I have a 2007 Fit Base I am going to put 16x7 wheels on it with 205/45r16. What offset will be needed with Tanabe GF210 springs? Will it need fender mods?

 

This really depends on your goals. I see people running +15 and liking the look and, I suppose, the rubbing sounds.

I can offer this...we have +40 16x7's and they rub in the rear when hitting dips with factory suspension. The rub point is a screw that holds on the rear bumper. I have worked that area to diminish the rubbing, but it still makes contact on big dips.

If you want no rubbing with no fender/mount modifications, you will want +43 or more offset. Somewhere around +48 puts the wheel back to centered when using a 7" width.

Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit is a great resource for "testing" different combinations. The factory sport wheels are 15x6 +53 with 195/55-15 tires so that you have a base wheel/tire combo to put in for the existing set up.

 

I should add that, strictly for looks, the +40 is an OK compromise between looks and rubbing.

But, I'm old. I probably would have run +25 when younger and not minded the diminished handling or rubbing.