Many motorcycle enthusiasts dream of custom bikes that reflect their personal style. A wider rear tire often tops the list of desired modifications, delivering a bold, powerful aesthetic. However, before you jump into this popular upgrade, you need to understand the factors that will make or break your project.
This rear motorcycle wheel guide will explore just how wide you can go, covering crucial aspects like your bike's frame, swingarm limitations, and how these changes affect your bike's behavior. We'll give you the knowledge to make an informed decision, ensuring your custom bike looks impressive and rides safely.
Know Your Motorcycle's Framework Before You Start
Before you can even consider a wider tire, you must evaluate your motorcycle's current structure. The bike's frame, swingarm, and final drive system create specific spatial limits that dictate the maximum wheel and tire size you can fit.
The swingarm, which holds the rear axle, presents the most immediate constraint. It has a fixed internal width, and if you force a tire that's too wide into this space, it will rub against the swingarm sides. This contact creates dangerous friction that quickly wears down your tire and can lead to a blowout.
Beyond the swingarm, you must consider the clearance around your final drive system. Whether you run a chain, belt, or shaft drive, it occupies significant space next to the wheel. A wider tire can easily interfere with the chain or belt, causing it to shred or snap while you ride. For shaft-driven bikes, the housing itself creates a solid, immovable barrier.
You must measure the available space carefully, accounting for tire expansion at high speeds and the side-to-side flex that occurs when you corner. If you ignore these fundamental constraints, you risk catastrophic failure and serious injury.
How Your Swingarm Controls Wheel Width
The swingarm directly determines whether you can successfully install a wider rear wheel. It's not just a simple bracket; it's an engineered component that works with the suspension to maintain rear-wheel alignment. When you decide to go wider, you have two primary options: modify your existing swingarm or replace it with a custom, wider one.
Modifying a stock swingarm requires complex work that only an experienced fabricator should attempt. This process usually requires a fabricator to cut the swingarm, widen it by welding in an additional section of metal, and reinforce it to handle the new stresses.
You must measure precisely and apply expert welding skills to avoid compromising the component's structural integrity. An improperly modified swingarm can fail under load, leading to a disastrous accident.
The more common and often safer solution requires you to purchase an aftermarket wide-tire swingarm kit. Manufacturers engineer these kits specifically for your bike model and the desired tire size.
They provide the necessary clearance and maintain the correct geometry for proper handling and suspension. While this costs more than modifying your stock swingarm, it eliminates the guesswork and provides a reliable, professionally manufactured solution for your wide-tire conversion.
How Width Transforms Your Bike's Handling and Performance
When you swap to a wider rear tire, you completely transform how your motorcycle handles. A wider tire creates more contact patch with the road, which boosts straight-line stability and gives you better traction when you accelerate hard. This stability advantage explains why drag bikes use extremely wide rear tires. However, you pay for this added stability with reduced agility.
Motorcycles turn by leaning, and a wider, flatter tire profile fights against this lean more than a narrower, rounder one. You'll need to push harder on the handlebars to start a turn, and the bike will feel less nimble in corners. You'll notice this effect the most on tight, technical road sections, where the bike feels slow and heavy to steer.
Your bike's tendency to "stand up" in corners also becomes more pronounced, forcing you to apply continuous pressure on the inside handlebar to hold your line. You'll need time to adapt to this altered handling behavior.
A wider tire transforms how the bike responds to road imperfections. The larger surface area makes the bike "track" or follow grooves and ruts in the pavement more aggressively, forcing you to work harder to maintain a steady path.
Plan for Offset and Final Drive Adjustments
When you bolt on a significantly wider wheel and tire, you'll likely find that it won't clear the final drive system. To create the space you need, you may have to offset the front and rear sprockets (for a chain or belt drive) or even the transmission output shaft itself. An offset pushes the drive system outward, away from the bike's centerline, to clear the wider tire.
Small offsets work well and rarely cause significant problems, but larger offsets stress the drivetrain components in new ways. For example, a substantial offset on a chain-drive bike loads the countershaft bearing within the transmission with additional lateral force, which can cause premature wear and failure. You must choose a high-quality offset kit designed to handle these loads.
For extreme widths like 360mm tires with Mammoth rims, you'll need a jackshaft or right-side drive (RSD) transmission. A jackshaft functions as a secondary shaft that transfers power from the transmission to a new sprocket location further out. An RSD transmission relocates the entire final drive to the right side of the motorcycle, maximizing clearance on the left.
Choose the Best Option for Your Ride
Your personal goals and riding style determine the correct rear tire width for your bike. Do you want to build a show-stopping custom bike that prioritizes visual impact above all else, or do you want a balanced blend of style and performance for your daily rider? Answer this question honestly, and it will help you decide.
If you value agility and how well your bike corners, increase your width modestly. Move up one or two sizes from the stock tire to get a more muscular look that won't drastically harm your bike's nimble handling. This approach often requires minimal or no modifications to the swingarm and drivetrain, making it more accessible and affordable.
On the other hand, if you envision a long, low chopper with the widest tire possible, prepare for a more involved and expensive project. This project will likely require a custom wide swingarm, offset kits, or a jackshaft, and you must consciously accept the altered handling characteristics.
When you reach the end of our guide on how wide you can go with your rear motorcycle wheel, you need to weigh the aesthetic benefits against the practical realities of cost, complexity, and changes in how your bike rides. Research your options and understand the trade-offs to create a motorcycle that makes you proud to ride and display. Visit DNA Specialty to find the components you need to turn your vision into reality.
