You also need to take in account the diff you have because there are a couple different final drives (fd).

 

mine is at 5th gear since auto tran....im running about 3200 rpm which seems high and not good on gas. had to replace throttle body about a yr ago to another oem used part. im running 20x9.5 245/35 for front wheels and
20x10.5 275/30 in rears.

 

mines 5th gear im running aftermarket 19's 235/45 front and 275/35 rear. stock was 19" 225/40 front 245/35 rear. at 80mph im at a good solid 3000 rpm or higher. havent checked in awhile

 

+1 def depends on MT or AT as completely different gear ratios.... Also aftermarket parts change it, but doesn't sound to absurd.

 

Put your car on a dyno that can hook into your obdII port. We only charge $30 for vehicle simulation and speedometer checks.

 

compared to what others have posted...seems like mine are about right rpm with my wheels

 

i knew what my wider wheels would do to my speedometer though. im not concerned about it, its a good 1-2mph off now but i might look into the dyno youre talking about. mssg me details please

 

Mine runs 3K RPM at about 80 MPH on my '04 6MT. Unless you swap in a different transmission, no mods that you do will affect your RPM's in each gear at a given speed. The speed is picked up from the transmission output shaft. Even if you put in a different rear end or bigger/smaller diameter rims/tires, it won't change the RPM's that you spin in each gear according to what the speed on your speedometer says. It will change your ACTUAL speed in each gear though, like if you were to measure it with a GPS... but your indicated speed on the speedometer will just be off from the real speed.

Things like spark plugs, air filter, superchargers, etc. won't change your gearing/rpms/speed readouts on the stock gauge cluster.

 

The width of your tires and/or rims has absolutely nothing to do with your speedometer. Changing the rolling DIAMETER of your tires will change the accuracy of your speedometer, however.