Ok I'm looking to get a set of 18x8 inch rims. The ones I have found come in 35 and 45 offsets. I'm going to run 245/40/18 tires. So which offset do I need to get?

 

You could stagger the offsets since the rear wheels sit in more compared to the front. +45 up front and +35 in the rear but may look odd if you rotate your tires.

If you don't want to stagger the offsets, just pick +35 for front and rear.

 

Only found one company that has the 35mm in stock. Have to finish a job next week to get the money to order them. Doing Yokohama advan sport a/s 245/40/18 tires.
The rims are 20lbs and the tires are 25lbs. Should be a few pounds lighter than the stock rims and toyo tires I have now.