You can use a penny for that. Put in between the threads then mark and measure the depth on the penny.
I inspect the tire and measure the tread depth.
Minimum tread depth for all 4 tires is 2/32"
When the tread gets low.
A penny can be used to measure for safe tread depth on your car tires. Hold the penny upside-down in a tread groove. If the top of Lincoln's head is visible above the tread wall, the tires are completely worn out, and need to be replaced, pronto.
The standard tread depth for tires is 2/32 of an inch. It is important to maintain this depth because adequate tread depth helps tires grip the road, improving traction and handling. Insufficient tread depth can lead to reduced performance, increased risk of hydroplaning, and decreased braking ability, posing a safety hazard.
According to CVC 27465(b), the minimum allowable tread depth for tires is 6/32 of an inch. This regulation ensures that tires maintain adequate traction and performance, especially in wet conditions. It's important for vehicle safety to regularly check the tread depth, as tires with insufficient tread can lead to reduced grip and increased risk of accidents. If the tread depth falls below this minimum, it's advisable to replace the tires promptly.
1.6 mm is the minimum
Slow down and make sure your tires have at least 2/32" of tread depth.
In Oregon, the minimum tread depth for tires, including those sold by Les Schwab, is 2/32 of an inch for safe operation. However, for optimal performance and safety, it is often recommended to replace tires when tread depth reaches 4/32 of an inch. Regularly checking tire tread depth can help ensure better traction and handling, especially in wet conditions.
1mm according to UK law
So they will grip when you lean the bike to turn.
When your tires have 2/32" tread depth left you need to replace them.