I drive a pretty much stock 50 3100 with a broken speedometer. I figure that as long as I don't drive it like I stole it, I won't be speeding excessively. They just don't go that fast.
Yeah im the same way, i switched my speedo and it broke again this time killing the gauge. Ive been given tickets but not for speeding.
I think if you going from 16s to 15s, unless the 15 is the same height, which would be really tall, then your speedo will say your going as faster then you actually are. (reassuring you your not speeding when following the speed limit)
