GMC Rally Tires

GMC Rally tire sizes span F78-14 and G78-14 for 1971-1974, G78-15 for 1971-1977, H78-15 for 1971-1974, 800-16.5 and 875-16.5 for 1971-1979, C78-15, E78-15, and F78-15 for 1975-1977, GR78-15, J78-15, and JR78-15 for 1975-1979, and FR78-15, HR78-15, and 8.75R16.5 for 1978-1979. Those sizes correspond to 14-inch, 15-inch, and 16.5-inch wheel applications depending on year and configuration.

The practical takeaway is that year alone does not identify the correct GMC Rally tire. Start with the model year, then confirm the wheel diameter stamped on the wheel or measured at the bead seat, and finally match the exact size shown in the year listing. That approach is especially important on 1975-1979 vans, where several 15-inch and 16.5-inch options can overlap.

On a GMC Rally, 800-16.5 and 875-16.5 are numeric bias-ply sizes. The leading number is the nominal section width with the decimal omitted, so 800 means roughly 8.00 inches wide and 875 means roughly 8.75 inches wide, while 16.5 is the required rim diameter. Both are truck-style 16.5-inch applications used across the Rally line from 1971 through 1979.

That means a GMC Rally with one of these sizes does not use a 15-inch wheel even if the van appears visually similar to another Rally from the same year. Confirm that the wheels are truly 16.5-inch before selecting one of these numeric sizes, because a 16.5-inch tire will not interchange with a 16-inch or 15-inch wheel.

A 1975 GMC Rally has 9 tire sizes listed because that model year includes several different wheel diameters and construction paths at the same time. The size spread covers multiple 15-inch bias-ply sizes, 15-inch radial sizes, and 16.5-inch truck-style sizes. That kind of overlap is typical of vehicles that could be configured for passenger use, heavier-duty work, or later-period radial applications.

The important next step is to identify the exact wheel diameter and whether the van is set up for bias-ply or radial tires. Looking only at the model year can easily point you to the wrong size, especially if the van has been restored, customized, or fitted with replacement wheels at some point in its life.

GMC Rally models in this range use 14-inch, 15-inch, and 16.5-inch wheel diameters. Early vans from 1971-1974 can be found with both 14-inch and 15-inch sizes plus 16.5-inch numeric truck sizes, while 1975-1979 vans continue with 15-inch and 16.5-inch applications. The rim diameter is the first fitment check because multiple tire codes from the same year can belong to different wheels.

A good rule is to inspect the wheel itself before deciding between an alphanumeric 15-inch tire like G78-15 or a numeric 16.5-inch tire like 800-16.5. On GMC Rally models, the wheel diameter determines which family of tires is even possible, and it narrows the remaining choices much faster than starting from appearance alone.

GMC Rally listings include both bias-ply and radial constructions, but they do not overlap in every size. Bias-ply choices include alphanumeric sizes such as F78-14, G78-14, G78-15, H78-15, and J78-15, while radial-coded sizes include GR78-15, JR78-15, FR78-15, HR78-15, and 8.75R16.5. The right choice depends first on which size and wheel diameter the van actually uses.

A period-correct restoration often stays with the original construction family already associated with the vehicle’s wheel and size range, while a later-era driver may be set up for radial sizing. The key is to match the construction to the correct size code first, then keep the set consistent across the axle and ideally all four corners.

A GMC Rally equipped with radial tires will usually feel different from one on bias-ply tires because the two constructions flex and track differently. In this size range, the radial options are the alphanumeric sizes with an R in the code, while the non-R alphanumeric sizes and numeric truck sizes listed here are bias-ply. That means the construction change is built directly into the size designation.

For a GMC Rally owner, the practical issue is consistency and intended use. If the van is being kept close to its earlier-period driving character, bias-ply may better suit that goal, while later radial applications can offer a different road feel. Whichever path you choose, make sure the wheels and the rest of the tire set match that construction.

A GMC Rally should not be treated casually when mixing bias-ply and radial tires, because the two constructions behave differently under steering, braking, and load. The size list itself shows that GMC Rally applications were offered in both forms, but that does not mean they should be intermixed without a clear reason and a well-planned setup. Mixed construction can produce uneven responses that are more noticeable on a tall, long-wheelbase van.

The safer practical approach is to keep the GMC Rally on one construction type throughout the vehicle whenever possible. If the van already has a mixed set from a previous owner, use the year listing and wheel diameter to determine which family belongs on the vehicle, then work toward a matched set rather than replacing one tire at a time with whatever seems close.

A 1978 GMC Rally can use FR78-15, GR78-15, HR78-15, J78-15, JR78-15, 800-16.5, 875-16.5, or 8.75R16.5. That spread means the van could be on a 15-inch passenger-style fitment or a 16.5-inch truck-style fitment, with both bias-ply and radial construction represented. The correct size is the one that matches the wheel diameter and configuration actually on the van.

Begin with the wheel, not the tire sidewall alone, especially if the GMC Rally has seen restoration work or replacement wheels. Once the rim diameter is confirmed, compare the size code to the year listing and keep construction type consistent. That process quickly narrows the options from eight listed sizes to the one family that belongs on your van.

GMC Rally tire offerings include blackwall, narrow whitewall, dual-white-stripe, and wide whitewall sidewall styles. The blackwall choices are concentrated in the truck-oriented STA lines and 16.5-inch applications, while narrow whitewall, dual stripe, and wide whitewall options appear in the passenger-oriented bias-ply sizes such as F78-14, G78-14, H78-15, and J78-15. That gives GMC Rally owners a wide visual range depending on the van’s use and presentation.

For a restoration, sidewall style should match the character of the specific GMC Rally rather than just the tire size. A custom or upscale passenger van may suit whitewall or dual-stripe styling, while a work-oriented or utility build may look more natural on blackwalls. Sidewall appearance should be chosen after the correct size and wheel diameter are confirmed.

GMC Rally tires in these sizes are available from Coker Classic, BFGoodrich, and STA. Coker Classic appears in several whitewall passenger sizes, BFGoodrich covers selected 14-inch and 15-inch whitewall and dual-stripe applications, and STA appears mainly in truck-style blackwall offerings including 15-inch and 16.5-inch sizes. The brand mix reflects the Rally’s split between passenger-van and heavier-duty fitments.

Brand choice should come after you determine the correct size family for the GMC Rally. Some brands are concentrated in decorative passenger-car style applications, while others focus on traction or transport-style utility tires. Once size and wheel diameter are settled, brand and sidewall style become the final tailoring choices.

GMC Rally tire series here include Coker Classic Bias Ply, Silvertown Classic Bias Ply, Super Traxion, Traxion, Transport Highway, and Super Transport. The Coker Classic and Silvertown Classic Bias Ply lines are passenger-style bias-ply offerings with whitewall or stripe sidewall treatments, while the STA series are more truck-oriented blackwall designs aimed at traction or highway service. Those series differences line up closely with the Rally’s broad range of uses.

For a GMC Rally owner, the series name is a clue to the vehicle’s intended personality once the size is correct. A passenger-focused van restoration may lean toward the classic whitewall bias-ply lines, while a more utility-oriented build may point toward the STA truck families. Series selection should refine the look and purpose, not replace the basic fitment checks.

A GMC Rally should be stored in a cool, dry, dark space with the tires kept away from direct sunlight, electric motors, welders, ozone sources, and petroleum contamination. Collector vehicles fare best when the tires are kept at proper inflation and the van is not left for months on a damp surface. Clean wheels and a stable indoor environment do more for tire life than occasional cosmetic treatment.

If the GMC Rally sits for long periods, roll it periodically or support it in a way that reduces long-term flat spotting and casing stress. That matters especially on older-style bias-ply tires and heavier van applications. Storage practices will not stop aging, but they can slow deterioration and help the tires stay rounder and more serviceable between drives.

Tires on a GMC Rally should be inspected before every road outing and more thoroughly at regular intervals during the driving season. Look for weather checking, tread separation signs, sidewall cracking, irregular wear, air loss, and wheel or valve-stem issues. On a collector van, long periods of inactivity can be as hard on tires as mileage.

A practical routine is to give the GMC Rally a quick visual and pressure check before each drive, then a more detailed inspection several times a year with the wheels turned and the sidewalls fully visible. Because many Rally applications use bias-ply or utility-oriented tires, catching small condition changes early is far better than discovering them once the van is already on the road.

A GMC Rally tire should be replaced when age, cracking, hardening, impact damage, casing distortion, or separation signs indicate the structure is declining, even if the tread still looks deep. Collector tires often age out long before they wear out. Tread depth alone is not a reliable guide on a low-mileage van that spends much of its life parked.

That is especially important on a GMC Rally because some listed sizes are older bias-ply and utility-style constructions that can look presentable while no longer being suitable for regular driving. If a tire’s age is uncertain, have it evaluated by a specialist during routine service and before any longer road use. Replacement decisions should be driven by condition and age, not appearance.

GMC Rally original-type fitment varies widely across the 1971-1979 range, with 14-inch, 15-inch, and 16.5-inch sizes all represented and both passenger-style and truck-style series available. The size families include bias-ply alphanumeric applications, later radial-coded alphanumeric sizes, and numeric 16.5-inch truck sizes. That breadth means there is no single original tire answer for every GMC Rally.

For restoration work, the right approach is to match the GMC Rally’s year, wheel diameter, and specific configuration first, then compare that with original paperwork, factory literature, or marque-club references. Tire size, sidewall treatment, and construction all influence how authentic the finished van looks, so the best result comes from identifying the specific vehicle rather than the model name alone.

Correct tire fitment can absolutely affect the presentation and judged credibility of a GMC Rally. Judges and experienced enthusiasts notice whether the wheel diameter, sidewall style, construction type, and overall stance suit the year and character of the van. A Rally wearing the wrong diameter or an obviously mismatched tire family can look off even to a casual observer.

For a higher-level restoration, use the GMC Rally year listing as the starting point and then refine the choice with period photos, build information, and marque-community guidance. Even when several sizes were available in a given year, selecting the one that matches the van’s trim, purpose, and appearance can make the difference between a merely acceptable restoration and a convincing one.

Correct sidewall style on a GMC Rally depends on the van’s intended character, because available options include wide whitewall, narrow whitewall, dual-white-stripe, and blackwall. Whitewall and stripe styles align with the passenger-oriented bias-ply offerings, while blackwalls appear in the more utility-focused STA lines and the 16.5-inch truck applications. The proper look is tied to the specific wheel and use case rather than the model name by itself.

A custom, family, or upscale GMC Rally restoration may call for one of the whitewall or stripe treatments, while a workmanlike or heavy-duty presentation may look more authentic on blackwalls. Once the correct size is confirmed, sidewall style becomes one of the most visible choices on the whole vehicle, so it is worth matching it carefully to the van’s original personality.

A GMC Rally can be driven on public roads when the tires are the correct size for the wheel, are in sound condition, and suit the van’s intended use. The range here includes passenger-style bias-ply tires, utility-oriented bias-ply truck tires, and later radial sizes, so safety starts with choosing the proper family rather than the closest-looking code. Tire age and overall condition matter just as much as the size itself.

Before regular road use, make sure the GMC Rally has a matched set with appropriate inflation, no visible structural issues, and no mismatch between wheel diameter and tire size. Because these vans can vary widely in equipment, the safest approach is a full pre-drive review of tires, wheels, brakes, and steering rather than focusing on tread alone.

Before driving a GMC Rally, check tire pressure, sidewall condition, visible cracking, tread wear, valve stems, wheel fasteners, and any sign that a tire has shifted or gone out of round after storage. Confirm that all tires match the wheel diameter and that construction type is consistent side to side. On a van, small tire issues are magnified by weight and body height.

It is also wise to walk around the GMC Rally after it has rolled a short distance and recheck for any tire that looks low or unstable. If the van has sat for a season, combine the tire check with a broader inspection of steering, brakes, and suspension. A careful pre-drive routine is one of the easiest ways to keep occasional-use collector vehicles enjoyable and predictable.

Appropriate speed for a GMC Rally on original-type tires depends on the construction, condition, and intended duty of the tire fitted. A van on older-style bias-ply or utility-oriented truck tires should be driven with more restraint than one on a properly matched radial setup, and any collector tire demands more caution than a modern daily-driver tire. Condition always overrides appearance or tread depth.

The sensible approach is to drive the GMC Rally at moderate speeds that suit the tire type, the weight carried, and the overall mechanical state of the van. If the tires are older, recently acquired, or of uncertain age, limit use to shorter trips until the entire vehicle has been inspected and you have confidence in how it tracks, brakes, and responds on the road.