The 2018 Lexus Trucks RX350 sits in the modern luxury crossover segment, combining everyday comfort with the road manners that made the RX one of Lexus’s most familiar nameplates. For owners, tire selection is less about vintage-style construction and more about matching the exact wheel setup on the vehicle. This RX350 uses radial tires in either 235/65R18 or 235/55R20, depending on configuration, with the F Sport tied to the 20-inch size. That makes wheel diameter the first thing to confirm before comparing replacement choices. Once the correct size is established, the decision shifts to road-use priorities, tread design, and maintaining the intended balance of ride quality, handling, and appearance.
Which Tire Size Is Right for The 2018 Lexus Trucks RX350
The 2018 Lexus Trucks RX350 uses two primary tire sizes, and the difference comes down to configuration and wheel diameter. Both are radial metric sizes, but one fits an 18-inch wheel and the other fits a 20-inch wheel, so confirming the actual rim diameter on the vehicle is the first step before selecting a tire. The F Sport uses the 20-inch fitment, while Base models may use either size.
235/55R20 is a modern metric radial size in which 235 identifies the nominal section width in millimeters, 55 is the aspect ratio, R indicates radial construction, and 20 is the rim diameter in inches. On the 2018 Lexus Trucks RX350, this size supports the larger-wheel setup and is the fitment used on the F Sport. Its overall proportions keep it closely aligned with the alternate 18-inch package while pairing with a different wheel diameter. This is the size to evaluate when the vehicle already has 20-inch wheels and you want to preserve the intended fitment and stance.
235/65R18 is a metric radial size that uses the same 235-millimeter nominal section width as the 20-inch option, but with a 65-series profile and an 18-inch rim diameter. For the 2018 Lexus Trucks RX350, this size applies to Base models equipped with the 18-inch wheel package. Its dimensions are close in overall diameter to the 20-inch fitment, but it is not the same tire and must match the wheel actually on the vehicle. This size is the right place to start when the RX350 has 18-inch rims and the goal is to keep the factory wheel diameter in service.
Sub-model fitment matters on the 2018 Lexus Trucks RX350 because the covered configurations do not all use the same tire size. Checking whether the vehicle is a Base model or an F Sport, then confirming the wheel diameter on the vehicle, will narrow the correct tire choice quickly.
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2018 Lexus Trucks RX350 Base
The 2018 Lexus Trucks RX350 Base can use either of the two primary radial sizes, depending on which wheel package is on the vehicle. That makes wheel confirmation especially important before ordering tires, since the correct choice follows the actual 18-inch or 20-inch rim setup rather than the model name alone.
The 2018 Lexus Trucks RX350 F Sport uses the 235/55R20 radial fitment. Tire selection for this sub-model centers on staying with the 20-inch wheel size and choosing a replacement that matches the vehicle’s intended wheel-and-tire package.
The tire sizes listed on this page assume factory-standard vehicle configuration. The following modifications may affect tire fitment and are not reflected in this guide:
Suspension changes (lowering, lift kits, spring replacements)
Body alterations (fender modifications, custom bodywork)
If your vehicle has been modified from factory specifications, verify tire clearance before purchase.
Frequently Asked Questions
These FAQs focus on the exact tire sizes used on the 2018 Lexus Trucks RX350, how Base and F Sport fitment differs, and what to check on the wheels, suspension, and tires before regular road use.
Tire Size & Fitment
What tire size fits a 2018 Lexus Trucks RX350?
The 2018 Lexus Trucks RX350 uses two primary tire sizes: 235/65R18 and 235/55R20. Both are radial metric sizes, and the correct one depends on the wheel package and sub-model. Base models can use either size, while the F Sport uses 235/55R20.
The key step is confirming the wheel diameter actually on the vehicle before choosing tires. Even though the two sizes are close in overall diameter, one is built for an 18-inch rim and the other is built for a 20-inch rim, so the tire must match the wheel exactly.
What size rim does a 2018 Lexus Trucks RX350 use?
A 2018 Lexus Trucks RX350 uses either an 18-inch or 20-inch rim, depending on configuration. The 235/65R18 tire fits the 18-inch wheel setup, and the 235/55R20 tire fits the 20-inch wheel setup. The F Sport is tied to the 20-inch fitment.
Checking rim diameter is the fastest way to avoid an ordering mistake. Reading the current tire sidewall, confirming the wheel size stamp, or checking the actual installed wheel package is worthwhile, especially on Base models that may appear similar externally while using different wheel-and-tire combinations.
Why does the 2018 Lexus Trucks RX350 have more than one tire size?
The 2018 Lexus Trucks RX350 has more than one tire size because different configurations use different wheel diameters. Base models may be equipped with either 235/65R18 or 235/55R20, while the F Sport uses 235/55R20. Both sizes are radial and serve the same model line with different wheel packages.
That means tire selection starts with identifying the exact setup on the vehicle rather than assuming every RX350 uses the same size. A Base model with 18-inch wheels needs a different tire than an RX350 with 20-inch wheels, even though both belong to the same year, make, and model family.
Choosing the Right Tire
What should I consider when choosing a tire for a 2018 Lexus Trucks RX350?
Start with the correct primary size for the vehicle’s wheel package: 235/65R18 or 235/55R20. The 2018 Lexus Trucks RX350 uses radial tires, so the first decision is not construction type but matching the tire to the actual wheel diameter and sub-model configuration.
After confirming size, compare the tire’s intended use against how the RX350 is driven. Daily highway use, seasonal conditions, ride comfort, and steering response can all influence the right choice, but none of that matters until the basic fitment is correct for the wheel and vehicle setup.
How do I choose between the available 2018 Lexus Trucks RX350 tire sizes?
There is no discretionary choice between 235/65R18 and 235/55R20 unless the wheel package itself is changing. Each size belongs to a different rim diameter, so the tire size is determined by the wheel already on the 2018 Lexus Trucks RX350 rather than personal preference alone.
For a Base model, verify whether the vehicle has 18-inch or 20-inch wheels before moving further. For an F Sport, the fitment centers on 235/55R20. Treat the wheel-and-tire package as a matched system, and check clearance and wheel specifications carefully before considering any change beyond the original size format.
What does 235/55R20 mean on a 2018 Lexus Trucks RX350?
On a 2018 Lexus Trucks RX350, 235/55R20 means a tire with a nominal section width of 235 millimeters, a 55-series aspect ratio, radial construction, and a 20-inch rim diameter. It is a modern metric radial size and is the fitment used on the F Sport.
Understanding the code helps prevent mismatched replacements. The last number must match the wheel diameter, and the width and profile work together to create the tire’s overall shape. A similar-looking size can still be wrong if the rim diameter or profile differs from what the wheel package requires.
Restoration & Appearance
Does correct tire fitment matter for a 2018 Lexus Trucks RX350 restoration or refurbishment?
Yes. Even on a modern luxury crossover like the 2018 Lexus Trucks RX350, correct tire fitment matters when refreshing the vehicle’s appearance and road manners. The right tire size preserves the intended relationship between wheel diameter, sidewall profile, and the overall look of the vehicle.
Appearance-focused work should still begin with the exact wheel-and-tire package already on the RX350. A Base model may use either 18-inch or 20-inch fitment, while the F Sport uses the 20-inch setup, so matching the proper size is part of keeping the vehicle visually consistent and mechanically appropriate.
How does tire size affect the appearance of a 2018 Lexus Trucks RX350?
Tire size affects both stance and sidewall proportion on a 2018 Lexus Trucks RX350. The 235/65R18 fitment uses a taller sidewall on an 18-inch wheel, while the 235/55R20 fitment pairs a shorter-profile tire with a larger 20-inch wheel for a different visual balance.
That difference is one reason the tire size should follow the actual wheel package instead of being chosen by looks alone. Keeping the correct size helps preserve the intended presentation of the RX350, while size changes outside the original fitment should be checked carefully for wheel compatibility and clearance.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2018 Lexus Trucks RX350?
Yes. Modifications can affect tire fitment on a 2018 Lexus Trucks RX350, especially if the vehicle has aftermarket wheels, altered suspension height, or body changes that reduce available clearance. Even when the tire size remains 235/65R18 or 235/55R20, wheel width and offset can change how the tire sits.
A modified RX350 should be checked for steering clearance, inner suspension clearance, and fender space before replacing tires. Keeping the original size helps, but fitment can still change when the wheel itself changes, so it is smart to verify the full wheel-and-tire combination rather than relying on size alone.
What should I inspect before driving a 2018 Lexus Trucks RX350 on new tires?
Before driving a 2018 Lexus Trucks RX350 on new tires, inspect tire pressure, confirm that all four tires match the intended size, and make sure the tires are mounted on the correct wheel diameter. It is also wise to check for any visible rubbing at full steering lock and during normal suspension movement.
A short initial road test can help confirm that the vehicle tracks normally and that there is no interference from wheels, liners, or suspension components. Rechecking pressure after the first few drives is also worthwhile, since correct inflation plays a major role in ride quality, handling, and tire wear.
How often should tires on a 2018 Lexus Trucks RX350 be inspected?
Tires on a 2018 Lexus Trucks RX350 should be inspected regularly, not only when tread appears worn. Frequent visual checks for cracking, cuts, bulges, uneven wear, and air loss are important, and they matter just as much on lower-mileage vehicles as on daily drivers.
Routine inspection helps catch alignment, inflation, or suspension issues before they shorten tire life. It also gives the owner a chance to confirm that the vehicle is still running the correct 18-inch or 20-inch fitment, especially if tires or wheels were changed by a previous owner or service shop.
