do i need to change speedo?

I'm thinking about putting the 2002 z28 rims 17x9 on my 94 z28. Would I need to send in my comp to have the speedo recalibrated to work with the tires, or would the speedo be pretty accurate?
Thanks

As long as the outside diameter of the new tires matches the outside diameter of your stock tires, it doesn't matter what the diameter or width of the wheel is. As an example, if your car left the factory with the Z-rated tires (245/50-16's), all these will have the same outside diameter, give or take a few 1/100ths of an inch:

245/50-16 = 25.65"
275/40-17 = 25.66" (typical size for a 17x9 wheel)
315/35-17 = 25.68"

275/35-18 = 25.58"
285/30-19 = 25.73"

None of those would require a PCM reprogram. The maximum error would be about 0.3%, or about 2/10ths of an MPH at 60 MPH.

If your car left the factory with the "base" tires (235/55-16), the outside diameter you are trying to match would be 26.18"

There should be a label on the door showing the tire size the car had from the factory. If you had the Z-rated tire option, the build code tag will show RPO "QLC".

OK thanks a lot!

FYI, I called my local dealership (Runde Auto Group) about bigger wheels than stock and was told that I could bring my car in and have them recalibrate the computer/speedometer while I wait for around $30+ tax. Not bad huh?

going from a 16x8 rim with 245/50/16 to a 17x9 or 17x9.5 with a 275/40/17 does not require a speedo change. i did this to my car a few years ago and the speedo stayed the same. like the other person said it might change it a half a mph @ 100+, but thats hardly recognizeable