i have a 95 cx eg with 205 40 17 on them will this mess with my speedometer readings? ive had people drive next to me before and said they were doin 5mph's more then me and we were goin the same speed!?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by northkai3 &raquo;</TD></TR><TR><TD CLASS="quote">i have a 95 cx eg with 205 40 17 on them will this mess with my speedometer readings? ive had people drive next to me before and said they were doin 5mph's more then me and we were goin the same speed!?</TD></TR></TABLE>

Yes.

You can use a tire calculator like this one to compare the outer diameters of two different tire sizes. Your car came with 165/70-13 stock tires when it was new. As you can see from the tire calculator, the 205/40-17 tires are 6.2 percent larger in outer diameter than your stock tires were. That means that your speedometer and odometer read lower than actual by approximately 6.2 percent. If your speedometer says you are going 75, you are indeed actually going 80 mph.

There may be other sources of speedometer and odometer error as well; for example, the difference between a tire that is new and one that is worn down to the treadwear indicator bars is around 2 percent.