rates ZM2-HDG4 at 310 ft-lb measured at the crank, 74 percent above the stock clutch. The disc is 8.8 in (224 mm) with ceramic pads on a 0.9375 in input shaft, and the complete kit weighs 12.4 lb.
The Heavy Duty diaphragm raises clamp load and resists deflection; ACT heat treats every diaphragm in four stages. The disc has four ceramic pads instead of a full ring of lining, and ACT says this layout makes engagement harsher but shifting faster, and that the 4-pad disc is well suited to smaller disc sizes in smaller engines, which is exactly the Miata. The spring center damps torsional vibration for quieter running and resists failure under hard use. ACT lists the feel as light to moderate pedal effort, aggressive engagement and OE to mild gear rattle, with moderate friction life.
Confirm slip with a full-throttle pull in fourth gear from low rpm; if the tach rises faster than road speed, the disc is not holding. A Miata with a worn master or slave cylinder can feel like a bad clutch too, with grinding into gears or a pedal that sticks, so check the hydraulics first. Our slipping diagnosis guide explains the road test, and shift flare versus slip helps sort out what you are feeling.
ACT builds several race versions on the same Heavy Duty plate. The ZM2-HDG6 6-pad sprung kit has the same 310 ft-lb rating with more pad area, which spreads wear and softens engagement a little. The ZM2-HDR4 rigid 4-pad kit drops the hub springs for a dedicated race car. For a car that still sees a lot of street miles, the ZM2-HDSS Performance Street kit is the smoother choice.
Our listing title says 1991, but ACT's application list for ZM2-HDG4 covers the 1990-1993 1.6L Miata and the 1994-2005 1.8L Miata, including the M Edition, 10th Anniversary, Shinsen and the 2004-2005 Mazdaspeed. It does not fit the 2006-up NC or later cars. Early 1.6L cars left the factory with a smaller clutch, and ACT's Miata flywheels are made for the 1994-up 1.8L clutch size, so 1990-1993 owners should plan on a matching flywheel and contact us before ordering. Confirm ZM2-HDG4 on the box, or send the year and VIN and we will check fitment.
A flywheel is not included.
| Brand | ACT |
| Part number | ZM2-HDG4 |
| Fits | ACT 1991 Mazda Miata HD/Race Sprung 4 Pad Clutch Kit |
| Vehicle fitment | Mazda Miata Hd/Race Sprung 4 (1991) |
| Type | Clutch Kits - Single |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Yes. ACT lists it for the 1994-2005 1.8L Miata, including the Mazdaspeed, as well as the 1990-1993 1.6L cars. It does not fit the NC or ND.
Both use the MZ012 Heavy Duty plate and are rated 310 ft-lb. ACT says the 4-pad disc gives harsher engagement but faster shifts and suits small discs in small engines; the 6-pad disc has more friction area for a slightly smoother bite.
You can, but expect aggressive, on-off engagement and some chatter in traffic. ACT rates pedal effort as light to moderate. If the car is mostly street driven, the HD Performance Street kit is a better match.
A flywheel is not included. At minimum resurface yours; on a 1990-1993 1.6L car plan on a flywheel made for the 1994-up 1.8L clutch size.
The Miata clutch hydraulics share brake fluid; bleed with DOT 3 and check the reservoir cap marking on your car.
