Join Date: 15th April 2006
Thanked 178 Times in 24 Posts
Yep. It's actually a common issue with all cars.
You notice it more with a digital read out more than a dial for obvious reasons.
The satnav speeds are definitely more accurate, but do suffer from a little bit of lag (around a second usually).
It's not a constant overreading either, as you point out. It's generally done deliberately so to lower the risk of the user speeding. If you ask people who have "got done" for speeding, they almost always say they thought they were going faster than the official reading.
My view on this is that it's a good thing - most people don't know about their cars overreading (and yes, I do realise that some speedos don't overread at all or very much) and it probably saves a few people some points.
I'm a big believer in not speeding, but even I will do 32 in a 30, 43 in a 40, 54 in a 50, 65 in a 60, and 76 in a 70 because I know I'm only doing the actual speed limit at these boundaries.
Of course, you have also remember that you're hardly ever going to "get done" for 10% over the limit, anyway, so there's usually an extra couple of mph grace on top of the overreading.
I think, overall this gives you the flexibility to do a bit more than the "speed limit" without breaking the law. We all know how easy it is (especially in the petrol) to go a bit over a specific speed as you pull away or whatever.