The Toyota 4Runner TRD Pro is a factory-built off-road powerhouse, but its 33-inch tires and modest suspension leave room for improvement. Lifting the truck unlocks the ability to run significantly larger tires like 33x10.50, 35x12.50, and even 37x13.50. However, each size demands a different combination of lift height, wheel offset, trimming, and supporting modifications. This guide breaks down exactly what is required to fit each tire size safely on a lifted 5th-gen 4Runner TRD Pro, covering clearance, drivability, and long-term durability.

Lift Overview and Tire Sizing Basics

Tire sizing can be confusing because two different systems are common. A tire labeled 33x10.50R17 means it is 33 inches tall, 10.5 inches wide, and fits a 17-inch wheel. The metric equivalent (e.g., 285/70R17) is also used. For this guide, we stick to the inch-based sizing most off-roaders use. The TRD Pro comes from the factory with a nominal 1-inch front lift (via TRD-tuned springs) and 33-inch tires, but the actual ride height varies. An aftermarket lift is required for anything larger.

Key numbers to remember: a 33x10.50 tire is roughly 10.5 inches wide; a 35x12.50 tire is 12.5 inches wide; a 37x13.50 tire is 13.5 inches wide. The width and diameter both affect clearance at the upper control arms, fender liners, body mounts, and frame rails.

Factors That Determine Tire Fitment

No two lift kits are the same, and tire fitment depends on more than just shock height. Below are the critical variables that affect whether a tire will clear without rubbing.

Lift Height and Suspension Geometry

Most 4Runner lifts range from 2.5 to 3.5 inches in the front and 1 to 2 inches in the rear. A 2.5-inch front lift (e.g., from an adjustable coilover) is the minimum for 35s, while 37s typically require a 3-inch front lift or more. However, lift height alone does not guarantee clearance; the suspension’s articulation and compression must also be considered. A taller lift can actually cause control arms to hit the frame more easily if not paired with proper bump stops and extended travel.

Wheel Offset and Backspacing

Wheel offset is measured in millimeters and determines how far the wheel sits from the hub. Stock TRD Pro wheels have a +4 mm offset. For larger tires, a lower offset (more negative) pushes the tire outward, reducing rubbing against the upper control arm and frame but increasing fender clearance issues. A common recommendation for 35s is 0 to -12 mm offset. For 37s, offsets around -25 to -38 mm are often used. Backspacing (the distance from the mounting pad to the inner rim edge) is the more critical number for frame clearance; values between 4.0 and 4.5 inches are typical for up to 35s, while 37s may need 3.5 inches or less.

Fender Clearance and Body Mount Chop

The front body mount on the 4Runner is a major obstacle. Even with a 2.5-inch lift, a 35x12.50 tire will contact the body mount at full lock without modification. A body mount chop (BMC) is necessary for 35s and mandatory for 37s. This involves cutting the offending section of the mount and welding a plate over it. Fender liners must also be trimmed or removed. Aftermarket fender flares can cover the extra tire width.

Suspension Upgrades

Larger tires add rotational mass and stress. For 35s, upgraded upper control arms (UCAs) are strongly recommended to correct camber and caster. For 37s, you should also consider a differential drop kit to lower the front differential and prevent CV axle binding. Rear suspension may require extended sway bar links and bump stops to prevent the tire from hitting the wheel well during compression.

Regearing

Stock gearing (3.91:1) is marginal with 33s and becomes inadequate with 35s and 37s. For 35x12.50 tires, regearing to 4.56 or 4.88 restores acceleration and reduces transmission hunting. For 37s, 4.88 is the minimum, but 5.29 gears are popular for those who tow or want highway drivability. Regearing also helps the drivetrain survive the added load.

Fitting 33x10.50 Tires

The 33x10.50 tire is the easiest upgrade and can often fit with a modest lift or even a stock TRD Pro with minimal trimming. It offers a good balance of off-road traction and on-road comfort.

Lift Requirements

A 1.5 to 2.5-inch lift in the front is sufficient. The 33x10.50 is narrow enough that it rarely contacts the upper control arm or frame. Many owners run this tire with factory wheels and no other modifications. If you have a TRD Pro with the stock 1-inch lift, you may only need to remove the front mud flaps and trim the fender liner slightly.

Wheel and Offset Recommendations

Stock wheels (+4 mm offset) work fine. Aftermarket wheels with 0 to +15 mm offset provide a slightly wider stance without aggressive rubbing. Backspacing of 4.5 to 5 inches is ideal.

Pros and Cons

  • Pros: Minimal cost, no BMC required, retains daily-driver comfort, no regearing necessary.
  • Cons: Still only 33 inches; ground clearance and approach angle improvements are moderate. Not as visually aggressive as bigger tires.

Fitting 35x12.50 Tires

The 35x12.50 is the most popular upgrade for lifted 4Runners. It transforms the truck’s capabilities and appearance, but requires a well-planned build.

Lift Requirements

A 2.5 to 3-inch front lift is standard. Some kits claim to fit 35s with a 3-inch lift, but in practice, even with a 2.5-inch lift, you will need a body mount chop. A lift that provides more travel (e.g., ICON Vehicle Dynamics coilovers) is recommended to avoid harsh bottoming.

Required Modifications

  • Body Mount Chop (BMC): Essential. Without it, the tire will hit the mount at full lock.
  • Fender Liner Trimming: Remove or cut the front liners to prevent rubbing during articulation.
  • Upper Control Arms: Aftermarket UCAs (e.g., SOTA Offroad) allow proper alignment and prevent tire-to-control-arm contact.
  • Wheel Offset: 0 to -12 mm offset with backspacing around 4.25 inches. Avoid excessive negative offset as it rocks the tire into the wheel well.
  • Rear Bump Stops: Extend or add bump stops to keep the tire from hitting the wheel well on compression.

Optional Upgrades

Regearing to 4.56 (or 4.88 if you plan to go larger later) dramatically improves drivability. A front differential drop of 1 inch reduces CV angle, especially if you have a 3-inch lift. Aftermarket fender flares are recommended if the tire sticks past the factory flares by more than 1 inch.

Fitting 37x13.50 Tires

37x13.50 tires are ambitious for a 4Runner and require a fully built suspension, extensive cutting, and significant drivetrain support. This is not a weekend project—it demands professional fabrication in many cases.

Lift Requirements

A 3 to 4-inch front lift is needed, but simply raising the truck is not enough. The suspension must be designed for high-clearance and controlled travel. A long-travel suspension system (e.g., from Total Chaos Fabrication) is ideal but expensive. For most owners, a 3-inch lift with extended bump stops and a body lift (1 inch) is a more practical approach.

Required Modifications

  • Body Mount Chop (BMC) plus additional frame clearancing: The 37x13.50 is so wide that the steering knuckle and sway bar links may also require clearance.
  • Front Bumper Modification or Replacement: Many aftermarket bumpers (e.g., CBI Offroad) are designed to accommodate 37s, but you may still need to trim the lower valance.
  • Regearing to 4.88 or 5.29: Mandatory. The 4Runner’s V6 struggles to turn 37s without gear help.
  • CV Axle Upgrades: Expect to replace CV axles with upgraded units (e.g., from RCV Performance) to handle the stress.
  • Rear Suspension Modifications: The rear wheel wells must be trimmed, and the inner fender liner removed. Extended bump stops and a Track Bar relocation bracket may be needed to center the axle.
  • Wheel Offset: -25 to -38 mm offset is typical, with backspacing of 3.5 inches or less. This pushes the tire well past the fenders, so aggressive flares are required.

Drivability and Safety Considerations

37-inch tires weigh over 80 pounds each. The braking system, steering, and wheel bearings are all pushed beyond factory limits. Upgraded brakes (e.g., Power Stop kits) are strongly advised. The added unsprung weight also increases wear on ball joints and bushings. Plan on frequent suspension inspections.

Conclusion and Final Recommendations

Choosing the right tire size after a lift depends on your budget, intended use, and tolerance for modification. Here is a quick summary:

  • 33x10.50: Best for light off-roading and daily driving. Requires minimal lift (2 inches or less) and almost no other changes.
  • 35x12.50: The sweet spot for serious off-road capability. Needs a 2.5-3 inch lift, BMC, aftermarket UCAs, and typically regearing. This is the most popular setup among 4Runner enthusiasts.
  • 37x13.50: Extreme performance for rock crawling and overlanding. Demands a 3-4 inch lift, extensive cutting, upgraded drivetrain components, and a significant financial investment. Not recommended for daily drivers.

No matter which size you choose, always verify clearances by cycling the suspension through full articulation with the tires mounted. Use a lift kit from a reputable manufacturer (e.g., Bilstein or Dobinsons) and have the work performed by a shop experienced with 4Runner lifts. A properly fitted tire setup not only looks aggressive but also ensures safe and reliable off-road performance for years to come.