Does changing the wheel/tire size to a non stock circumference/width affect the motor in a negative way? Allow me to elaborate, my EP3 is a 2005 model. As you all know the stock tire size is 205/55/16. Not too long ago I swapped wheels and tires and now my tire size is 215/45/17. Now I know the car's wheels and tires were "upsized" and according to the Miata tire size calculator here are my specs:

stock tire diameter: 24.9in
new tire diameter: 24.6in

stock tire circumference: 78.2in
new tire circumference: 77.3in

stock tire revs per mile: 811
new tire revs per mile: 819

*A difference of -1.0%

Now here are my questions, my revs per mile has increased from 811 to 819. Does that mean my motor is working harder than normal? Also since my revs per mile has increased does that mean my car is racking up miles faster than the norm? So what happens when people go "wide/aggressive" do they take note of all this or simply ignore it? Shouldn't one have the speedo recalibrated for the new tire size?

 

You obviously will see a slight change in the accuracy of your speedometer... Honestly your engine won't force more, it just the tire will spin 819 times in a mile then 811 but its still a mile... meaning you aren't putting necessarily more miles on in that sense.

Don't worry about it so much the changes are so minimum and having the extra rubber on the EP3 is night and day difference... I would go back. I have 215-45-17 also!

 

I wonder how much mine has changed going from 215 to 225/45/17

 

Thanks for the input DaveSi677!

And yes I love the 215/45/17 set up.

 

Use the Miata tire size calculator.

http://www.miata.net/garage/tirecalc.html

 

I have an 03 Type S. I used to do a lot of auto X-ing. I switched from stock 16's to 05-06 stock 17's.
2 things I noticed instantly. The steering feel became sloppier. Seem to have more play and not be as "sharp." And acceleration suffered. Well the FD in the 05-06 is smaller to compensate for the larger wheels. And the steering rack, struts, whole front suspension geometry in the 05-06 is diffrent. (not sure what the difference is with the rack, but it likely has to do with number of "teeth" in the gear assembly.) With that being said the motor will not be affected negatively at all.

 

That's really odd because 17's did the opposite to me. Maybe it was your tire choice and not so much the wheel size.

 

Same goes with me; from OEM 16 set up to 16" with wider tires, and then to 17" with 235 front and 225 rear. These changes improved mine.

 

Do you auto X?? Track?? Canyon run?? My tire choice has been the same for 8 years runing. Azenis. I buy a new set every year.

 

Curious OP have you gone for an alignment?