Speedo Reading Fast

[hawkeye357]

Hi all, I think this question has been talked abought before but is it possable to recalibrate the speedo, I have just replaced the little black box behind the glove box,( thanks to the fourum for the infomation on how to do this), and now the speedo is reading between 6-8 mph faster acording to my tomtom and a speed board near my brothers. a couple of mph you can live with but 6-8 mph is a bit high.

[Doggy]

Now this is speculation, so no gaurantees.

Your car being a D8, I'm assuming the black box gives out an analogue signal proportional to speed,
(i.e. 0 - 5 volts = 0 - 130 mph or something similar).

If this is the case, & you can identify the connections, (I can't - don't have a D8 diagram), it should be possible to connect a high-value, (say 100k ohm), potentiometer across signal ouptput from the black box & ground. You can then connect your speedo between the wiper of the pot and ground - this should give you the ability to adjust the speedo reading (downwards only) to the required value.

(If anbody knows this is impractical, PLEASE SAY SO)

[peugeot406rapier]

just do 22-24 mph through town..much easier

[poddack]

leave it, Peugeot speedo's and fuels gauges aren't renowned for their accuracy

[DiscoPol]

you think the pug speedos is bad, I have a BMW 740 as my real car and it has never in its life read anywhere near what the sat nav says im doing

even with a change of wheels up to 18s, it still reads about 7% out, always up though, which has saved my bacon on a couple of occasions
i would say live with it and be happy in the knowledge that when you do nip past a camera or waiting plod it might just save you a few quid and those precious points

after all you know how far out it is, might just be worth checking on an ongoing basis with the sat nav though

[mjb]

Virtually all car speedos tend to read 5-10% high, 406s are set to just shy of 10%, the VAGs I've driven tend to be 6%

This is an intentional thing by the manufacturers - the 406 is aware of exactly how fast it's going (presuming no huge wheels or a defective sensor) and the D9s are able to put the needle exactly where they want on the dial with impressive speed and precision (evident when doing a self-test)

[DiscoPol]

Found this on a mooch about

"The European regulation, ECE-R 39, is more concise, stating essentially that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70). Never low. Not even if somebody swaps a big set of 285/35R-18s for stock 255/45R-16s.

There's your explanation of high-reading European speedometers, with the highest readings on Porsches and BMWs"

Explains a lot, so your speedo may be out but its not unusual in any way at all, if it wasnt for sat nav i dont think many of us would even know

[DaiRees]

the 406 is aware of exactly how fast it's going (presuming no huge wheels or a defective sensor) and the D9s are able to put the needle exactly where they want on the dial with impressive speed and precision (evident when doing a self-test)

That answers something for me, I always wondered why the speedo on mine reads 33 when the sat-nav reads 30 and then 73 when the sat-nav reads 70, always assumed that the reading (and therefore the error) would be linear, but apparently not! It seems that the car knows to tell me actual +3 mph.... clever!

Of course this means that I drive everywhere at speed limit +3

[swiss]

OK, you probably won't like this but just so you have it as an option:

Split the dash down so you expose the dial faces. Pull the needle rest from the speedo, then pull the needle and pop it back on a little further anticlockwise. Head out with your satnav and check the correlation between computer and gauge. Keep fiddling with it until you get it close enough for you.