1973 GMC C/K Pickup Tires

A 1973 GMC C/K Pickup does not use one universal tire size. Depending on the exact sub-model, GVWR, and wheel setup, primary sizes include 700-15, G78-15, L78-15, H78-15, 700-16, LR78-15, 875-16.5, 950-16.5, 750-16, 800-16.5, and 10-16.5.

The right choice starts with identifying whether the truck is a C1500, K1500, C2500, K2500, C3500, or K3500, then confirming the installed rim diameter. Many nearby configurations use different 15-inch, 16-inch, or 16.5-inch wheels, and some light-duty versions also introduce a radial fitment alongside bias-ply sizes.

The 1973 GMC C/K Pickup uses three different rim diameters across the model range: 15-inch, 16-inch, and 16.5-inch. The correct rim diameter depends on the specific sub-model and GVWR, with lighter-duty trucks commonly appearing in 15-inch fitments and heavier-duty versions moving into 16-inch or 16.5-inch truck sizes.

That distinction matters because a 16-inch tire does not mount on a 16.5-inch wheel, even though the numbers appear close. Before choosing a replacement tire, check the wheel already on the truck and compare it to the exact sub-model fitment, especially on work trucks that may have seen wheel changes over time.

The 1973 GMC C/K Pickup covers a wide span of half-ton, three-quarter-ton, and one-ton trucks in both 4x2 and 4x4 form, and that broad range leads to multiple tire sizes. Different GVWR ratings, wheel diameters, and heavy-duty applications create separate fitments rather than one size shared across the entire lineup.

In practical terms, the truck’s badge alone is not enough for tire selection. A C1500 on 15-inch wheels and a K3500 on 16.5-inch heavy-duty wheels may both be 1973 GMC pickups, but they need very different tires, so the exact sub-model and wheel setup should always be verified first.

LR78-15 is a radial fitment for the 1973 GMC C/K Pickup. It appears on certain light-duty C1500 and K1500 applications, while most other primary sizes across the 1973 C/K range remain traditional bias-ply truck or passenger-style fitments.

That makes LR78-15 important because it changes the tire-selection conversation from size alone to construction as well. The truck should be checked to confirm that it is one of the specific LR78-15 applications and that its 15-inch wheels match the tire’s rim-width requirements before moving away from a bias-ply setup.

G78-15 can be compared with 205R15, P215/75R15, P225/70R15, and 710R15. H78-15 can be compared with 215R15, P225/75R15, P235/70R15, and 760R15. L78-15 can be compared with 235R15, P235/75R15, P255/70R15, and 820R15, with the 710R15, 760R15, and 820R15 serving as bias-look radial options.

Those equivalents give the owner several radial sizing approaches, from Euro-metric 80-series style sizing to P-metric 75- and 70-series alternatives, plus a radial designed to retain a more traditional visual profile. Even so, wheel width, actual wheel diameter, and truck clearance should be checked before treating any equivalent as a ready substitute.

Start by confirming that the truck’s original size has a stated radial equivalent and that the wheel diameter is correct for that equivalent. For the 15-inch bias-ply sizes with radial alternatives, rim-width range also matters, and the truck’s current wheel should be checked against the equivalent tire’s intended fitment range.

A conversion should also take the truck’s actual setup into account. Aftermarket wheels, suspension changes, steering-stop adjustments, or body modifications can all affect clearance, and a restored truck may have different priorities than a regularly driven one. Matching the tire to the truck’s use is just as important as matching the size code.

Begin with the truck’s exact sub-model, GVWR, and wheel diameter, because this model range uses multiple 15-inch, 16-inch, and 16.5-inch primary tire sizes. After size is confirmed, the next considerations are construction, sidewall appearance, tire series, rim-width compatibility where stated, and whether the truck is being restored, shown, or driven in regular service.

A light-duty 15-inch truck may allow more appearance variation, including whitewall choices, while a heavier 16-inch or 16.5-inch application usually leans toward truck-oriented blackwall tires. It also helps to compare load figures and intended tread character where available, especially on trucks expected to carry weight or see longer road use.

Sidewall options for the 1973 GMC C/K Pickup vary by size but include blackwall, wide whitewall, narrow whitewall, and dual-white-stripe styles. The broadest sidewall variety appears in several 15-inch sizes such as L78-15, while many heavier-duty 16-inch and 16.5-inch truck sizes are offered primarily as blackwalls.

That gives owners two different selection paths. A restoration-oriented light-duty pickup may lean toward a traditional whitewall presentation, while a work-focused or heavier truck often stays visually consistent with a blackwall truck tire. The correct size and wheel should still be settled first, since appearance choices only matter after fitment is right.

Tires for the 1973 GMC C/K Pickup are available from Firestone, BFGoodrich, Coker Classic, STA, Lester, Avon, and Tornel, depending on the size. Brand availability changes across the fitment range, with some sizes offering several classic and truck-oriented choices while others, especially heavier-duty applications, stay more limited.

The better way to use brand choice is as a comparison tool after the correct size is known. Some brands appear in classic bias-ply passenger-style lines, others in military or truck-focused series, and one 15-inch radial-style fitment appears under Firestone, so the truck’s role should guide the comparison.

A period-style starting point for a 1973 GMC C/K Pickup is the primary size tied to the truck’s exact sub-model, using the original fitment family rather than jumping straight to a modern substitute. For many trucks in this range, that means a bias-ply tire in the proper 15-inch, 16-inch, or 16.5-inch size.

After the correct size is identified, appearance can be refined through sidewall and tire-series choice. Light-duty trucks may offer whitewall or blackwall options, while heavier-duty versions tend to stay with blackwall truck tires. When strict originality matters, vehicle-specific photos, dealer literature, and marque references are worth reviewing before final selection.

Tire construction changes the visual character of a restored 1973 GMC C/K Pickup as much as the sidewall itself. A bias-ply tire gives the truck a more traditional period presentation, while a radial can alter the look even when it is offered in a vintage-style size or with a bias-profile radial design.

That difference matters most on 15-inch applications where both bias-ply and radial-related choices enter the conversation. Owners focused on authenticity of stance and overall presentation often stay close to the original construction type, while those prioritizing road use may look at radial alternatives after confirming wheel and clearance compatibility.

Yes, modifications can affect tire fitment on a 1973 GMC C/K Pickup. Aftermarket wheels, changes in wheel width or offset, suspension lifts or lowering, and body or brake changes can all alter how a tire sits in the wheel opening, even when the size matches a known original fitment family.

That matters even more on this truck because the model line already spans 15-inch, 16-inch, and 16.5-inch wheels from the factory. A modified truck should be checked for steering clearance, fender clearance, and actual wheel dimensions before replacement tires are chosen, especially when moving between bias-ply and radial constructions.

Before driving a 1973 GMC C/K Pickup on new tires, inspect the wheels for the correct diameter and condition, make sure the tires are mounted in the proper size, and verify that inflation is appropriate for the tire and vehicle setup. It is also smart to check lug hardware, valve stems, and visible clearance at the fenders and steering components.

A short initial road test can reveal rubbing, pull, or vibration that was not obvious in the shop. On older trucks, it also helps to look over suspension and steering wear, because loose front-end components can make a new tire feel wrong even when the size itself is correct.

Tires on a collector 1973 GMC C/K Pickup should be inspected regularly for cracking, bulges, cuts, flat spotting, uneven wear, and signs of air loss. Pressure should be checked even when the truck is driven only occasionally, because collector vehicles often spend long periods parked and can develop condition issues before tread wear becomes obvious.

Storage habits matter too. Keeping the truck away from prolonged sunlight, excess heat, moisture, and ozone sources helps preserve tire condition, and moving the vehicle occasionally can reduce flat spotting. Before any longer drive, give the tires and wheels another close look, especially on trucks carrying older heavy-duty bias-ply sizes.