So they will grip when you lean the bike to turn.
Turning on a bicycle is different than in a car. When you turn on a bicycle you lean the entire bike to the side. This causes the sides of the tires to contact the pavement. The tread on the sides of the tires is there for this exact reason. Without it, you would probably skid out when you try to turn.
The "tread" is the part of the tire that is supposed to touch the ground. A tire with no tread would be a tire that is not supposed to touch the ground. You may be wondering why tires have a pattern of grooves (a.k.a., voids) in the tread. They're for bad weather. The grooves allow rain, and (if they're wider) mud and snow to squelch out from under the tire so that the tread can come into contact with something solid on which to get a grip.
the tread is part of the tyre that is supposed to touch the ground
Hydroplaning occurs when the tires' tread is unable to expel enough water to maintain a rubber contact patch on the road. The function of tread is to allow the "high" part of the tread pattern to cut through by forcing water (and other road grit) into channels and grooves surrounding the tread blocks. When the water gets too deep for the tread grooves to cut through it and force it between the tread blocks, the "high part" of the tread blocks lose contact with the pavement and looses traction by hydroplaning.
"Check the tread by using the "penny test." Take a penny, and place it upside down with Lincoln facing you in the center of the tread (at the thickest part of the tire).If you can see the very top of Lincoln's head or the copper above it, replace the tires immediately.If Lincoln's hair on the top of his head is partially visible, it is time to go shopping for tires.If you cannot see the hair on the top of his head (if the coin is inserted enough that the tire tread is at least as deep as Lincoln's forehead), your tires do not need replacing yet. " ~ WikiHow
According to most states' laws (including North Carolina), tires are legally worn out when they have worn down to 2/32 Place a penny into several tread grooves across the tire. If part of Lincoln's head is always covered by the tread, you have more than 2/32" of tread depth remaining.
It is usuall on the inner part of the tread, the tread lugs are worn with dips in it. It is different then feathered tires which have 1 edge of the tread worn more than the other- It can seen when bad, but it is easier to feel by running your had front to back and vis-versa. It will feel shaper in one direction. Scalloped is usually due to damaged/worn parts, feathered is normally due to excessive toe condition.
Look for any obvious signs of damage such as bulges or cracks. Next test the tread using a penny. Place a penny head down in the tread. If you can still see part of Lincoln'shead, the tire is worn.
A motorcycle club is just only a part of a motorcycle organization.
The tread is what grips the road.
Several websites sell used part online, including tires. Locally, you many want to try a local dealer or maintenance shop and speak with them.
It can be, when referring to part of a tire. The verb to tread means to walk.