Speedo / Tacho Accuracy

hi,
i am pretty new to defenders and have a question regarding the speedo and odometer, the 90 iv'e recently purchased has reasonably over large in diameter tyres , when put against my friends disco the diameter difference is considerable. i think it is rinning somewhere around 750's and are general grabber .
The speedo seems to read almost spot on but the odometer seems to be almost 30% out is this possable. the distance i travel to work is nye on 12 miles in my old car but the 90 reads only 9 miles, when filling up the tank the odometer is saying im only getting around 200 miles to the red from brimming, but the maths says it should be reading around 285.
Could the diameter of the tyres throw the odometer out that much with the mph still being right
any thoughts on this greatfully recieved

Perhaps you have miscalculated? Or your odometer is on the way out? Or the previous owner has been fiddling with the speedo?

have you got a smartphone?? if so theres a number of apps to measure speed/distance, this is by far the easiest comparison.

If odo is out, speed must be too, they work off tha same drive (having said that, mine underreads about 10% but odo is about right.

It's quite funny how much the milage must be out on most defenders.

My speed reads 10/15% out with standard size alloys and tyres, ie 30mph is at 35 and 70mph is at 80/85.

With 150,000 miles on the clock, it could have ran a good 20,000 more! Well, that's assuming the speed and distance are linked??

Stulios said:

It's quite funny how much the milage must be out on most defenders.

My speed reads 10/15% out with standard size alloys and tyres, ie 30mph is at 35 and 70mph is at 80/85.

With 150,000 miles on the clock, it could have ran a good 20,000 more! Well, that's assuming the speed and distance are linked??

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Thats a good point!

Mines the same, 80 on the speedo is actually 70 and 35 on the speedo is 30

mines on standard tyres 235/85s on a 110, 35 is indeed 30, and 64/5 is 56 (presuming the trucks im following are doing 56/my phone is accurate)

All (factory original) speedo's read higher than what the actual speed is - Saves the manufactures being blamed for you getting caught speeding.

joeypica said:

All (factory original) speedo's read higher than what the actual speed is - Saves the manufactures being blamed for you getting caught speeding.

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But not as much as talked about above. If I drive round at 30mph on the speedo I'm well under the speed limit. I can drive at 34/5 on the speedo and still be under.

I have 265 75 tyres and my millage dont match my speedo but wen i go past a speed check it reads spot on

I run on 750x16's and my speedo is to within a couple of mph, although the trip meter on the odo has stopped working!

well i checked the odometer against the trip on my tom tom and i travelled 14.8 miles and the odometer only read 10 miles, calculating that up works out at .7 of a mile out so on a tank full worked ou that on the 200 mile shown on odometer to red line actually equates to 285 miles.
on 40 lts of fuel = 33 mpg which is good in my book.

still troubled by the inaccuracy of the odometer.. i know the speedos always read under but expected the millage to be pretty accurate,, my astra previouse to the 90 was spot on on millage just under read on mph by the usuall 10%
is it possable to get the odometer re calibrated or is it ****ted.!!!