MPH accuracy?

Tyre wear makes less difference than the tolerance allowed by regs - and in any case only ever makes the speedo read higher. The actual error between a new and barely legal tyre is about 2%. Obviously this does depend on the tyre size, but it's good enough for jazz.

Other variables would presumably be tyre pressure versus loading, and speed.

Chris

I'm sure they all make a minor difference. But in general will make the speedo read higher than true. So even less excuse for allowing such a tolerance at manufacture. It may have been needed in the days of eddy current speedos - although some makers managed to make those pretty accurate too - but is just plain silly in these days of pulse counting types. And if the odometer has a similar error, you'll be servicing the car earlier than needed. And calculating better MPG than it actually is achieving. ;-)

Going by my sat-nav on a number of occasions, the speedo on my Focus is only just legal. It shows 33 @ 30, with a similar percentage error throughout the range.

The odometer is actually pretty much spot-on.

Chris

Yes - this is often the case. Which means the maker deliberately has the speedo reading high. Think Ford have always been one of the worst offenders. Autocar used to give true speed against readings - dunno if they still do. And some makers were consistently worse than others.

The Nokia Lumia app almost always knows the right speed limit, and bleeps at you if exceeded. Even in motorway roadworks it is almost as easy to check the phone as the speedo, provided you have a suitable mount.

When I was using a lot of hire cars, I used to check speedos against motorway kilometer posts with a stopwatch (conditions permitting: drive at 120 kph, 30 seconds per km is correct, 33 seconds is 10% slow). It was evident that Fords were more accurate than anything else, usually about 3%. The same seems to be true using GPS.

That app sounds useful. I'm looking for my first smartphone, and am homing in on a Nokia Lumia; without too much elaboration of an off-topic subject, what is your opinion of it in less than 5000 words. ;-)

I have an older Lumia 710. As a phone it does all the phone things - SMS and Loudspeaker well enough. As a smartphone, it is an old Windows Phone

Nokia Drive is brilliant. You can download the maps so you can use the GPS with no data or phone connection, it has the speed limits warning as described Newshound, and although I have only ever used it a handful of times, it works very painlessly indeed.

Another nice thing about smartphones in the car is that they can be used for music from MP3 files (if your car doesn't have this feature already incorporated), and if you have a good data allowance, you can get all sorts of weird and wonderful internet radio stations on the move!

Just whatever you do, no matter what smart phone you get, make sure you get an in-car charger for it, because the battery life is as dreadful as you'd expect for a pocket computer ;)

Yes, should have said that. Screen does eat the amps. I leave GPS and bluetooth on by default, having a GPS tracker logging three hour walks does not deplete the battery significantly.

Thanks, guys. I have good walk logging using a SatMap, but it rankles that my daughters seem to use their iPhones to keep in close touch over

My first Nokia Lumia phone, a 925, has a bug - the GPS keeps cutting out. So my speed ranged from almost stationary to about 135 mph. And maybe jumped half a mile or turned 180 degrees around. However, when it worked, it was good.

The 1520 I now have is far better and I very much like the Nokia software. If they make it available on Android/IOS (and rumour suggests that is a possibility), and their ability to re-route based on traffic is good, then I would happily pay for it on my Android phone - maybe even partner's IOS phone.

I have always tried to check speedo accuracy. They seem to have got worse over the years! Best I had was a Saab 900 - almost spot on.

At least some 925s have problems - like I mentioned in another post, GPS going AWOL for a few seconds every so often. Some have reported extremely poor battery life though mine was OK-ish.

The 1520 is a beast. Far better than the 925. No hardware issues (unless you fall onto it on the pavement when the screen cracks). Too big for some but it makes using it much nicer. Good battery life - only GPS seems to really have a big impact.

But my Nexus 7 (which I tether to my 925, 1520 or Galaxy S2 depending which one I have with me) is even nicer.

Does that mean the milometer also reads 7% over?

I have a Nexus 7, but I won't be carrying it on walks. The SatMap with a 60k x 60k map card covers most walks we do.

No.