Hey Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
swift6
Yoda
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Just so you know, 185/70's are undersized for stock dimensions so using those as a guide means you started with an error. The original 185R15's had closer to an 80 aspect ratio (185/80R15) giving around a 26.7" rolling diameter. A 25.2" rolling diameter shows speedometer error of 5.5% thus showing 60mph on the speedo equals 56.7mph. That of course assumes that the speedo is accurate to begin with. A 25" rolling diameter is 6.3% error dropping your real speed to 56.2mph.
My tires are slightly undersized on my TR6 (25" rolling diameter) and when tested against other cars and mobile radar units I have about a 5mph error on my speedo. When my speedo shows 60 radar units show 55-57mph. I just think of it as insurance against speeding tickets since I'm actually going slower than I usually think I am. /ubbthreads/images/graemlins/grin.gif
My tires are slightly undersized on my TR6 (25" rolling diameter) and when tested against other cars and mobile radar units I have about a 5mph error on my speedo. When my speedo shows 60 radar units show 55-57mph. I just think of it as insurance against speeding tickets since I'm actually going slower than I usually think I am. /ubbthreads/images/graemlins/grin.gif