Tyre safety

Running-in Period

In order for new tyres to provide optimum performance, they should be ridden very cautiously for the first 100 miles in order for the tyre surface to be “Scrubbed-In” (rubbing with abrasive materials has little or no effect) and allow the bead to seat correctly.

Directly after new tyres are fitted, sudden acceleration, maximum braking, and hard cornering must be avoided. This will allow the rider to adjust to the feel and handling characteristics of the new tyre, and for correct tyre scrubbing to achieve optimum grip level.

Tyre Rims

In the past the development of tyre and rim technology has led to various rim constructions. Over the years with the application of both theory and experience two basic rim systems have been developed, one for tubeless tyres and the other for tube type tyres.

Tyres which use an inner-tube, that is tube type tyres (TT), the WM rim is used (fig 1).

Tubeless tyre (TL) rims, MT, (fig 2) have a hump in the profile which prevents the tyre from slipping down to the well due to air loss.

Tyre Types

Crossply (or Bias Ply) tyres

In todays market the crossply tyre is the "classic" design. Its advantages are its straightforward structure and its sturdy sidewalls, which particularly in off-road use offer many benefits (impact protection). Crossply tyres have a maximum design speed of 240 km/h (150 mph).

The crossply tyre is identified by the - in the designation on the tyre wall E.g. 140/70 -17 M/C 66H

Bias belted tyres

The bias belted tyre is the precursor of the radial tyre. Whilst the casing is still crossply in design, the tyre features a belt, usually made from Kevlar. Suitable for speeds up to 250 km/h (156 mph).

The bias belted tyre can be recognised by the B (=bias belted) in the designation on the outside of the tyre. E.g.: 150/70 B 17 69H TL

Radial tyres

Radial tyres feature a casing angle of approx. 90° to the circumferential direction (direction of travel) and a belt angle of 0 - 25° approximately. The belt, located under the tread area, gives the tyre stability and permits far higher speeds, as the centrifugal force deformation is substantially lower.

Reduced material thickness in the sidewall section means the tyre heats up less and the high speed strength is further increased.

In terms of riding dynamics, modern motorcycles are geared to radial tyres. As an example, a bias ply tyre "grows" by approximately 2 cm on average at a speed of 210 km/h (131 mph), whereas a comparable radial tyre only expands by a few millimetres.

The radial tyre can be recognised by the R in the designation on the outside of the tyre.

Tyre Pressures

Motorcycle manufacturers always go into the subject of air pressure in great detail in their manuals. It is possible to find instruction on air pressure for every driving situation.

The manufacturers make a distinction between load (riding solo or with a pillion passenger, with or without luggage) and speed (on secondary roads or motor-ways).

Naturally in such a short fitment guide it is not possible to give the necessary tyre pressure details for every motorbike and because of this we refer you to the recommendations of the motorcycle manufacturers.

From years of experience we are aware that motorcyclists sometimes ride on tyres for which the air pressure is not suited to the driving conditions. We do however advise that you always ride at the highest pressure level given in the manual.

Some amount of comfort will be lost, but that loss will be outweighed by improved safety. In addition the rolling resistance will be lower which will help to save fuel.

Incorrect inflation pressure reduces the service life and may have a negative influence on the riding characteristics of the motorcycle.

Under-inflated tyres flex excessively, easily overheat and can suffer damage. Over-inflation can cause uneven wear. Improper inflation, either too high or too low, can adversely affect overall handling and ride quality.

Tyre pressure should be measured when the tyres are cold. During riding, the tyre becomes warm and the tyre pressure is therefore higher (up to 0,5 bar). This excess pressure should not be released, as it will automatically be re-balanced, out as the tyre cools down again.

As a rule the tyre pressure for long distance, touring riding should be 0.2 bar (3 psi.) higher. The same also applies to a bike with a fully laden rear axle.

Puncture Repairs.

A British Standard exists for puncture repairs, BS AU159f :1997

The following is a brief outline of the standard in relation to tyre repair

Up to J speed rating , 2 repairs per tyre are permitted, not exceeding 6mm in diameter

K speed rating up to V speed rating, 1 repair per tyre, not exceeding 3mm in diameter

Repairs to be made with mushroom type plugs

All major manufacturers, with the exception of Michelin approve repairs as stated above.

Michelin approve 2 repairs, not exceeding 6mm, to all of its tyre range

Inner Tubes should not be repaired, and a new tube should be fitted