I have a general question which I know someone should be able to answer. I'll start with an example. The new Civic Si comes with 215/45-17 wheels/tires, but you can upgrade to 215/40-18 wheels/tires. Does the Vehicle Speed Sensor change to make up for the increase in rolling diameter? If it doesn't, Is there any calibration for the speedo? Is the VSS responsible for any/all calibration? Thanks

 

The difference in outer diameter between those two sizes is only about 0.6 percent, so there is no need for any change in the speed sensor or in the calibration of the speedometer.

By comparison, the difference in outer diameter between a tire that is brand new, and one that is worn and ready for replacement, is about 2.0 percent. So there is always the possibility of a little bit of error, beyond what you can calibrate for.

The 0.6 percent difference between those two tire sizes is too small to worry about.

 

At what point would you say the VSS/ speedometer would need to be recalibrated? And is that possible?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 96GSRcx &raquo;</TD></TR><TR><TD CLASS="quote">At what point would you say the VSS/ speedometer would need to be recalibrated?</TD></TR></TABLE>

It's at a point where you shouldn't be using that tire size.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 96GSRcx &raquo;</TD></TR><TR><TD CLASS="quote">And is that possible?</TD></TR></TABLE>

I don't know.