Speed on speedo or road pilot, witch is most accurate??

[Teg_Ben]

I have just installed my 'Road Pilot' in in my car. The speed on the speedo is abot 4-5% higher than that on the RP. I thought these gps speed camera detectors where ment to be spot on?

If they are, then the dc5's speedo is out a fair bit (more than my other cars ive had it in).

Any one else notice this?? :?

 

[Ezza]

Your car speedo doesnt take into account all other factors e.g Tyre pressure, weight. I think your RP should be more accurate

 

[tedg]

GPS

Most cars have put mine in reads 2-3% low. My teg is about 4-5% low..... i blame the conversion box

 

[dan the man]

every car is out roughly

although at 31 my gps says 30 so mine pretty accurate--at 165 im doing 160 so mine must be a very good unit.

Ive also looked into a C4 in traffic at its digital readout on the dash and it was bang on :shock: :lol:

 

[C&S Evo7]

by law your cars speedo must not read over. i.e when you are reading 30 you must be doing under 30.
the standalone gps based systems are accurate but don't update fast enough, the better systems which use a wheel speed input are more accurate.

The speedo is mechanical from the wheels to the drive gear in the gearbox where it turns into an electrical signal, There are lots of factors which affect your speedos reading, weight is not one . Tyre size (how many of you with (wrong) 40 series paradas??) and wear, and of course gearbox mods you may have done final drive or a new diff etc these are likely to have the most influence on the reading

 

[Neil_H]

GPS is the most accurate, as already mentioned speedos are calibrated to under-read (can be up to 10%).

 

[Wardy7]

Can you take your car to a garage to get them to test it or is there somewhere to go to test it as I don't have any gps devices.

Cheers
Wardy

 

[Wardy7]

**edit**
Double post

 

[Duncs]

your car would have a 'speedo' check as part of the ESVA so it will be as stated above really ie fairly accurate but not as GPS.
if you stick to what it says on the clock you are not going to get in trouble are you