My friend said if i get a wheel thats 3 inchs bigger then it will make my car "alot slower".Any truth to that????? its a 85 gs

 

my mistake, 1 inch bigger

 

it depends on your tire profile size (aspect ratio) i think the general rule of thumb is that every inch you go bigger, you get a tire with a profile size 5mm smaller. This keeps the circumfrence of the tire relativly close to stock or what ever you started out with

 

You will want to keep the overall diameter as close to stock as possible. Any time you go with a wider tire or taller wheel, you need a lower aspect ratio to compensate.
As for making you slower: Bigger wheels usually weigh more. Unfortunately, the lower profile tires aren't usually light enough to compensate for the extra wheel weight and you wind up having to spin up more weight when accelerating. I switched from the stock 15" "Baloney slicer" wheels on my FC to a set of stock 16" TII wheels because I just couldn't live with the sidewall flex. I gained about 8lbs on each corner and I could really feel the loss of acceleration, especially getting off the line. (I got my *** handed to me by a lightly modded Integra at the dragstrip)
So the bottom line is go as big as you want, but keep the wheel weight in mind if you want to be fast.

 

Dia, shape, weight of wheel and tire combined will increase or decrease the moment of inertia of the rotating mass. Larger moment or inertia needs more torque to accelerate the wheel which makes the car accelerate slower. Smaller moment or inertia will be the opposite.

 

hmm,the reason i ask is because there is not alot of choice for tires on a 13 " wheel

 

I would agree that there wouldn't be many good choices in 13".
There's an '85 GSL-SE autoxing in my class who's running 205s 16x7 wheels and it works fine for him. Just make sure to get the right offset and check the weight of the wheel...

 

LOL!!!!!

Go with some bigger wheelios. You will be fine. If you are very concerned with weight, look into the Toyo T1-S tires. They are extremely lighweight tires.