The 2021 GMC Trucks Sierra 1500 sits in the modern full-size pickup market where trim level, wheel package, and intended use can change the tire conversation quickly. From work-oriented configurations to upscale Denali and off-road-flavored AT4 models, this truck was offered with several factory-size paths rather than one universal fitment. Every primary fitment here is a radial, but the actual size ranges from 17-inch through 22-inch wheel packages. That makes the real decision less about bias-ply versus radial and more about confirming the exact sub-model and wheel diameter first, then choosing the right size, load capability, and sidewall presentation for how the truck is equipped and used.
Which Tire Size Is Right for The 2021 GMC Trucks Sierra 1500
The 2021 GMC Trucks Sierra 1500 uses seven primary tire sizes, and they vary by sub-model and wheel diameter. The first step is confirming the exact Sierra 1500 trim and whether the truck is on 17-inch, 18-inch, 20-inch, or 22-inch wheels. Once that is settled, the choice becomes selecting the correct radial size and then comparing available product details such as load specification, tire series, and sidewall style where applicable.
265/60R20 is a metric radial size in which 265 identifies the nominal section width in millimeters, 60 is the aspect ratio, R designates radial construction, and 20 is the wheel diameter in inches. On the 2021 GMC Trucks Sierra 1500, this size belongs to a modern truck fitment built around a 20-inch wheel package. It represents one of the lower-profile factory-style sizes used on this model, giving buyers a size that should be matched carefully to the truck's exact trim and wheel setup. Confirming the sub-model and existing wheel diameter is the key step before moving forward with this size.
265/65R18 is a metric radial size that uses a 265-millimeter nominal width, a 65-series profile, and an 18-inch rim diameter. For the 2021 GMC Trucks Sierra 1500, this size sits in the middle of the factory fitment range and is used on certain trims rather than across the entire model line. Its proportions make it important to verify against the truck's current wheel package before selecting a replacement. Buyers considering this size should focus on matching the trim-level fitment and then comparing available tire choices for the kind of road, trail, or mixed-use driving the truck sees.
275/60R20 is a metric radial size with a 275-millimeter nominal width, a 60-series aspect ratio, and a 20-inch wheel diameter. On the 2021 GMC Trucks Sierra 1500, it appears across several sub-models, making it one of the more widely used 20-inch fitments in the lineup. The added width compared with a 265-size makes wheel match and clearance worth checking if the truck has been altered from its original setup. This size is a practical focal point for owners of 20-inch Sierra trims who want to keep the truck in its proper fitment family.
275/65R18 is a metric radial size that combines a 275-millimeter nominal width with a 65-series profile on an 18-inch wheel. For the 2021 GMC Trucks Sierra 1500, this fitment is tied to specific configurations rather than the whole model range. Available product choice in this size includes BFGoodrich All-Terrain T/A KO2 with raised white letter sidewalls, which gives it a distinctly truck-oriented appearance as well as a recognizable series identity. This size deserves a careful wheel check first, especially on trucks that may have moved between factory-style 18-inch and 20-inch packages over time.
255/70R17 is a metric radial size using a 255-millimeter nominal section width, a 70-series profile, and a 17-inch rim diameter. On the 2021 GMC Trucks Sierra 1500, it serves specific 17-inch wheel applications and should not be treated as a universal Sierra size. Its narrower section compared with the 265 and 275 sizes in this lineup makes it especially important to stay with the correct trim-level fitment rather than choosing by wheel diameter alone. Buyers with 17-inch trucks should verify both the exact sub-model and the current wheel setup before selecting this size.
265/70R17 is a metric radial size that uses a 265-millimeter nominal width, a 70-series profile, and a 17-inch wheel diameter. For the 2021 GMC Trucks Sierra 1500, it applies to certain 17-inch configurations and offers an alternative within that wheel class depending on sub-model. Product choices in this size include BFGoodrich All-Terrain T/A KO2 in raised white letter form, with versions that differ in load capacity and weight. That makes this size less about finding any 17-inch tire and more about matching the truck's intended duty and confirming the wheel width and load needs.
275/50R22 is a metric radial size in which 275 is the nominal width in millimeters, 50 is the aspect ratio, and 22 identifies the wheel diameter in inches. On the 2021 GMC Trucks Sierra 1500, this is the largest wheel-package fitment in the group and belongs to specific upper-trim applications rather than the full model line. Its lower-profile layout means wheel confirmation is especially important before replacement, since a 22-inch package is not interchangeable with the truck's 17-, 18-, or 20-inch factory-size families. Owners should verify both trim and wheel diameter before narrowing product options in this size.
Tire fitment on the 2021 GMC Trucks Sierra 1500 varies meaningfully by sub-model, so trim identification matters before choosing a replacement. Some versions share certain sizes, but the full lineup spans 17-inch, 18-inch, 20-inch, and 22-inch wheel packages, making sub-model and wheel confirmation the first step.
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2021 GMC Trucks Sierra 1500 AT4
The 2021 GMC Trucks Sierra 1500 AT4 uses multiple radial tire sizes across 18-inch and 20-inch wheel packages, so there is no single AT4 fitment to assume without checking the truck first. Tire selection starts with confirming the exact wheel diameter already on the truck, then choosing the correct size within that setup.
The 2021 GMC Trucks Sierra 1500 Base uses radial tire sizes tied to 17-inch wheel packages, with more than one width and profile combination possible. That means replacement choice should follow the actual wheel-and-tire setup on the truck rather than the Base name alone.
The 2021 GMC Trucks Sierra 1500 Denali uses radial fitments associated with either a 20-inch or 22-inch wheel package. Because those wheel diameters are not interchangeable, Denali owners should confirm the current wheel size first and then stay within the correct size family for the truck's setup.
The 2021 GMC Trucks Sierra 1500 Elevation centers on a single radial size, which makes fitment more straightforward than some other Sierra trims. The main job here is confirming that the truck is still on its correct 20-inch wheel package and has not been changed to a different wheel diameter.
The 2021 GMC Trucks Sierra 1500 SLE spans several radial tire sizes across 17-inch, 18-inch, and 20-inch wheel packages. That broad spread makes wheel confirmation especially important before selection, since the SLE name alone does not narrow the truck to one tire size.
The 2021 GMC Trucks Sierra 1500 SLT uses more than one radial fitment, including both 18-inch and larger wheel-package options. Selecting the right tire depends on identifying the current wheel diameter first, then choosing the proper size for that exact SLT configuration.
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.
Best 2021 GMC Trucks Sierra 1500 Tires for Sale
Available product coverage for the 2021 GMC Trucks Sierra 1500 includes BFGoodrich All-Terrain T/A KO2 choices in select 17-inch and 18-inch sizes. The current options center on radial truck tires with raised white letter sidewalls, with differences in load specification, weight, and approved rim-width range.
Common questions for the 2021 GMC Trucks Sierra 1500 usually come down to identifying the right tire size by trim and wheel diameter, then comparing radial choices, appearance details, and practical fitment checks before road use.
Tire Size & Fitment
What tire size fits a 2021 GMC Trucks Sierra 1500?
The 2021 GMC Trucks Sierra 1500 uses several tire sizes rather than one universal fitment. Depending on sub-model and wheel package, the primary sizes are 255/70R17, 265/70R17, 265/65R18, 275/65R18, 265/60R20, 275/60R20, and 275/50R22, all in radial construction. That range covers 17-inch, 18-inch, 20-inch, and 22-inch wheel diameters across the Sierra lineup.
The practical takeaway is that the right size starts with the exact trim and the actual wheels on the truck. A Base, SLE, AT4, SLT, Denali, or Elevation may use different diameters and profiles, and a truck may also have changed wheels after delivery. Checking the existing sidewall size and confirming wheel diameter before replacement keeps the selection process on the correct track.
What size rim does a 2021 GMC Trucks Sierra 1500 use?
A 2021 GMC Trucks Sierra 1500 can use 17-inch, 18-inch, 20-inch, or 22-inch rims, depending on the sub-model and tire package. The associated tire sizes are built around those wheel diameters, including 255/70R17 and 265/70R17 on 17-inch rims, 265/65R18 and 275/65R18 on 18-inch rims, 265/60R20 and 275/60R20 on 20-inch rims, and 275/50R22 on 22-inch rims.
Rim diameter is the first fitment checkpoint because a tire must match the wheel exactly. A 20-inch tire cannot mount on an 18-inch wheel, and a 22-inch Denali-style fitment is in a completely different size family from a 17-inch Base setup. Looking at the tire sidewall and measuring the installed wheel package prevents ordering a size that belongs to a different Sierra configuration.
Why does the 2021 GMC Trucks Sierra 1500 have more than one tire size?
The 2021 GMC Trucks Sierra 1500 was offered in multiple trims with different wheel packages, so several tire sizes are correct depending on configuration. Base and SLE models can use 17-inch fitments, AT4 and SLT can use 18-inch or 20-inch sizes, Denali can use 20-inch or 22-inch sizes, and Elevation uses a 20-inch fitment. All of those are legitimate Sierra 1500 fitment paths.
That variety means size selection should follow the exact truck instead of the model name alone. Trim level, wheel diameter, and any later wheel changes can all affect which size belongs on the vehicle. The easiest way to narrow it down is to match the current sidewall size to the truck's sub-model and confirm that the wheels still correspond to the intended Sierra fitment family.
Choosing the Right Tire
What should I consider when choosing a tire for a 2021 GMC Trucks Sierra 1500?
Start with the exact Sierra 1500 sub-model and the wheel diameter already on the truck, because this model uses several radial sizes across 17-inch, 18-inch, 20-inch, and 22-inch packages. After the size is confirmed, compare the tire's intended use, approved rim-width range where available, load specification, and any visible details such as sidewall style or tire series.
The best comparison process is practical rather than broad. A truck used for highway driving may lead to different priorities than one that sees rougher surfaces, and a 17-inch fitment has different product considerations than an 18-inch all-terrain choice. Matching the tire to the truck's actual setup and expected use helps narrow the field without drifting into a size that belongs to another Sierra trim.
What sidewall styles are available for 2021 GMC Trucks Sierra 1500 tires?
Among the currently available products for this 2021 GMC Trucks Sierra 1500 fitment group, the visible sidewall style is RWL, or raised white letter. That sidewall treatment appears on BFGoodrich All-Terrain T/A KO2 options in select 17-inch and 18-inch sizes such as 265/70R17 and 275/65R18. It gives those tires a more traditional truck-performance appearance than a plain black sidewall.
Sidewall style matters most after the correct size has been settled. A raised white letter tire can change the look of the truck significantly, but it still has to match the proper Sierra fitment and wheel package first. Buyers comparing appearance should also review the tire series and load specification so the tire suits the truck's real use, not just the visual presentation.
What brands offer tires for the 2021 GMC Trucks Sierra 1500?
The currently available products for this 2021 GMC Trucks Sierra 1500 fitment set include BFGoodrich. The brand appears in select radial truck sizes through the All-Terrain T/A KO2 line, including 265/70R17 and 275/65R18 applications. Those options pair the Sierra's correct size-based fitment with a recognizable all-terrain series and raised white letter sidewall presentation.
Brand should be part of the comparison, but not the only one. The correct size, wheel diameter, approved rim-width range, and load specification still determine whether a tire belongs on a particular Sierra setup. Once those fitment basics are covered, brand and series become useful ways to sort the available choices by intended look and truck use rather than by name alone.
Restoration & Appearance
Which tire should I choose for a period-style 2021 GMC Trucks Sierra 1500?
A period-style choice for a 2021 GMC Trucks Sierra 1500 usually means staying with the truck's correct factory-size family and wheel diameter rather than mixing in a different trim's package. For trucks covered by the available product range, BFGoodrich All-Terrain T/A KO2 options in sizes such as 265/70R17 or 275/65R18 provide a truck-appropriate, contemporary appearance tied to legitimate Sierra fitments.
Appearance still has to follow fitment discipline. A 17-inch Base or SLE setup should stay in its proper size range, while a Denali on 22-inch wheels belongs to a very different visual and dimensional package. Matching the sub-model and wheel diameter first keeps the truck looking right for its configuration and avoids choosing a tire only because the style seems appealing.
How does tire construction affect the appearance of a restored 2021 GMC Trucks Sierra 1500?
For the 2021 GMC Trucks Sierra 1500, the primary fitments are radial throughout, so the appearance question is less about bias-ply versus radial and more about the exact size, wheel diameter, and sidewall treatment. A 17-inch or 18-inch all-terrain radial with raised white letters presents the truck differently than a lower-profile 20-inch or 22-inch fitment, even though all are radial designs.
That means visual consistency comes from staying within the truck's correct trim-level size family. The tire's profile, section width, and sidewall style all influence whether the truck looks work-oriented, off-road leaning, or more upscale. For an appearance-driven project, compare the existing wheel package first, then choose a tire that supports the intended look without crossing into a different Sierra fitment group.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2021 GMC Trucks Sierra 1500?
Yes, modifications can affect tire fitment on a 2021 GMC Trucks Sierra 1500 even when the tire size itself is correct for a stock configuration. Aftermarket wheels, offset changes, suspension lifts or drops, leveling kits, and body changes can alter steering clearance, fender clearance, and how a given 17-inch, 18-inch, 20-inch, or 22-inch tire package sits on the truck.
A modified Sierra should be checked as it exists now, not only by the trim name on paper. Wheel diameter, wheel width, and the current sidewall size should all be confirmed before replacement, especially if the truck has moved away from its original setup. Looking for rubbing marks at full lock and under suspension movement helps catch issues before a new set goes into service.
What should I inspect before driving a 2021 GMC Trucks Sierra 1500 on new tires?
Before driving a 2021 GMC Trucks Sierra 1500 on new tires, inspect the installed size against the wheel diameter, confirm inflation pressure, and make sure the tires seat properly on the wheels. It is also smart to check valve stems, lug torque, visible sidewall condition, and basic clearance around the fenders, suspension, and steering components once the truck is back on the ground.
A short, careful road check is worthwhile before normal use. Listen for rubbing, feel for vibration, and recheck pressure after the initial drive. Trucks that use larger wheel packages or carry all-terrain tires deserve extra attention to clearance at full steering lock and over uneven pavement. Catching a fitment or installation issue early is easier than discovering it during regular driving or towing use.
How often should tires on a 2021 GMC Trucks Sierra 1500 be inspected?
Tires on a 2021 GMC Trucks Sierra 1500 should be inspected regularly, not only when they look obviously worn. A routine visual check for uneven tread wear, punctures, cuts, bulges, embedded debris, and air loss helps catch problems early, and pressure should be monitored consistently as part of normal truck maintenance. That matters across the full Sierra size range, from 17-inch through 22-inch packages.
Inspection becomes even more important if the truck sits for long periods, carries heavier loads, or sees rougher road surfaces. Looking over the sidewalls and tread before longer drives can reveal aging or damage that is easy to miss during everyday use. Keeping the correct size on the correct wheel and watching condition over time gives the Sierra a much better chance of trouble-free road use.
