Actual speed/distance covered

I have a FL1 '99 with 215/65/16 wheels on.

I know my speedo doesn't read correctly, can anybody tell me how far it's out?

All speedos read differently, there is no one figure for them all.

I used my GPS/Sat Nav to find the correct speedo reading of my boat versus the onboard speedo.

If I do that I can work out how many % my milometer is out as well!
Cheers for that Bigeeeee.

biggeeeee is right, we don't know how inaccurate anyones' speedo is when it left the factory.

I also use my Sat-Nav as a check on my speedo.

I know that with the tyres I have on at the moment the speedo reads 3mph slow at 70mph - I'm only doing 67mph.

There is a website with a handy calc. that tells you what % difference you will have by changing wheel / tyre size and how far out it will be in mph.

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Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter. Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size. Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits.

European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers http://en.wikipedia.org/wiki/Speedometer#cite_note-3are similar to the UNECE regulation in that they specify that:

• The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
• The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.

The standards specify both the limits on accuracy and many of the details of how it should be measured during the approvals process, for example that the test measurements should be made (for most vehicles) at 40, 80 and 120 km/h, and at a particular ambient temperature. There are slight differences between the different standards, for example in the minimum accuracy of the equipment measuring the true speed of the vehicle.
The UNECE regulation relaxes the requirements for vehicles mass produced following type approval. At Conformity of Production Audits the upper limit on indicated speed is increased to 110 percent plus 6 km/h for cars, buses, trucks and similar vehicles, and 110 percent plus 8 km/h for two or three wheeled vehicles which have a maximum speed above 50 km/h (or a cylinder capacity,

Thanks for the comprehensive explaination dwabbit i, sort of, always thought that would be the case.
I'm just trying to get a better mpg figure for my motor, it does follow that if the speedo is inaccurate the milometer will be too! Is this the case?

SV thanks I went on that site before but I don't know the original tyre diameter that LR used when setting up the speedo

Original tyre options were 195/80 R15 or 215/65 R16 which have a rolling radius of 215.20cm & 215.48 cm respectively so are as near as dammit the same size.....

As far as makes sense the speedo would be callibrated the same for the two sizes to save costs on needing to produce/source 2 seperate units.

Basically I reckon your speedo & odometer will be pretty much right as far as the factory is concerned, allowing of course for about 10% speedo error.... Hope that makes sense

Makes sense to me,but will the odometer also have this 10%?
cheers RED 109 CSW

Always know about the speed part but never thought about the mileage covered.

I'd have thought if the sensor is the same then yes that would be out as well.

You could do a test using gps to show covered distance say 5 miles and set the trip to 0 first. Then compare the two.


KevStorr WM06 WA039

Cheers Vinnie i'll have to try that.
It may not change the mpg figure as much as I originally thought but will be nice to know the exact reading.