Speedo under reading by quite a bit ...

[ste_brough]

The speedo on my 1.2 clio is under reading by about 5-6mph. What could this be? E.g. I've used GPS to measure my speed and when the car shows 25mph the GPS thing shows 31mph ..... could be dangerous when going through speed cameras!

Any ideas?

Steve

 

[C.slicker]

What tyres do you have fitted mate?

 

[DougClio16v]

GPS is never correct with the car's speed!!! My GPS speedo is always about 5mph out of sync.

What size are your wheels?

 

[ste_brough]

No alloys, just steelies. Not too sure on tyre size ....

I also got my girlfriend to drive at 30 mph in front of me, when I matched her I was doing just over 20mph according to my speedo.

The GPS has been tested in another car and it read under the speedo reading. E.g. car was doing 32mph and GPS showed 30mph. Which is about right giving that most speedos over-read slightly.

 

[edde]

No alloys, just steelies. Not too sure on tyre size ....

I also got my girlfriend to drive at 30 mph in front of me, when I matched her I was doing just over 20mph according to my speedo.

The GPS has been tested in another car and it read under the speedo reading. E.g. car was doing 32mph and GPS showed 30mph. Which is about right giving that most speedos over-read slightly.

GPS sounds like tis wrong cars speedo underread ie 30mph indicated has to under law be at or under 30mph in real world.

if ou car doesn't have ABS as I'd guess then speedo output is form the gearbaox so unlikly its that problem.

If you have ABS then maybe the teeth on the sensors is wrong.

 

[MillerLight]

i woulnd worry. if you get done speedng. swear blind you were not speeding. then get your speedo recalibrated and show it to them and u will get off. (unless you are 10mph over)

 

[black kro]

as said, should be the other way (by law) i.e. optimistic

 

[Djw John]

What tyre size is on the steelies?

 

[Ryan]

I thot GPS was more accurate than speedo's? may be wrong tho

 

[ste_brough]

Yes I think GPS is more accurate than a normal speedo, tyres are 165-65-14. If anything the speedo should over-read.

 

[LEEDASH]

ive also got a 1.2 running on i think ren 19 original allloys 5 spoke and 185 55 r15 tyres,my speedo is always flickering around 20-40mph mark but after that ok,but when speaking to a mechanic he said it prob to do with a cog in the gear box not going around right at low speed,what tyres do you recomend clio peeps ?