On-line calculators - wheel sizes, spring rates

Changing your wheel size? This calculator compares the numbers of what you have, to what you want.

tacomaworld.com/forum/tirecalc.php

Here's a coil spring rate calculation page.

pontiacracing.net/js_coil_spring_rate.htm

This one is useful for wheel offset and tyre changes.

http://www.rimsntires.com/specspro.jsp