speedo

[lamby]

my speedo has always been over by about 15 mph,but have found out that the speedo was calibrated for kmh when new,don,t know if speedo is original but my question is,is it the cluster that does it or the axle sender?

[Brianmoooore]

Not quite sure what you're asking, but AFAIK, all E30s use the same speedo drive parts in the diff., whether they are for a Km/hr market or a M.P.H. one.
The main difference at the speedo end is the scale under the needle, and IIRC, the odometer is changed from one to the other by changing the intermediate gears between the odometer drive motor and the odometer counter wheels. There is a number in very small font on the speedo dial, which is the number of pulses the odometer needs to record one mile or one Km.
All speedos are designed by law to over read - their purpose is not to tell you how fast you are going, but to enable you to avoid breaking speed limits, and this has to hold true for the lowest rolling radius tyres amongst the options for the car, when they are worn down to the limit, and when slip angles are at their highest on wet roads.
There is an adjustable pot. on the speedo circuit board which I've read can be used to correct the reading to some degree.

[lamby]

ok i,ll try another cluster,the car spent time abroad when new and on the options list was speedo calibrated for kmh but mph left on dials? why i don,t know but car reads at kmh speeds on the mph so if it reads 60 i,m doing 75,not the other way.short way of putting it,car is reading kmh speeds but with mph dials