I’m a bit concerned your magnets maybe too small to generate enough flux to fully saturate the speedo poles.
But maybe it will work
If your Speedo still reads low when you are done I would suggest larger magnets
You can’t go too big, the poles have to reach their saturation point.
That and adding the nuts and metal to complete the flux path adds reluctance to the circuit which also reduces available flux.
Larger magnets bridged pole to pole is what worked for me.
-s
