FWIW Here's the best tire combos I'd recommend for 18s/19s/20s, then pick proper wheel widths/offsets to get them to fit~
18s
235/45 & 265/40 (0.07%)
245/45 & 275/40 -0.07%
255/45 & 285/40 -0.22%

19s
225/45 & 255/40 0.06%
235/40 & 265/35 -0.37%
235/40 & 275/35 0.67%
245/40 & 275/35 -0.52%
245/40 & 285/35 0.51%

20s
235/35 & 275/30 0.07%
245/35 & 285/30 -0.07%

This calculator should be used when trying new setups~
https://www.myg37.com/forums/tire_rim_calculator.php

Keep in mind the variances with a minus sign have smaller rear diameters, this isn't as good since the rears wear faster, this will cause the variance to increase over time. Not a big deal when you're starting at zero or close, but if you're already almost at 1% variance this needs to be considered. None of the above combos should have enough rear wear to be a issue but

There's been a few that have run 305s but you'd need a lot of positive offset, like a +50. I ran 295s on 10+45 and they just squeezed inside the fenders at in-spec camber. If you run 305s in back on an AWD you'd have to run a 255 or 265 in front of the proper series to get your variance under 1%.

 

305's are a really tight fit on a G sedan. I'm currently running 305/25R20's on the rear of mine, but I've had the rear fenders widened by almost 1-1/2" per side to help give me enough clearance without running crazy negative camber. Now I've got room for 325's but my wheels are only 10-1/2" wide so I'm pretty much at my limit with the 305's and my current wheels

 

I love the back fat tire look, gives it a nice plump VQ booty look.
I'm running 245/40/19 front and 285/35/19 rear.

 

Anyone here besides jotech have TE37 style wheels?

 

Haven't seen any around here, a couple coupes but no sedans that I can recall. Over on G35driver there's quite a few, but that would be on the 1st gen Gs.

Looking good BTW, c1utchh

 

Glad to see this thread is still active.

 

thanks blnewt!!!

I'm expecting a lot more goodies by the end of the month to finish my air flow management.... Ark Grip CBE, Berks HFC, and to top it all off Admintunings custom built intakes tuned by R/T Tuning. Cant wait tbh, I have been X'ing out days on my calendar all month.

 

Wow, nice way to top of the summer! Look forward to your impressions & pics.

 

I have 20x10.5 at all four corners, so I'm doing a square set up with either 275's or 285's. Have you had any rubbing in the rear with your 285/35/19?

 

There's no rubbing because I have a camber kit installed front and back. running negative camber pack and front.

 

Depending on your wheel offset you should be able to run 285's in the rear without any rubbing with minimal excessive negative camber. I had 285's on my Volk GT30's in 20"x10.5" +37mm and around -2.5° rear camber for years without any rubbing.

 

My offset is +28
I can't figure out if 275 or 285 will be a better option. I'm pretty sure I'll have to order my tires so I will need to get it right the first time. Hopefully I can stop by a local shop that works on modded cars to get a better idea of what fat tire option will work best with my wheels.

 

20x10.5 +28 is way aggressive for a sedan, a +40 is about what you'd need to run 275s and a +45 to run 285s unless you want to really go heavy camber. To get those to work without fender work or extra camber a 255/35 is your best option.

 

Im heading off to china for a bit, but once I come back, throwing my winters on. Running 245/45/18 tires on 18x9+26 wheels all around. Cant wait to show off my fake rays hahahahaha

 

Yup, as Brad already mentioned, 20x10.5" +28 is pretty aggressive and is going to make it very tough to fit wide rubber on the rear. You are most likely going to have to run a pretty stretched tire set up and some heavy negative camber to clear in the rear without any fender modifications. Don't think you'll be able to make 285's or 275's to work... even 265's will probably require around -2.5° to -3° camber in the rear. I started with 265's on the rear of mine with 20x10.5" +37 wheels and that set up still required around -1.9° or -2° negative camber in the rear. That became around -2.2° camber when I went to 275's. Then I needed around -2.5 or so when I switched to 285's. Subtract another 9mm (almost 3/8") of offset and your set-up will be even tighter.

Have fun in China, Andy!