The 2021 Mercedes-Benz Trucks GLS450 sits in the modern full-size luxury SUV class, where ride quality, highway stability, and a substantial road presence all matter as much as day-to-day usefulness. On this vehicle, tire selection is tied closely to the exact wheel setup, because the GLS450 uses radial sizes on both 20-inch and 21-inch rims, including a staggered 21-inch arrangement with different front and rear fitments. That makes the real decision less about vintage-style construction and more about confirming the correct configuration before comparing tire dimensions. Owners should match the tire size to the vehicle's specific setup, then check wheel diameter, front-to-rear sizing, and overall clearance before replacement.
Which Tire Size Is Right for The 2021 Mercedes-Benz Trucks GLS450
Three tire sizes apply to the 2021 Mercedes-Benz Trucks GLS450, and the correct choice depends on the exact wheel and axle configuration. One setup uses a 20-inch rim with 275/50R20, while the 21-inch arrangement uses 275/45R21 in front and 315/40R21 in the rear. Confirming the actual rim diameter and whether the vehicle has a staggered front-and-rear setup should come before selecting replacement tires.
The 275/50R20 size is a metric radial format: 275 is the nominal section width in millimeters, 50 is the aspect ratio, R indicates radial construction, and 20 is the wheel diameter in inches. On the 2021 Mercedes-Benz Trucks GLS450, this size belongs to the 20-inch wheel configuration rather than the staggered 21-inch setup. Its overall dimensions place it in the same general diameter range as the 21-inch fitments, but the wheel diameter is different. Choose this size only after confirming the GLS450 is equipped with 20-inch wheels.
The 275/45R21 size is a metric radial with a 275-millimeter nominal section width, a 45-series profile, radial construction, and a 21-inch rim diameter. On the 2021 Mercedes-Benz Trucks GLS450, this size is used in the front position on the staggered 21-inch setup. It carries nearly the same overall diameter as the other GLS450 fitments, but it is paired with a wider rear tire rather than used at all four corners. This is the right size to evaluate when replacing front tires on a 21-inch staggered GLS450.
The 315/40R21 size is a metric radial format with a notably wider 315-millimeter nominal section width, a 40-series profile, radial construction, and a 21-inch wheel diameter. On the 2021 Mercedes-Benz Trucks GLS450, it serves as the rear tire in the staggered 21-inch arrangement. That wider section distinguishes it clearly from the front 275/45R21 and means it should be treated as a position-specific fitment rather than a universal GLS450 size. Check rear wheel width and confirm the vehicle's front-to-rear sizing before replacement.
Fitment on the 2021 Mercedes-Benz Trucks GLS450 changes by configuration rather than staying the same across every sub-model entry. Checking whether the vehicle uses the 20-inch setup or the staggered 21-inch front-and-rear arrangement is the key first step before choosing tires.
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2021 Mercedes-Benz Trucks GLS450 4Matic
The 2021 Mercedes-Benz Trucks GLS450 4Matic uses the 275/50R20 radial size on a 20-inch wheel setup. Tire selection here centers on matching that size and confirming the vehicle has the 20-inch configuration rather than the staggered 21-inch arrangement.
The 2021 Mercedes-Benz Trucks GLS450 4Matic Front uses 275/45R21 as the front radial fitment in the 21-inch staggered setup. That means front tire replacement should be handled as part of a position-specific combination, not as a same-size fitment shared with the rear axle.
The 2021 Mercedes-Benz Trucks GLS450 4Matic Rear uses 315/40R21 as the rear radial fitment for the staggered 21-inch configuration. The wider rear sizing makes wheel and axle position especially important when selecting replacements for appearance, clearance, and proper front-to-rear matching.
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 2021 Mercedes-Benz Trucks GLS450, including 20-inch versus 21-inch fitment, staggered front-and-rear sizing, wheel confirmation, tire selection, and the maintenance checks that matter before regular road use.
Tire Size & Fitment
What tire size fits a 2021 Mercedes-Benz Trucks GLS450?
The 2021 Mercedes-Benz Trucks GLS450 uses three radial tire sizes depending on configuration: 275/50R20, 275/45R21, and 315/40R21. The 20-inch setup uses 275/50R20, while the 21-inch staggered setup uses 275/45R21 in front and 315/40R21 in the rear.
That means the first step is confirming whether the GLS450 has 20-inch wheels or the 21-inch front-and-rear staggered arrangement. A 21-inch front size should not be treated as the rear size, and a 20-inch tire should not be chosen simply because the overall diameter looks similar. Check the existing tire placard, wheel diameter, and axle position before replacing anything.
What size rim does a 2021 Mercedes-Benz Trucks GLS450 use?
The 2021 Mercedes-Benz Trucks GLS450 uses either a 20-inch or 21-inch rim, depending on the setup. The 275/50R20 tire belongs to a 20-inch wheel, while the 275/45R21 front and 315/40R21 rear sizes are used on 21-inch wheels.
Rim diameter is the most important fitment checkpoint on this vehicle because the GLS450 does not use a single wheel size across every configuration. Looking only at tire width or overall appearance can lead to the wrong choice. Verify the wheel diameter stamped on the wheel or shown on the tire sidewall, then confirm whether the vehicle is square or staggered before ordering replacements.
Why does the 2021 Mercedes-Benz Trucks GLS450 have more than one tire size?
The 2021 Mercedes-Benz Trucks GLS450 has more than one tire size because it was fitted with different wheel setups. One configuration uses 275/50R20, while the 21-inch setup is staggered with 275/45R21 in front and 315/40R21 in the rear.
This matters because a staggered arrangement uses different tire sizes by axle, not just by trim label. Replacing tires without checking the actual wheel and axle position can create mismatched sizing on the vehicle. Confirm the wheel diameter first, then verify whether the GLS450 has the 20-inch all-around setup or the 21-inch front-and-rear combination before selecting tires.
Choosing the Right Tire
What should I consider when choosing a 2021 Mercedes-Benz Trucks GLS450 tire?
Start with the exact tire size already assigned to the vehicle's configuration: 275/50R20 for the 20-inch setup, or 275/45R21 front and 315/40R21 rear for the 21-inch staggered setup. On the GLS450, the size and axle position matter more than general tire category language because the fitment is configuration-specific.
After the correct size is confirmed, compare the tire's intended use against how the SUV is driven, then verify wheel diameter, wheel width, and front-to-rear matching. A rear 315/40R21 should be evaluated as a rear fitment, not a universal replacement. If the vehicle has been modified with different wheels or suspension changes, recheck clearance before installing new tires.
How do I choose between the available 275/45R21 and 315/40R21 tires for a 2021 Mercedes-Benz Trucks GLS450?
On a 2021 Mercedes-Benz Trucks GLS450 with the 21-inch setup, the 275/45R21 and 315/40R21 sizes are not interchangeable choices. The 275/45R21 size is used at the front, and the 315/40R21 size is used at the rear as part of the staggered arrangement.
The real comparison is not front versus rear as an either-or purchase, but whether each position is being replaced with the correct size for that axle. Keep the front and rear roles separate, and check that the wheels on the vehicle still match the intended setup. If previous owners changed the wheels, confirm both diameter and width before choosing replacement tires.
What rim-fitment details should I compare when choosing tires for a 2021 Mercedes-Benz Trucks GLS450?
The first rim-fitment detail is diameter, because the 2021 Mercedes-Benz Trucks GLS450 uses both 20-inch and 21-inch wheel setups. The second is whether the vehicle uses the staggered 21-inch arrangement, where the front and rear tires are different sizes and should stay matched to their axle positions.
Wheel width and actual installed wheel design also matter, especially with the wider 315/40R21 rear size. A tire can share a similar overall diameter with another GLS450 fitment and still be wrong for the wheel. Check the existing wheel measurements, inspect for aftermarket changes, and make sure the tire selected matches both the rim diameter and the vehicle's front or rear position.
Restoration & Appearance
Does correct tire fitment matter for a 2021 Mercedes-Benz Trucks GLS450 restoration or appearance refresh?
Yes. Even on a modern luxury SUV like the 2021 Mercedes-Benz Trucks GLS450, correct tire fitment has a major effect on stance, proportion, and the vehicle's intended appearance. Using 275/50R20 on the 20-inch setup or the proper 275/45R21 front and 315/40R21 rear combination on the 21-inch setup keeps the visual balance consistent with the wheel package.
Appearance changes quickly when the wrong axle size or wheel diameter is used, especially on a staggered configuration. A rear tire that is too narrow or a front tire mounted where a rear size belongs can alter the SUV's look and compromise fitment. Any appearance-focused tire replacement should begin with the actual wheel setup already on the vehicle.
How does tire sizing affect the appearance of a 2021 Mercedes-Benz Trucks GLS450?
Tire sizing affects both visual proportion and wheel-to-body balance on the 2021 Mercedes-Benz Trucks GLS450. The 20-inch 275/50R20 setup presents a different look than the 21-inch combination, and the staggered 21-inch arrangement adds a visibly wider rear tire with the 315/40R21 size.
That wider rear section is part of the vehicle's overall presentation, so replacing it with the wrong width can change the look immediately. Matching the correct front and rear sizes helps preserve the intended stance and keeps the wheel package visually consistent. Before choosing by appearance alone, confirm the current wheel diameter and whether the SUV still retains its original-style sizing layout.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2021 Mercedes-Benz Trucks GLS450?
Yes. Wheel changes, suspension alterations, spacers, and ride-height modifications can all affect tire fitment on a 2021 Mercedes-Benz Trucks GLS450. That is especially important on the 21-inch setup, where 275/45R21 front and 315/40R21 rear sizes already depend on a staggered layout and proper wheel matching.
A GLS450 with aftermarket wheels may still carry the same sidewall numbers but have different wheel widths or offsets that change clearance. Check steering clearance at full lock, look at inner fender and suspension space, and make sure front and rear positions remain correctly matched. Any modified vehicle should be measured directly before a new tire set is chosen.
What should I inspect before driving a 2021 Mercedes-Benz Trucks GLS450 on new tires?
Before regular road use, confirm that the 2021 Mercedes-Benz Trucks GLS450 has the correct tire size at each position and that the tires are mounted on the proper wheel diameter. Then inspect inflation, valve stems, wheel fastener torque, and visible clearance around the fenders, suspension, and steering components.
A short check after installation helps catch problems early. Look for rubbing marks, uneven seating, vibration, or any sign that the front and rear tires were mixed on a staggered setup. It also helps to recheck pressure after the first drives and inspect the sidewalls for cuts or bulges, especially if the vehicle has seen curb contact or recent wheel work.
How often should tires on a 2021 Mercedes-Benz Trucks GLS450 be inspected?
Tires on a 2021 Mercedes-Benz Trucks GLS450 should be inspected regularly, not only when tread looks worn. A quick visual check before longer trips and a more careful inspection at routine service intervals helps catch irregular wear, air loss, cuts, cracking, or damage that may be harder to notice on a large SUV.
This is especially useful on the staggered 21-inch setup because front and rear tires are different sizes and should wear in ways that match their positions. Watch for unusual shoulder wear, vibration, or handling changes that could point to alignment or pressure issues. Vehicles that sit for extended periods also deserve inspection for flat spotting, aging, and pressure loss before returning to the road.
