1979 GMC Jimmy Tires

A 1979 GMC Jimmy uses three primary tire sizes: 700-15, H78-15, and L78-15. All three are bias-ply fitments for 15-inch rims, and both the C1500 4x2 and K1500 4x4 are associated with that same size group rather than a separate sub-model-specific tire listing.

That means the next step is confirming which wheels are actually on the truck today. Many surviving Jimmys have had wheel, suspension, or use changes over the years, so the best choice is the size that matches the rim width, overall look, and intended duty rather than assuming every 15-inch tire suits every setup.

The listed tire fitments for a 1979 GMC Jimmy all use a 15-inch rim diameter. That applies across 700-15, H78-15, and L78-15, so the wheel diameter remains consistent even though the tire sizing systems differ between the numeric and alphanumeric bias-ply formats.

Rim diameter is only part of the fitment picture, especially on a truck that may have seen years of changes. Wheel width still matters, and the available products show that different tires in these sizes are intended for different rim-width ranges, so checking the actual wheels before choosing a tire avoids an appearance or compatibility mismatch.

The covered 1979 GMC Jimmy sub-models share the same group of primary tire sizes. Both the C1500 4x2 and K1500 4x4 are associated with 700-15, H78-15, and L78-15, all in bias-ply construction on 15-inch rims.

Shared size coverage does not mean every Jimmy still has the same wheel setup in practice. A buyer should still confirm the truck’s current rims, intended use, and the type of tire desired, since the available choices range from whitewall passenger-style bias-ply tires to more truck-oriented blackwall tread patterns.

H78-15 is a primary bias-ply tire size for the 1979 GMC Jimmy. In this application, it is part of the truck’s original-style fitment group, and the available H78-15 products remain bias-ply tires rather than primary radial fitments.

A radial option can still be considered, but it should be treated as an equivalent rather than the same construction. Owners comparing bias-ply and radial paths should think about wheel width, the truck’s present setup, and whether the goal is a traditional period-style appearance or a radial alternative that still works within the vehicle’s 15-inch wheel format.

For H78-15, radial equivalents include 215R15, P225/75R15, P235/70R15, and 760R15 as a bias-look radial. For L78-15, the equivalents are 235R15, P235/75R15, P255/70R15, and 820R15 as a bias-look radial. Both size groups also carry a 6-8 inch recommended rim-width range for the equivalent selections.

Those choices give a mix of tall metric radials, more familiar P-metric options, and bias-look radial styling. Even when the rim diameter matches, an equivalent should still be checked against the truck’s actual wheel width, steering clearance, and overall stance before making the switch from a primary bias-ply fitment.

Start by matching the radial equivalent to the original bias-ply size the truck is using, since H78-15 and L78-15 each have their own equivalent group. Wheel diameter must stay correct, and wheel width should also be verified because the equivalent radial selections are associated with a 6-8 inch rim-width range.

The truck’s actual setup deserves a close look before any construction change. Steering clearance, fender room, suspension condition, and the wheel choice already on the vehicle can all affect the result, so the safest approach is to confirm dimensions and compatibility rather than treating a radial equivalent as automatic.

The first decision is choosing the size that matches the Jimmy’s current 15-inch wheel setup, since this model uses three different primary bias-ply sizes. From there, compare whether the truck needs a more passenger-style period look, a truck-oriented tread, or a size that also opens the door to radial-equivalent alternatives.

Product differences matter once the size is settled. Sidewall treatment, tire series, rim-width compatibility, load figures where stated, and the truck’s intended use all help narrow the choice, especially on a vehicle that may serve as a restoration project, weekend cruiser, or more utility-minded vintage truck.

1979 GMC Jimmy tires are available in several sidewall styles depending on size. Blackwall choices appear across all three primary sizes, while wide whitewall options appear in 700-15, H78-15, and L78-15. L78-15 adds narrow whitewall and dual-white-stripe selections for owners who want a broader restoration-style appearance range.

That variety lets the tire shape the truck’s overall presentation as much as the wheel does. A blackwall often suits a more utilitarian or truck-focused look, while whitewall and stripe designs lean more toward period-style visual detail, so the right choice depends on how stock, upscale, or work-oriented the Jimmy is meant to appear.

Tires for the 1979 GMC Jimmy are available from Firestone, BFGoodrich, Coker Classic, and STA across the listed primary sizes. Brand availability varies by size, with 700-15 showing the broadest spread, H78-15 combining Coker Classic and STA choices, and L78-15 bringing together Coker Classic, BFGoodrich, and STA options.

Brand alone should not decide the purchase. The more useful comparison is how each brand’s offering aligns with the truck’s size, desired sidewall style, tread character, and wheel compatibility, since some choices are clearly restoration-oriented while others lean more toward truck-duty or military-style presentation.

A period-style 1979 GMC Jimmy starts with one of its primary bias-ply sizes: 700-15, H78-15, or L78-15, depending on the wheel setup on the truck. From there, the available range spans traditional blackwall truck tires as well as whitewall bias-ply choices that create a more dressed, late-1970s presentation.

The right selection depends on how the Jimmy is being interpreted. A utility-focused truck may look most natural on blackwalls or truck-pattern tires, while a restoration-minded build may call for a cleaner whitewall treatment, and anyone chasing exact originality should compare the finished choice against vehicle-specific historical references.

Tire construction changes the look as well as the feel of a restored 1979 GMC Jimmy. The primary fitments are bias-ply, which keeps the truck in its original-style sizing family, while H78-15 and L78-15 can also be matched to radial equivalents, including bias-look radial alternatives that maintain a more traditional visual impression.

That choice often comes down to priorities. A straight bias-ply setup keeps the restoration closely aligned with the truck’s period tire format, while a bias-look radial can preserve more of that vintage appearance than a modern-looking metric conversion, provided the wheel width and overall fit still suit the truck.

Yes, modifications can affect tire fitment on a 1979 GMC Jimmy even when the truck is staying within its listed 15-inch rim diameter. Changes to wheel width, wheel offset, ride height, springs, steering components, or body clearance can all alter how well a 700-15, H78-15, or L78-15 tire works on the vehicle.

That is especially important on older trucks that may have changed hands several times. A Jimmy with aftermarket wheels or suspension changes should be measured carefully before selecting a new tire, because the published size alone does not account for altered clearances or the visual effect of a modified stance.

Before driving a 1979 GMC Jimmy on new tires, inspect the wheels for correct diameter and condition, confirm the tires are seated properly, and make sure inflation is appropriate for the chosen tire. It is also wise to check for any interference at full steering lock and look over suspension and steering parts for obvious wear.

A short initial drive followed by a recheck is a smart habit on a vintage truck. That second look can reveal early rubbing marks, air loss, or wheel hardware issues before they become bigger problems, and it helps confirm that the selected size truly suits the Jimmy’s present-day setup.

Collector-use tires on a 1979 GMC Jimmy should be inspected regularly for pressure loss, uneven wear, cuts, bulges, and sidewall cracking, especially if the truck spends long periods parked. Vintage vehicles often accumulate age faster than mileage, so condition matters just as much as tread depth on 700-15, H78-15, or L78-15 tires.

Storage practices also influence long-term service. Keeping the Jimmy away from prolonged sunlight, heat, moisture, and ozone sources helps protect the tires, and moving the truck periodically can reduce flat-spotting concerns, particularly with bias-ply construction on a vehicle that is driven only seasonally or on weekends.