I've been wondering about my tach & speedo since I got it on the road. I
think my tach indicates about 500RPM less than true engine speed. Along
those same line, I don't trust my speedo either (yet) and plan to take both
to a speedometer shop next week. I just drive side streets & keep up with
traffic so it hasn't been an issue yet.
Anyway, I crunched all of the figures and here's what I got:
SPEED TACH
35 2173
45 2794
55 3415
65 4036
75 4657
This is based on 4th gear (1:1) and 4.11:1 rear end on 22.25" diameter tires
which is about what my Brazilian made "Deluxe Classic" 155/80R13s are. (I
think Deluxe Classic is Portuguese for Darn Cheap....) Slightly larger
tires yield slightly lower RPM for a given speed or slightly higher speed
for a given RPM.
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