Speedy Speedo
 

Was driving home last night along a Devonshire B road and noticed the speedo was indicating something over 70mph. No way I thought, so today I had a little drive with my Garmin sat nav in the car which indicated that the speedo was fast by 6/7 mph at a genuine 60mph. That's 10% plus error. Is this normal? anyone else noticed this on their own cars?. My car is on it's original wheels with correct size tyres.

Most manufacturers over read their speedo readouts. It's nothing unusual.

I agree they certainly used to but I thought more modern stuff was reasonably accurate. This sat nav has been used in my Mercedes van and my sons Toyota, both these vehicles are accurate to 1 or 2mph.

Michael,

There's a lengthy thread somewhere on this subject with many diverse views including just whether sat. nav. readings are themselves reliable.

If you have a message centre in your instrument pack, a digital speed display can be activated by T4. This will give you the more "accurate" speed you desire. Since the same signal drives both this digital display and the analogue dial, its likely that the error was deliberate as pab suggests.

Simon

Apparently there is an EU directive that dictates speedo's misread, so in a 30 mph area your speedo says 30 mph but you are doing 26/27 mph.
Lot's of threads on here about it, I now rely on my Sat/Nav for a true reading, after all if it accurately shows when I pass a side road, it must be very accurate at showing my speed.

Lot's of threads on here about it but most of us find, to get an accurate speed reading, let the needle point 5 mph above the speedo marking.

I take your point and see the logic, agree re sat nav but as I said previously, two other cars I checked were almost spot on speed wise.

most speedo's are between 4 and 10% over actual
the digi speedo on the ipk is more accurate but depends on tyre size and pressure..

As tyres wear out they could be anything up to 30mm smaller on the circumference over new tyres. So maybe manufactures build this in. Not sure though

I think I'm right here but if you can pin point just how far out your speedo is, Klarzy can make you a re-calibrated speedo facia.

If I'm wrong I'm sure Klarzy will correct me.:Holly2: