Mark P

It'll suggest the closest profile for a given wheel diameter and tire width, as well as showing you how far off your speedo will be.

click the link below (or my sig pic) and then "Tire Calculator"<ul><li><a href="http://drive.to/marksa4">Mark P's Quattrobonium</a></li></ul>

Ray Khan

is this assuning we have 16" or 15" stock wheels, or are they the same OD?

Mark P

if you tried those tire combinations, you would see that one is 0% from ideal, so thus that must be the one I based it off of.

I did think this over a fair amount, and here's my thoughts:

The speedo is probably set for one tire size, regardless of what tires you get on your car (ie sport pkg).
The four tire options are:
1.8T stock (15's)
1.8T Sport (16's)
2.8 stock (16's)
2.8 Sport (16's)

so therefore, I went with the 16's.

Silver Sasquatch

You should add 100 mph and/or 120 mph, not just 60 mph. We all drive faster than 60. ;-&gt;

Jenner

For example if you go from a 205/55/16 to a 235/40/17 the difference is -1.9%(in otherwords your gearing change based on wheel diameter makes acceleration increase and decreases top speed)

Mark P

the speed section tells you if you are going faster or slower.

so, then it's just a matter of which is closest to the stock size, so I decided against +/-

However, I did think of putting it back, just to give the user a better visual feeling of where 0% would be.