size diffrence??? Options

[mandrek]

is there a size difrence between the 95 ST stock wheel's and the 2000 gts stock ones??? i'm reffering in particular to the total wheel diamiter.

this question comes forom the fact that i just took a nice high-way trip and got to run some calculations in relation to my speed/recorded miles (trip meater)/acctual miles (mile markers). and there was some dicrepencey.

in particular i drove for 80MPH for exactly one hour... and the trip meater reccorded that i had drove 75Miles, but the mile-markers and signs that i was useing as a guide, showed that i had in fact driven more than 80miles.

my ST is my bro's old car, and he installed some EL guages a long wile back. one thought that i have is that eaither one or both of the speedo/tach needles is misplaced. but not vary noticable. he also used to have some 17"s on the car and he never notised any descrepencey. but my trip, confirms that something is a-miss. just covering all the bases here, cuz i do allot of highway driving and like to cruze @ about 80MPH. i've only had this car for like, a month (on the road that is).

but have noticed that other car's tend to act like i'm going too slow, or too fast... eh...

what ever info you all can give me to help, would really help alot. i'm looking at getting some newer 17"'s here soon, as well as a shock/springs/coil-over. and i would like to make sure that my in fo that i'm getting from my israments is as accurate as posible.

(hence avoiding as much falls attention from the cops as posible (thinking that ur doing 80 and ur acctualy doing 85/90mph (well u get the idea)))

[Galcobar]

Plus there's the issue of matching the tire to the original diametre. That's the thing with plus-sizing (bigger wheel, slimmer tire), the acceptable margin of error is +/- 3% -- combine that with tire wear, or lack thereof, would easily account for the five-mile discrepancy.

Get the stock wheel and tire diametre for the car, and use that as a base for your plus-sizing calculations.