Is Speedometer adjustable?

I'm posting this here because more people in 3series... My speedometer is 5-8mph incorrect (pacing with various friends). Is there a procedure I can do to make speedometer recalibrate on a 1997 Z3 (1.9L from 318i) ?? My manual says 225/50Z16's, I have 225/50R16's.

Yes it is adjustable and BMW's typically tell you that you are running a few miles faster than you actually are (could help save you a few speeding tickets)

As far as your tire size... 225/50Z16's, are the same size as 225/50R16's
Width/Ratio/SpeedRating/RimSize.

TireRack.com can explain the numbers more effectively. The R tires aren't rated to go as fast as the Z but they will last longer.

Thanks for the tire website. Good info.

Is there something I can do to get the speedometer to recalibrate or is that a dealer only procedure ?

I believe it is a dealer only thing.

I though when were saying 3 seris we were talking about 323s 325s etc and z3s went under the z3 section? well anyhow, my z3 runs a little fast too

Yikes! My local Dealer says +/-5% plus 2.5mph off is within BMW acknowledged specs. He says for example at 50mph the speedometer on all BMW's could be reading from 43 to 57 per BMW. Says BMW even has a service bulletin on it. Sounds like very sloppy tolerances to me. Anybody have any additional info on this issue?