My sawblades were recently replaced by 350z rims and tires. Now I feel that because of the larger size of the new wheels, the speedometer isn't reading the correct speed.

 

You feel?

Use the tire calc web site to calculate actual speedo error based on tire size.

 

LOL!!! Is that even possible !!!??? Experts, please step in!!

 

Yes, it's possible.

 

I was the **** in an earlier thread, so I'll be the helpful one here.
http://www.miata.net/garage/tirecalc.html
This is what you need. You'll just have to remember how much you are off by now and keep it in mind when you are running away from the cops.

 

I don't want to be driving close to a cop when the speedometer is reading 65mph and I'm actually doing like 70 or 73mph.

 

stock size-215/60R15

present size (front)-215/50R17 (rear)225/50R17

 

Here's another resource. You can compare stock sizes and other sizes side by side and it'll tell you how far off your speed will be in percentage...
http://1010tire.com/TireSizeCalculator.asp

 

its not going tomake that big of a difference but you should still get it checked out

 

so if you get a 100 inch rims
that your speedometer will say 15mph
and you are really going at 100mph!!!!!
or get a smaller rims lie 7 inch rims and watch your
speedometer go up to 500mphs in 5secs

 

rims size dont mean jack....its all in the circumfrance of the tire mounted to the rim.....if the tire is taller then ur going faster than u the speedo says....if ur tire is shorter ur not going quite as fast as the speedo says.....now the actually % off all veries on how tall or how short ur tires are than approx diamter of 25.3" but usually ur not far off enought to even notice the speedo change..nad ur current 215/50/17 are very close to the original tire size....so dont worry.....and PS wider tires in front we have FWD

 

Incase you haven't done it yet... the stock tire is only 1.2% smaller which means when your speedometer says you are going 60mph you are really going 60.7mph... less than 1mph difference at 60mph. Stop worrying.