S60 speedo accuracy (UK)

I confess.

Yes, my name is Stewart, and I, too, am a marker post counter.

Not on a regular basis, you understand, but once, out curiosity, I counted the posts over an indicated mile on my trip meter.

1. Exactly.

To confirm this, I counted them over 10 miles.

You are obviously much younger than me; I realised straight away that they were at half furlong intervals. There are 8 furlongs (220 yards) to a mile. An odd unit these days, but it equates to the length of a cricket pitch, and one furlong by one furlong is ten acres.

So, half a furlong is 110 yards, which is slightly over 100 meters.

I would hazard a guess that your accuracy with the throttle, with reading the meter while driving, and with the time taken for the meter to respond may all contribute to the extra 3.5% error.

So, who noticed my (ahem) deliberate mistake?

A *chain* (22 yards) is the length of a cricket pitch - a chain is a tenth of a furlong.

Come to Melbourne (or anywhere in Victoria for that matter)Australia. The money hungry incompetents in Spring Street as well as the tunnel visioned Police here allow you a 1-3% leniency on your speed. Pretty much every car - including new ones are out by more than that. And they try to convince us it is in our own interests.....

How did we get idiots like this?

My understanding was that the speedo cannot under read (obviously) but can over read by up to 10% at speeds above 10mph. Therefore, by that your speedo is within tolerance.

David.

I used to quote this 10% rule, too, then I'm sure I discovered it was 5% (don't think I dreamt it, anything's possible). However, the Statutory Instrument 1996 No. 3013 (The Motor Vehicles (Approval) Regulations 1996) which I looked up this morning, actually states:

"For all true speeds of between 25 mph and 70 mph (or the maximum design speed if lower), the difference between the indicated speed and the true speed shall not exceed V/10 + 6.25 mph (where V = the true speed of the vehicle in mph)"

which puts a different perspective on things, and seems to suggest that at at true 60, the speedo could read 72.25mph, which is more like a 20% allowance. Interesting that "10%" seems to be lodged in the mind of most people.

Looks like my error is well within range, but still disappointing in a modern car in my view.

Tim

I was looking for the right one but it wasn't turning up. Well done!

Well, the point is to stop people speeding, driving at an indicated 70 and finding your doing much less isn't much of a problem. I have to say that my Saab compares well between the speedo and a GPS, no more than a couple of mph out by my reckoning (and ability to accurately read the speedo).

David.

Not that this helps much, but a few years ago on a cruise in my '98 V70 to Montreal (500 km away) on the highway which has kilometer markers I tested my accuracy. To get to a true 120 km/hr I had to set the speedo to read 123. At this speed (cruise control) the average speed indicator in the trip computer read exactly 120 after resetting. Also, over 200 km my odometer didn't even vary 0.1 km!

No, metric is a daft system.

Madness.