Well....
The 315s will "fit". Hell, pay the tire install guy enough of a "bonus" and they'll make almost any tire fit on any rim

. However, it will definitely be running the tire on too narrow a rim.
This has several consequences, all bad :
- <LI>Puts stress on the sidewall of the tire, causing heat buildup, making pulling a "Ford Explorer" more likely. This can be overcome SOMEWHAT by inflating to a higher pressure, but not eliminated. I would definitely worry about this, especially on a "heavy" car like ours where the tire is gonna be close to at it's load limits anyways<LI>Narrow rim keeps the tire from unwrapping properly, reducing the contact patch on the ground. Not good for traction.<LI>Appearance-wise, the tire won't look at good as it would on a wider rim
For occasional drag use only, you'll probably get away with it. If you're gonna drive it on the street much (and especially if you like to take corners with any kind of "authority"), I wouldn't do it.
If you wanna run 315s, I would seriously look into having the rims widened and then run GOOD spacers as necessary to make the backspacing correct.
Just because it CAN fit doesn't mean it's a good idea
285's fit just fine, and look great. Trust me, I know
