17 Inch Rims On 35 Inch Tires

Let's talk about a popular, and sometimes tricky, modification: running 35-inch tires on 17-inch rims. While seemingly straightforward, it's a setup that demands careful consideration and planning to ensure optimal performance, safety, and compatibility with your vehicle. We'll delve into the technical aspects, potential challenges, and necessary adjustments. Consider this your comprehensive guide to understanding the ins and outs of this wheel and tire combination.

Understanding the Basics: Tire and Wheel Dimensions

Before we dive in, let's clarify the terminology. When we say "35-inch tires," we're referring to the overall diameter of the tire when inflated. The "17-inch rims" specify the diameter of the wheel itself. These are two distinct measurements, and their relationship is crucial for a proper fit.

A tire size is typically expressed in a format like 315/70R17. Let's break that down:

315: This is the tire's section width in millimeters. It represents the width of the tire at its widest point.
70: This is the aspect ratio. It indicates the tire's sidewall height as a percentage of its section width. In this case, the sidewall height is 70% of 315mm.
R: This indicates a radial tire construction, which is standard for most modern vehicles.
17: This is the rim diameter in inches. It indicates the diameter of the wheel the tire is designed to fit.

So, while a 35-inch tire generally implies a certain diameter, the actual dimensions can vary slightly depending on the specific tire manufacturer and model. Always refer to the tire manufacturer's specifications for the most accurate information. You can find this printed on the tire's sidewall and usually on their official website.

Why Choose 17-Inch Rims with 35-Inch Tires?

There are several compelling reasons why someone might opt for this combination:

Aesthetics: For many, it's simply about the look. A larger tire on a smaller rim can give an aggressive, off-road appearance. The increased sidewall provides a visual statement.
Off-Road Performance: Larger tires improve ground clearance and allow you to navigate obstacles more easily. A smaller rim, like a 17-inch, with a taller sidewall (thanks to the 35-inch tire) provides better "floatation" on soft surfaces like sand or mud. The increased sidewall also allows for lower tire pressures when off-roading, further improving traction and ride quality.
Cost: In some cases, 17-inch rims might be more readily available or more affordable than larger diameter wheels suitable for similar overall tire diameters.
Ride Quality: The increased sidewall height allows for more cushioning, potentially improving ride quality on rough roads compared to larger wheels with lower profile tires.

Considerations and Potential Challenges

While the benefits are appealing, running 35-inch tires on 17-inch rims isn't without its challenges. Careful planning and addressing these issues are crucial.

Fitment and Clearance

This is the most critical aspect. 35-inch tires are significantly larger than the factory-equipped tires on most vehicles. You need to ensure they physically fit within the wheel wells without rubbing against the fenders, suspension components, or frame. Consider the following:

Lift Kit: In most cases, a suspension lift is required to accommodate 35-inch tires. The amount of lift needed depends on the vehicle and the specific tire dimensions. Research lift kits designed for your vehicle and the desired tire size. A body lift, while less ideal for off-road performance, can also provide additional clearance.
Wheel Well Modifications: Even with a lift, you might need to trim or modify the wheel wells to prevent rubbing, especially during articulation (suspension movement). This could involve cutting and reshaping the fender liners, and potentially even welding in new metal to reinforce the areas.
Backspacing and Offset: Backspacing is the distance from the wheel's mounting surface to its inner edge. Offset is the distance from the wheel's mounting surface to the wheel's centerline. Choosing wheels with the correct backspacing and offset is critical for ensuring proper tire clearance and preventing rubbing on suspension components. Incorrect backspacing can cause the tires to rub on the control arms, brake calipers, or even the frame.
Turning Radius: Larger tires can reduce your vehicle's turning radius. Be aware that you might need more space to make turns.

Gearing

Increasing tire size effectively changes your vehicle's overall gear ratio. Larger tires require more engine torque to turn, which can lead to:

Reduced Acceleration: Your vehicle will feel slower off the line.
Decreased Fuel Economy: The engine has to work harder to maintain speed.
Strain on the Transmission: The transmission is subjected to increased stress.

To compensate, consider re-gearing. This involves replacing the gears in your differentials with gears that have a lower (numerically higher) ratio. This will restore some of the lost power and improve fuel economy. The optimal gear ratio depends on your vehicle, engine, transmission, and driving style. Consult with a professional to determine the appropriate gear ratio for your needs. Consider using online gear ratio calculators for initial estimations but always confirm with expert advice.

Braking Performance

Larger tires increase the rotational inertia of your wheels, which can negatively affect braking performance. It takes more energy to stop larger, heavier tires.

Longer Stopping Distances: You'll need more distance to come to a complete stop.
Increased Brake Wear: Your brakes will wear out faster.
Potential for Brake Fade: During repeated hard braking, your brakes can overheat and lose effectiveness.

To address this, consider upgrading your brake system. This could involve:

Larger Brake Rotors: Larger rotors provide more surface area for heat dissipation.
Improved Brake Calipers: Upgraded calipers provide more clamping force.
High-Performance Brake Pads: High-performance pads offer better friction and heat resistance.
Stainless Steel Brake Lines: Stainless steel lines reduce brake line expansion, providing a firmer pedal feel.

Speedometer and Odometer Calibration

Larger tires will throw off your speedometer and odometer readings. Your speedometer will likely read lower than your actual speed, and your odometer will record fewer miles than you've actually traveled.

To correct this, you'll need to recalibrate your speedometer and odometer. This can be done using a speedometer calibrator device. Some vehicles allow you to adjust the tire size setting in the vehicle's computer system. Consult your vehicle's owner's manual or a qualified mechanic for specific instructions.

Tire Pressure Monitoring System (TPMS)

After changing tire sizes, your TPMS might not function correctly. Ensure your TPMS sensors are compatible with your new wheels and tires. You might need to reprogram the TPMS sensors or replace them with sensors that are designed for the new tire pressure range.

Load Rating

It is critically important to ensure that the tires you select have a load rating that meets or exceeds the manufacturer's recommendations for your vehicle. Overloading tires can lead to tire failure, which can be extremely dangerous.

Wheel Width

Tire manufacturers specify an approved range of wheel widths for each tire size. Selecting a wheel width outside of this range can compromise handling, tire wear, and safety. Consult the tire manufacturer's specifications to determine the correct wheel width for your chosen 35-inch tires.

Installation and Professional Assistance

Installing 35-inch tires on 17-inch rims, along with the necessary modifications, is a complex process. It's generally recommended to seek professional assistance, especially for:

Lift Kit Installation: Installing a lift kit requires specialized tools and knowledge. Improper installation can compromise the vehicle's safety and handling.
Wheel Well Modifications: Cutting and welding on the vehicle's body requires expertise to ensure structural integrity.
Re-Gearing: Re-gearing differentials is a precision task that requires specialized tools and knowledge. Incorrectly installed gears can lead to premature wear and failure.
Brake System Upgrades: Installing brake system upgrades requires careful attention to detail and proper torque specifications.

A qualified mechanic can ensure that the installation is done correctly and safely. They can also help you choose the right components and address any potential issues.

Conclusion

Running 35-inch tires on 17-inch rims can be a rewarding modification, providing enhanced aesthetics, improved off-road performance, and a unique driving experience. However, it's crucial to approach this modification with careful planning and a thorough understanding of the technical aspects involved. By addressing the potential challenges and seeking professional assistance when needed, you can ensure a safe and enjoyable outcome. Remember to prioritize safety and research diligently before making any modifications to your vehicle. Always consult with qualified professionals to ensure your modifications are performed correctly and meet all applicable safety standards.