Grip of the tire
The tire of the wheel ensures, in addition to the suspension, for grip with the road surface. The grip on the road surface is dependent on the coefficient of friction between the road surface and the tire and the force with which the tire rests on the road surface.
This is a general law for the friction force. This is only dependent on the coefficient of friction of the materials and the force with which the materials are pressed against each other.
By increasing the surface friction does not increase. Also the use of the profile has no effect on the friction. Profile only enhances grip on uneven surfaces.
The higher the friction coefficient, the better the grip. Rubber generally has a high coefficient of friction with other materials.
The human skin has a very high coefficient of friction. Teflon and nylon have again a very low coefficient of friction, so that these materials are very suitable for sliding bearings and inner lining of cables.
The coefficient of friction of most materials at standstill is higher than in movement. An object which force is applied will remain silent first.
The friction force is then equally large as or larger than the force which is exerted on the object. At the moment that the force is greater than the force of friction the object is sliding.
At that time, reduces friction, which reduces drag on the object and suddenly the object moves forward or shoots off. If at a tire, the drive force, or the braking force or the lateral force becomes larger than the maximum frictional force the tire is not rolling anymore but starts to slide.
A tire that will slip suddenly gets much less grip on the road surface and slips away. The effect that an object suddenly slips because the coefficient of friction at rest or rolling is higher than when sliding is indicated with stick-slip.
Stick-slip occurs when cycling in the contact between road surface and tire, at the contact between brake pads and brake surface, between the outer and inner cable of the brake and suspension front and rear forks.
Stick Slip suffer in case of tires to the sudden slipping of the tire, in suspension forks for the poor and not directly respond to the suspension and the brakes to the blocking of the brake and the poor grading of the brake.
The friction between two materials is much less if there is liquid between the two materials. The liquid ensures that there will be a film between the two materials. For bearings, it is advantageous to lubricate.
In case of rain, the grip of the tire on the road is much less, thats why a bike in the rain flies faster off the road , and you can brake less hard. Also by loose sand and gravel reduces grip on the road surface. The loose sand grains work like balls in a ball bearing, and ensure that the wheel can roll and slade. By the rolling is a light profile indeed meaningful.
The tire can slip away when a cyclist brakes too hard, too hard acceleration or hard going through the bend. In one corner a rider must be very careful with braking and turning. Due to the increase of the force on the wheel through the brake and turn on the power the force can suddenly become larger than the frictional force. At that moment, the wheel will slip.
By applying profile on a tire, the grip can be increased when driving on irregular surfaces. Instead of frictional force between the tire and the surface, there is then a normal force between the side of the profile and the surface
For rugged terrain is particularly profile in the transverse direction suitable . For a better cornering grip profile is better suited in the longitudinal direction, because you tend to slip sideways.
Theoretically, has a narrow tire as much grip as a broad band. The larger contact area of a broad band will in practice have more grip because loose gravel, oil spots, blemishes have less disruptive influence.