Classic Tyres: 590x15 & Crossply Explained

For owners of cherished classic cars, the question of suitable tyre replacement is often a complex one. When your vehicle originally specified a 590x15 tyre size, you're almost certainly looking at a sporting machine from the golden era of motoring, the 1950s and 1960s. These tyres, while perhaps seemingly obscure to modern drivers, were carefully chosen by manufacturers to complement the performance and handling characteristics of these iconic vehicles. This article aims to demystify the choices available for your 590x15 shod classic, delve into the world of crossply construction, and explain why the 'bigger is better' tyre philosophy often falls short when it comes to preserving the authentic driving experience.

Choosing the Right Radial for Your 590x15 Classic

If your classic beauty is an MGA Twin Cam or a Daimler SP250 Dart, you have a couple of excellent radial tyre options that respect the car's original design. For a balanced and enjoyable driving experience, the 165HR15 Pirelli Cinturato is a highly recommended choice. These tyres are renowned for their supple ride and predictable handling, offering a delightful connection to the road. Should your driving predominantly involve longer journeys on motorways, the 165VR15 Michelin XAS presents an even more capable option. Its V-speed rating indicates a higher performance threshold, making it ideal for sustained higher speeds while maintaining excellent stability and comfort.

For the Austin Healey, which originally fitted the now-discontinued 590H15 Dunlop RS5, the recommendation shifts slightly. We strongly advise fitting the 180HR15 Michelin XAS. This tyre is a touch taller than the 165 section, and this subtle increase in sidewall height is surprisingly beneficial for the Healey. It complements the car's gearing, providing a slightly more relaxed cruising experience and a little extra clearance over those ubiquitous speed bumps. While this slightly larger tyre can sometimes cause minor clearance issues on the inner wings of an MGA or Daimler Dart, it's often a worthwhile compromise for the Austin Healey's specific requirements.

The Misconception of Fatter Tyres

A common, yet often misguided, belief among classic car enthusiasts is that fitting wider, 'fatter' tyres will automatically improve handling. While it's true that modern tyre sizes like 185/70R15 or 195/65R15 might offer more outright grip in a straight line, reduce wheel spin, and improve dry braking performance, this comes at a significant cost to the car's original character. These benefits are often outweighed by a deterioration in the nuanced handling that makes classic cars so special.

The increased contact patch of these larger tyres, when cornering, can lead to a more abrupt breakaway. Instead of the gentle, progressive slide that many classic cars are designed to exhibit, you might experience a more sudden loss of traction. This effect is often exacerbated when fitting more modern tyre constructions, such as a 195/65R15, which are designed with different chassis dynamics in mind. To truly benefit from wider tyres, you would typically need to undertake significant chassis modifications – stiffening springs, altering camber and caster angles – essentially transforming your classic into a track-focused machine, which is rarely the desired outcome.

If, however, you are determined to fit larger, wider tyres on your MGA, Daimler Dart, or Austin Healey, it's crucial to choose options designed with classic car applications in mind. The 185/70R15 Pirelli Cinturato CN36 or the track-oriented 185/70VR15 Avon CR6ZZ are excellent choices. These tyres feature carcass constructions specifically engineered to work harmoniously with the suspension and steering geometry of classic vehicles, offering a more sympathetic upgrade.

Understanding Crossply Tyres: Not All Old Tyres Are Bad

The term 'crossply' might conjure images of poor handling and a harsh ride, but this reputation is often unfairly earned. The reality is that many of these perceptions stem from driving on severely degraded, ancient crossply tyres that are long past their best. Fitting a fresh set of modern crossply tyres can, in many cases, completely transform the driving experience of a classic car, restoring its original handling feel.

What is a Crossply Tyre?

The fundamental difference between crossply and radial tyres lies in their construction. In a crossply tyre, the cords in the fabric plies are laid at an angle of approximately 45 degrees to the direction of travel. These plies are then layered in alternating directions, creating a robust, yet less flexible, tyre structure. The exact angle can vary by up to ten degrees either side of 45 degrees, depending on the tyre's intended application.

Decoding Crossply Sizing

The sizing system for crossply tyres is refreshingly straightforward. Take, for example, a 640-15 tyre. The '640' indicates the approximate section width of the tyre in inches, while the '15' denotes the rim diameter it is designed to fit. Occasionally, you might encounter a letter within the sizing, such as 820H15. In this instance, the 'H' signifies the tyre's speed rating, with 'H' typically denoting a maximum speed capability of 130 mph.

The Missing Profile

Unlike their radial counterparts, crossply tyres generally do not explicitly state their aspect ratio or 'profile' in the size description. This is because crossply sidewalls are typically designed to be roughly the same height as the tyre's width, often falling between 96% and 100% of the section width. For context, even the tallest radial tyres usually have an aspect ratio of 80%.

Radial vs. Crossply: The Debate

The debate over whether to switch from crossply to radial tyres on classic cars is a passionate one. While the allure of modern radial technology is strong, it's essential to remember that vehicle manufacturers invested heavily in research and development to match tyre characteristics with their chassis designs. Often, switching to radials can inadvertently compromise the intended driving dynamics of a classic car.

However, there are instances where radial tyres offer undeniable advantages. Cars that were on the cusp of the radial revolution, such as the original Mini and the Jaguar E-type, were initially equipped with crossply tyres but later saw many models transition to radial fitment. Furthermore, some tyre sizes that were traditionally crossply are now available in radial construction. Examples like the 550R16 and 670R16 offer the authentic aesthetic of a crossply tyre combined with the superior road-holding and handling benefits of a radial construction.

The Cardinal Rule: Never Mix Tyre Types

While obscure legislation might, in some jurisdictions, permit the use of different tyre types on different axles (radials at the rear and crossply at the front, but never the reverse, and never on the same axle), this practice is strongly discouraged. The fundamental rule, which should never be broken, is to never mix radial and crossply tyres on the same vehicle. The vastly different handling characteristics and responses of these two tyre constructions can create unpredictable and dangerous situations. Adhering to a consistent tyre type across your vehicle is paramount for safety and predictable handling.

Tyre Size Comparison Table

Frequently Asked Questions

Q1: Are crossply tyres the same as radial tyres?
No, they are fundamentally different in their construction. Crossply tyres have plies layered at an angle, while radial tyres have plies running radially across the tyre.

Q2: Can I fit modern 185/70R15 tyres to my 590x15 car?
You can, but it's important to choose tyres with a carcass designed for classic cars, like the Pirelli CN36 or Avon CR6ZZ. Be aware that wider tyres may require chassis modifications or clearance adjustments and can alter the car's original handling feel.

Q3: Is it safe to mix radial and crossply tyres on my car?
Absolutely not. Never mix radial and crossply tyres on the same vehicle, as their different handling characteristics can lead to dangerous instability.

Q4: What does the 'H' mean in a tyre size like 165HR15?
The 'H' indicates the tyre's speed rating, signifying it is designed for speeds up to 130 mph.

Q5: Why are some people against fitting radial tyres to classic cars?
Some enthusiasts believe that fitting modern radials can compromise the original handling balance and feel that manufacturers carefully engineered into their classic vehicles. However, with the right tyre choice, radials can offer significant improvements.

In conclusion, while the temptation to fit the widest, grippiest tyres available might be strong, for owners of classics originally fitted with 590x15 tyres, understanding the nuances of tyre construction and respecting the original design intent is key to preserving the authentic and enjoyable driving experience. Choose wisely, and savour the journey.