how much of a difference is a 40 series from a 35 series from a 30 series?the wheel setup is 18/19 or 19 all around but it depends on how noticable the different series will be.

 

It depends on the width of the tire, as the "30" is a percentage of the tire width. For example, a 285/40 is going to have a larger sidewall than a 255/40.

Here is a fantastic little tire size calculator...

http://www.miata.net/garage/tirecalc.html

Just plug in whatever tire you want to run up front into the "stock" tire size. Then put the tire size you want to put in the rear in the "new" tire size. It will give you overall diameter, radius, sidewall, circumferance, and revs per mile.

I run 255/40/18 in the front, and a 295/30/19 in the rear. Both tires have the exact same radius and diameter. There is a .5" difference in the sidewall, its not really noticeable.

 

exactly what i wanted to know..thanx

 

Here's another one.
Tire Calculator