Harley-Davidson Motorcycle Tire Size Guide: How to Read Tire Sizes & Find the Right Fit
A Harley-Davidson tire size can look like a password:
180/55B18 M/C 80H BW
Every part of that code tells you something important. It identifies the tire's nominal width, profile, construction, wheel diameter, motorcycle application, load capacity, speed rating and sidewall style.
Reading only the first and last numbers is not enough.
A tire can physically fit an 18-inch wheel and still be wrong for the rim width, motorcycle weight, front/rear position or required construction. That matters on any motorcycle, but especially on a heavyweight Harley that may carry a passenger, luggage and hundreds of pounds of additional load.
This guide explains how to read Harley tire sizes, compare metric and alphanumeric markings, understand load and speed ratings, identify bias-ply and radial construction, and verify whether a tire actually fits your motorcycle.
The safe shortcut:
Start with the tire specifications in your Harley-Davidson owner's manual or on the motorcycle's tire-information label. Match the original size, construction, load rating, speed rating and front/rear application unless an approved alternative has been confirmed for your exact motorcycle.
Ready to look at current options? Shop motorcycle tires at Skyway Cycle Supply and verify your exact year, model and position before ordering.
In this guide:
How to Read a Metric Harley Tire Size
Harley-Davidson's motorcycle tire guide identifies three common sizing formats: metric, alphanumeric and inch. Metric sizing is the most common format on modern motorcycle tires. We will use a size found on current Harley Touring motorcycles as the example:
180 / 55 B 18 M/C 80 H BW
| Marking | Meaning | In This Example |
|---|---|---|
| 180 | Nominal tire section width in millimeters | Approximately 180 mm wide |
| 55 | Aspect ratio | Sidewall height is approximately 55% of the nominal width |
| B | Belted-bias construction | Bias carcass with a stabilizing belt |
| 18 | Required rim diameter in inches | Fits an 18-inch-diameter rim |
| M/C | Motorcycle tire designation | Designed as a motorcycle tire |
| 80 | Load index | A standardized maximum-load category |
| H | Speed symbol | H-rated under the specified test conditions |
| BW | Sidewall style | Blackwall |
What Does the First Number Mean?
The first number is the tire's nominal section width in millimeters. On a 180/55B18, that number is 180.
It is not a guarantee that every 180 tire measures exactly 180 millimeters when mounted. Actual width can vary by tire design, manufacturer and the rim width used for measurement. Product specifications commonly list an approved rim-width range and a measured width on a specified rim.
This is one reason “it is still a 180” does not settle fitment by itself.
What Does the Aspect Ratio Mean?
The second number describes the sidewall height as a percentage of the nominal width. It is not a height in millimeters.
For a 180/55 tire:
180 mm × 0.55 = approximately 99 mm of sidewall height
That height applies from the bead area toward the tread on each side of the wheel. A rough unloaded diameter estimate would be the 18-inch rim plus two sidewalls. Actual mounted diameter can differ, so use the tire manufacturer's published dimensions when clearance or gearing is important.
A lower aspect ratio generally creates a shorter sidewall. A taller ratio creates more sidewall height and usually changes overall diameter, ride height and tire profile.
What Does the Letter B or R Mean?
The construction letter sits between the aspect ratio and rim diameter:
- B means belted-bias construction
- R means radial construction
- A dash or no construction letter generally indicates conventional bias-ply construction
A 180/55B18 and a 180/55R18 are not the same construction. Never treat the B and R as optional characters.
What Does the Rim Number Mean?
The number following the construction letter is the wheel's bead-seat diameter in inches.
A 180/55B18 requires an 18-inch-diameter rim. A 16-inch tire cannot be installed on an 18-inch rim, even if the tire width looks appropriate.
Rim diameter is only half of the wheel question. Rim width also matters because it changes the mounted tire profile and must fall within the tire manufacturer's approved range.
How to Read an Alphanumeric Harley Tire Size
Older Harleys and classic-style applications often use an alphanumeric size such as:
MT90B16 72H WW
Harley-Davidson explains this code as follows:
- M identifies a motorcycle tire
- T is part of the width code; MT corresponds to roughly a 130 mm class
- 90 is the aspect ratio
- B identifies belted-bias construction
- 16 is the rim diameter in inches
- 72 is the load index
- H is the speed symbol
- WW identifies a whitewall
Reference charts often place MT90 in the same general size family as 130/90 and older 5.00/5.10-inch designations. That does not mean every MT90 and every 130/90 are guaranteed substitutes.
Approved rim range, actual width, diameter, construction, load index and manufacturer fitment still need to be checked. Treat conversion charts as a starting point, not authorization to install a different tire.
How to Read an Inch-Size Motorcycle Tire
Vintage and reproduction tires may use a numeric inch format such as:
4.00-18 64S
- 4.00 is the nominal tire width in inches
- 18 is the rim diameter in inches
- 64 is the load index
- S is the speed symbol
When no aspect ratio is shown in this older format, the tire uses the convention associated with that sizing system rather than a modern low-profile ratio. Harley-Davidson notes that reproduction tires in this numeric example are bias-ply.
Vintage fitment deserves extra care. Wheel condition, rim profile, tube requirements, fender clearance and the tire's approved rim width should all be verified before installation.
Understanding Motorcycle Tire Load Index
The load index is the number immediately before the speed symbol. It represents the maximum load assigned to that tire under specified conditions. It is a per-tire rating—not a simple statement of how much the whole motorcycle can weigh.
Common indexes found around Harley applications include:
| Load Index | Maximum Load per Tire | Where You May See It |
|---|---|---|
| 54 | 467 lb / 212 kg | Narrower front-tire applications |
| 61 | 567 lb / 257 kg | Modern Touring front example |
| 62 | 584 lb / 265 kg | Cruiser front example |
| 67 | 677 lb / 307 kg | Mid-size front or rear applications |
| 73 | 805 lb / 365 kg | Heavy cruiser fronts and some wide radial fronts |
| 77 | 908 lb / 412 kg | Heavy cruiser rear applications |
| 80 | 992 lb / 450 kg | Heavyweight Touring rear example |
| 81 | 1,019 lb / 462 kg | Select reinforced heavyweight rears |
Do not select a lower load index because the tire size itself matches. The motorcycle manufacturer chose the tire specification around the bike's weight, load distribution and intended passenger/cargo capacity.
Also remember that adding the two tire capacities together is not a new GVWR for the motorcycle. The frame, suspension, wheels and other components have their own limits. Use the motorcycle's published Gross Vehicle Weight Rating and loading guidance.
Understanding Motorcycle Tire Speed Ratings
The speed symbol follows the load index. Examples include 61H, 77H and 73V.
| Speed Symbol | Rated Speed |
|---|---|
| P | 94 mph / 150 km/h |
| S | 112 mph / 180 km/h |
| H | 130 mph / 210 km/h |
| V | 149 mph / 240 km/h |
| W | 168 mph / 270 km/h |
This is a controlled rating, not a recommended road speed. It assumes the tire is correctly mounted, inflated, loaded and in appropriate condition.
Your replacement tire should meet the motorcycle manufacturer's specified speed rating. Choosing a lower rating can affect the tire's suitability even if you never intend to approach the rated maximum.
Bias-Ply vs Belted-Bias vs Radial Harley Tires
The tire's construction affects heat, sidewall behavior, stability and handling.
Bias-Ply
Bias-ply tires use reinforcing cords arranged diagonally from bead to bead, with alternating layers crossing each other. They are common on cruisers and classic Harley applications where load support, durability and a particular ride feel are priorities.
Belted-Bias
A belted-bias tire adds a stabilizing belt beneath the tread. It is identified by the letter B, as in 130/90B16.
Radial
Radial tires use cords running more directly across the tire from bead to bead, with belts supporting the tread area. They are identified by R, as in the current Sportster S sizes 160/70R17 and 180/70R16.
Do not change from B to R—or mix construction types front and rear—based only on a matching width and rim diameter. Use the motorcycle and tire manufacturers' approved fitment information.
Tube-Type vs Tubeless Harley Tires
A tire size does not tell you everything about whether the wheel needs a tube.
- TL generally identifies a tubeless tire
- TT generally identifies a tube-type tire
Cast wheels are normally designed as tubeless systems. Traditional wire-spoke wheels often require tubes because the spoke holes pass through the rim and cannot retain air by themselves.
There are important exceptions. Some newer laced wheels use sealed rims or alternative spoke placement and can run tubeless. In its guide to tubeless versus tubed motorcycle tires, Harley-Davidson notes that most Original Equipment Harley tires are tubeless, but a tire may still require a tube when installed on a conventional laced wheel.
Check the wheel as well as the tire. Do not assume that every spoked wheel needs a tube or that every tire labeled tubeless can be installed without one on your rim.
What Do BW, WW, WWW and Other Sidewall Codes Mean?
Sidewall appearance codes vary by manufacturer and listing, but common Harley-related abbreviations include:
- BW — Blackwall
- WW — Whitewall
- SWW — Slim whitewall
- WWW — Wide whitewall
- RWL — Raised white letters
These codes describe appearance, not fitment or performance. A whitewall and blackwall may share a basic size while still differing by product line, construction or availability.
Current Harley Tire Size Examples
The table below uses published 2026 Harley-Davidson specifications to show how much sizes can differ across the lineup. It is an illustration—not a replacement fitment chart for other years.
| 2026 Model | Front Specification | Rear Specification | What It Shows |
|---|---|---|---|
| Street Glide | 130/60B19 M/C 61H | 180/55B18 M/C 80H | Heavy Touring load indexes with belted-bias construction |
| Road Glide | 130/60B19 M/C 61H | 180/55B18 M/C 80H | Same published base sizes as the current Street Glide |
| Low Rider S | 110/90B19 62H | 180/70B16 77H | A 180 rear does not always mean an 18-inch rim or 55-series profile |
| Heritage Classic | 130/90B16 73H | 150/80B16 77H | Traditional 16-inch sizing with taller sidewalls |
| Sportster S | 160/70R17 73V | 180/70R16 77V | Radial construction and V speed ratings |
A 2006 Street Glide, 2016 Road Glide and 2026 Street Glide may not share the same specifications. Always use your exact year and model rather than copying a size from another rider's bike.
If you ride a Road Glide, Street Glide, Road King or Ultra, our Harley Touring tire guide compares tire families after you have confirmed your correct size.
Can You Install a Wider Rear Tire on a Harley?
Sometimes—but it is not a free upgrade.
A wider tire can change steering effort, lean behavior and the shape of the tread when installed on a given rim. It can also create clearance problems with:
- Swingarm
- Belt or chain
- Fender and internal wiring
- Brake components
- License-plate or lighting hardware
- Saddlebags and custom bodywork
If a wider tire requires squeezing it onto a rim outside the approved range, its final profile may be very different from what the manufacturer designed. Wider does not automatically mean a larger contact patch, better handling or more traction.
Harley-Davidson recommends using the original size and tire specification. Custom wheel or wide-tire conversions should be planned as a complete system, not by guessing at one larger number.
What Happens If You Change the Aspect Ratio?
Changing from a 55-series to a 60- or 70-series tire changes sidewall height and usually overall diameter.
That can affect:
- Ride height
- Steering geometry
- Fender and swingarm clearance
- Effective gearing
- Speedometer and odometer readings
- Operation or calibration of wheel-speed-based systems
- Sidewall flex and ride feel
Do not assume that a taller tire is acceptable because the rim diameter stays the same.
Can You Mix Bias-Ply and Radial Tires?
Only use a mixed construction when the motorcycle and tire manufacturers specifically approve that combination.
The front and rear tires work as a system. Their carcass behavior, profile and response affect how the motorcycle steers and stabilizes. A size that physically mounts does not prove that a bias front and radial rear—or the reverse—will produce an approved handling combination.
Can You Mix Tire Brands or Models?
Follow the approved front/rear pairing rather than mixing tires solely because the sidewall sizes match. Tire profiles, compounds, tread behavior and construction can differ between brands and product lines.
Harley-Davidson warns against mixing approved tire brands on the same motorcycle. The safest path is a matched combination listed by the motorcycle or tire manufacturer for your application.
If you are deciding between two matched tire families, see our Dunlop American Elite vs Michelin Commander III comparison.
Harley Tire Fitment Checklist
Before ordering, confirm every item below:
- Exact year and model: Do not search only “Harley Touring” or “Softail.”
- Front or rear position: Motorcycle tires are position-specific unless clearly marked otherwise.
- Complete tire size: Match width, aspect ratio, construction and rim diameter.
- Load index: Meet the motorcycle manufacturer's specification.
- Speed rating: Meet the specified rating for the motorcycle.
- Approved rim width: Confirm your rim falls inside the tire manufacturer's range.
- Tube requirement: Verify the tire and wheel combination—not just the tire marking.
- Matched pair: Confirm the front and rear models are approved to work together.
- Wheel modifications: Measure and verify any aftermarket wheel or wide-tire conversion.
- Clearance: Check fender, swingarm, belt, brake and wiring clearance.
- Rotation direction: Install according to the arrow and front/rear markings.
- Inflation specification: Use the motorcycle manufacturer's recommended cold pressure.
If rain performance matters, confirm fitment first and then use our guide to the best Harley tires for rain and wet weather to compare appropriate options.
Where to Find Your Harley's Correct Tire Size
Use these sources in this order:
- Owner's manual: Look for the tire specifications and cold-pressure table for the exact model.
- Motorcycle tire-information label: Check the frame label for original specifications.
- Current tires: Read both sidewalls, but confirm they are actually the correct fitment rather than assuming a previous owner chose correctly.
- Tire manufacturer fitment guide: Verify the exact product, front/rear pairing and approved rim range.
- Professional verification: Use a qualified motorcycle tire installer when the wheels or chassis have been modified.
For a stock motorcycle, year/make/model lookup is usually the fastest route. For a modified motorcycle, you need the actual wheel dimensions and clearance in addition to the VIN-era model information.
Frequently Asked Questions
What does 130/90B16 mean on a Harley tire?
It identifies a nominal 130 mm section width, a sidewall height approximately 90% of that width, belted-bias construction and a 16-inch rim diameter. The full sidewall code should also include a load index and speed symbol.
Is MT90B16 the same as 130/90B16?
They are commonly placed in the same general size class, and Harley-Davidson identifies MT as roughly a 130 mm width code. They are not automatically interchangeable. Compare actual dimensions, approved rim range, load index, construction and the manufacturer's fitment listing.
What does 73H mean on a motorcycle tire?
The 73 is the load index, corresponding to 805 pounds or 365 kilograms per tire under specified conditions. The H is the speed symbol, corresponding to 130 mph or 210 km/h under the rating conditions. It is not a recommended riding speed.
What does 80H mean on a Harley rear tire?
The 80 load index corresponds to 992 pounds or 450 kilograms per tire under specified conditions. H is the speed symbol. Current base Street Glide and Road Glide specifications use an 80H rear tire.
What is the difference between 180/55B18 and 180/55R18?
Both share a nominal 180 mm width, 55 aspect ratio and 18-inch rim diameter. The B tire is belted-bias; the R tire is radial. They should not be treated as interchangeable unless specifically approved for the motorcycle.
Can I use a car tire on my Harley?
Motorcycle tires are designed around motorcycle rims, lean angles, profiles and handling loads. Use the motorcycle tire type and fitment specified by the motorcycle manufacturer rather than selecting a tire only because it can be forced onto a similarly sized rim.
Do front and rear Harley tires have to be the same size?
No. Most motorcycles use different front and rear sizes because the tires perform different steering, braking, acceleration and load-carrying roles. Follow the specified matched front and rear combination.
Can I use a tubeless tire on a spoked Harley wheel?
It depends on the wheel. Many traditional laced wheels require an inner tube, while some newer sealed or externally laced designs are tubeless. Verify the wheel and tire combination for your exact motorcycle.
Where is the tire manufacture date?
Look for the DOT code on the sidewall. The final four digits identify the production week and year. For example, 3525 means the tire was manufactured during the 35th week of 2025.
Should I use the pressure printed on the tire sidewall?
Not as your normal street-pressure target. Use the motorcycle manufacturer's recommended cold pressures from the owner's manual or tire-information label. The sidewall pressure relates to the tire's rated conditions and maximum load information.
Find Tires That Fit Your Harley
The safest tire choice begins with the complete specification:
Year + model + front/rear position + full size + construction + load index + speed rating + wheel type
Once those details match, you can compare the features that make one tire better for your actual riding—mileage, rain performance, handling, whitewall appearance or touring stability.
SHOP MOTORCYCLE TIRES AT SKYWAY CYCLE SUPPLY
Continue Reading
- Best Tires for Harley-Davidson Touring Motorcycles
- Dunlop American Elite vs Michelin Commander III
- Best Harley Tires for Rain & Wet Weather
Fitment and safety note: This guide explains common tire markings and is not an application-specific authorization. Always verify the complete tire specification, approved rim range, wheel compatibility and manufacturer fitment for your exact motorcycle. Modified motorcycles may require professional measurement and verification.