[ALfemale]

My speedometer is black pinned at 10mph and I believe the Tach is black pinned at 1000 rpms as well (memory is faulty and not able to look at it right now) The tach runs true, but not the speedometer. From reading above messages are all speedometers wrong then? I know the Spider is roughly 10mph (I figure since it starts from 10mph that it's roughly 10mph even with the 16" rims) but starting to have misgivings when I was PASSED by two OTHER yahoos when I thought I was going about 92/93mph. So now I am wondering if it isn't maybe 20mph off. Sure thought I was going faster. Maybe will have to do the cell phone chase car thing as well to get a more accurate idea. What is the formula for tach/speed ? 3000 rpms is roughly 60 mph, yes?