Annoying speedos!

[BigJL]

Nope, not the ones you wear when swimming... the damn thing in the car!

So I know that the speedometers in most cars can be out by a couple of mph, but when checking against the TomTom's speed reading my speedo is out by about 10-12 mph. So at a real GPS 50mph, the car says I'm doing 60+mph.

The LCD one and the needle both say the same thing. I sometimes get a diagnostic code L pop up (erratic road speed sensor).

Wossgaawinon?

J

[s6boy]

Justin it could be the sensor but this usually (in my experience) meant that the speed reading fluctuated a lot when at a steady speed. If the reading is stable at constant speed it could be the rear tyres/ wheels have been upgraded from original build. When I had 255/35's put on to replace 245/40's at the same revs same gear I found I was 2mph slower on my gps. So wheel tyre combinations do have a big effect. Just think of the positives though, increased bragging rights and you'll be safer from getting pulled for speeding!

[Big Al.]

Might be some crud on the sensor, might need resetting or replacement.

BTW they all do that sir!

[glow worm]

Both my BMW, Tuscan and Chim read higher than my TomTom, the faster you go the more difference...2 mph @ 30, 5 @ 50 , 10 @ 100.

[ian_r]

speedo's are always a estimate anyway on cars, never 100% accurate just a guide, hence the tolerences in speed cameras. gps usualy slow as well so its a no win situation, lol.

[BigJL]

Yeah, I thought it was a "They all do that, Sir!" thing... just a bit annoying though not having an accurate reading, especially on the motorway. It'd be nice to get a GPS based sensor somehow attached to the car which the LCD and needle could run off...

Hmmm... I wonder how easy it would be to go about doing that?

[Bodmin]

How close is your Tom Tom (or equivalent device) to the instrument pod as there have been some reported instances of electrical signal interferance causing erratic fault codes to appear.

I am not saying this is the case but it may be worth moving the Tom Tom first & again before buying a speed sensor.

Bodmin

[BigJL]

I've tried moving it and it doesn't make a difference. I wonder if I could rip the GPS out of my old phone and attach it to the car somehow?!