See my sig. With what I'm running, my speedo didn't change much at all.
Try this calculator. Not as many calculations as the one above. I know it says Miata, but I think size is size and you should get the same result.
http://www.miata.net/garage/tirecalc.html
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BLADE
'86SE
Engine rblt by Jasper (Going V8 in 2004..Hopefully)
Hypertech Chip
Low-temp Fan Switch
Low-temp Thermostat
Grand Am rear brakes
215/45-17 front, 235/45-17 rear Falken Ziex ZE-502
[This message has been edited by Blade_69 (edited 03-23-2004).]