The 2018 GMC Trucks Sierra 1500 sits in the full-size pickup market as a modern truck that can range from straightforward work use to upscale trim and appearance-focused configurations. That matters for tire selection because this Sierra 1500 does not rely on one universal fitment across the lineup. Depending on sub-model, it uses radial sizes from 255/70R17 up to 285/45R22, with wheel diameter playing a major role in the decision. Product choice shown here is concentrated in 265/70R17, where BFGoodrich All-Terrain T/A KO2 options use a raised white letter sidewall. Before choosing a tire, confirm the exact trim and wheel setup currently on the truck.
Which Tire Size Is Right for The 2018 GMC Trucks Sierra 1500
Five primary tire sizes apply to the 2018 GMC Trucks Sierra 1500, and they vary by sub-model and wheel diameter. The first step is identifying the exact trim and confirming whether the truck has 17-inch, 18-inch, 20-inch, or 22-inch wheels. Once that is settled, the decision shifts to selecting the right radial size for the truck's intended use and present wheel setup.
255/70R17 is a metric radial size in which 255 is the nominal section width in millimeters, 70 is the aspect ratio, R indicates radial construction, and 17 is the wheel diameter in inches. On the 2018 GMC Trucks Sierra 1500, this size is part of the 17-inch fitment group used on certain sub-models rather than the entire lineup. Its dimensions place it within the truck's modern factory-style sizing range for this generation. This is the size to evaluate when the truck is still on its 17-inch wheel setup and the goal is to stay with the proper diameter class.
265/70R17 follows the same metric radial format, with a 265-millimeter nominal section width, a 70-series profile, radial construction, and a 17-inch rim diameter. For the 2018 GMC Trucks Sierra 1500, it serves specific 17-inch wheel applications and also has the clearest product variety shown here. Available examples include BFGoodrich All-Terrain T/A KO2 tires with raised white letter sidewalls, along with differences in load specification and weight. This size deserves a closer look when the truck is being used with a 17-inch wheel and tire choice needs to balance fitment with intended truck use.
275/55R20 is a metric radial size where 275 is the nominal section width in millimeters, 55 is the aspect ratio, R marks radial construction, and 20 is the wheel diameter. On the 2018 GMC Trucks Sierra 1500, this size belongs to 20-inch wheel applications used by certain trims rather than every Sierra 1500 configuration. Its sizing reflects a lower-profile look than the 17-inch and 18-inch options while still remaining within the truck's primary fitment range. This is the size to confirm when the truck carries factory-style or replacement 20-inch wheels and trim-specific fitment is the deciding factor.
285/45R22 uses the modern metric radial system, with 285 as the nominal section width in millimeters, 45 as the aspect ratio, radial construction, and a 22-inch wheel diameter. Within the 2018 GMC Trucks Sierra 1500 range, this size is tied to select upper-end configurations that use 22-inch wheels. The shorter sidewall profile gives it a distinctly different wheel-and-tire presentation from the 17-inch and 18-inch fitments. This is the right size to evaluate only after confirming that the truck actually has the matching 22-inch wheel setup and enough clearance for that configuration.
265/65R18 is a metric radial tire size meaning 265 millimeters of nominal section width, a 65-series aspect ratio, radial construction, and an 18-inch rim. For the 2018 GMC Trucks Sierra 1500, it fits within the group of trim-dependent primary sizes and sits between the 17-inch and 20-inch fitments in wheel diameter. That makes it a useful middle-ground size for trucks equipped with 18-inch wheels. This is the size to compare when the current wheel package is 18 inches and the goal is to maintain the truck's intended fitment range without moving to a different rim diameter.
Tire fitment for the 2018 GMC Trucks Sierra 1500 changes by sub-model, so trim identification matters before anything else. Several trims use more than one primary size, and wheel diameter is often the quickest way to narrow the correct choice.
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2018 GMC Trucks Sierra 1500 Base
The 2018 GMC Trucks Sierra 1500 Base uses 17-inch radial tire fitments, with either 255/70R17 or 265/70R17 depending on configuration. Tire selection starts with confirming which 17-inch setup is on the truck now, then comparing the available options within that size.
The 2018 GMC Trucks Sierra 1500 Denali uses larger-diameter radial fitments, with 20-inch and 22-inch applications represented. That makes wheel diameter the key checkpoint before choosing a replacement tire, especially on trucks that may have had wheels changed over time.
The 2018 GMC Trucks Sierra 1500 Elevation Edition is the most straightforward trim here because it centers on one primary radial size. Selection is less about sorting through multiple fitments and more about confirming the existing 20-inch wheel package and choosing the right tire style for the truck's use.
The 2018 GMC Trucks Sierra 1500 SLE spans several primary radial sizes across 17-inch, 18-inch, and 20-inch wheel applications. A buyer should confirm the actual wheel diameter first, then match the tire size already associated with that specific truck configuration.
The 2018 GMC Trucks Sierra 1500 SLT covers multiple radial fitments, including 18-inch, 20-inch, and 22-inch wheel packages. Tire choice depends on identifying the current wheel setup first, since moving between those diameters is not simply a matter of picking another tire in the same model line.
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 2018 GMC Trucks Sierra 1500 Tires for Sale
Current product selection is centered on 265/70R17, where BFGoodrich All-Terrain T/A KO2 options are available in radial construction with raised white letter sidewalls. The main comparison points in the product grid are load specification, rim-width compatibility, and tire weight within that size.
The questions below focus on Sierra 1500 tire size differences by trim, wheel-diameter fitment, available 265/70R17 product choices, and the checks that matter before putting a truck back on the road.
Tire Size & Fitment
What tire size fits a 2018 GMC Trucks Sierra 1500?
The 2018 GMC Trucks Sierra 1500 uses five primary radial tire sizes: 255/70R17, 265/70R17, 265/65R18, 275/55R20, and 285/45R22. Those sizes are not universal across the whole model line, because different Sierra 1500 sub-models use different wheel and tire combinations.
The most important step is matching the tire size to the exact trim and wheel diameter currently on the truck. A Base, SLE, Denali, or SLT can have different fitments, and modified trucks may no longer match their original setup, so the sidewall marking and actual wheel size should both be checked before buying.
What size rim does a 2018 GMC Trucks Sierra 1500 use?
A 2018 GMC Trucks Sierra 1500 can use 17-inch, 18-inch, 20-inch, or 22-inch rims depending on sub-model and tire size. The 17-inch fitments pair with 255/70R17 or 265/70R17, the 18-inch fitment uses 265/65R18, the 20-inch fitment uses 275/55R20, and the 22-inch fitment uses 285/45R22.
That means wheel diameter needs to be confirmed before tire shopping, especially on trucks that may have had wheels upgraded or swapped. Reading the tire sidewall is helpful, but checking the actual wheel diameter prevents ordering a tire that matches the truck name but not the truck's present wheel package.
Why does the 2018 GMC Trucks Sierra 1500 have more than one tire size?
The 2018 GMC Trucks Sierra 1500 has more than one tire size because the lineup includes several sub-models with different wheel packages. Base, SLE, SLT, Denali, and Elevation Edition trims do not all use the same diameter or profile, so the truck can appear with 17-inch through 22-inch tire-and-wheel combinations.
That variation makes trim and wheel confirmation more important than relying on the model name alone. Two Sierra 1500 trucks from the same year can need different tires, and a replacement should match the actual sub-model setup on the vehicle rather than assuming one size covers the entire range.
Choosing the Right Tire
What should I consider when choosing a 265/70R17 tire for a 2018 GMC Trucks Sierra 1500?
For a 2018 GMC Trucks Sierra 1500 using 265/70R17, start with correct wheel diameter and then compare the product's construction, load specification, rim-width range, and intended use. Available examples in this size include radial BFGoodrich All-Terrain T/A KO2 tires, and the options differ in weight and max load capacity.
A truck used for everyday road driving may call for different priorities than one that sees heavier-duty service or more aggressive terrain. It also helps to confirm that the wheel width falls within the tire's stated range and that the overall truck setup has not changed from stock through wheel, suspension, or trim-level changes.
What sidewall styles are available for 2018 GMC Trucks Sierra 1500 tires?
Within the currently shown Sierra 1500 product selection, 265/70R17 options are available with an RWL sidewall, meaning raised white letters. That styling is tied to the BFGoodrich All-Terrain T/A KO2 products shown here and gives the tire a more traditional truck appearance than a plain black sidewall treatment.
Sidewall style is mostly an appearance decision unless a specific product line also changes the tire's construction details or usage focus. It still makes sense to choose the sidewall treatment after confirming the correct size first, because the right look only matters once the tire matches the truck's actual wheel and trim configuration.
What brands offer tires for the 2018 GMC Trucks Sierra 1500?
The currently shown product assortment for the 2018 GMC Trucks Sierra 1500 includes BFGoodrich in 265/70R17. Those products are part of the All-Terrain T/A KO2 series and are offered in radial construction with raised white letter sidewalls.
Brand is only one part of the decision, especially on a truck with several possible original size groups. It is smarter to narrow the search by the truck's exact tire size and wheel diameter first, then compare brand-specific details such as series, rim-width range, weight, and load specification within that correct fitment.
Restoration & Appearance
Which tire should I choose for a period-style 2018 GMC Trucks Sierra 1500?
A period-style approach on a 2018 GMC Trucks Sierra 1500 usually starts with keeping the truck in its proper trim-specific tire size and wheel diameter rather than changing to a dramatically different package. Since this Sierra uses modern radial sizes, staying with the correct 17-inch, 18-inch, 20-inch, or 22-inch fitment preserves the truck's intended overall look more effectively than forcing another size.
Appearance decisions then come from the tire line and sidewall treatment available in that correct size. On trucks using 265/70R17, the BFGoodrich All-Terrain T/A KO2 with raised white letters creates a distinctly truck-oriented presentation, but exact originality questions are best checked against trim-specific GMC literature or marque references.
Does correct tire fitment matter for a 2018 GMC Trucks Sierra 1500 restoration?
Correct tire fitment matters on a 2018 GMC Trucks Sierra 1500 because wheel diameter and tire profile shape the truck's stance as much as they affect compatibility. A Sierra restored or refreshed with the wrong diameter class can look noticeably different from the trim's intended presentation, even before any driving issues are considered.
Fitment also influences practical details such as wheel clearance and the relationship between tire size and the truck's trim-specific character. Using the proper primary size for the actual sub-model keeps the project grounded, and any departure from that baseline should be checked carefully against the truck's current wheels and suspension condition.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2018 GMC Trucks Sierra 1500?
Yes, modifications can affect tire fitment on a 2018 GMC Trucks Sierra 1500. Wheel swaps, changes in wheel width, suspension lifts or drops, and body or fender alterations can all change how a tire sits in the wheel opening, even when the size looks close to one of the truck's original fitments.
That is especially important on a Sierra 1500 with several factory diameter groups ranging from 17 to 22 inches. A modified truck should be checked for steering clearance, fender clearance, and actual wheel dimensions before ordering replacement tires, because the current setup may no longer match the trim's original tire size path.
What should I inspect before driving a 2018 GMC Trucks Sierra 1500 on new tires?
Before driving a 2018 GMC Trucks Sierra 1500 on new tires, inspect wheel condition, valve stems, lug hardware, and basic suspension and steering condition. The new tires should also match the truck's actual wheel diameter and approved size group, and inflation should be set appropriately for the installed tire and vehicle use.
A short visual and functional check after installation helps catch problems early. Look for rubbing at full steering lock, uneven seating on the rim, unexpected air loss, or vibration that suggests a mounting or balancing issue, especially if the truck has aftermarket wheels or has moved between one of the Sierra's several wheel-diameter fitments.
How often should tires on a 2018 GMC Trucks Sierra 1500 be inspected?
Tires on a 2018 GMC Trucks Sierra 1500 should be inspected regularly rather than only at replacement time. Routine checks should include tread condition, visible cuts, punctures, sidewall damage, air pressure, and any uneven wear pattern that may suggest alignment, balance, or suspension issues.
Inspection becomes even more important when the truck sees mixed use, sits for extended periods, or runs larger wheel packages where sidewall height is reduced. A quick walk-around before longer trips and a closer check during normal service intervals help catch small issues before they become clearance, handling, or tire-life problems.
