Speedos..

Not,not the trunks prefered by Tom Dailey or Saville,but the ones in Bay window vans...Are they accurate? or are they over, or under?...Is 30 mph really 30mph, for example...?

 

Mine is spot on when stationary and in reverse...the trouble only starts when moving forward.

Serious though mine is a couple of mph out when compared to sat nav indication.

 

It depends on what the circumference of your front wheels are as it's driven from wheel rotations.

Mine is pretty much spot on compated to my sat nav.

 

Unlikely, unless you're lucky. Probably overeads by 10%. If you change your wheel diameter or profile, it all goes out the window.

 

Well , does depend ... on say ,wheel size (perhaps tyres?)is 30mph ever 30mph ?very much doubt it, so many variables thou would find it doleful to argue point with plod, i.e. someone else moving adjacent to yourself at 30mph? or as a anything moving thru space will keep moving in an uniform speed/direction until acted upon by a.n. other object,also whilst the speed of light is absolute ,if in the physical world anything in the physical world got to be close to the speed of light it would be seriously flat and seriously heavy so no chance of speed of light there then eh!for myself , I work speed limit on basis everyone is overtaking me so therefore I must be 1mph from a speed ticket.(at least)o.k.a.>trust a gauge ? no chance >not even the fuel gauge , in fact cancel that >especially the fuel gauge.

 

My tom tom is always at least 5mph ahead.

 

The speedo on my bay is more accurate than the one in my 2002 Ibiza. It's pretty much bang on at 30mph, but its about 2-3mph out at 60. My Ibiza is 10% out at all speeds.

 

As judged by one of those speed cameras that shows your approaching speed, mine reads about 35 when the camera says 30 - I have standard wheels / tyres.

 

Mine is a few mph optimistic. Doesn't seem to be a %, more just 3-4mph.

 

It's not going to be bang on is it? It reads 10mph when you're stationary.

 

I'd never noticed that

 

Mine gets progressively inaccurate the faster I go. Checked with the sat nav at 30 the speedo reads 27. At 50 the speedo reads 43. At 70 the speedo reads 63, and when the sat nav shows 90 the silly speedo show 81. Couldn't check it any faster because I had some wheel imbalance between 90 and 95 so I eased off and I'll try again after I've had the wheels balanced.

 

So how accurate are sat nav speeds ?

 

Very.

 

Very what ? 1-2 % 5-10 %. . Both my Audi and seat leon read about 5 mph difference from sat nav ?

 

Much better than that, I'd think, depending on the algorithms in the satnav. They'd calculate the distance between two accurate locations, say every second, together with how long it took you to get there.

All car speedos tend to err on the optimistic side - I think they're allowed 10% over reading. If they under read, even electronic ones, could lead to all kinds of legal probs. There's also tyre wear, etc that may affect it. A satnav neither knows nor cares about such things.

 

Hmm...interesting...the coppers clocked me at 36 last friday,but i was coming out of a real slow corner and im sure i was doing under 30,just,as that corner is too fast to go over it... ...

 

Mine just points to 80 kph. Don't matter what I'm doing, cruising round the town, speeding down the motor way or parked on my drive. To be fair I don't think mine works

 

^^^ Helpful...