Wheel and tire size affecting motor negatively?

[DRP967]

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?

[talonXracer]

The extra width will impact the engine far more than that miniscule change in dia.

The stock speedo is already a few % off by design. Honda lost a class action law suit over it.

[Zzyzx]

To add to Talon, going to a 17" wheel with out significantly reducing that wheels weight will detrimentally impact your cars acceleration and braking rates.

The rotational inertia/polar moment of inertia of your drive wheels a is very influential...

[Zzyzx]

Elaborate please

Rolling resistance. It takes more effort to accelerate and subsiquently keep a wider tire rolling then it does to accelerate & keep a narrow tire rolling.

[ep3jd]

What about a wider wheel but the same size tire? Ie; stretching a 205 on a larger wheel

[Zzyzx]

I would say you'd be giving up more by going with the narrower tire then you'd gain by slightly reducing the tires rolling resistance, from a performance stand point. As in, the wider tire will give you more traction for acceleration, where as the narrow tire (with a stiff side wall) would save you a little gas while cruzing down the freeway.


The much bigger issue here is the increase in wheel diamiter, which has a signifigant impact on the wheels total rotational inertia.

[talonXracer]

stretching tires should be left for the ricers...


The difference in size of your tire dias is not that far different than between a new and a used tire of the same exact tire.


Whenever I get new tires/wheel combo I use a GPS to see what my actual ground speed is at the usual speed limits and just make a mental note