Plus Sizing Explained: The Pros and Cons of Upsizing Your Tires

Plus sizing is a popular tire upgrade method that involves increasing wheel diameter while decreasing sidewall height to maintain a similar overall tire diameter. This approach allows for a more aggressive look and potentially improved handling without drastically affecting speedometer accuracy or gear ratios.

What Exactly is Plus Sizing?

Plus sizing follows a simple principle: for every inch you increase in wheel diameter, you decrease the tire's aspect ratio (sidewall height) to compensate, keeping the overall diameter approximately the same.

For example, if your vehicle comes with 205/65R15 tires from the factory:

• A "plus one" upgrade would be 215/55R16
• A "plus two" upgrade would be 225/45R17

Notice how the first number (section width) typically increases slightly with each step up, while the second number (aspect ratio) decreases more significantly.

The Benefits of Plus Sizing

Improved Handling and Performance

One of the primary reasons drivers choose to plus-size is enhanced handling:

1. Better cornering stability: Wider tires provide more rubber on the road for improved grip.
2. Reduced sidewall flex: Lower profile tires have stiffer sidewalls that flex less during cornering, providing more precise steering response.
3. Enhanced braking performance: The larger contact patch can improve braking distances on dry surfaces.

Aesthetic Improvements

Many vehicle owners plus-size primarily for appearance benefits:

1. More aggressive stance: Larger wheels with lower-profile tires give vehicles a sportier, more performance-oriented look.
2. Better wheel visibility: Lower profile tires expose more of the wheel design, showing off custom or premium wheels.
3. Modern styling: Contemporary vehicle design trends favor larger wheels, making older vehicles look more current with a plus-size upgrade.

Tire Availability

For some enthusiasts, plus sizing opens up a wider selection of performance tire options:

1. Performance compounds: Many ultra-high-performance tires are only available in lower profile, larger wheel diameter sizes.
2. Specialized tires: Track-day tires, summer performance tires, and other specialized rubber often requires plus sizing.

The Drawbacks of Plus Sizing

Ride Quality Considerations

The most commonly cited downside to plus sizing is decreased ride comfort:

1. Harsher ride: Less sidewall means less cushioning between the road and your vehicle, resulting in a firmer and potentially less comfortable ride.
2. Increased road noise: Lower profile tires often transmit more road noise into the cabin.
3. Greater impact sensitivity: Lower profile tires are more susceptible to damage from potholes and road hazards.

Cost Considerations

Plus sizing almost always increases costs across multiple dimensions:

1. Higher tire prices: Larger, lower-profile tires typically cost more than standard sizes.
2. Increased wheel expenses: Larger diameter wheels, especially lightweight performance options, can be significantly more expensive.
3. Shorter tire lifespan: Performance-oriented tires often wear faster than standard touring tires.
4. Potential for more damage: Lower profile tires and larger wheels are more susceptible to damage from potholes and curbs.

Performance Trade-offs

Not all performance changes are positive when plus sizing:

1. Potentially reduced acceleration: Heavier wheels and tires increase unsprung weight, which can negatively impact acceleration.
2. Possible reduction in fuel economy: Wider tires create more rolling resistance, and heavier wheels require more energy to rotate.
3. Reduced off-road and winter capability: Lower profile tires generally perform worse in snow, mud, and off-road conditions.

Important Considerations Before Plus Sizing

Load Rating and Speed Rating

When plus sizing, you must maintain or exceed the original tire's load and speed ratings:

1. Load index: Ensure the new tires can support at least the same weight as the original tires.
2. Speed rating: Maintain or exceed the vehicle's original speed rating to preserve safety margins.

Clearance Issues

Larger wheels and wider tires may create fitment problems:

1. Fender clearance: Wider tires may rub against fenders, especially during turns or when going over bumps.
2. Suspension clearance: Ensure adequate space between the tire and suspension components throughout the suspension's travel.
3. Brake caliper clearance: Some larger wheels may not clear brake calipers without spacers or specific wheel designs.

Impact on Vehicle Systems

Plus sizing can affect various vehicle systems:

1. Speedometer accuracy: Even small changes in overall diameter affect speedometer readings.
2. ABS and stability control: These systems rely on consistent wheel speed data and can be affected by diameter changes.
3. Suspension geometry: Wider tires may change scrub radius and other suspension characteristics.

How to Plus Size Correctly

Step 1: Use a Tire Size Calculator

Start by using our Tire Size Calculator to compare different tire sizes and understand the dimensional changes.

Step 2: Research Vehicle-Specific Fitment

Every vehicle model has different constraints:

1. Check enthusiast forums for your specific vehicle
2. Look for "fitment guides" specifically for your make and model
3. Consider consulting with a professional wheel and tire specialist

Step 3: Consider a Conservative Approach

If you're new to plus sizing, consider these guidelines:

1. Start with a "plus one" size rather than jumping directly to "plus two" or larger
2. Stay within 3% of the original overall diameter
3. Be conservative with width increases, especially if you're not also installing suspension modifications

Step 4: Budget for All Related Expenses

Remember to factor in all related costs:

1. Four new tires
2. Four new wheels
3. Possible TPMS sensors
4. Professional mounting and balancing
5. Proper alignment after installation

Real-World Examples

Example 1: Honda Civic Sport Upgrade

• Factory size: 235/40R18
• Plus one upgrade: 245/35R19
• Results: Improved cornering grip, more aggressive stance, slightly firmer ride

Example 2: Toyota RAV4 Upgrade

• Factory size: 225/65R17
• Plus one upgrade: 235/55R18
• Plus two upgrade: 245/45R19
• Results: Progressive improvements in handling sharpness with corresponding decreases in ride comfort; modest aesthetic improvements

Conclusion

Plus sizing can be an effective way to improve both the appearance and handling characteristics of your vehicle when done correctly. However, it's important to weigh the benefits against the potential drawbacks and to ensure that your new tire and wheel package is appropriate for your specific vehicle and driving needs.

Before making a final decision, use our Tire Size Calculator to understand exactly how different plus-sized options will affect your vehicle's dimensions, speedometer accuracy, and overall performance.

Remember that the most successful plus sizing upgrades are those that balance aesthetic desires with practical considerations of comfort, durability, and performance across all driving conditions you're likely to encounter.