1975 Triumph Tire Fitment Guide

1975 Triumph vehicles use three sizes across two models. The Spitfire uses either 155R13 radial or 560-13 bias-ply tires, both on 13-inch rims. The TR6 uses 185R15 radial tires on 15-inch rims. Rim-width ranges also differ by size: 155R13 products fit 4.00 to 5.50-inch rims, 560-13 products fit 3.50 to 4.50-inch rims depending on brand, and 185R15 products fit roughly 4.5 to 6.5-inch rims.

That means year and make alone are not enough for a final choice. A Spitfire owner still needs to decide between the two 13-inch constructions, while a TR6 owner needs the 15-inch radial size that belongs to that model. Checking the actual wheel width before ordering is especially important on older British sports cars, where replacement wheels, restorations, and long ownership histories can introduce changes from original specification.

On a 1975 Triumph Spitfire, 560-13 is a numeric bias-ply size. The 5.60 figure refers to the nominal section width in inches, written without a decimal in the size code, and the 13 identifies the wheel diameter in inches. It is a traditional bias-ply format rather than a modern metric radial designation, which is why it looks very different from a size such as 155R13.

That older sizing style matters because it usually points the buyer toward a period-correct restoration approach rather than a late-style radial conversion. On the Spitfire, 560-13 also brings sidewall appearance choices, including Narrow Whitewall and Wide Whitewall versions. The right choice depends less on raw fitment than on the look you want and whether the car is being judged for originality or driven more frequently on modern roads.

No. 1975 Triumph models split by model line. The Spitfire uses two 13-inch sizes, 155R13 and 560-13, while the TR6 uses a single 15-inch size, 185R15. There is no shared all-model size across the 1975 Triumph range, and the wheel diameter difference alone separates the TR6 from the Spitfire before any discussion of construction or sidewall style begins.

That is why identifying the model should be the first step in any tire search for 1975 Triumph. Once the model is confirmed, the remaining decisions become much simpler: Spitfire owners compare radial and bias-ply character within the 13-inch family, while TR6 owners can focus on which 185R15 sidewall treatment and brand best suits the car's intended use and presentation.

That choice applies to the 1975 Triumph Spitfire, not the TR6. The 155R13 is a radial 13-inch fitment, while the 560-13 is a numeric bias-ply 13-inch fitment. Both belong to the Spitfire size family, but they reflect two different approaches: one follows the later radial convention, and the other keeps the earlier bias-ply style and appearance more closely tied to classic-car restoration practice.

A Spitfire built for show presentation or a strongly period-correct look often points buyers toward 560-13, especially when whitewall styling is part of the finished car. A Spitfire meant for frequent road use may lead owners toward 155R13 for its radial construction and familiar modern sizing logic. Confirm wheel width before making the switch, since the acceptable rim-width range is not the same across those two sizes.

1975 Triumph tire choices cover a broad sidewall range. The Spitfire's 155R13 radial options are available in Blackwall form, while its 560-13 bias-ply choices include Narrow Whitewall and Wide Whitewall versions. The TR6's 185R15 radial options expand that palette further with Blackwall, Narrow Whitewall, and Redline treatments depending on brand and series.

For a 1975 British sports car, Blackwall is usually the safest visual direction when the goal is a restrained factory-era appearance, especially on a driver-oriented roadster. Whitewall and redline styles can still be appropriate when they match a specific restoration vision or period accessory look. Sidewall style changes the visual character of the car far more than many owners expect, so it is worth choosing with the finished stance and trim in mind.

1975 Triumph fitments are covered by several established brands, but the brand mix depends on size. The 155R13 Spitfire radial comes from Michelin and Dunlop. The 560-13 Spitfire bias-ply size comes from BFGoodrich and Firestone. The 185R15 TR6 radial size comes from Coker Classic and Michelin.

Brand choice on a classic Triumph usually comes down to the combination of size, sidewall appearance, and construction style you want rather than make loyalty alone. A buyer narrowing in on a Blackwall radial has different options than someone aiming for a whitewall bias-ply look, and the TR6's 185R15 category opens a different set of sidewall treatments than either Spitfire size. Choose the size first, then compare brands within that fitment.

Rim width depends on the size. For 1975 Triumph Spitfire applications, 155R13 radial tires fit 4.00 to 5.50-inch rims, while 560-13 bias-ply tires fit 3.50 to 4.50-inch rims depending on the brand, with some versions centered around 3.50 to 4.00 inches and others extending to 4.50 inches. For the 1975 Triumph TR6, 185R15 radial tires fit roughly 4.5 to 6.5-inch rims depending on the specific product.

Those ranges matter because a tire can share the correct wheel diameter yet still be unhappy on the wrong wheel width. That is especially relevant for Spitfire owners comparing 155R13 and 560-13, since both are 13-inch tires but do not share identical rim-width windows. Measuring the actual wheel before purchase is the simplest way to avoid a mismatch on an older car that may have seen wheel changes over the years.

Tube requirements vary by size and by product. The 185R15 Michelin XVS products for the 1975 Triumph TR6 are marked TL, indicating tubeless construction, while the 155R13 Michelin XAS is also marked TL. Other products in the same general size family do not always carry the same marking in the visible size description, so tube status can vary by product rather than staying uniform across every tire for 1975 Triumph.

That means the wheel and the exact tire both need to be considered together. A tubeless-marked tire still needs a wheel in suitable condition, and older wheels can introduce their own sealing questions even when the tire itself is capable of tubeless use. If originality or wheel condition points you toward tubes, match the setup to the tire's design and verify the valve stem and rim condition at the same time.

A 1975 Triumph Spitfire's two size choices, 155R13 and 560-13, both use a 13-inch rim diameter, so they share the same basic wheel diameter requirement. That means original-diameter Spitfire wheels can often accept either size in principle, but the acceptable rim-width range is different between the radial and bias-ply options and should be checked against the exact tire being considered.

The practical issue is not bolt pattern or diameter so much as wheel width and the character you want from the car. A narrow original wheel may suit the 560-13 bias-ply very naturally, while a wider 13-inch wheel may better align with a 155R13 radial. Looking at the wheel stamp or measuring bead-seat width is a smarter step than assuming every original-looking Spitfire wheel is identical.

A 1975 Triumph should be stored in a cool, dry, dark place away from direct sunlight, electric motors, battery chargers, furnaces, and other ozone sources that accelerate rubber aging. Keep the tires properly inflated, avoid letting the car sit in standing moisture, and move it periodically if possible. On cars fitted with bias-ply tires, long static storage can encourage more noticeable flat-spotting than a comparable radial setup.

Owners who put a Spitfire or TR6 away for the season often benefit from rolling the car a short distance every few weeks or using stands in a way that does not leave suspension components hanging improperly. Tire covers help in bright garages, and clean concrete is better than dirt or damp flooring. Good storage habits preserve both appearance and drivability, which matters on low-mileage collector cars more than annual mileage totals do.

On a 1975 Triumph, tire age usually matters more than tread wear. Collector-car tires often age out before they wear out, so a useful rule is to start evaluating them closely around five to seven years and to treat the ten-year mark as a serious replacement point regardless of remaining tread. The DOT date code on the tire sidewall is the best starting point for determining actual age.

A Spitfire or TR6 that only sees fair-weather weekend use can still be riding on old rubber that looks presentable from a few feet away. Sidewall cracking, hardening, and repeated air loss are stronger warning signs than mileage alone on this kind of car. Age-based replacement is especially important when planning highway trips, tours, or any use that asks more of the tire than short local drives.

Tires on a 1975 Triumph should be inspected before every drive and again before any longer outing. Check inflation, tread wear, cuts, sidewall cracking, bulges, and any sign that the tire is no longer holding pressure consistently. If the car uses a tube-type setup or a tire whose installation calls for tubes, include the valve stems and any history of slow leaks in that inspection routine.

Classic British sports cars often spend long stretches parked between outings, which makes regular quick checks more important than they are on a modern daily driver. A two-minute walkaround can catch a soft tire, a cracked sidewall, or damage from storage before it becomes a roadside problem. The spare should also be inspected and inflated, since it may be as old as the road tires or older.

For a 1975 Triumph Spitfire, the period-correct baseline is bias-ply construction, with 560-13 representing that traditional style, while 155R13 reflects the radial sizing path also associated with later driving use and replacement practice. No original-equipment brand should be assumed without model-market confirmation. British sports cars of this era could vary by destination market and by what dealers or owners fitted early in the car's life.

If the goal is strict authenticity, confirm the car's market, production period, and judging standard before committing to a brand or sidewall treatment. Marque clubs, factory literature, and event rulebooks are the best places to settle those finer points. For many restorations, the most important authenticity decisions are the size family, construction type, and sidewall appearance rather than chasing a single assumed brand name.

Yes, correct tire fitment can matter noticeably when showing a 1975 Triumph. Judges and knowledgeable enthusiasts often look at whether the size is appropriate to the model, whether the construction type suits the period, and whether the sidewall treatment fits the car's original market character. A modern-looking radial or a sidewall style that clashes with the car's era can stand out even when the wheel diameter itself is correct.

That does not mean every show car must wear the same tire, but it does mean the tire should support the story the restoration is trying to tell. A Spitfire restored to factory flavor may call for different visual choices than a driver-oriented car, and a TR6 wearing redlines makes a different statement than one on blackwalls. Event standards vary, so the final authority should be the relevant Triumph club or judging body.

A 1975 Triumph TR6 belongs to a period when radial construction was already an appropriate and expected fitment for many sports cars, and its 185R15 size aligns with that character. The available TR6 products stay within radial construction while offering different sidewall styles such as Blackwall, Narrow Whitewall, and Redline. Original-equipment brand assumptions should still be checked against market-specific literature rather than taken for granted.

For restoration work, the key is choosing a 185R15 that matches the car's intended presentation. A subdued touring look may point toward blackwalls, while a more stylized period presentation may lean toward redlines or a narrow whitewall depending on the car's story and market context. Owners pursuing high-level authenticity should verify details through TR6 marque resources before finalizing the sidewall style.

1975 Triumph tires can be suitable for highway use when the size, condition, and speed rating match the car and the way it is driven. The 155R13 Spitfire radial options include H-rated products with a 130 mph ceiling, while the 185R15 TR6 radial options include H-rated products at 130 mph and V-rated products at 149 mph. Bias-ply 560-13 Spitfire tires belong to a more traditional construction category and should be driven with that in mind.

On a classic Triumph, tire limits are only one part of the highway picture. Brakes, suspension condition, alignment, wheel condition, and the overall mechanical state of the car often matter more in real-world touring than the top-end speed letter alone. A sound radial setup is a natural fit for regular road use, but any 1975 sports car should be approached with realistic expectations and a thorough pre-drive inspection.

Inflation pressure should follow the car's factory guidance first, then be checked against the tire manufacturer's rated limits for the exact size and product. Among 1975 Triumph products with stated figures, 560-13 carries 850 pounds at 30 psi and one 185R15 radial carries 1,355 pounds at 35 psi. Those numbers are load-and-pressure ratings for those tires, not a blanket setting to apply across every Triumph size or model.

The practical approach is to start with the owner's manual or marque-correct pressure recommendation for your model, then make sure the tire you choose is being used within its own specifications. A Spitfire on 560-13 and a TR6 on 185R15 should not be treated as if they need the same pressure just because both are classic Triumphs. Pressure should always match the exact car, tire, and intended load.

Before a longer drive in a 1975 Triumph, inspect all four tires and the spare for cracking, cuts, bulges, uneven wear, and proper inflation. Check valve stems, and if the setup uses tubes or has a history of slow leakage, pay close attention to pressure retention before departure. Wheel nuts, jack equipment, and the condition of the spare matter just as much as tread depth on an older touring car.

Tires are only one part of the pre-trip routine on a Spitfire or TR6. Brake feel, steering response, fluid levels, cooling health, and charging system behavior deserve the same attention, especially on cars that may sit between outings. A classic sports car that feels fine on a short local drive can reveal problems at sustained road speed, so a careful inspection before leaving is time well spent.