Can i adjust speedometer

I'm going to install some 15x8 6 hole Enkeis with 195/50 15 tires soon. Is there a way to adjust the speedometer since tire size is going to mess with it?

You should be able to measure the circumference of each tire, inflated and carry these dimensions to Mazda and get a new speedometer cable gear (replaces the one on the end of the cable in the transmission.)

Maybe back in the day you could do that, nowadays, probably not available. Also, the speedometer gear and gear on the drive shaft in the transmission is a matched set. So removing the tail shaft of the transmission is required to change the gear, huge pain in the arse. My speedo reads 22% fast, and I have just gotten used to what it reads vs actual speeds. There are websites online that you put your tire size in and it will tell you how much out your speedo will be.

If the plastic gear on the cable is the same as a Ranger, which it should be, here is a site with gear/teeth color code. And no, the tailshaft gear does not have to be touched

http://www.explorerforum.com/forums/showthread.php?t=158739&highlight=gear