Speedometers

[JeffL]

I've always been LED to believe that car manufacturers set speedometers to read 10% higher than the car is actually travelling. Reason being they don't want to get sued by a driver who is fined for exceeding the speed limit when said driver has relied on the speedometer. Now that maybe bunkum, I don't know, it's just what I was told many years ago! So I thought it a good idea to get opinions, preferably fact, on the situation and what better place than the 'wise level-headed' Lexus owners on this site! I was prompted to ask as I just came across a discussion elsewhere on speedometers and the following was stated.

Every speedometer is different. Some speedometers read exactly true and some speedometers over-read. If the speedometer overreads it can do so by any amount it is set to. Some are set to overread by a couple of percent, others 5%, 10% or even more. Legally speedometers can overread by up to 10% plus a few mph on top - quite a significant extent.  In reality most modern speedometers overread by some amount but less than 10%. Some by up to or over 10%. Some are entirely accurate .

I'm not advocating here that we exceed the speed limit, just that If we are allowed to do say 70 on a motorway, is it reasonable for us to travel at a speed where the speedometer is reading 77 or 80?

[Guest]

Yes

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[NemesisUK]

As your quoted text reads, some speedometers can be quite accurate, some less so and it can be significantly variable throughout any one manufacturer's models. That said I think it risky to travel at the speeds you suggest as being reasonable.

[Herbie]

Have a read of this:

https://www.thecarexpert.co.uk/how-accurate-is-a-car-speedometer/

[Guest]

5 hours ago, NemesisUK said:

As your quoted text reads, some speedometers can be quite accurate, some less so and it can be significantly variable throughout any one manufacturer's models. That said I think it risky to travel at the speeds you suggest as being reasonable.

Risky? Reasonable?

[NemesisUK]

1 hour ago, Comedian said:

Risky? Reasonable?

It's not difficult..

Drive to the reading on the speedometer, don't try second (GPS) guessing it. The time 'saved'  would be insignificant.

Speed limits are a limit, not a target. 

 

[Guest]

10 hours ago, NemesisUK said:

It's not difficult..

Drive to the reading on the speedometer, don't try second (GPS) guessing it. The time 'saved'  would be insignificant.

Speed limits are a limit, not a target. 

 

Sorry dad 

 

[ColinBarber]

On 12/17/2018 at 3:30 PM, JeffL said:

Every speedometer is different. Some speedometers read exactly true

Not on Toyota/Lexus UK vehicles, all service manuals I've seen state that at 60 mph, if the speedo reads 60 mph then it is faulty and should be replaced.