Accurate Odometer

[everitj]

Just somthing that occured to me the other day.. My speedo over reads by quite a bit. Never got round to putting the GPS in it but I would recon it's reading about 10mph over 70-80. Getting worse the faster you get.. Would this mean that the millage on my car is in fact less than it says on the odo..?? It would seem from doing a search on this that it is not that easy to get this problem sorted.. Would a new sender make any difference??

[K4TRV]

Speed and odometer whilst driven from same source are not necessarily displaying same error. That is, there is a hysterisis error in the needle showing the precise measured speed and the odometer reading the distance covered.

Speedos can "over-read" by up to 10% max error, but odo's are usually within 3/5%.

If you've covered 60,000 miles and have a 5% error in over-reading distance, that's about 3K extra.

Is it really worth it to change the sensor under the car above the propshaft at the front of the diff..........or just leave it as it is ?????????

Try your GPS and see what it reads?

Probably TADTS

Trev McM

[Dave 500]

I thought mine was fast then tested it with the help of a GPS and at 70 on the clock the GPS was reading 70.04 not bad. Could be worth a check before ripping the car a part it.

[everitj]

Yeah will check. However i recon it's well over.. I would say 90 indicated is more like 70 thinking about it...

[chris_chim]

Measured my speedo with GPS. It is bang on at 30 but overeads by about 10% at an indicated 80.
The odometer doesn't seem to be affected in the same way (but then it just counts pulses from the gearbox (or diff?) rather than driving a needle.
Don't think changing the sender will make any difference. Changing the speedo might (but more likely wouldn't). It would be cheaper to get the speedo calibrated.