I was just thinking....

jojo

jojo

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....with regards to the 10% out rule on our speedometers. If the speed is approx. 10% out, then is the mileage 10% out, since the the signal for the odometer is likely to be the same one as the speedo right? So a car that has travelled 11k miles, could actually be infact a 10k miles car, no?!
This in effect would have ruined my mpg figures I've been calculating for the last few years also, so anyone else got an opinion on this? :jump:

Now where did I puy my medication? :tocktock:
 
audi upgrades
It makse sense but not what i wanted to read on a friday afternoon as my head hurts....
 
jojo said:
....with regards to the 10% out rule on our speedometers. If the speed is approx. 10% out, then is the mileage 10% out, since the the signal for the odometer is likely to be the same one as the speedo right? So a car that has travelled 11k miles, could actually be infact a 10k miles car, no?!
This in effect would have ruined my mpg figures I've been calculating for the last few years also, so anyone else got an opinion on this? :jump:

Now where did I puy my medication? :tocktock:
Click to expand...

...Only made worse by wheels that throw the speedo reading out even further...
 
You've got to include the tyre wear in the calculation - wearing down from 8mm tread to 2mm will alter the wheel circumference and make it over read even more....
 
No the over reading is calibrated into the speedo itself not the speed sensor, i.e. if you sit at a constant 70mph on the motorway, then reset the trip computer to show average mph, it'll actually show you a lower more accurate reading, so the mileage is pretty accurate, only affected by incorrect wheel/tyre size.
 
My satnav said 142 when my speedo said 146 so the regs may say you've got 10% but in fact your speedo is probably more accurate than that. ****** Germans and their engineering, it has to be right. Even my FJ12 clocked 496 miles and the sat nav said 487, and thats a 1988 model with a cable driven speedo off the front wheel.
 
jcs356 said:
You've got to include the tyre wear in the calculation - wearing down from 8mm tread to 2mm will alter the wheel circumference and make it over read even more....
Click to expand...

Now we are talking, more factors to look out for - get in there! :)
 
AndyMac said:
No the over reading is calibrated into the speedo itself not the speed sensor, i.e. if you sit at a constant 70mph on the motorway, then reset the trip computer to show average mph, it'll actually show you a lower more accurate reading, so the mileage is pretty accurate, only affected by incorrect wheel/tyre size.
Click to expand...

Just to make this thread last a bit longer Andy, IS THAT A FACT?
 
fjtwelve said:
Even my FJ12 clocked 496 miles and the sat nav said 487, and thats a 1988 model with a cable driven speedo off the front wheel.
Click to expand...

So in 496 miles, you spent 13 or them wheel spinning or doing doughnuts(or is it donuts?)?
 
bravepilot said:
Jojo, if you're worried about it, you should use the Honda Jazz that you have more often! My Audi is 5mph out, but the Jazz is spot on! :respekt:
Click to expand...

LOL! It's my Honda Jazz that got me thinking, as it's an Import model called a Honda Fit! It has some kind of chip thing at the back of the clock to reduce the KM signal into MPH signal, but it's still a good 10% out, as I was following the missus at a constant 70mph on her speedo, but mine was around the 77-78 mark, tried it at 80ish also, and still 10% out!
 
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