wheel size/computer question

[rjw1]

Can you swap factory 17's to factory 18's without reprogramming the computer?

[Steel Chicken]

a fun thing to see how much your new tire/wheel combo will be off.
http://www.miata.net/garage/tirecalc.html

[rjw1]

stock 17's
245/45-17 = 25.7" overall diameter

stock 18's
235/40-18 = 25.4" overall diameter

Is this correct?

Anyone buy a car with factory 17's and have the dealer swap them for factory 18's? Did they alter the computer?


Thanks

[Snafu]

They won't change the computer for such a minor difference. You would only see a fraction of a mph difference at well over 100mph. ABS will remain unaffected as well.

You can switch between wheel sizes however you like as long as you adjust the tire size to compensate for the change. It is the "Rolling Diameter" that you want to remain consistent...this is wheel plus tire sidewall (which I think you know).

For example, we sell 18" and 19" wheel/tire combo's all the time with 245/40/18, 275/35/18, 245/35/19, and 275/30/19 tires and there is no need to adjust the computer.

Hope that helps. :thumbs:

[rjw1]

They won't change the computer for such a minor difference. You would only see a fraction of a mph difference at well over 100mph. ABS will remain unaffected as well.

You can switch between wheel sizes however you like as long as you adjust the tire size to compensate for the change. It is the "Rolling Diameter" that you want to remain consistent...this is wheel plus tire sidewall (which I think you know).

For example, we sell 18" and 19" wheel/tire combo's all the time with 245/40/18, 275/35/18, 245/35/19, and 275/30/19 tires and there is no need to adjust the computer.

Hope that helps. :thumbs:


Thanks

Dealers are so full of crap.

[Scyry]

Speed will be 98.83% of your original speed. 1.16% is nothing, you'll be doing 65.76mph when your car reads 65mph.