Tires size questions....

[19Eclipse90]

Yes I know another tire size question, please don't hate on me because I tried to read up on what I could before I came around to posting a new thread.
This is for my 1g FWD that is lowered 1.0"-1.5". I'm going to put some 17x7 wheels with a 42mm offset on them. After reading the rules of thumb and trying to figure out what I would need through the mathematics of the situation, I've decided I've gotten lost and don't know what is going on.
I understand that 7inches wide is 178mm (177.8mm for the picky) and that this should be 70%-90% the width of the tire. By doing trial and error, I found that 80%, which is the median there, of a 225 is about 180mm. I don't know if 70% or 90% is better, which is where my question is. Would I be okay running a 225 tire?
Then I read another rule of thumb that if you go up +1 in rim size (from 16" to 17") that your tire size should go -5. With that I should be running 50. Then I went onto the tire calculator and find that to be as accurate as possible with the speedo that I should run a 45 with a 225.
Sorry if that doesn't make any sense, basically I want to run a 225/45/17 on my 17x7 with 42mm offset. Car is lowered 1.0"-1.5" and it is a 1g FWD. If anyone can let me know if this would be an ideal choice, or give me insight on what would be better, I'd appreciate it. TIA
Brian

Edit: This was clearly not a performance-based decision. 225/45/17 works fine; have been running them on 17 x 7 and 17 x 6.5 wheels (two different cars) for many years now.

 

[weith1111]

This will tell you what width/profile/diameter you need to keep your speedo close to accurate:
http://www.dsm.org/tools/tiresize.htm
As far as the rim width, go onto tirerack.com (a page like this: http://www.tirerack.com/tires/Spec....ightTire=245YR7GFTAKDR&leftTire=245YR7GFTAKDL) and look at the suggested rim widths. There is a range that will be acceptable, and it can vary slightly by tire type and profile. A 225 tire is usually acceptable on a 6-8 inch rim. Obviously the smaller rim will be bulging the tire and the larger rim will be stretching the tire, with somewhere in between the optimal width.

Hope that helps and good luck!

 

[DSMSpyder99]

225/45/17 will be fine for a 7" width, many people run those tires on the smaller GSX rims. Also the offset it good to no rubbing.

 

[DGajre777]

Sorry if that doesn't make any sense, basically I want to run a 225/45/17 on my 17x7 with 42mm offset.

This combo is the most widely used combo. You'll be fine.

 

[19Eclipse90]

Awesome, thanks guys!! Rep points all around!

 

[eclipsegsx1736]

It'll work fine, but you really should consider going wider. I think everyone should get at least 17x8 wheels, 17x7.5 if you have to... You can run wider tires, better steering response, etc. Why not?