speedo reading

[hefti]

Does a replacement engine and gearbox affect the reading on the speedo. So my speedo says Im doing 60 I was convinced it was.50 downloaded two different GPS speedos for my phone which suggest the speedo is about 10mph out? Is this modern tech's readout correct or should I trust my speedo a bit more?

[itchyfeet]

Speedo comes off the front wheel so no.
incorrect diameter front wheels will affect it.
It was typical of the period to have speedo's reading up to 10% over
GPS will be very accurate, your speedo will not.

[Mocki]

GPS is only accurate on the flat. If you go up or down a steep hill it will be incorrect for a period of time .
However it's lts more accurate than a vw speedo!
Standard t25 wheels with correct tyres ( 14x185) and the correct speedo head for the van will be approx 5mph faster than actual speed at registered 55mph ( so you will be doing 50mph )

[jamesandtheopenroad]

I've got 195's on mine and against a gps mph app, the speedo was pretty much spot on.