Harley Davidson Bolt Size Chart: A Comprehensive Guide

As a motorcycle enthusiast, I know that customizing and maintaining a Harley-Davidson requires attention to detail and understanding the various components. One of these essential components is the bolts used in the assembly of the motorcycle. To ensure a perfect fit and prevent damage, it’s crucial to know the different sizes of these bolts and how they relate to the specific Harley-Davidson model. In this article, we’ll be focusing on the Harley-Davidson bolt size chart that you might find valuable in optimizing your riding experience.

When working on a Harley-Davidson, I’ve noticed that the brand uses various types of bolts throughout the motorcycle, each designed for specific purposes. For instance, there are hex head cap screws, which are common in Harley-Davidson Sportster models with axle sizes of 25mm and ¾ inches. Knowing these details not only makes it easier for me to find replacement parts but also lets me enjoy a safer and smoother ride on my beloved motorcycle.

Bolt Sizing Basics

When discussing Harley Davidson bolt size charts, it’s important to break down the essentials of bolt sizing. I often refer to size charts, which are organized charts representing both inch and metric bolt sizes. They help me identify the correct bolt size for various nuts, components, and fasteners on my Harley Davidson motorcycle.

In terms of bolt sizing, I tend to focus on the thread size, which is a crucial parameter for the overall bolt size. For Harley Davidson motorcycles, key sizes are typically found within the 45, 74, and 80 ranges, which are commonly used in various fastening applications on the motorcycle.

Bolt sizes are generally measured in terms of diameter, thread pitch, and length. For instance, a bolt size might be represented as 1/4-20 x 1.5, which means the diameter is 1/4 inch, the thread pitch is 20, and the length is 1.5 inches. I make sure to be mindful of these measurements when selecting bolts for my bike.

It’s also worth noting that different types of fasteners may be used in various parts of the Harley Davidson motorcycle. For example, hex bolts are used in both rear and front sections of the bike. These threaded bolts have a hexagonal head and are a prominent style on Harley Davidson motorcycles. They feature different sizes and threads, which can be found in the bolt size chart below:

Bolt LocationBolt Size (SAE)Bolt Size (Metric)
Derby Cover1/4″-20M6-1.0
Primary Inspection Cover1/4″-20M6-1.0
Cam Cover1/4″-20M6-1.0
Transmission Side Cover1/4″-20M6-1.0
Front Brake Caliper Mounting3/8″-24M10-1.5
Rear Brake Caliper Mounting3/8″-24M10-1.5
Front Fender Mounting5/16″-18M8-1.25
Rear Fender Mounting5/16″-18M8-1.25

When working with bolt sizes, I always keep in mind the conversion between inch and metric measurements. For instance, a 1/4-inch diameter bolt is approximately 6.35mm. This helps me make the right choices even when dealing with metric components.

Types of Bolts and Nuts

In this section, I will discuss the various types of bolts and nuts used in Harley-Davidson motorcycles. It is essential to know the right bolt sizes and types to ensure proper maintenance and assembly of your motorcycle. There are many different types of bolts and nuts, but I will focus on the most commonly used ones in Harley-Davidson motorcycles.

Types of Bolts

Hex Head Bolts: These bolts have a hexagonal head and are one of the most common types of bolts used in Harley-Davidson motorcycles. Their size varies, with the handlebar riser mounting bolts being 5/16-18 x 7/8″ for the front axle and 3/8-16 x 1″ for the rear axle, according to the Harley-Davidson bolt size chart.

Allen Head Bolts: Also known as socket head bolts, Allen head bolts have a cylindrical head with a hexagonal socket. They are widely used in Harley-Davidson motorcycles because they provide a clean appearance and allow for greater torque without damaging the bolt head. Some Harley-Davidson bolts, such as fine thread smooth socket head bolts, come in various sizes like 1/4″-28.

Button Head Bolts: These bolts feature a round head with a hexagonal socket and are often used in locations where appearance is important. Harley-Davidson uses button head bolts in certain applications like 1/4-20 x 1-1/2 socket button head screws.

Types of Nuts

Hex Nuts: These are the most common type of nuts used in conjunction with hex head bolts. Hexagonal in shape, they provide a secure fit for various components on a Harley-Davidson motorcycle.

Nylock Nuts: Nylock nuts are designed with a nylon insert that locks onto the threads of the mating bolt, providing resistance to vibration and ensuring the nut doesn’t loosen over time. They are a popular choice for applications that require a secure and long-lasting connection, making them suitable for use in Harley-Davidson motorcycles.

Flange Nuts: These nuts have a flange, or a built-in washer-like area, around their base that helps distribute the load evenly across a wider surface area. This feature makes them a good choice for bolting parts together with a strong, vibration-resistant connection in Harley-Davidson motorcycles.

Individual Components

As someone who’s passionate about Harley Davidson motorcycles, I’d like to share some information about the different bolt sizes in various individual components. In this section, we will cover bolt sizes for Frames, Clamps, Handlebars, Brackets, and Breather Bolts.


The frames of Harley Davidson motorcycles have been designed with various bolt sizes, depending on the specific model and year of the bike. For example, the Sportster models typically use axle sizes of 25mm and ¾ inches, which are ideal for small- to medium-sized wheels. Other options include 20mm and 1 inch, which can handle larger wheels and tires.


Clamps are essential for securing various components of a Harley Davidson motorcycle together. The bolt sizes for clamps can differ based on the specific part, such as the exhaust clamp, riser clamp, or hose clamp. In general, you may encounter bolt sizes that range from smaller ones like 1/4-20 to larger ones like 1/2-13.


The handlebars on a Harley Davidson motorcycle play a crucial role in the rider’s comfort and control over the bike. Bolt sizes for the handlebar components can vary depending on the model or aftermarket parts used. Standard sizes include 5/16-18 or 3/8-16, but 1/4-20 or 10-24 can also be found on certain models and accessories such as grips and mirrors.


Brackets are used to support and attach various components like saddlebags, footpegs, and exhaust systems to the motorcycle’s frame. Bolt sizes for brackets can range from smaller ones like No. 8-32 to larger ones like 1/2-13 or even unique sizes like No. 4-40. It is crucial to check your specific motorcycle’s manual or consult with your mechanic to avoid incompatibility issues when replacing brackets’ bolts.

Breather Bolts

Breather bolts are used to release crankcase pressure in Harley Davidson motorcycles, especially in the air cleaner assembly. The size of breather bolts can differ based on the specific engine type, but common sizes include 1/4-20, 5/16-18, or 3/8-16. It’s important to install the correct breather bolt size to ensure proper ventilation of the engine and maintain optimal performance.

Transmission and Tire Bolts

When it comes to working on my Harley-Davidson motorcycle, it’s essential to know the correct bolt sizes. This is especially true for the transmission and tire areas of the bike. I find that having a proper bolt size chart is highly beneficial and saves me time when I need to replace or tighten certain bolts.

For the transmission bolts, there are a few different sizes to keep in mind. The 3/8-inch size hex bolts (9/16-inch hex) are used for attaching the transmission to the engine mounting screws source. The 5/16-inch size hex bolt (1/2-inch hex) is used for securing the engine case screws.

As for the tire bolts, it’s important to be aware of both the front and rear bolt sizes for various Harley-Davidson models. For example, Softail models from 2007 to 2017 use a 12mm front and rear bolt, while Road Glide models from 2017 to 2022 use a 19mm front and rear bolt. Dyna models from 2008 to 2017 may use 8-19mm front and rear bolts, while Fat Boy models from 2000 to 2017 have a range of 10-19mm for both front and rear bolts. Trike models from 2009 to 2021 use a 12mm front bolt and an 11mm rear bolt, and Touring models from 2008 to 2021 use 12mm bolts for both front and rear.

It’s worth noting that the size of hex-head handlebar riser mounting bolts on a Harley-Davidson motorcycle is typically 5/16-18 x 7/8″ for the front axle and 3/8-16 x 1″ for the rear axle.

Knowing the correct bolt sizes for my Harley-Davidson will allow me to keep it running smoothly and securely. With this information in hand, I can spend less time worrying about repairs and more time taking in the sights.

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