The speedo drive pinion has to match the diameter and tooth pitch of the drive in the gearbox, it is a myth that you can fit different coloured pinions with different numbers of teeth into a box to adjust the reading on the speedo. Our 8v with standard gearbox has a red drive pinion and has had 120 & 160 clocks in without issue. You can fit a different colour pinion but it must have the same diameter and number of teeth and pitch as the standard red one or it will get mashed up.