Genuine Mazda M8 × 20mm Flange Bolt – 12mm Hex Head • 9946-30-820

Genuine Mazda 9946-30-820 M8 × 20mm Flange Bolt – 12mm Hex Head

Replacement Genuine Mazda flange bolt for Mazda MX-5 Mk3, Mk3.5 and Mk3.75 NC models and Mazda MX-5 Mk4 ND/RF models, with the exact mounting position depending on the vehicle and assembly.

This is an M8 × 20mm threaded fastener with a 12mm hexagonal head and integral flange. Confirmed MX-5 uses include the Mk3 NC underbody Y-brace and lower dashboard mounting, together with the Mk4 ND/RF brake-pedal and air-cleaner housing mounting points.

The integral flange distributes the clamping load across the mounting surface and allows the bolt to fit the original Mazda assembly without a separate conventional washer. The same OE fastener is used by Mazda in several different body, chassis, battery, transmission and mounting applications.

These bolts may require replacement when the original fastener is corroded, seized, stretched, rounded, damaged or missing following previous dismantling. A damaged bolt can prevent the associated bracket or component from being tightened correctly.

• Part type: Flange bolt / mounting fastener
• Thread size: M8
• Nominal threaded length: 20mm
• Head size: 12mm hexagonal head
• Primary use: Secures compatible Mazda brackets, braces, pedals, housings and supporting components
• Confirmed MX-5 NC uses: Underbody Y-brace and lower dashboard-to-chassis mounting
• Confirmed MX-5 ND/RF uses: Brake-pedal and air-cleaner housing mounting
• Quantity per vehicle: Varies according to mounting position
• Quantity supplied: 1 bolt
• Brand: Genuine Mazda
• Part No.: 9946-30-820
• Also referenced as: 994630820

Fitment advice: This bolt is used in multiple locations and the required quantity varies by assembly. Compare the thread diameter, length, head size and original mounting position before installation. A matching part number provides the most reliable confirmation where the vehicle has previously been modified or dismantled.

Other items to consider: Inspect the associated bracket, brace, captive nut, threaded mounting point and nearby fasteners for corrosion, damaged threads or distortion. Where several matching bolts secure the same assembly, replacing any similarly damaged fasteners should be considered.

Useful tools / consumables: 12mm socket or spanner, ratchet, extension bar, torque wrench, penetrating fluid, wire brush and suitable thread-cleaning tools. Anti-seize compound should only be used where permitted by the relevant Mazda workshop procedure, as lubrication can alter the achieved clamping load.

Difficulty guide: DIY Difficulty: Easy to Moderate. Difficulty depends on the mounting location. Air-cleaner and dashboard fasteners are generally accessible using basic tools, while underbody brace work requires the vehicle to be raised and supported safely on suitable stands or a lift.

Why Genuine Mazda? Genuine Mazda fasteners are manufactured to match the original thread, length, head profile, flange diameter and material specification required by the vehicle assembly. Using the correct fastener helps provide suitable thread engagement, component clearance and clamping force.

What’s in the box: One Genuine Mazda M8 × 20mm flange bolt, part number 9946-30-820.

Installation notes: Clean the threaded mounting point and check that the replacement bolt turns freely by hand before tightening. Position the associated component correctly and tighten the bolt to the torque specified for that exact mounting location. Do not substitute a generic torque figure solely from the bolt dimensions, as the required setting can vary according to the assembly and material being secured.