1973 Triumph Tire Fitment Guide

1973 Triumph vehicles use four sizes across four models. The GT6 and Spitfire share 155R13 radial and 560-13 bias-ply fitments on 13-inch rims. The Stag uses 185R14 radial on a 14-inch rim, and the TR6 uses 185R15 radial on a 15-inch rim. Rim-width ranges appear across several of these sizes: 155R13 spans 4.00 to 5.50 inches, 560-13 spans 3.50 to 4.50 inches depending on the tire, 185R14 spans 4.00 to 6.50 inches, and 185R15 spans 4.5 to 6.50 inches.

The practical takeaway is that year and make alone are not enough for a 1973 Triumph. You need to identify the model first, then match the wheel diameter and construction that belong to it. GT6 and Spitfire owners have the added choice between a bias-ply and a radial on the same 13-inch wheel diameter, while Stag and TR6 owners are selecting within a single radial size. That makes the model page and the actual wheel measurement especially important before committing to any product.

On a 1973 Triumph, 560-13 is a numeric bias-ply size. The 5.60 figure is the nominal section width in inches, and the 13 is the wheel diameter in inches. This size belongs to the GT6 and Spitfire, not the Stag or TR6. In current reproduction form it appears with classic sidewall treatments such as Narrow Whitewall and Wide Whitewall, which reinforces its period character compared with the radial alternative for those same cars.

That code matters because it signals both fitment and driving character. If your GT6 or Spitfire is being kept close to an earlier showroom look or judged restoration style, a 560-13 bias-ply is often the direction enthusiasts consider first. If your car is driven more regularly and you are comparing against the radial option, the choice becomes less about wheel diameter and more about whether you want bias-ply authenticity or radial manners on the road.

No, 1973 Triumph models do not all use the same tire size. The GT6 and Spitfire share two 13-inch options, 155R13 and 560-13, while the Stag uses 185R14 and the TR6 uses 185R15. That means the make spans three different rim diameters in the same model year: 13, 14, and 15 inches. Even where the section width appears similar in naming style, the model application still changes the correct choice.

For a buyer, that means the first question is always which 1973 Triumph you own. A TR6 tire search should not be approached the same way as a Stag search, and neither should be mixed with the GT6 or Spitfire fitments. The only shared-size situation is between the GT6 and Spitfire, and even there you still need to decide whether the car should wear a bias-ply or a radial. Identifying the model early prevents ordering a tire that is correct for the marque but wrong for the car.

If you own a 1973 Triumph GT6 or Spitfire, the choice between 155R13 and 560-13 is primarily a choice between radial and bias-ply construction. The 155R13 is a metric radial offered in Blackwall form, while the 560-13 is a numeric bias-ply available with classic whitewall treatments. Both fit 13-inch applications for those two models, but they represent different period cues and different on-road behavior.

Owners pursuing a more historically authentic presentation often lean toward the 560-13 bias-ply, especially when sidewall appearance is part of the car's overall look. Owners who expect more regular road use often prefer the 155R13 radial because it keeps the same general fitment category while moving to a more modern construction. The key is to decide what role the car plays first, then verify the wheel width so the specific tire matches the rim correctly.

1973 Triumph tires are available in several sidewall styles depending on size. The 155R13 radial comes in Blackwall form, the 560-13 bias-ply appears in Narrow Whitewall and Wide Whitewall versions, the 185R14 radial comes in Blackwall and Narrow Whitewall, and the 185R15 radial is available in Redline, Blackwall, and Narrow Whitewall. Sidewall style is therefore tied closely to the specific model and tire size rather than being interchangeable across the whole range.

For most 1973 Triumph buyers, sidewall choice is about the finished look of the car as much as the fitment itself. Blackwalls generally suit a restrained sports-car presentation, while whitewalls or redlines can shift the visual character significantly. A careful restoration should consider the market the car was sold in, the way the car will be judged, and whether the sidewall style fits the model's personality. Choosing the correct sidewall after confirming the correct size helps the tire look intentional rather than merely compatible.

Several brands cover 1973 Triumph fitments, but they vary by size. Michelin and Dunlop appear in 155R13 for the GT6 and Spitfire, BFGoodrich and Firestone cover 560-13, Michelin, Phoenix, and Vredestein cover 185R14 for the Stag, and Coker Classic plus Michelin cover 185R15 for the TR6. That gives each model a different mix of brand character depending on whether the tire is a small-car radial, a classic bias-ply, or a larger touring radial.

The brand decision should come after you settle the correct size and construction. Once you are within the right fitment, the more useful comparison points are sidewall style, rim-width range, and in some cases speed rating. Triumph owners often have strong preferences tied to the look they want the car to project, so brand heritage can matter, but it should not outweigh the basic requirement that the tire match the model, wheel diameter, and intended use of the car.

Rim-width ranges for 1973 Triumph tires depend on size. The 155R13 radial fits rims from 4.00 to 5.50 inches. The 560-13 bias-ply spans 3.50 to 4.50 inches depending on the exact tire. The 185R14 radial covers 4.00 to 6.50 inches, and the 185R15 radial covers 4.5 to 6.50 inches. Those ranges are wide enough that two tires with the same nominal size may still favor slightly different wheel widths.

That is why measuring the actual wheel is worth the effort before choosing a tire, especially on a car that may have had wheels changed during its life. A GT6 or Spitfire owner comparing 560-13 against 155R13 should pay particular attention to rim width because both fit 13-inch wheels but do not share the same full width range. Staying inside the published width range helps preserve intended tire shape and makes the final fitment more predictable.

On the 1973 Triumph GT6 and Spitfire, both 155R13 and 560-13 use the same 13-inch rim diameter, so the original wheel diameter is compatible with either size category. That shared diameter is what makes it possible to compare a radial and a bias-ply option on the same model without changing to a different wheel size. The remaining variable is rim width, since the acceptable width range is not identical between the two sizes.

In practice, that means many owners can stay on original-style 13-inch wheels and choose the construction that best suits the car's purpose. Before making that switch, verify the actual wheel width rather than assuming every factory or replacement wheel falls in the same range. That one measurement tells you whether the wheel is appropriate for the tire you want, and it is the cleanest way to avoid forcing a shared-diameter fitment onto a wheel that is too narrow or too wide.

A 1973 Triumph should be stored in a cool, dry, dark space away from direct sunlight, electric motors, welders, furnaces, and other ozone-producing equipment. Keep the tires clean, maintain inflation, and move the car periodically so the same section of tire is not carrying the load for months at a time. On the GT6 or Spitfire, the bias-ply 560-13 is more prone to flat-spotting during long static storage than the radial alternatives used elsewhere in the Triumph range.

If the car will sit for an extended season, many collectors either roll it occasionally or support it in a way that reduces constant tire loading. That matters on any 1973 Triumph, but especially on low-mileage cars that spend more time parked than driven. Good storage habits help preserve sidewalls, reduce vibration from temporary flat spotting, and make the first drive of the season easier on both the tire and the suspension.

On a 1973 Triumph, tire life is usually judged more by age than by mileage, because collector cars often cover relatively few miles each year. A sound rule is to begin evaluating tires closely once they are around five to seven years old and to treat ten years as a serious replacement threshold regardless of tread depth. The DOT date code on the tire is the reference point for age, and visible cracking or persistent vibration can shorten that timeline.

That approach is especially important on cars like the Spitfire, GT6, Stag, and TR6 because they may look fine cosmetically while the rubber has aged beyond what a casual glance suggests. A low-mileage tire is not automatically a young tire. If you are assessing an unfamiliar car, age should be one of the first things you check before planning regular use, weekend touring, or a long event drive.

Tires on a 1973 Triumph should be inspected before every drive and again before any longer outing. Look for sidewall cracking, cuts, bulges, uneven tread wear, embedded debris, and any sign that the tire is not holding pressure consistently. If your car runs a tube-type setup or an older bias-ply combination, the condition of the valve stem and the general air-retention behavior deserve extra attention as part of that routine.

A quick inspection matters because classic sports cars and touring cars often go from short local use to an all-day drive with little warning. Catching a pressure loss or sidewall problem in the garage is far better than discovering it after the car is loaded and hot on the road. Building a simple pre-drive check into your routine also helps you spot suspension or alignment issues early, since those often reveal themselves through unusual tire wear.

For a 1973 Triumph Spitfire, the period conversation usually begins with the two 13-inch fitments associated with the model: 560-13 bias-ply and 155R13 radial. By the early 1970s, radial adoption was well underway in many European applications, but bias-ply sizing still remains relevant when a car is being restored to a specific earlier look or market presentation. The safest historical approach is to treat both construction types as important fitment paths for this model year and confirm market-specific details through marque references.

That matters because originality on a Spitfire can mean different things depending on where the car was sold, how it was delivered, and what standard a show or club uses. A buyer restoring one carefully should verify not only the size but also the sidewall style and general visual character expected for that car. Marque clubs, factory literature, and long-time Triumph specialists are the best final check when authenticity matters as much as drivability.

Correct tire fitment absolutely matters when showing a 1973 Triumph, especially in concours or authenticity-focused judging. Size, construction type, rim diameter, and sidewall style all influence whether the tire looks appropriate for the model and era. A radial on a car judged for strict originality where a bias-ply presentation is expected can draw attention, and an aggressive sidewall treatment on a model that should appear restrained can do the same.

For that reason, show preparation should begin with the exact model and the judging standard you expect to face. A GT6, Spitfire, Stag, and TR6 each carry different visual expectations, and those expectations can be as important as simple mechanical fit. Event rules vary, so consult the hosting club or marque experts before finalizing the tire choice. That step often resolves questions that size alone cannot answer.

For the 1973 Triumph TR6, both Michelin XVS and Coker Classic appear in 185R15 radial form, but they differ in presentation and speed-rating detail. Coker Classic is offered as a Redline 185R15 with a load figure of 1,355 pounds at 35 psi, while Michelin XVS appears as Blackwall and Narrow Whitewall versions in 185HR15 and also as a Blackwall 185VR15. Rim-width compatibility overlaps broadly, with both covering common TR6 wheel widths in the 15-inch category.

That means the decision is less about basic fit and more about the look and rating you want the TR6 to carry. A Redline changes the car's visual tone immediately, while Michelin's Blackwall and Narrow Whitewall versions stay closer to a more understated period-touring appearance. If you are trying to align the tire with a particular restoration theme or event standard, compare the sidewall presentation first and the speed-rating designation second.

1973 Triumph tires can be suitable for highway driving when the correct size is chosen, the tires are in sound condition, and the speed rating matches the way the car will be used. The radial options shown here include H-rated tires with a 130 mph ceiling and, in 185R15 for the TR6, a V-rated option with a 149 mph ceiling. The 560-13 bias-ply fitment for the GT6 and Spitfire is a more traditional construction and should be approached with the expectations appropriate to a classic bias-ply tire.

On most well-kept Triumphs, overall mechanical condition is just as important as the tire itself. Brakes, suspension, steering, alignment, and wheel condition all shape how secure the car feels at sustained road speeds. For buyers choosing among fitments, the bigger question is usually whether the car will be used as a period-correct weekend machine or a regularly driven classic. Matching the tire construction to that role is one of the most important safety decisions you can make.

Inflation pressure for 1973 Triumph tires should not be guessed across models or borrowed from a different size. Some current tires in these fitments include rated pressure figures such as 850 pounds at 30 psi for 560-13, 1,323 pounds at 35 psi or 51 psi depending on the 185R14 tire, and 1,355 pounds at 35 psi for one 185R15 radial. Those figures describe the tire's load-and-pressure capability, not necessarily the factory operating pressure for your specific Triumph.

The best practice is to start with the original owner's manual or factory recommendation for the exact model, then confirm that your chosen reproduction or radial tire is being used within the manufacturer's published limits. A TR6 should not automatically use the same pressure logic as a Stag, and a GT6 or Spitfire on bias-ply should not simply mirror a radial setup. Pressure is one of the few adjustments that changes ride, wear, and handling immediately, so it deserves model-specific attention.

Before taking a 1973 Triumph on a longer drive, inspect each tire for cracking, tread damage, punctures, bulges, and uneven wear. Confirm cold pressure, look at the valve stems, and make sure the spare is usable and inflated. On cars that have spent long periods parked, pay close attention to age, flat spotting, and any sign that the tire has hardened or begun to separate. That basic inspection should happen before luggage goes in the car and before the first highway mile.

A longer trip in a classic Triumph also calls for a broader check of wheel fasteners, brakes, steering play, fluid levels, and charging-system health. Tires are only one part of the equation, but they are the part touching the road and the part most likely to reveal a problem early. Taking ten minutes to inspect them carefully often determines whether the drive feels relaxed and enjoyable or turns into preventable roadside trouble.