Message Forums

It is very difficult to be sure about your own speed, let alone somebody else's.

I drove my wife's car to Birmingham yesterday,so I transferred my Tomtom to her car for the journey, I set off at a steady 70mph according to the speedo when i checked the speed on the Tomtom it registered 63mph, In my own car the difference is 2mph. Now whether either reading is accurate is debatable, but the fact remains that 70 mph in her car is considerably slower than 70mph in mine.

Checking speed vs speedo is easy in France. On the autoroute, set cruise control and count km posts with a stop watch, the posts are numbered every 100m decimal 1, 2 ,3 etc. The more kms covered at fixed speed, the more accurate the calc. Possible in France when there is no other traffic in sight. Usually shows speedo reads 5 to 8 % high depending on vehicle.

Never found a stretch of road in UK to keep constant speed for long enough to matter. Usually concentrate on driving to suit conditions, both in front, and behind.

FM

Quote: Originally posted by michael on 25/2/2009

---

in engineering school was always taught that a speedometer was celebrated at plus and minus 5% error.that is many many years ago they are possibly more accurate now.i approached a sign yesterday that gives your speed,sign said 27 when i looked it was 30 on the speedometer.

---

Hi

This post has generated a lot of intrest as i thought it would but what surprises me is most people seem to be talking about the speedo and assume it was wrong now im not going to get in to argument about it but if your towing a caravan and your overtaking a few cars then i think you would know your speeding even if not doing 80 and if his speedo was saying 60 then i better get mine fixed lol.

Gerry