The 1981 GMC Trucks C2500 Sierra Grande sits in the square-body era, a period prized for straightforward working-truck engineering and lasting collector appeal. Whether preserved as a heavy-duty pickup, used for vintage hauling duty, or restored as a clean original-style truck, tire choice matters because this model spans more than one wheel and construction setup. The 1981 GMC Trucks C2500 Sierra Grande uses 7.50R16, 8.75R16.5, 9.50R16.5, and 950-16.5 fitments, with radial applications on 16-inch and 16.5-inch wheels and a bias-ply 950-16.5 option on 16.5-inch wheels. That makes wheel diameter, sub-model details, and intended appearance just as important as the tire itself.
Which Tire Size Is Right for The 1981 GMC Trucks C2500 Sierra Grande
Four primary tire sizes apply to the 1981 GMC Trucks C2500 Sierra Grande, and they do not all serve the same truck configuration. Fitment varies by sub-model, wheel setup, and construction, and this truck uses both 16-inch and 16.5-inch rims. Before choosing a tire, identify the exact sub-model and confirm the wheel diameter already on the truck, because that determines whether the correct path is one of the radial sizes or the 950-16.5 bias-ply fitment.
Fit(s): (7/16 & 1/2 inch studs)(GVWR 6400) and (9/16 inch studs)(GVWR 6400)
Construction: Radial|Rim: 16 in
7.50R16 is a vintage numeric radial size in which 7.50 represents the nominal section width in inches, R identifies radial construction, and 16 is the rim diameter. On the 1981 GMC Trucks C2500 Sierra Grande, it belongs to specific GVWR and stud combinations rather than every configuration. Its radial construction makes it a distinct fitment choice compared with the truck's bias-ply 950-16.5 applications. This size is most important to owners who need to confirm that their truck is equipped with a 16-inch wheel before comparing any replacement options.
Fit(s): (7/16 & 1/2 inch studs)(GVWR 6400) and (9/16 inch studs)(GVWR 6400)
Construction: Radial|Rim: 16.5 in
8.75R16.5 is another vintage numeric radial size, using an inch-based section width followed by radial construction and a 16.5-inch rim diameter. For the 1981 GMC Trucks C2500 Sierra Grande, this size appears on certain 6400 GVWR configurations and shares the same general radial fitment family as 7.50R16 and 9.50R16.5. Its main significance is that it uses a 16.5-inch wheel, which is not interchangeable with a 16-inch rim. Buyers considering this size should verify both the truck's exact sub-model and the actual wheel diameter before moving any further.
Fit(s): (7/16 & 1/2 inch studs)(GVWR 6400) and (9/16 inch studs)(GVWR 6400)
Construction: Radial|Rim: 16.5 in
9.50R16.5 uses the same vintage numeric radial format, with 9.50 as the nominal section width, R for radial construction, and 16.5 for rim diameter. On the 1981 GMC Trucks C2500 Sierra Grande, it applies to certain radial-equipped 6400 GVWR versions rather than the full model range. Because it shares its wheel diameter with 8.75R16.5 but not with 7.50R16, the first practical step is confirming the existing wheel and truck configuration. This size matters most when the goal is to stay with the truck's 16.5-inch radial setup rather than shift to a different wheel arrangement.
Fit(s): (7/16 & 1/2 inch studs)(GVWR 8600), (9/16 inch studs)(GVWR 8600), Bonus Cab (7/16 & 1/2 inch studs) Front, Bonus Cab (7/16 & 1/2 inch studs) Rear, Bonus Cab (9/16 inch studs) Front, and Bonus Cab (9/16 inch studs) Rear
Construction: Bias Ply|Rim: 16.5 in
950-16.5 is a numeric bias-ply size in which 950 indicates the nominal section-width class and 16.5 identifies the rim diameter. On the 1981 GMC Trucks C2500 Sierra Grande, this size appears on 8600 GVWR applications and the Bonus Cab front and rear positions. Available choices include STA Traxion and STA Super Transport, both in Blackwall form within truck-oriented tire series. This size is the key fitment for owners trying to preserve a traditional heavy-duty bias-ply presentation while confirming that the truck is still using the correct 16.5-inch wheels.
1981 GMC Trucks C2500 Sierra Grande Sub-Model Tires
Sub-model fitment on the 1981 GMC Trucks C2500 Sierra Grande is not one-size-fits-all. Tire choice depends on GVWR, stud specification, and whether the truck is a standard Sierra Grande or a Bonus Cab, so confirming the exact configuration is the first step before selecting a tire.
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1981 GMC Trucks C2500 Sierra Grande (7/16 & 1/2 inch studs)(GVWR 6400)
This 6400 GVWR Sierra Grande uses radial fitments and may be found with 7.50R16, 8.75R16.5, or 9.50R16.5 depending on the wheel setup. The practical decision here is confirming whether the truck carries 16-inch or 16.5-inch wheels before comparing replacement sizes.
1981 GMC Trucks C2500 Sierra Grande (7/16 & 1/2 inch studs)(GVWR 8600)
This 8600 GVWR Sierra Grande uses the 950-16.5 bias-ply fitment. Tire selection centers less on multiple sizes and more on retaining the proper 16.5-inch wheel setup while choosing between the available truck-oriented bias-ply series.
1981 GMC Trucks C2500 Sierra Grande (9/16 inch studs)(GVWR 6400)
This 6400 GVWR version follows the same radial fitment pattern, using 7.50R16, 8.75R16.5, or 9.50R16.5 depending on configuration. The most important check is the actual wheel diameter on the truck, since both 16-inch and 16.5-inch radial setups appear in this sub-model group.
1981 GMC Trucks C2500 Sierra Grande (9/16 inch studs)(GVWR 8600)
This 8600 GVWR Sierra Grande uses 950-16.5 in bias-ply construction. For replacement planning, the emphasis is on maintaining the correct heavy-duty fitment and confirming the existing wheel dimensions before selecting between the available STA options.
1981 GMC Trucks C2500 Sierra Grande Bonus Cab (7/16 & 1/2 inch studs) Front
The front fitment for this Bonus Cab configuration uses 950-16.5 bias-ply. That points the selection process toward traditional heavy-duty truck tires and makes 16.5-inch wheel confirmation especially important before any replacement decision.
1981 GMC Trucks C2500 Sierra Grande Bonus Cab (7/16 & 1/2 inch studs) Rear
The rear fitment for this Bonus Cab configuration also uses 950-16.5 bias-ply. Matching the rear tire correctly means staying focused on the truck's existing 16.5-inch wheel setup and choosing the tire series that best suits restoration or working-truck use.
1981 GMC Trucks C2500 Sierra Grande Bonus Cab (9/16 inch studs) Front
This Bonus Cab front application uses 950-16.5 in bias-ply construction. Buyers looking at replacements should treat wheel confirmation as essential and then compare the available blackwall truck series within that exact size.
1981 GMC Trucks C2500 Sierra Grande Bonus Cab (9/16 inch studs) Rear
This Bonus Cab rear application uses the same 950-16.5 bias-ply fitment. That keeps the selection process straightforward, with attention centered on the proper 16.5-inch wheel, traditional truck appearance, and the specific series differences among the available options.
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 1981 GMC Trucks C2500 Sierra Grande Tires for Sale
Available product choices center on 950-16.5, with STA offering the Traxion and Super Transport series in Blackwall bias-ply construction. Both are made to order and share the same 16.5-inch rim diameter, truck-oriented character, and narrow heavy-duty rim-width range.
Owners of a 1981 GMC Trucks C2500 Sierra Grande usually need to sort out sub-model fitment, 16-inch versus 16.5-inch wheels, radial versus bias-ply construction, and restoration-minded tire selection. These FAQs focus on those decisions and the checks worth making before road use.
Tire Size & Fitment
What tire size fits a 1981 GMC Trucks C2500 Sierra Grande?
The 1981 GMC Trucks C2500 Sierra Grande uses four primary tire sizes: 7.50R16, 8.75R16.5, 9.50R16.5, and 950-16.5. The first three are radial fitments used on certain 6400 GVWR configurations, while 950-16.5 is a bias-ply fitment used on 8600 GVWR applications and Bonus Cab front and rear positions.
The key is not picking from a general size list, but matching the exact truck configuration and wheel already on the vehicle. This model spans both 16-inch and 16.5-inch rims, so checking the sub-model, GVWR, stud specification, and actual wheel diameter should come before comparing any tire options.
What size rim does a 1981 GMC Trucks C2500 Sierra Grande use?
A 1981 GMC Trucks C2500 Sierra Grande uses either a 16-inch or 16.5-inch rim, depending on the tire size and truck configuration. The 7.50R16 fitment uses a 16-inch rim, while 8.75R16.5, 9.50R16.5, and 950-16.5 use 16.5-inch rims.
That difference matters because a 16-inch tire and a 16.5-inch tire are not the same thing, even when the sizes look close at a glance. Before replacing tires, inspect the wheel stamping or measure carefully so the truck's current wheel diameter matches the tire size under consideration.
Why does the 1981 GMC Trucks C2500 Sierra Grande have more than one tire size?
More than one tire size appears on the 1981 GMC Trucks C2500 Sierra Grande because fitment changes with sub-model details such as GVWR, stud specification, and Bonus Cab applications. Some versions use radial sizes in 16-inch or 16.5-inch form, while others use the 950-16.5 bias-ply size.
That means tire selection starts with vehicle identification, not brand or sidewall preference. Once the exact sub-model is confirmed, the next step is verifying whether the truck still has its original wheel type or has been changed over time, since that can alter which size remains appropriate today.
Choosing the Right Tire
What should I consider when choosing a 950-16.5 tire for a 1981 GMC Trucks C2500 Sierra Grande?
Start by confirming that 950-16.5 is the correct fitment for the specific 1981 GMC Trucks C2500 Sierra Grande configuration, since this size belongs to 8600 GVWR and Bonus Cab applications. From there, the choice comes down to bias-ply construction, 16.5-inch wheel compatibility, and the available STA series within that size.
STA Traxion and STA Super Transport share Blackwall styling, truck-oriented construction, and the same 2780@60 psi load figure, but they differ by series and weight. Comparing rim-width specification, intended use, and the kind of period-style appearance the truck should carry will make the product grid much easier to sort.
What brands offer tires for the 1981 GMC Trucks C2500 Sierra Grande?
Current product choices for the 1981 GMC Trucks C2500 Sierra Grande are available in 950-16.5 from STA. Within that size, the brand offers the Traxion and Super Transport series, both built as Blackwall bias-ply truck tires for 16.5-inch applications.
Brand is only one part of the decision on this page, because the larger issue is making sure the truck actually uses the 950-16.5 fitment. Once that is confirmed, compare the two available STA series by rim-width specification, weight, and the kind of heavy-duty or restoration-oriented presentation you want from the finished truck.
What tire series are available for the 1981 GMC Trucks C2500 Sierra Grande?
For the 950-16.5 fitment used on certain 1981 GMC Trucks C2500 Sierra Grande applications, the available tire series are STA Traxion and STA Super Transport. Both are bias-ply Blackwall truck tires built for 16.5-inch wheels and carry the same published maximum load capacity of 2780@60 psi.
Series choice becomes meaningful when the size, wheel diameter, and construction are already settled. A buyer comparing these two should look at the truck's intended use, whether a more work-truck or restoration-style presentation is desired, and whether the wheel width falls within the published 6.50 to 6.75 inch range.
Restoration & Appearance
Which tire should I choose for a period-style 1981 GMC Trucks C2500 Sierra Grande?
A period-style choice starts with using the tire size and construction that match the truck's actual configuration. On the 1981 GMC Trucks C2500 Sierra Grande, that may mean one of the vintage-style radial sizes on 6400 GVWR applications or the 950-16.5 bias-ply fitment on 8600 GVWR and Bonus Cab versions.
Appearance and authenticity are shaped by more than brand alone, especially on a square-body truck that may have seen wheel swaps over the years. Owners pursuing exact restoration standards should verify the truck's equipment history first, then choose the tire size and series that preserve the correct visual stance and wheel relationship.
How does tire construction affect the appearance of a restored 1981 GMC Trucks C2500 Sierra Grande?
Tire construction changes the visual character of a restored 1981 GMC Trucks C2500 Sierra Grande because bias-ply and vintage-style radial tires do not present exactly the same way on the truck. In this fitment range, 950-16.5 is the bias-ply choice, while 7.50R16, 8.75R16.5, and 9.50R16.5 are radial applications.
That difference can influence how traditional or updated the truck looks, especially around the sidewall profile and overall stance. For a restoration-minded build, construction should match the truck's intended presentation as closely as its mechanical setup allows, rather than being treated as a purely cosmetic afterthought.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1981 GMC Trucks C2500 Sierra Grande?
Yes, modifications can affect tire fitment on a 1981 GMC Trucks C2500 Sierra Grande. Wheel changes, suspension alterations, ride-height changes, or axle-related modifications can all influence whether a tire still has the correct rim diameter, wheel width, and clearance relationship for the truck.
That is especially important here because this model already spans both 16-inch and 16.5-inch wheel setups from the start. A truck that has been updated over time should be checked carefully at the wheel, not judged only by model name, so the selected tire matches the hardware actually mounted on the vehicle.
What should I inspect before driving a 1981 GMC Trucks C2500 Sierra Grande on new tires?
Before driving a 1981 GMC Trucks C2500 Sierra Grande on new tires, inspect the wheels for correct diameter and condition, confirm the tires are seated properly, and check inflation pressure. It is also wise to look over the suspension, steering components, and brake hardware on a truck that may have spent long periods parked.
A short test drive should be followed by another inspection for rubbing, uneven seating, or any sign of contact at full steering lock or suspension movement. Collector and working trucks alike benefit from a careful recheck after initial miles, since aged wheels or changed components can reveal fitment issues only once the truck is moving.
How should tires on a collector 1981 GMC Trucks C2500 Sierra Grande be maintained?
Tires on a collector 1981 GMC Trucks C2500 Sierra Grande should be maintained with regular pressure checks, visual inspections, and clean storage conditions. Even a lightly driven truck can develop age-related issues such as cracking, flat spotting, cuts, bulges, or slow air loss, especially when it sits for long periods.
Storage habits matter almost as much as mileage on an older truck. Keeping the vehicle away from prolonged sunlight, moisture, excessive heat, and ozone sources helps preserve tire condition, and periodic movement can reduce set-in wear patterns while giving you a chance to inspect tread and sidewalls before road use.
