HELLO - I some help understanding tires and the number on the sides...

FOR EXAMPLE:

Say I have a tire that is 215/ 40 18
and another guy tells me that 235/ 40 18
is better what does this mean?

What do the 215 & 235 numbers mean?
What do the 40 numbers mean?

What is tread width?

Thanks for the help

 

Take 185/60-14 for example

The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4 In the example above, the width is 185mm or 7.28".

The second number is the aspect ratio. This is a ratio of sidewall height to width. In the example above, the tire is 7.28" wide, multiply that by the aspect ratio to find the height of one sidewall. In this case, 185x0.60=111mm or 7.28"x0.60=4.36".

The last number is the diameter of the wheel in inches.

You can see an example here: Tire Tech. Calculating Tire Dimensions

Width x Aspect Ratio = Section Height x 2 = Combined Section Height + Wheel Diameter = Tire Diameter

 

1. 215 or 235 is the width of the tire in mm. 235 is better because it is wider and has more rubber contact with the road.

2. 40 is the a ratio to 100. Which indicated the height of one of the side walls for the tire, it is calculated by taking, eg:
40/100 x 235 = 0.4 x 235 = 94mm
That means the distance between the rim to the edge of the tire is 94mm.

3. Tread width is either the width of the tire, I think or the distance between the treads on the tire (not sure).

 

Tread width is how wide the tires tread slab is. The tread slab and sidewall are two separate pieces. A wider tire is better for handling, but makes the car harder to gut thru debris like ice, snow, and water.