Mileage restricted car deals

[Fogey]

So, we have discussed on here before about the fact that most speedometers are inaccurate. I recall someone saying that they are supposed to be set up so that you will never be going faster than the speed shown on the speedometer. Presumably the issue is the correct measurement of the mileage actually travelled, - so that if the speedometer is saying 50mph you're actually doing 45mph, - so you're doing 45 miles for every 50 miles your mileage clock claims (assuming an error of 10%).

 

On that basis, if you are on a mileage restricted contract, where you pay an additional charge for the mileage over the limit, it is entirely possible that you're paying for mileage you haven't done.

 

Anybody want to correct me on this?

 

Also, those of us who claim mileage for work are presumably over claiming without trying?

[Flexo]

The error applied to the speed reading is deliberate because an over-reading speedometer is OK but an under-reading one isn't. It doesn't necessarily mean that the same error is on the mileage.

[alchresearch]

I've had many cars over the years, but never had one which has had a mileage discrepancy like you describe. If they did, sat navs and mileage values on road signs would be pointless.

[Santo]

The error applied to the speed reading is deliberate because an over-reading speedometer is OK but an under-reading one isn't. It doesn't necessarily mean that the same error is on the mileage.

 

That's my understanding. The speedo is actually a sensor in the transmission rather than measuring true distance divided by time like a sat-nav. And it overreads to account for tyre wear etc.

[Janus]

That's my understanding. The speedo is actually a sensor in the transmission rather than measuring true distance divided by time like a sat-nav. And it overreads to account for tyre wear etc.

 

My bold above

I`ve never come by that aspect. What does it mean?

[sgtkate]

This might answer your question. Older cars they ran off the same system so I suppose it's possible the odometer could be inaccurate, but newer cars with electronics use a different system to measure speed and mileage:

https://www.quora.com/Does-the-speedometer-and-odometer-work-in-tandem

 

Gotta say it's a good question!

[phil752]

My bold above

I`ve never come by that aspect. What does it mean?

 

I see the point as tyres wear from 8mm tread depth to say min legal 1.6mm the diameter of the wheel reduces, so it would have to turn more to travel the same distance. This would intern make the gear box transmission spin faster for given speed. But would this not increase the error in the speed o reading more miles than actually travelled. or have i got the last bit the wrong way round

[Santo]

I see the point as tyres wear from 8mm tread depth to say min legal 1.6mm the diameter of the wheel reduces, so it would have to turn more to travel the same distance. This would intern make the gear box transmission spin faster for given speed. But would this not increase the error in the speed o reading more miles than actually travelled. or have i got the last bit the wrong way round

 

Hmmm...can't say I've ever thought about it....

[alchresearch]

That's my understanding. The speedo is actually a sensor in the transmission

 

It can also be in the ABS sensor.

[highflyer14]

I think your theory is probably right but the "extra" mileage will be very small. How else would finance company's measure mileage for restricted millage contracts ?