Washer

What Are Washers and Why Do They Matter?

It is easy to overlook the humble washer in a pile of fastener hardware, but these small components play an outsized role in the integrity of any assembly. A washer is a thin, typically disk-shaped plate with a central hole designed to work in tandem with bolts, nuts, and screws. Washers distribute the clamping load of a fastener across a wider surface area, protecting the material beneath from damage, preventing loosening due to vibration, and compensating for surfaces that may not be perfectly flat or aligned.

In automotive, powersports, and small engine applications, washers appear in virtually every corner of a build — from cylinder head and rod bolt assemblies to suspension components, transmission housings, and outdoor power equipment. Choosing the right washer is not simply a matter of finding one that fits. Material, finish, thickness, hardness, and geometry all determine whether a washer will hold up under heat, vibration, torque, and load cycles over the long term.

Types of Washers

• Flat (Plain) Washers: The most common type, used to spread fastener load and protect mating surfaces. Available in SAE and metric sizing.
• Lock Washers: Split or toothed designs that resist loosening caused by vibration and dynamic loads — critical in engine and drivetrain applications.
• Fender Washers: Feature an oversized outer diameter to spread load across thin sheet metal, historically used on body panels and fenders.
• Chamfered Washers: Designed specifically for use with high-strength bolts to ensure proper seating and precise load distribution at the fastener head.
• Insert Washers: Specialty washers used to protect the top of a hole from galling or deformation, especially important in high-load or frequently serviced areas.
• Sealing Washers: Incorporate a rubber or soft metal element to create a fluid-tight seal around fasteners — common in oil drain plugs and fuel system connections.

Top Washer Brands

ARP (Automotive Racing Products) is the dominant name in high-performance and racing washers. Founded in 1968, ARP set out to solve fastener failures in performance engines and has since grown into one of the most respected fastener manufacturers in the industry. Their washers are parallel-ground and hardened, available in premium chrome moly with a black oxide finish or polished stainless steel, and offered in both SAE and metric sizes — including specialty chamfered and insert washer configurations built for demanding motorsports and diesel builds.

Genuine OEM washers are the go-to choice when restoring a vehicle or small engine to factory specification. Using Genuine parts ensures dimensional accuracy and material compatibility exactly as the original manufacturer intended, making them ideal for warranty repairs and precision restorations.

Auveco is a well-established supplier of automotive body hardware and service supplies, offering a broad assortment of washers suited for professional shop use. Their catalog covers a wide range of sizes and styles, making them a reliable source for technicians who need consistent, high-quality hardware across many makes and models.

Briggs & Stratton washers are engineered specifically for small engine and outdoor power equipment applications. As one of the world's largest producers of small gasoline engines, Briggs & Stratton produces OEM-spec washers designed to fit their mowers, generators, and pressure washers precisely — ensuring correct torque values and long-term durability in the field.

B & B Performance rounds out the lineup with washers tailored for performance builds. Their hardware is designed alongside performance engine components, making their washers a natural fit for builders who want matched, purpose-built hardware throughout a high-output engine assembly.

What to Consider When Buying Washers

When selecting washers, start with the correct inner diameter to match your fastener, and verify the outer diameter provides sufficient load-spreading for your application. For performance or high-heat environments, opt for hardened steel or stainless materials over standard zinc-plated hardware. In applications subject to constant vibration — such as exhaust systems, suspension mounts, or small engine decks — a locking washer or serrated flange design adds an important layer of retention security. Always match washer grade to the grade of your bolt for a balanced, reliable assembly.