Speedo Wrong by 7mph
 

My seedo recons I'm doing 80 and my sat Nav say's 63 .
I've got the original spec 16" wheels that came with the Connie so how do you recalibrate it?

Thread moved to appropriate forum. Re-direct left in old.

I make that 17mph. :eek:
If it is 7mph that would be 10% out, which many people report as their error.

I would not take the Gps as gospel as they invariably under read. Unless you are in the cruise, at a constant speed, on a level and straight road.

Are you running on 215/55s on the 16 inch wheels?

Maybe the poster should make sure what the situation really is.

Many Rovers over read by about 5 to 7 per cent on speed.

According to my Sat Nav while tootling along at an indicated 70 showing on the speedo of my CDTI I am actually doing 65

It is actually a very precise amount of over read on all cars, derived from the O/S ABS sensor, then fed into the IPK. The IPK then adds a precise +% so as to deliberately over read. The only possible small variations are in tyre size (upto 1mph), or much less likely (because an ABS fault would appear) as fault in the ABS sensor.

There is not as yet a known fix for it, other than getting the IPK with matrix display, reprogrammed by a T4 guru to show the correct speed data in the display. The IPK is fed accurate data, only the analogue speedo is tweaked in software to show the +5% - everything else is fed with correct speed data.

Your GPS can be relied upon to be accurate on a reasonably straight and level road, where you have good reception.

Until the OP confirms what size tyres the car is running and the actually speed discrepancy, not sure anyone will be able to help him further! :shrug:

Personally, Ed's speedo over-reads by about 2 mph at 80 mph, which I'm more than happy with! :}

Is the OKP original,
Is the needle on zero when standing still,
Is tyre size and inflation correct,

Normally I fins most cars versus GPS have a -2 mph differential on flat straight road @ 80 MPH.
Most IPK needles are 4-10% higher than reality
The message centre IPK's with MPH display I have seen are pretty much spot on.

My own IPK displays 72 needle versus 68 Digital versus 70 GPS

Yes there is Harry!

Correcting the speedometer reading in a Rover 75

Simon

As I don't have access to that....

If that method involves adjusting the ABS pulse to the entire IPK, then it will cause the rest of the IPK to under read.