Ok so. Main question before I dive in and spend $900+ on my tires for my new powder coated C6 rims... (=D)

First off. I know I need a one inch spacer for the rims to fit, which I think.. is huge! Also my front wheels are the same size as the ones I'll be putting on. (Well, almost I currently have 275/40?17 and I am going to 285,40r18s) with the whole extra inch.. would that affect the way I turn my front wheels?

Now on the backs... its less of a problem because I'm not turning the wheel, but I am going bigger.. much bigger. My current rear wheels are the same as my front. 275s on 17" rims. But ill be going to 305s on 19s. Which will look awesome!
But other than me drooling over the rims every time I look at them its made me think...
With wheels that wide, well maybe not the width, maybe the fact that they will be sticking out farther. Will it change the place in which the car puts the pressure? Making my tires wear at an uneven rate?

Can I use the stock camber settings when I get the car alligned after the wheels are on? (Same for the toe)

I've been reading a lot on this subject. My car is an '85. No what I read was that in '84 GM had the cacaster set to 3.0 degrees and in 85 set to 3.8 and in 86 set to 6.0. Why such a drastic change? And would it be benificial if I set mine to 6.0 or left it stock?

 

massive caster is great.

 

Very informative! Lol

 

its a personal choice on the caster, they added it to make the steering less 'darty' and it will make your steering return to center quicker, you dont need it and should drive what you have first.
Most of us run 315's on the rear with out issue
your fronts are only 1/2" wider on the inside, the other 1/2" is on the outside so you wont notice that much either, may rub a bit on hard corners but I doubt it
make sure you have 'hub centric ' spacers/adapters
if your alignment is good now, it will be good then

 

Yeah, they put in more caster in an attempt to reduce the tendency for the wide tires to track hard on ruts in the road.

 

Why such a tall tire on the front? The 285/40/18 is more than 1" taller than the OEM size. If I were you I would go with a 275/35/18.

As others mentioned, dont worry about the caster. Your old alignment (if correct) will still be good with the new setup.

 

If the vertical center line of the wheel is moved closer to or farther away from the front spindle or if a taller wheel/tire is used all that will change is the tire scrub radius. Caster, camber & toe remain unchanged.

Changing the scrub radius has little effect on DD's unless it is changed drastically.
Example: Installing reversed wheels with negative backspace on the front. The vehicle steering will be "twitchy" with poor straight line tracking. Ricer cars are also a good example.

Track cars benefit from correct backspace wheels which equates to a correct scrub radius.

I run 285-40-18's on 4 corners, 90 Vette with stock 55mm positive back space. There is minimal difference in steering feel or driver input required.

More scrub radius info here or google scrub radius.
http://en.wikipedia.org/wiki/Scrub_radius

 

I can't find 315s in any size. So I would assume that since you said most of us its an extremely popular size? I can't find any? I think I like the Invos. Ill see if they have any

 

Try 325's & a different aspect ratio of 30 or 35 for a 19" wheel.

 

I actually just bought some 325/30s and 275/35s. Thanks for the advice! Now what I have gathered is the allignment should stay the same.

 

Yes alignment will be the same, and that is a much better tire choice!

 

sumitomo, actually , I saw them recommended on here, several are running them, tried them and went to BFG KDW's larger size though. my point was that you could go to a larger tire, not interested in arguing, just trying to help