SO.. I installed the wrong size winter tires on my speed, how off will my tach be?

[carbon3]

So after doing some reading I realized I installed the wrong size winter tires on my speed3, I installed some 205-50-17 nordfrost 5, turns out I should have gotten 215 instead, should I change tires or it insnt that bad? How off will my tach be? 3-4km?

[MajesticBlueNTO]

So after doing some reading I realized I installed the wrong size winter tires on my speed3, I installed some 205-50-17 nordfrost 5, turns out I should have gotten 215 instead, should I change tires or it insnt that bad? How off will my tach be? 3-4km?

the simplest tire calculator on the internet (http://www.miata.net/garage/tirecalc.html)

your speedo will read 2.1% too fast. when it reads 100km/h, you're actually travelling 97.9km/h

[froggy]

215's at the same aspect ratio?

[WeatherB]

I'm assuming you've got a pre-2010 Speed3...

Speedometer Difference: 2.154% too fast
Diameter Difference: 2.11%

[carbon3]

Yeah sorry,
I have a 2009.

[SKYMP3]

IMO it should be alright. ideal is < 3%...2.1 is not way off.
205/50/17 is the stock Mazda3 size, I honestly see nothing wrong to put it on a MS3.

[carbon3]

Good to know,
Thanks guys