How To READ your Tire Size

When you see something like 215/60R15
215 is the width of the tyre in millimetres.
60 is the aspect ratio or tyre profile.
R means it is radial construction(most tyres are radial)
15 is the diameter of the wheel rim in inches.

What's a tyre's profile?

Tyre profile is the hieght of the sidewall (the wall at the side of the tyre). The profile is expressed as a percentage of the tyre's width. Eg. 215/60R15 tyre has a profile or sidewall that is 60% of the 215mm (width). A low profile tyre is generally 50% or below, down to as little as 30% with ultra low profile tyres. Spot or high performance vehicles are mostly fitted with tyres that have lower profiles.

Low profile tyres give you greater control and better handling on corners, they can give a slight hard time ride. Also, going to a lower profile on the same size wheels will alter your speedometer reading so you'll need to fix that up before you hit the road. There are as many considerations when it comes to choice of tyres

What is Speed Rating?

speed rating is how fast the tyre can gothe higher the number the faster(in plain and simple english)

but the manufacturers dont always guarantee that. because it doesnt mean that low numbers are low on speeds