Hey guys will I have to do any modification to put 16x8 inch 88-92 Formula wheels on my son's 86 Firebird with 15's currently on it. Will it increase or decrease my tire choices. Thanks for your help.

 

the wheel should fit perfect. however on your tire choices will limit you to a lil shorter of a tire.

 

the 15" came with 215/65/15 tires if i remember correctly. if you want to have a correct speedo reading, you'd need 245/50/16 tires like the stockers, or use these two links to find equivalents:
http://www.miata.net/garage/tirecalc.html
http://www.dsm.org/tools/tiresize.htm

oh btw i was wondering if there was anything else you should swap, like the chassis suspension bumper stops? they are different for the 16" wheels imho

 

i got a T/A 85, the info about the car on this said i should have 16's. i got 15's now, so i should upgrade? im thinking im getting jiped on the odometer because of having non stock 15

 

Wheels diameter makes ZERO difference to your speedometer. It is the overal tire diameter that maters.

Bigger rim = shorter sidewall, for the same overal diameter.

 

23/60/15