Harley-Davidson Forks Types and How to Identify Them
Identifying which exact fork (front end) is on your Harley-Davidson motorcycle can be problematic. Especially with older bikes, many parts of motorcycle forks can be changed to different styles, or replaced with aftermarket parts. In this article we share photos and identifying characteristics for a variety of front ends found on Harleys. Use the photos below to help differentiate which front end you have on your Harley Big Twin or Sportster.
Types of Harley-Davidson Motorcycle Forks
There are multiple types of motorcycle forks, and many components. For the general purpose of this article we will focus on the main components of forks found on Harleys over the years.
Here's a basic diagram of components that make up a motorcycle front end.
The 'fork' on a motorcycle consists of multiple components. The triple trees (also known as yokes) hold the fork tubes (which contain the fork springs), and are fastened to the neck of the frame by the steering stem. At the bottom of the fork tubes are the lower legs, often referred to as sliders. The sliders house the dampening assemblies, which vary based on the brand and type of fork. The front axle is located perpendicular and engages the sliders.
Harley-Davidsons typically have a 1" outside diameter steering stem. 1977 & earlier Sportsters had a 7/8" stem, which was changed to 15/16" for 1978-1981. After 1981 all Sportsters had a 1" steering stem, including all 39mm Narrow Glide forks.
The size of a fork, for instance, "39mm", is in reference to the outside diameter of the fork tubes themselves. Modern Harley-Davidsons tend to have much larger diameter fork tubes than earlier models, with 49mm being a common size. Typically, the larger and heavier the model motorcycle, the more heavy-duty, and thus larger diameter, the fork tubes and entire fork assembly.
Early Sportsters had a 33.4mm (actually 1.312" diameter, which converts to 33.325mm) front end, which are easy to identify by their drum brake.
Todd Muller's Harley Sportster Ironhead with 33.4mm, drum brake front fork.
After the 33.4mm forks the 35mm Kayaba forks were introduced, which featured a single disc brake, quite an improvement over the earlier drum brake. The Kayaba forks were only around a few years until the 35mm Showa forks became the stock front end found on Harley Sportsters and FX models. The 35mm Showa forks come in both single and dual disc brake versions.
Tim Fiorucci of Fiorucci Fabrications built this 1973 Harley Ironhead Sportster Chopper, which has a single disc 35mm Kayaba front fork on it, as the stock bike would have.
39mm Narrow Glide forks are produced by Showa (who also supplied the earlier 35mm forks found on earlier models) and were supplied on Harley-Davidson Sportsters, and some Big Twin models such as FXRs, starting in 1987.
Anna Moore's Evo Harley Sportster has a Showa 39mm Narrow Glide front end.
Harley Big Twins had 41mm 'Wide Glide' front ends for many years, though current late-model Big Twins now have 49mm fork tubes. Early 41mm Wide Glide forks (1949-1971) had drum brakes, though 1972 on up had disc brakes.
Wide Glide, Mid Glide and Narrow Glide Front End - Harley Forks
The distance between the fork tubes varies between different front ends and model motorcycles, and is determined by the center-to-center spacing of the fork tube bores on the triple trees. The term Narrow Glide refers to a front end with closer fork tube spacer than a Wide Glide front end, which is traditionally a 41mm Harley Big Twin fork. There is also a Mid Glide fork, where the fork tube spacing is between that of a Narrow Glide and a Wide Glide. A 39mm Mid Glide fork is found on Harley-Davidson Sportster Forty-Eight models from 2010-2015, for instance.
The Harley-Davidson Sportster 48 has a Mid Glide front end.
Note that with custom parts, or machining of stock parts, you can build a front end that combines non-standard fork tube diameters and widths. Note that this changes the width of axle needed, as well as wheel spacers. It will also affect the spacing of the brake caliper(s) to the brake rotor, as the brake caliper is mounted to the fork slider and will move inward or outward with different fork tube spacing.
An example of a front fork made from modified stock parts is boring 39mm Narrow Glide triple trees to accept 41mm (wide glide) fork tubes. Aftermarket, narrow triple trees are also available for a skinny, chopper front end. Many options exist for wide glide, mid glide and narrow glide triple trees that accept various size fork tubes, allowing many custom fork variations.
Harley-Davidson Fork Tube Center-To-Center Dimension
Fork Tube Center-To-Center Dimension
Narrow Glide front end
Mid Glide front end
Wide Glide front end
Harley-Davidson Fork Tube Diameter Chart by Year Ranges
|Year Range||Models||Fork Tube Diameter||Brake|
|Big Twins (FL, etc.)||41mm||Drum|
Big Twins (FL, etc.)
|2006-up||Many Big Twins (FXDB, FXDI, FXDCI, FXD35, FXDWGI)||49mm||Disc|
|1957-1972||Sportster, 71-72 FX Superglide||1.312" (33.4mm)||Drum|
|1973-1975||Sportster & FX, etc. (Kayaba)||35mm||Disc|
|1975-1986||Sportster & FX, FXE, FXR etc. (Showa)||35mm||Disc|
|1987-up||Sportster, Seventy-Two, FXR, FXLR etc.||39mm||Disc|
Now you know the details and the basics of how to identify Harley forks, maybe it’s time to get into work. Follow our awesome how-to guides below to understand more about Harley’s front end.
- How to customize a Harley Narrow Glide 39mm front end
- Easy Install: 39mm Fork Shrouds on Harley-Davidson Sportster
- How to install a 39mm Burly Fork Lowering Kit on Harley-Davidson XL Sportster
33.4mm Fork Identification
The 33.4mm (1.312") fork was stock on Harley K-models (the predecessor of the Sportster), Sportsters, and early Superglide (Big Twin) models until about 1972. These forks were all drum brake, and the sliders are steel.
35mm Kayaba Fork Identification Photos
35mm Showa Single Disc Brake Fork Identification Photos
35mm Showa Dual Disc Brake Fork Identification Photos
39mm Narrow Glide Showa Fork Identification Photos
Note: the front end in this photo has longer-than-stock fork tubes
Wide Glide Fork Identification Photos
Some more photo examples:
Christian Newmans Harley Sportster chopper with customized Showa 39mm Narrow Glide front end. Photo by: David Carlo.
Josh Kohn's Magnum at Fuel Cleveland with 35mm front end, which would have originally been found on a Sportster or FX model Harley. Photo by David Carlo.
Nick Barkley's Harley has a 41mm Wide Glide front end. Photo by David Carlo.
Rob Hultz Shovelhead with a 41mm Wide Glide front end. Note how different a Wide Glide can look depending on the length of the fork tubes. Photo by David Carlo.