Posts Tagged ‘Load’

Cross Ply tyres versus Radial Ply Tyres

Cars make use of the radial tyres entirely but the ones fitted to motorbikes retain the cross-ply form of construction and even the tyre engineers state that radial tyres are not appropriate for motorbikes. This is in fact quite right as cars and motorbikes are very different and should have different tyre requirements. However, of late the radial tyres are considered to have benefits to offer to motorbikes as well.
Several piles of cord are laid on top of each other at a bias angle of 40 to 50° to make a cross ply tyre. This consequence in the creation of a cross at an direction of 80 to 100°. The layered and angled structure of ply tyres results in the tread not reacting in exact symmetry to that of the loads applied.
The symmetry is completely lacking in cross ply tyres and this can cause the tyre to run to one side nonetheless while rolling on a completely level and even surface. This effect is known as “Ply Steer”. The cross manufacture of the carcass efficiently forms parallelograms of thread imbedded in the rubber, this is not a sturdy form of construction and under driving or braking torque, upright load and centrifugal sound effects these parallelograms deform, which allows squirming of the contact area and tyre toss or diameter enlargement at elevated pace, reducing constancy and heating the tyre. Such heating eventually manifests itself as amplified rolling conflict.
By simple observation one can conclude that radial tyres create a greater and wider area of impression compared to the cross ply tyres. Such a fact highlights that radial tyres have better grip than cross ply tyres. Again in loaded conditions the radial tyres outscore the cross ply tyres as they have larger contact area with the surface of the road as they the tendency to become littile bit flat which is not the case in cross ply tyres.
Radial tyres contain less plies that is generally confined to one or two than the cross ply tyres that require three to four plies, so as to have greater flexibility in sidewalls. To maintain the entire tyre stiffness the reduction of sidewall height is required and thus results in lower profiles of 50 to 70 %. On the other hand the cross ply tyres make use of 90 to 100% of the profile. The lower profiler is an indication of having smaller diameter. The cross ply tyres have larger diameters in comparison to radial tyres of the same size. This trend contributed to the growth of 17” wheels while leading to the decline of the popular 16” wheels.
In the year 1984 radial tyres were introduced for the first time. The bias belted tyres were the most commonly used tyres until then. The cross-ply tyres were the next in line of production, which added circumferential belt plies. As and when the developments took place the older technology got replaced with newer ones giving way to improved tyre strength, agility and overall performances.

Properties of tyres

Tyres are an integral element in any bike and their main function is to transmit all the forces amid the bike and road. The properties of tyre are one aspect that is better if it remains constant. The tyres are the key to the handling properties of bikes. The vehicle manufacturers specify the properties of the tyres that are provided along with the new bikes.

But the same cannot be said about the after market tyres which are completely different from the original tyres. Even if they may be similar in design their handling characteristics can differ a lot since the forces generated between the tyres and the ground will determine the machine’s behavior.

The engineering involved or the sophisticated designing and fabrication in manufacturing of tyres is always hidden from the users due to the simplicity and multitude of tasks they are able to achieve. The earliest versions of pneumatic tyres were used for increasing the comfort level and decrease the load on wheels. The modern day bikes make use of suspension systems but it is the tyres that are responsible for absorbing the initial shocks from road.
The various criteria depending on which the tyre has to be chosen depends on:
 Driver’s safety
 Handling
 Comfort
 Service life
 Economy
 Environmental compatibility
Ensuring the driver’s safety is of prime concern and this is achieved by letting the tyre to sit firmly on the rim. Such an arrangement is possible by implementation of a special bead design and making use of safety rim.

Handling of tyres is also a key feature that allows one to make decisions based on the type of vehicle they will use. Smaller vehicles should be provided with thin tyres for better handling and larger ones such as cars or trucks may need broader and bigger or smaller tyres to achieve the same.

Compromising on the comfort by going for style is never advisable. Lean and thinner varieties of tyres may be quite appealing to use but one should tread with caution and always look for tyres that are recommended by the manufacturer and should not opt for cheaper variants as well.

The tyres come with a shelf life that is mentioned by the manufacturer and one has to take care to purchase tyres that have longer shelf life and only buy the original ones to avoid problems related to its cheaper variants. Tyre manufacturers also offer free services for increasing the longetivity of the tyres and repair some of the minor wear and tear too.