Wheel Tire Fitment for 70 Challenger... help.

[EvilTwin]

I am trying to decided on an exact wheel / tire combo. My Challenger has the stock LCA's and springs with upgraded front and rear sway bars. I want the car to have a pro-touring type look and so am wanting to lower the car an inch or so and put big billett wheels on it..
essentially I want to put 18's on the front and 20's on the rear. I know this is not everyone's taste but I like it.

From reading I believe that the front should have close to a 26" tire max - any taller and I would have clearance issues with the fender or UCA.
For the rear... it should be 28" (max is 30"). This should tuck underneath the wheel well without issues if the backspace is correct.

So, here is what I am thinking.

Front Wheel Size: 18x8 - 4.5 BS
Front Tire Size: 235/45-18 (or 245/45-18)
Front Tire Width: 235 mm (9.3'')
Sidewall Height: 106 mm (4.2'')
Overall Diameter(Height): 669 mm (26.3'')

Rear Wheel Size: 20x9.5 - 5.5 BS
Rear Tire Size:285/35-20
Rear Rire Width: 285 mm (11.2'')
Sidewall Height: 100 mm (3.9'')
Overall Diameter(Height): 708 mm (27.9'')

I am wanting to order something right away.. so I need confirmation as to whether or not this will fit. Please post pic if you have them!

Thanks - Brent

[DriverzInc]

We have run an 19x8 on the front with a 4.75" backspace, and a 20x10 on the rear with a 5.5" backspace with a 245/35/19 and 285/35/20 rear and it worked well.

The problem with ordering a 20x9.5 is it is not a softlip outer rim, but a standard rim size, so you don't get the nice smooth lip on the front side of the wheel. If that is what you want, then go for it in the 9.5, but if you want "softlip" then it will have to be a 10". This is assuming you are looking at two piece billet wheels like Rushforth Wheels, Budnik, or something similiar.

What wheels are you looking at?

[EvilTwin]

DriverzInc... I talked to my builder today and measure everything two more times. measured both sides too... I ended up coming up with the exact same thing you just stated.
I am 95% sure I will end up going with Centerline Laser wheels

Front - 18x8 - 5" BS with 245/45R18 (25.7" Tall, 3.9" Sidewall, 9.6" wide)
Rear - 20x8 - 5.5" BS with 285/35R20 (27.9" Tall, 3.9" Sidewall, 11.2" wide)

I am having trouble finding a match set of tires though... can't find a 285/35 anywhere. What brand of tire did you use? Any ideas?