ok so i have hp tuners and i just bought new set of tires for my car. i went from 195/65/15 to 205/50/15.
i went to wild weasel's how to page and came up with this:
Stock Tire
Sidewall: 5.0in
Radius: 12.5in
Diameter: 25in
Circumf: 78.5in
Rev/m: 807
New Tire
Sidewall: 4.0in
Radius: 11.5in
Diameter: 23.1in
Circumf: 72.5in
Rev/m: 847
then it says:
"Speeedometer reading with non-stock tire is 7.6% too fast. when your speedo read 60mph, you are actully going 55.4
which leads me into this question......I have HP Tuners and if i go to speedo opion it brings up "VSS Pulses Per Mile" @ 24212 and also has "VSS Trans Revs Per Mile" @ 2747.7535..........so if wild weasels calculations are saying im 7.6% off and im doing 55.4mph when speedo says im doing 60mph...what if i decreased the numbers i just mentioned by 7.6% would that bring it back to corrected mph reading on the speedo?
24212 x .076=1840.112 (rounded to 1840)
24212 - 1840= 22372<-------corrected VSS Pulses Per Mile?
2747.7535 x .076= 208.829266 (rounded to 208.8293)
2747.7535 - 208.8293= 2538.9242 <-------Corrected VSS Trans Revs Per Mile??
or am i doing the inverse operation and should add them instead of subtracting?