speedo pinion gear selection
speedo is off about 5mph........... @35 it reads 40, @ 55mph it reads 61.
You have two problems;
from 34 to 40 is a 14.38% difference, but
from 55 to 61 is only 10.90%
When a speed-O is out, it is always a linear progression.
When changing rear gears, the new Speed-O tooth count is always the same % difference as the gear% change.
so like going from 3.55s to 3.91s is 3.91/3.55= plus 10.14%, which would require a tooth difference of the same 10.14% .. Since the 3.91s are now gonna spin the driveshaft faster for a given roadspeed, the speed-O will be faster, so you gotta install more teeth to slow it down. So if your 3.55s had a speed-O with xx number of teeth, the 3.91s would require; xx times 1.1014..
The numbers will typically only get you to within about 2.6%.
For instance if your combo requires a 1.5% change at 39 teeth; then 40 is 40/39=1.0256; which is a difference of ~2.6% whereas
38/39 is .9744; a difference of 2.6% again. In either case. your Speed-O will remain out be 2.6 less 1.5= 1.1% ...........
In your case; you are getting two conflicting change requirements, namely 14.38% and 10.9%. So IDK: maybe your cable needs lubricating first; IDK.
