1966 Triumph Tire Fitment Guide

1966 Triumph vehicles use six sizes across four model groups. The Triumph 2000 uses 175R13 or 650-13, the Spitfire uses 155R13 or 560-13, the Sports Six uses 155R13 or 560-13, and the TR3, TR4, and TR4A use 165R15 or 590-15. The 13-inch sizes stay with the 2000, Spitfire, and Sports Six families, while the TR sports cars move to 15-inch sizes. Rim width ranges where available are 4.50 to 5.00 inches for 650-13, 4.00 to 5.50 inches for 155R13, 3.50 to 4.50 inches across 560-13 products, 4.50 to 6.00 inches for 165R15, and 4.00 to 4.50 inches for 590-15.

The practical takeaway is that year and make are only the starting point for 1966 Triumph fitment. You need to know the exact model before choosing a size, then confirm that your wheel diameter and width suit that tire. That matters especially if a car has had wheel changes over the years or if you are comparing a restoration-oriented bias-ply fitment with a radial alternative in the same model family.

On a 1966 Triumph, 650-13 is a numeric bias-ply size. The 6.50 figure is the nominal section width in inches, and the 13 is the wheel diameter in inches. The dash format identifies it as an older bias-ply sizing convention rather than a modern metric radial code. For 1966 Triumph applications, that size belongs to the Triumph 2000.

That code helps you separate the traditional sedan fitment from the radial alternative used on the same model group. If your 2000 is being restored with a strong period look in mind, 650-13 keeps you in the correct bias-ply family. Before committing to any tire in that size, verify that your wheel falls within the appropriate width range and confirm whether the sidewall treatment you want is narrow whitewall or wide whitewall.

On a 1966 Triumph, 155R13 is an older Euro-metric radial size. The 155 is the nominal section width in millimeters, the R identifies radial construction, and the 13 is the wheel diameter in inches. Because no aspect ratio is written into the code, it follows the period Euro-metric convention commonly associated with roughly 80-series radials. For 1966 Triumph use, this size fits the Spitfire and Sports Six.

That makes 155R13 easy to distinguish from the 560-13 bias-ply size used on the same small sports-car platform. Owners often arrive at this size when they want a radial while staying in the correct 13-inch fitment family. Check the actual sidewall marking on the tire you choose, since some versions include tubeless marking and some show more complete speed and load information than others.

For a 1966 Triumph 2000, both 650-13 and 175R13 belong to the same model group, but they represent different construction eras. The 650-13 is a bias-ply size with whitewall options from Coker Classic and US Royal, while 175R13 is the radial counterpart within the 13-inch family. The decision is usually about how you want the car to present and feel, not about crossing into another model’s fitment.

Owners restoring a 2000 with a distinctly mid-1960s appearance often gravitate toward the bias-ply option, especially when whitewall styling is part of the car’s visual identity. Drivers who want a more modern radial character on the road usually focus on 175R13 instead. Start by confirming that you are working with a Triumph 2000 and not one of the sports-car models, since those use different sizes even though some of them also ride on 13-inch wheels.

Sidewall treatment varies quite a bit across 1966 Triumph sizes. The radial 155R13 appears in blackwall form, while 165R15 is available in blackwall, narrow whitewall, and wide whitewall. Among the bias-ply sizes, 650-13 comes in narrow whitewall and wide whitewall, 560-13 comes in narrow whitewall and wide whitewall, and 590-15 comes in blackwall and wide whitewall. That gives the 1966 Triumph range a broad spread from sporty blackwall presentation to more decorative whitewall styles.

Choosing the right sidewall style depends on the model and the kind of restoration you are aiming to achieve. A Spitfire or TR often looks most at home with a more sporting presentation, while a 2000 sedan can support a more formal whitewall look without feeling out of character. If you plan to show the car, check event and marque expectations first, because sidewall style can affect how authentic the finished car appears.

Several brands cover 1966 Triumph fitments, but the mix changes by size. Coker Classic and US Royal cover 650-13, Michelin and Dunlop cover 155R13, BFGoodrich and Firestone cover 560-13, Coker Classic, American Classic, Firestone, and BFGoodrich cover 165R15, and BFGoodrich and Avon cover 590-15. That spread gives buyers a choice between well-known American reproduction lines and period-appropriate European names on some of the sports-car sizes.

The brand question matters most after you have narrowed the car to the correct size. A Triumph 2000 owner shopping 650-13 will be choosing among a different group of brands than a TR4A owner shopping 165R15 or 590-15. Once the size is settled, compare sidewall appearance, construction type, and any speed or load markings that matter to how you plan to use the car.

Rim width requirements vary by size on 1966 Triumph vehicles. The 650-13 bias-ply tires suit 4.50 to 5.00-inch rims, 155R13 radials suit 4.00 to 5.50-inch rims, 560-13 bias-ply tires span 3.50 to 4.50 inches depending on brand, 165R15 radials suit 4.50 to 6.00-inch rims, and 590-15 bias-ply tires suit 4.00 to 4.50-inch rims. Those ranges are an important part of choosing between the two size paths offered for each model group.

Wheel width is one of the first things to confirm on any 1966 Triumph that has been restored, modified, or simply owned by several people over the years. A tire may share the correct diameter yet still be a poor match for the wheel if the width is outside the accepted range. Measuring the actual wheel before ordering is especially worthwhile when switching between a narrow bias-ply fitment and a radial option on the same model family.

Inner-tube requirements on 1966 Triumph tires depend on the exact product and size rather than following one universal rule. The Michelin 155R13 carries a TL tubeless marking, while the Dunlop 155R13 uses a different sidewall notation and should be checked individually. The bias-ply products shown here do not carry a consistent tube marker in the size code, so tube use should be matched to the tire’s sidewall wording and the construction of the wheel itself.

That means the wheel is just as important as the tire when you are setting up a 1966 Triumph. Original-style wheels, wire-wheel applications, and older rims may have different sealing needs than later tubeless-ready designs. Before mounting, confirm both the tire’s sidewall marking and whether your wheel condition and design support tubeless use, rather than assuming that every tire in a given size follows the same tube policy.

A 1966 Triumph stores best in a cool, dry, dark space away from direct sunlight, electric motors, welders, battery chargers, and other ozone-producing equipment. Keep the tires clean, properly inflated, and off damp concrete if possible. Bias-ply tires such as 650-13, 560-13, and 590-15 are more prone to temporary flat-spotting during long periods of inactivity, while radial sizes such as 175R13, 155R13, and 165R15 generally tolerate static storage a bit better.

If the car will sit for months, roll it periodically or place it on stands to reduce prolonged loading in one position. That matters on lightweight British cars because owners often use them seasonally and let them rest through winter. A breathable car cover and a quick pressure check before and after storage go a long way toward preserving sidewalls, reducing deformation, and making the car ready for a smoother return to the road.

Tires on a 1966 Triumph should be judged primarily by age and condition rather than mileage alone. Collector cars often accumulate very few miles, yet the rubber still ages from time, heat cycles, sunlight, and storage conditions. A sensible routine is to begin evaluating them carefully around five to seven years of service and to treat the ten-year point as a serious replacement consideration, using the DOT date code and the tire’s condition together.

That approach is especially important on classic Triumphs because a car can look fresh and still be riding on old rubber with hardened sidewalls or internal age-related deterioration. Tread depth by itself is not enough. If a car has sat for long periods, has uneven wear, or shows sidewall checking, replacement often makes more sense than trying to stretch a few more seasons out of tires that are already well into their age cycle.

A 1966 Triumph should have its tires inspected before every drive and again before any longer outing at sustained road speeds. Look for cracking, weathering, cuts, bulges, punctures, uneven wear, and pressure loss. On tube-type or possibly tube-equipped setups, pay close attention to valve stems and any signs of slow leakage, since an older collector car may sit long enough for small issues to become noticeable only when the car is put back into service.

Frequent inspection matters because classic Triumphs are often driven intermittently rather than daily. A quick visual walkaround and pressure check can catch aging sidewalls or a weakening stem before they become a roadside problem. It is also smart to inspect the spare, because many vintage cars still carry an old unused spare that looks excellent but may be decades past the point where it should be trusted for real road use.

A 1966 Triumph Spitfire originally belonged to an era when bias-ply tires were still standard on many sports cars, even as radial adoption was growing in certain markets. Within the correct fitment family for the Spitfire, 560-13 represents the period-style bias-ply route and 155R13 represents the radial alternative. That makes the bias-ply size the usual starting point for owners pursuing a factory-era appearance, while the radial serves owners who want an accepted later-style road-going substitute.

Original-market details could vary by destination, dealer practice, and how the car was equipped over time, so marque-club guidance is worth consulting if you are restoring for judging. Brand should not be assumed without car-specific evidence, but size, construction, and sidewall character are the big authenticity markers. For a show-focused Spitfire, those details are usually more visible and more likely to be scrutinized than many owners expect.

Correct tire fitment absolutely matters when showing a 1966 Triumph, especially in classes that emphasize originality. Judges and knowledgeable enthusiasts often notice whether the car is wearing the proper size family for its model, whether the construction matches the era, and whether the sidewall style looks appropriate for the car’s period and market character. A TR4A on a 15-inch radial and a Spitfire on a 13-inch bias-ply each send a different visual message even before anyone looks deeper.

The more serious the judging environment, the more important those distinctions become. A radial on a car restored for strict factory presentation or a decorative whitewall on a sports-car build that should appear more sporting can draw attention for the wrong reasons. If the goal is concours authenticity rather than casual enjoyment, check event rules and consult Triumph marque specialists before finalizing size, construction, and sidewall style.

For a 1966 Triumph Spitfire or Sports Six using 155R13, both Michelin XAS and Dunlop SP Sport Aquajet are blackwall radial choices, but they differ in sidewall marking detail and wheel-range information. The Michelin carries a 155HR13 78H TL marking and fits 4.00 to 5.50-inch rims, while the Dunlop appears as 155R13 78H and carries a 937-pound load figure. Both share an H speed rating, which corresponds to a 130 mph ceiling.

That means the choice is less about size and more about the exact product profile you want on the car. Owners should compare wheel width first, then look at the sidewall appearance and markings they prefer for a 1960s British sports-car presentation. If authenticity of visual detail matters as much as road use, the exact wording and look of the sidewall can influence the final decision almost as much as the underlying radial construction.

1966 Triumph tires can be suitable for highway driving when the correct size, condition, inflation, and construction are matched to the car. The radial 155R13 choices carry an H speed rating with a 130 mph ceiling, and one 590-15 bias-ply option from Avon also carries an H rating. Other sizes here do not consistently show speed letters in their sidewall markings, so the individual tire’s stated rating should be checked before relying on it for sustained-speed use.

On a car of this age, tire rating is only part of the safety picture. Brakes, steering, suspension wear, wheel condition, and alignment are often more limiting than the tire itself in normal modern traffic. A well-sorted Triumph on fresh, properly inflated tires is a very different highway car from one still running old rubber or neglected chassis parts, so evaluate the whole package rather than focusing on speed rating alone.

Inflation pressure on 1966 Triumph tires should start with the vehicle manufacturer’s recommendation for the specific model, then be checked against the tire’s own rated load-and-pressure information. Among the sizes here, 650-13 carries 1,150 pounds at 32 psi, 560-13 carries 850 pounds at 30 psi, 165R15 ranges from 1,168 pounds at 35 psi to 1,170 pounds at 36 psi, and 590-15 ranges from 1,018 pounds to 1,050 pounds at 32 psi. Those figures are load-reference values and should not be swapped from one size to another.

The key point is that a reproduction or replacement tire may not mirror the pressure habits of another size, even on the same year and make. Start with the car’s handbook or marque guidance for front and rear pressures, then confirm that the tire you choose supports that use safely. If the car feels vague, tramlines, or shows unusual wear, revisit inflation only after confirming alignment and overall suspension condition.

Before a longer drive in a 1966 Triumph, inspect each tire for cracking, cuts, bulges, uneven wear, and proper inflation, then check the spare as seriously as the four on the car. Look closely at valve stems, especially on older wheels or any setup that may use tubes. If the car has sat, take a short local drive first to feel for vibration, pulling, or flat-spotting before committing to a full day on the road.

Tire checks should be part of a broader pre-trip inspection on any vintage Triumph. Wheel fasteners, steering play, brake response, fluid levels, cooling-system health, and charging performance all matter on a longer outing. A car that is mechanically eager around town can still reveal age-related weaknesses once speeds rise and distances grow, so giving equal attention to tires and basic chassis systems is the smartest way to prepare.