DIAGONAL AND RADIAL RAILS. PLUSES and MINUSES
Why are they called that? In a diagonal-ply tire, the cords in the carcass ply are laid diagonally from bead to bead. Because of the necessity of crossing the tracks of two adjacent carcass ply layers, the number of ply layers must be even, for example 2, 4, 6 or 8. Pros of diagonal tires Diagonal tires have a simpler design and therefore less cost and difficulty to repair. They have better side wall (sidewall) strength. They are also better at cushioning shock loads transmitted to the vehicle when driving on roads with minor potholes, when crossing pavement seams, etc.
Cons of diagonal tires During the change of load and oscillation during driving the tire tread of a diagonal tire undergoes increased deformation (“crumpling”), as a result of which the grooves of the pattern are compressed and the protrusions slip on the bearing surface. This increases the grip capabilities of these tires.
Why are they called radial tyres? Radial tires don’t have their carcass ply threads crossing each other like diagonal tires, but rather a radial (or meridional) arrangement, i.e. the direction of the carcass threads is from bead to bead. Radial tires are available in tubed and tubeless designs. The metalcord is a thin steel wire bracing consisting of 23 layers of steel wire of a diameter of between 0.15 and 0.25mm. Metal cord is characterized by high strength, low elongation in comparison with textile cord, high resistance to heat aging and better thermal conductivity. Radial tires are of two types: – with synthetic fibers in the carcass and metal cord in the breaker (combined); – with synthetic fibers in the carcass and textile fibers in the breaker Nylon cord in the carcass and metal cord in the breaker allow to increase the tire strength in the tread zone, protect its carcass from damage, reduce distribution of cracks in the tread. The radial design of the tire is always fixed with the letter R in its marking, e.g. 175/70R14. (Sometimes this letter is mistakenly thought of as indicating some sort of “fitment radius” of the tire. In fact, it is the fitting diameter, not the radius, that is measured on the tire. ) There is no R in the diagonal tire size designation, for example 6.50-15.
The advantages of radial tires are that the radial carcass strands carry only radial loads. Compared to diagonal tires, this considerably reduces the tension of the threads and allows the carcass of radial tires to be manufactured with less ply (twice as many) under the same load, which ensures better heat dissipation during driving, especially in hot weather (less chance of “explosion”). The number of ply construction for radial tires is odd, since each layer of cords operates independently with radial thread direction. Radial tires offer better grip than diagonal tyres. This is achieved by the greater contact area with the road surface and the use of an ultra-modular tread pattern (metal cord, etc.) A rigid breaker in radial tires reduces tread deformation and the contact patch is virtually unchanged in shape. The groove volume is therefore not reduced and the tread protrusions do not slip. Radial tires are characterised by: better load-carrying capacity (by 15…20%); increased maximum speed; lower weight (by 3…4%); better radial elasticity (by 20…30%), and lower temperature rise (by 20…30%) in comparison with diagonal tires. Radial tires improve safety of vehicle operation due to: – improved driving stability and controllability; – increased traction on roads with dry and wet surfaces; – reduced risk of mechanical damage and punctures in the tread zone.
Disadvantages of radial tires Radial tires have a higher cost and increased lateral elasticity. The radial arrangement of the cords reduces the sidewall strength of the tire wall. The sidewalls of radial tires are more prone to damage than diagonal tires under severe road conditions when driving on deep ruts, especially when the tire air pressure is low, and when hitting kerb stones.
Nonetheless, radial tires have virtually superseded diagonal tires, which are now used almost exclusively on trucks. They are almost never used on cars, and neither are tubed tires.
Radial and diagonal tires – everything you need to know about them
Today let’s determine which tires are best, the advantages and disadvantages of both types. Let’s get acquainted with the differences in design. Consider the area of application, properties and how they are marked.
The peculiarity of the construction of this type is the presence of several layers in the carcass. Each of them is laid relative to each other at an angle. It is 40-45 degrees. Because of this, it is necessary to use many layers, the number of which is a multiple of two. Their intersection is exactly in the middle, in the center of the tire’s contact patch.
- Simple design. Low purchase and repair costs.
- High resistance to lateral cuts.
- It better mitigates wheel impacts when driving over road bumps.
- When the wheel is loaded and wobbles, the tread crumples. The protrusions slip, the tire’s traction properties deteriorate, and the grooves get narrower.
- Worse heat dissipation.
- Can only be run with a inner tube.
The layers of cords in the tire carcass do not cross each other. They are made in the form of meridians – from one edge of the tire to the other. The point of contact with the road surface is reinforced with metal cords. This helps dissipate heat away from the tire more quickly, and it absorbs most of the load. It also prevents tread distortion and keeps the tread pattern constant.
The only disadvantage is considered weakness to side cuts. Since the number of threads in the carcass of radial tires is less and they are laid in a radial direction, they are easier to damage, unlike diagonal tires, where they intersect.
- Radial bars are made of steel or brass wires, while diagonal bars are made of nylon or nylon.
- Different number of carcass layers: radial – 1, diagonal – 2 or more.
- In the first case, there is no camera inside, in the second case, there is. The tires with diagonal arrangement of threads are used only with a camera.
- Because of the different number of layers, they have different weights.
- Some have a steel breaker, others do not.
Which is better?
Radial tires are the best. Although they are more expensive and weaker to side cuts, they are more durable. Such tires can withstand heavy loads, their tread does not change shape when the car moves, which means that the contact patch of the wheel with the road is not reduced. Less wear and longer retain safe tread depth.
Good handling at all speeds and on all types of surfaces. Resistant to frontal puncture, less weight, and therefore fuel economy .
Therefore, tires with radial arrangement of cords are more popular. Even in agricultural machinery they are used. Thanks to their design, they redistribute the weight of the vehicle over the entire area of the wheel, without damaging the root system of the plants.
How they are marked
The marking of radial and diagonal tires is different. In the first case, the English letter “R” is applied to the side surface. That’s why many people confuse it with the radius, this is incorrect, R is radial .
In the second case, the tire is marked with the letter “D” – diagonal. More often in the marking put a dash before its diameter.