Harley Davidson Bolt Size Chart: A Complete Guide

Harley Davidson bikes have multiple bolt sizes in front and rear axles. The dimensions of these bolts vary depending on the position they are to be used. The size chart of the bolts will give you a good view of this. 

Bolts in the Harley Davidson bikes are prone to rusting no matter how iconic those are. Since knowing bolt size is crucial for bike maintenance, having a broad idea is essential. Let us explore the bolt sizes and other factors relevant to the rest of the article.

Harley Davidson Bolt Size Chart

Bolt sizes in the Harley Davidson motorcycles differ due to bike models and production year. Below here, we have included a chart that’ll give you a good view of the bolt sizes:

Model/Production YearFront BoltRear Bolt
Softail (2007-17)12 mm12 mm 
Road Glide (2017-22)19 mm19 mm
Dyna (2008-2017) 8-19 mm8-19 mm
Fat Boy (2000-2017)10-19 mm10-19 mm
Trike (2009-2021) 12 mm11 mm
Touring (2008-2021)12 mm12 mm

Read Also: Harley Davidson Tire Pressure Chart – Ride Safe And Steady

Types Of Bolts Used In Harley Davidson

Both in the rear and front parts of your Harley, multiple types of bolts are used.

Among them, we will be discussing some of the prominent styles in the section below:

Hex Bolts

It’s a form of a threaded bolt, which comes with a hexagonal shape on its head. Usually, these types of bolts require tightening and loosening with a wrench. 

Given its multiple requirements, you’ll find both threaded and partially threaded hex bolts.

In your Harley, gripping the hex bolts is easily possible through multiple angles using the right tools. It makes the process easier for loosening and tightening the bolts.  

That said, the sizes of hex bolts on Harleys may vary depending on models and specific component elements. Some of the most common sizes are ¼”-20, 5/16″-18, 3/16″, ⅜’ etc.

Read Also: Harley Davidson Air Suspension Chart – Find The Ideal Pressure

Torx Bolts

Torx bolts are one of the primary bolt types used in Harley Davidson bikes. These fasteners are perfect for gripping multiple components. 

One good trait about these bolts is that they are less damage-resistant. Also, the fastenings are considerably tighter.

These bolts also come with a higher surface area for torque application. Tool slippage and effectiveness are way better than most other bolt types.

Moreover, these universal bolts are available in different sizes for Harley bikes, and some of the most common sizes are – 5/32″, ¼, “3/16”, T25, T27 etc.

Allen Head Bolts

These bolts are also known as allen head screws. It is one of the most popular fasteners with multipurpose usage. You’ll see a hexagonal shape on its head, similar to hex bolts. 

Both hex bolts and allen bolts can be loosened or tightened with the help of hex keys. That said, these bolts are relatively lighter than most other ones. 

You can remain tension-free as these bolts don’t damage the surroundings during installation or removal. 

Moreover, allen bolt size requirements are different for various components in the Harley bikes. The most common sizes are – ⅜”, 5/16″, 7/16″ etc.

Read Also: Harley Davidson Fluid Capacity Chart: A Must-Read Resource

What Are Some Of The Common Harley Davidson Bolt Sizes?

There is a set of different bolt types used for various components. Sizes of all these bolts will be rare due to the different functionalities of the components. That said, some of the standard bolt sizes in Harley Davidson are as follows:

  • ⅜” – These bolts have 16 threads on every inch. You can use them mostly on engine mounts and foot pegs. 
  • ½” – Frames and engine mounts are the primary usage points for these bolts.
  • 5/16″ – These come with 18 threads per inch and are primarily used in the brake calipers, clamps and foot controls.
  • 7/16″ – Perfect for usage in important and heavy components. These have 14 threads on every inch.
  • ¼”– Perfect for usage in the mirrors and covers. These bolts have the highest number of threads among all bolts.

Read Also: Harley Exhaust Fitment Chart: Road to Perfect Fit For Your Harley

How Can You Use Size Chart For Repair And Upgrades?

If some of your bolts are damaged or need replacing a component, you must identify the bolt size. You may use the chart properly to know the following things:


When you know the bolt type you need, you should check the specific dimensions for the components. Use a thread pitch gauge tool to measure the dimension and then consult the chart for replacement. 


Bolt upgradation is needed when you plan to improve the aesthetics and strengthen the attachment. It may give you a view of the compatibility of your bike model with a higher-grade bolt type.


The chart’s most basic usage is knowing the exact bolt size for replacement. The chart lets you know the appropriate sizes for all the necessary bolts.

Read Also: Harley Davidson Bulb Replacement Chart [An Extensive Guide!]


Choosing a specific bolt size for your Harley Davidson model can be confusing if you are new to this. We have answered some of the most asked queries below to address this situation.

Are Harley Davidson Bolts Metric Or Standards?

Most of the Harley Davidson bolts aren’t confined to a specific method. You’ll find them using both methods, meaning the bolts have different measurements.

What Is The Thread Size Of A Harley Stem?

The thread size of a Harley stem is 24 threads per inch. These are hexagon nuts with a diameter of 1^.

What Size Bolts Does A Harley Seat Require?

The seat bolt, irrespective of the Harley model, has a size of 5/16″ with 24 threads per inch. On most models, you’ll find these solo mounting bolts for seats.

What Are Breather Bolts On Harley Davidson Motorcycles? 

These are bolts that are essential components for the custom air cleaner. You must need these bolts to integrate the bracket and ensure the attachment.

Final Thoughts 

Bolt sizes differ between models and component types. You must know the exact type for a particular component in your Harley.  That is why you must adequately know the bolt chart size.

We suggest you choose the bolt sizes after properly inspecting the requirements. The chart we provided would help your case the best. Still, for any confusion, do let us know.

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