1979 GMC C/K Pickup Tires

A 1979 GMC C/K Pickup does not use one universal tire size. Fitments include 700-15, GR78-15, HR78-15, 650-16, L78-15, LR78-15, 875-16.5, 950-16.5, 750-16, 9.50-19.5, 8.75R16.5, 8.75-16, 10-15, and 10-16.5, depending on the exact C- or K-series model, GVWR, and wheel setup.

The best starting point is the truck’s exact sub-model and current wheel diameter, because this model line spans 15-, 16-, 16.5-, and 19.5-inch rims. Some applications also have more than one size within the same sub-model, so checking the tire already on the truck, the wheel stamp, and overall clearance is smart before moving to brand or style selection.

The 1979 GMC C/K Pickup uses several different rim diameters rather than one standard size. Depending on the configuration, the truck may use 15-inch, 16-inch, 16.5-inch, or 19.5-inch rims. Rim diameter follows the tire size itself, so a 700-15 or L78-15 fits a 15-inch rim, while sizes such as 750-16, 875-16.5, and 9.50-19.5 correspond to their matching wheel diameters.

That variation is why wheel confirmation matters before selecting tires. Trucks in this era were often worked hard, upgraded, or converted to different wheels, and some sub-models were available with more than one rim diameter. Reading the size on the existing tire is helpful, but verifying the wheel itself is the safer step when the truck’s history is unclear.

The 1979 GMC C/K Pickup covers a wide range of half-ton, three-quarter-ton, one-ton, two-wheel-drive, four-wheel-drive, and high-GVWR applications, so tire size changes with the truck’s intended load and wheel package. That is why the lineup includes lighter 15-inch sizes, several 16- and 16.5-inch truck tires, and even a 19.5-inch application on a heavier-duty C2500 configuration.

Within some sub-models, more than one size also appears because the truck could be equipped differently from the factory or changed later in service. Instead of assuming all C1500s or all C3500s use the same tire, match the exact designation on the truck to its wheel diameter and operating role before choosing a replacement.

That depends on the exact 1979 GMC C/K Pickup configuration. Some fitments are primary bias-ply sizes such as 700-15, 750-16, 875-16.5, and 950-16.5, while others use radial formats such as GR78-15, HR78-15, LR78-15, or 8.75R16.5. The truck does not have one universal construction, so the first job is identifying which size and construction belong to the specific sub-model and wheel setup.

Once the correct fitment is known, the decision becomes one of appearance, intended use, and setup compatibility. A bias-ply tire preserves a more traditional truck presentation, while a radial-format application follows the construction already tied to that configuration. Any change in construction should be checked against wheel width, wheel condition, and vehicle clearance before regular road use.

L78-15 has four radial-equivalent options for the 1979 GMC C/K Pickup. Those are 235R15 as an 80-series metric radial, P235/75R15 as a 75-series P-metric radial, P255/70R15 as a 70-series P-metric radial, and 820R15 as a bias-look radial equivalent. The associated rim-width range for these equivalents is 6-8 inches.

Each option gives a different path away from the original alphanumeric bias-ply format, either through a more traditional metric radial convention, a P-metric profile choice, or a bias-look radial intended to retain a vintage visual style. They should still be checked against the truck’s wheel width, overall dimensions, and clearance rather than treated as automatic replacements.

Yes, a bias-look radial appears in this fitment family. LR78-15 is available as a Firestone bias-look radial for certain 15-inch applications, and 820R15 is a bias-look radial equivalent associated with the L78-15 size. That means some 1979 GMC C/K Pickup configurations do have a radial option that keeps a more traditional visual character than a modern-looking replacement tire.

A bias-look radial can make sense when the goal is to keep vintage truck style without staying strictly with a full bias-ply construction. The important next step is confirming the exact primary size on the truck, along with wheel width and wheel condition, because not every C/K sub-model uses the same 15-inch tire format or the same construction.

Start with the exact size and wheel diameter required by the truck’s sub-model, since the 1979 GMC C/K Pickup spans many fitments from 700-15 up to 9.50-19.5. After that, compare construction type, brand, tire series, and sidewall style where those choices exist. Some sizes are passenger-style bias-ply or radial fitments, while others are clearly truck-oriented tires with heavier-duty tread patterns and load-focused specifications.

The right choice depends on how the truck will actually be used. A restoration-minded half-ton may lean toward a traditional sidewall treatment, while a working three-quarter-ton or one-ton may need a more commercial-style series. Matching the tire to wheel width, axle use, and the truck’s current configuration is more important than choosing by appearance alone.

Sidewall style depends heavily on the tire size. Across the available 1979 GMC C/K Pickup products, choices include blackwall, wide whitewall, narrow whitewall, and dual-white-stripe treatments. Smaller and more passenger-oriented sizes such as 650-16, 700-15, 750-16, and L78-15 show the widest cosmetic variety, while many heavier truck sizes such as 875-16.5, 950-16.5, and 10-16.5 stay strictly blackwall.

That distinction matters because sidewall appearance can change the truck’s character even when the size remains correct. A whitewall may suit a restoration-oriented light-duty pickup, while a blackwall truck tire often better matches a work-focused or utility presentation. The sidewall choice should come after confirming the correct size, rim diameter, and construction for the specific sub-model.

Brand availability varies by size, but the 1979 GMC C/K Pickup has options from Firestone, BFGoodrich, Coker Classic, STA, Garfield, Lester, Goodyear, Excelsior, and Tornel in the applicable fitments. Some sizes, especially 650-16, 700-15, 750-16, and L78-15, offer broad brand coverage, while other heavy-duty sizes such as 875-16.5, 950-16.5, and 10-16.5 are much narrower in brand choice.

That means brand shopping starts only after the truck’s exact size is confirmed. On a light-duty pickup, the decision may involve appearance-oriented differences between blackwall and whitewall offerings, while a heavier truck may be choosing mainly among tread series in a single brand family. Comparing size, wheel compatibility, and intended use will narrow the field more effectively than brand name alone.

A period-style choice starts with using the exact primary size that belongs on the truck’s specific sub-model and wheel diameter. On a 1979 GMC C/K Pickup, that could mean a numeric bias-ply size such as 700-15, 650-16, 750-16, or one of the heavier 16.5-inch truck sizes, or it could mean a period radial format such as HR78-15 or LR78-15 on certain applications.

Once the fitment is correct, the visual direction becomes clearer. Bias-ply construction usually supports a more traditional truck presentation, while a period-style radial can still look appropriate for a late-1970s build. When exact originality matters, compare the truck against marque references, original paperwork, or other vehicle-specific historical sources before choosing a brand or sidewall treatment.

Tire construction changes more than ride feel on a restored 1979 GMC C/K Pickup; it also influences the truck’s visual stance and period impression. A bias-ply tire generally preserves a more traditional vintage-truck look, especially in numeric truck sizes, while radial-format tires such as GR78-15, HR78-15, LR78-15, or 8.75R16.5 reflect the later-1970s move toward radial applications on certain configurations.

That is why restoration goals should be decided before the final tire purchase. A work-oriented truck may look most convincing on blackwall truck tires, while a lighter-duty or appearance-focused pickup may call for a different sidewall treatment. The smartest approach is to establish the correct size first, then choose the construction that best matches the truck’s intended era presentation.

Yes, modifications can change tire fitment on a 1979 GMC C/K Pickup even when the tire size looks close on paper. Aftermarket wheels, suspension lifts, lowering, axle swaps, brake conversions, or body changes can alter the wheel diameter, wheel width, or available clearance. That matters even more on this truck family because it already spans several factory wheel diameters and multiple tire constructions.

A modified truck should be checked at the wheel, not just by model name. Confirm the actual rim diameter and width, then look at steering travel, fender clearance, and space around suspension components before selecting a replacement. That extra step helps avoid choosing a tire that matches the badge on the fender but not the setup currently under the truck.

Before driving a 1979 GMC C/K Pickup on new tires, inspect the wheels for cracks, rust, bent flanges, and correct diameter, then verify lug hardware, valve stems, and overall wheel condition. It is also smart to check alignment basics, steering play, suspension wear, and brake function, especially on a truck that has sat for long periods or carried heavy loads in the past.

New tires perform best when the rest of the truck is ready for road use. Air pressure should match the tire’s service needs, and the tires should be rechecked after initial miles for seating, air loss, and any signs of rubbing. A careful inspection is especially important on multi-application trucks like the 1979 C/K, where wheel changes over time are common.

Collector-truck tires should be maintained with regular pressure checks, visual inspections, and clean storage habits. On a 1979 GMC C/K Pickup, look for cracking, cuts, bulges, flat spotting, uneven wear, and slow air loss, especially if the truck is driven only occasionally. Low-use vehicles can appear fine at a glance while still carrying age-related issues that deserve attention before the next drive.

Storage conditions matter almost as much as mileage. Keeping the truck away from prolonged sun, heat, standing moisture, and ozone sources helps preserve the tires, and moving the vehicle periodically can reduce set-in flat spotting. Before a longer road outing, inspect the spare as well, since older trucks often retain one that matches the era but not roadworthy condition.