Re: CLASS RACER wall of SHAME ....
 

The wider wheel allows a "larger" contact patch of the slick, so they make it so it has say 4" back spacing instead of needing 3 6/32nds back spacing mainly because off the shelf wheels are easier to find then custom offset.

Re: CLASS RACER wall of SHAME ....
 

You would need a wider rear not a narrowed rear to use more back space.

Re: CLASS RACER wall of SHAME ....
 

Yeah, that explanation was as clear as mud..lol. Well, think of it like this. Axles are like the extension on your impact, the longer and/or smaller diameter the extension is, the more torque you lose at the socket. Short as possible and as large/thick as possible transfers more power to the wheel. So you ALWAYS shorten to shortest possible to make the wheel/tire fit.....even though technically you are not supposed too

Re: CLASS RACER wall of SHAME ....
 

Narrowing a rear end in a stock bodied car is a matter of a few inches, so I don't think it affects torque application that much. Race axles are super hard and I don't think they twist much behind 300 to 600 HP. Factory Showdown and FSS cars are different animals. I've heard CJ Mustangs have running gear more equivalent to ProMod than anything else. From the factory...

Re: CLASS RACER wall of SHAME ....
 

another thing to remember is that whenever you maximize back spacing ( make it greater) you are actually adding weight to the rim/wheel because they have to add additional material to make the wheel stronger/thicker to handle the tree on the wheel/rim--don't believe me take two of the same brand 15" x 12" wheels one with a 2 inch backspace and the other say a 5-6 inch backspace and notice the weight difference--FED 387