The 2018 Mercedes-Benz Trucks GLS550 sits in the modern full-size luxury SUV class, blending substantial road presence with the kind of all-weather touring capability buyers expect from a 4Matic-equipped vehicle. On a vehicle this size, tire choice affects more than appearance alone, because ride quality, steering response, and overall stance are closely tied to the original fitment. The 2018 Mercedes-Benz Trucks GLS550 uses a 295/40R21 radial tire, which places it firmly in modern metric sizing on a 21-inch wheel. That means the main decision is less about sorting through multiple sizes and more about confirming wheel setup, preserving the intended proportions, and choosing a tire suited to how the vehicle is actually driven.
Which Tire Size Is Right for The 2018 Mercedes-Benz Trucks GLS550
The 2018 Mercedes-Benz Trucks GLS550 uses one primary tire size: 295/40R21 radial on a 21-inch rim. The covered 4Matic sub-model shares that same fitment, so the key decision is not choosing between multiple factory sizes, but making sure the wheel setup is correct and selecting a tire that matches the vehicle's intended road use, ride character, and overall look.
A 295/40R21 size uses modern metric radial sizing, with 295 indicating nominal section width in millimeters, 40 representing the aspect ratio, and 21 identifying the wheel diameter in inches. Radial construction suits the GLS550's contemporary SUV layout and keeps the fitment aligned with the vehicle's original modern tire format. This size is primarily about maintaining the proper wheel diameter, width relationship, and overall stance rather than choosing among vintage-style construction types. It is the right starting point for owners who want to keep the vehicle on its correct 21-inch fitment and avoid issues created by mismatched wheel or tire dimensions.
Fitment is straightforward for the covered 2018 Mercedes-Benz Trucks GLS550 sub-model. The main step is simply confirming that the vehicle is the 4Matic configuration and that it still carries the correct 21-inch wheel setup before choosing tires.
1
2018 Mercedes-Benz Trucks GLS550 4Matic
The 2018 Mercedes-Benz Trucks GLS550 4Matic uses the 295/40R21 radial tire size. For tire selection, that means the focus stays on confirming the existing wheel dimensions and choosing a road-use tire that preserves the SUV's intended proportions and handling balance.
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 2018 Mercedes-Benz Trucks GLS550 tire size, 21-inch rim fitment, sub-model consistency, tire selection priorities, and the checks worth making before regular road use or after wheel and suspension changes.
Tire Size & Fitment
What tire size fits a 2018 Mercedes-Benz Trucks GLS550?
The 2018 Mercedes-Benz Trucks GLS550 uses a 295/40R21 radial tire. That is the primary fitment for this vehicle, and it matches a 21-inch wheel diameter with a modern metric radial size format rather than an older numeric or alphanumeric sizing system.
That answer is most useful when the SUV still has its original wheel setup. A GLS550 with aftermarket wheels, staggered sizing, or prior tire substitutions should be checked carefully so the actual wheel diameter and tire size on the vehicle match before a replacement is selected.
What size rim does a 2018 Mercedes-Benz Trucks GLS550 use?
The 2018 Mercedes-Benz Trucks GLS550 uses a 21-inch rim with its 295/40R21 tire size. In that size code, the final number, 21, is the wheel diameter in inches, so the tire is built specifically for a 21-inch wheel.
Wheel diameter is only part of the fitment picture, especially on a modern SUV. Wheel width and the vehicle's actual wheel setup should still be confirmed, because a tire can share the same 21-inch diameter while still being a poor match for the wheel or for the GLS550's clearance requirements.
Does the 2018 Mercedes-Benz Trucks GLS550 4Matic use the same tire size?
Yes. The covered 2018 Mercedes-Benz Trucks GLS550 4Matic uses the same 295/40R21 radial tire size. That makes sub-model fitment straightforward here, since there is not a second primary tire size to sort through within the covered configuration.
Even with consistent sub-model sizing, it is still smart to inspect the vehicle before replacing tires. A previous owner may have changed wheels or fitted a different tire size, so matching the new tire to the actual wheel diameter and current setup remains an important final check.
Choosing the Right Tire
What should I consider when choosing a 295/40R21 tire for a 2018 Mercedes-Benz Trucks GLS550?
Start with the correct size, 295/40R21, and make sure the GLS550 is still running the proper 21-inch wheel setup. Because this is a modern radial fitment, the goal is usually to keep the intended proportions, road manners, and wheel-to-tire relationship rather than experimenting with a different primary size.
After size confirmation, compare the tire's overall role on the vehicle. A GLS550 used mainly for everyday road driving may call for different priorities than one kept as a low-mileage luxury SUV, but in either case wheel compatibility, clearance, and maintaining the correct fitment should guide the final choice.
How do I choose between the available 295/40R21 tires for a 2018 Mercedes-Benz Trucks GLS550?
The first filter is always fitment accuracy. Any 295/40R21 under consideration needs to suit the GLS550's 21-inch wheel setup and intended use, since this vehicle has one primary tire size rather than a mix of different factory sizes.
Once the size is settled, compare practical factors such as how the vehicle is driven, whether the current wheels are original or aftermarket, and whether maintaining the original stance matters most. A tire that matches the vehicle's dimensions and setup cleanly is more useful than simply choosing by appearance alone.
What rim-width specifications should I compare when choosing 2018 Mercedes-Benz Trucks GLS550 tires?
Rim-width compatibility matters because a 295/40R21 tire is designed around a certain wheel width range, not just a 21-inch diameter. The tire size may be correct on paper, but the wheel still needs to suit that tire's intended mounting profile for proper fitment.
That becomes especially important if the GLS550 has replacement wheels or a non-original wheel package. Checking actual wheel width before mounting a new tire helps avoid poor sidewall shape, uneven fitment, or clearance concerns, and it is a sensible step any time the vehicle's wheel history is uncertain.
Restoration & Appearance
Which tire should I choose for a period-style 2018 Mercedes-Benz Trucks GLS550?
For a period-style presentation on a 2018 Mercedes-Benz Trucks GLS550, the right starting point is keeping the original-size 295/40R21 radial format. This is a modern luxury SUV, so preserving the correct contemporary size and wheel diameter matters more to the overall look than chasing an older construction style.
Appearance on a newer collector vehicle is often tied to stance and proportion rather than sidewall ornamentation. A tire that keeps the proper 21-inch fitment and fills the wheel opening as intended will usually support a more authentic late-model look than a size change made only for visual effect.
Does correct tire fitment matter for a 2018 Mercedes-Benz Trucks GLS550 restoration?
Yes, correct tire fitment matters on a 2018 Mercedes-Benz Trucks GLS550 even though it is a newer vehicle than traditional collector cars. The proper 295/40R21 size helps preserve the SUV's intended proportions, wheel presentation, and the overall visual balance that defines its original road-going character.
A restoration-minded owner should pay close attention to what is actually on the vehicle before replacing tires. Changes to wheels or tire dimensions can alter the look quickly, so matching the correct size and confirming the wheel setup is an important step in keeping the vehicle visually consistent.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2018 Mercedes-Benz Trucks GLS550?
Yes. Modifications can affect tire fitment on a 2018 Mercedes-Benz Trucks GLS550 even when the original size is 295/40R21. Aftermarket wheels, suspension changes, altered ride height, or body modifications can all change the space available around the tire and the way the tire sits on the wheel.
That is why replacement should begin with the vehicle as it exists today, not just the original specification. Checking wheel diameter, wheel width, and visible clearance at the fender and suspension helps confirm whether the GLS550 still supports the intended fitment without rubbing or other avoidable issues.
What should I inspect before driving a 2018 Mercedes-Benz Trucks GLS550 on new tires?
Before regular road use, inspect the wheel and tire setup for correct size, proper mounting, and adequate clearance. It is also wise to check tire pressure, look over the sidewalls and tread area for any visible damage, and make sure the wheels and lug hardware are in sound condition.
A short, careful test drive is a sensible next step after installation. Any vibration, rubbing, or unusual steering feel should be addressed early, especially on a vehicle with large 21-inch wheels, because catching a fitment or mounting issue quickly is easier than diagnosing it after extended driving.
How often should tires on a 2018 Mercedes-Benz Trucks GLS550 be inspected?
Tires on a 2018 Mercedes-Benz Trucks GLS550 should be inspected regularly, not just when replacement time arrives. A visual check for cracking, cuts, bulges, uneven wear, and gradual air loss is worthwhile on any vehicle, and it is especially useful on an SUV that may alternate between frequent road use and longer parked periods.
Inspection is also important after impacts, seasonal storage, or any wheel service. Even with the correct 295/40R21 size, a tire's condition can change before tread wear alone suggests replacement, so routine checks help catch aging or damage before it affects road manners or overall safety.
