Any wear that is more obvious in one area or on one side is improper.
It is an indicator of tire tread wear.
Yes, because the tire gets hot and this causes the tread to wear faster.
Tread wear indicator
It really does not matter how many there are as there are several around the tire. When the tread wear indicators appear flush with the tread you have 1/16" tread left and should look to replace the tires very soon.
When the tire tread wears down to the wear bars, the tires are ready for replacement.
Completer wear of tread surface -(creating an unsafe tire ! )
It is the rubber marker within the tread to show tread depth. It is also known as a tread wear indicator
In the middle of the tread area,
Tread wear indicator
A flat tire can lead to reduced tread wear and sometimes blowouts.
There is no correct answer tread wear rating's can only be compared within the tire manufacturer itself aka a michelin to a michelin or a goodyear to a goodyear. You can not compare a michelin to goodyear or yokohama
The three important tire checks to make are proper inflation(pressure), adequate tread(tread depth), and normal wear(wear and tear).