Speedo Accuracy

[BigChris]

Well having bought a cup last monday, i haven't really driven it since.

Took it on a decent run up to thorpe park yesterday - great day shame about the weather, and i highly recommend the "stealth" ride it was awesome.

Anyway, on leaving my house a few miles up the road there is a speed camera, 30mph limit.. i went through it as normal at 30mph - (it is one of those "older" spec cameras with the white flash, and the tracking lines in the road) - as far as i am aware they can't do you going towards it? only away from it? correct me if i am wrong)

The camera flashed as i headed towards it, and i was :S to say the least - i thought nothing of it, as i am going 30mph and carried on my way.

Anyway, coming onto the motorway i switched on my GPS (tomtom) to get me to thorpe park, and first thing i noticed was the the speedo reading compared to that of the GPS - it was 7/8mph out across the range - BUT in the wrong direction. When i am doing 30mph on the speedo i am actually doing 37/38mph on the GPS!!!

so you can imagine i began to panic, as i went through a series of spec cameras either in the week, so i could have been totting up points all week.

I have booked my car in with renault tomorrow morning to have it checked out - but can i honestly defend myself?

The car is a 100% standard cup, so its not down to the wheels.

 

[AlexS]

s**t, get it looked at fella, mine over reads substantially compared to the gps.....

 

[DougClio16v]

GPS is usually out about that much. My Navman always says im doing 6ish mph over the limit, but I go by whatever my speedo reads. Speedo's are never 100% accurate anyway and usually no more than a couple of mph out.

 

[BigChris]

indeed, but then my TomTom has been in my impreza, 106, and 306 and it has always been lower than the speedo by 4/5mph... not over...

also the fact the camera flashed sort of suggests a fault somewhere.

 

[McBunny]

gps is close to the real speed than a speedo but usually the speedo over reads

 

[BigChris]

as you say mcbunny, speedo is normally over the actual speed... not under

 

[AlexS]

When was the last MOT and would this be something they should have checked?

 

[BigChris]

fair point there alex, i think it was MOT within the last 3 months; ill have to check this.

 

[RichMcc]

GPS (only tried tomtom) has never matched the speedo of any car Ive driven...

 

[Benbosh]

Hey mate, mine has always been spot on according to tom tom anyway.
hmmm maybe go see jonee mate he may be able to shed some light

 

[Chris n nic]

Something obviously wrong there m8.....I think they are quite accurate usually. About 2mph out (at least at 100mph they seem to be)

Chris

 

[edde]

Legally all speedos have to under read ie 30mph in real life shows as 30mpr or less on the speedo over 70 they don't have to be though but thy are often about 5% under reading.

Check your GPS was accurate.

If the speedo is overreading then you have grounds to claim against Renault for the speedo oint if you get any. Then aain somehting gone wrong either the speedo is wrong (never heard of one) or the gearbox has been chnaged for another one and the speedo outputs worng or you have the wrong tyres etc.

 

[duncansharp]

Legally all speedos have to under read ie 30mph in real life shows as 30mpr or less on the speedo over 70 they don't have to be though but thy are often about 5% under reading.

Check your GPS was accurate.

If the speedo is overreading then you have grounds to claim against Renault for the speedo oint if you get any. Then aain somehting gone wrong either the speedo is wrong (never heard of one) or the gearbox has been chnaged for another one and the speedo outputs worng or you have the wrong tyres etc.

Edde, i thought all speedo had to over-read. ie speedo says 30, actually about 27. Usually 5-10% over isn't it?

 

[edde]

Legally all speedos have to under read ie 30mph in real life shows as 30mpr or less on the speedo over 70 they don't have to be though but thy are often about 5% under reading.

Check your GPS was accurate.

If the speedo is overreading then you have grounds to claim against Renault for the speedo oint if you get any. Then aain somehting gone wrong either the speedo is wrong (never heard of one) or the gearbox has been chnaged for another one and the speedo outputs worng or you have the wrong tyres etc.

Edde, i thought all speedo had to over-read. ie speedo says 30, actually about 27. Usually 5-10% over isn't it?

Yep sorry i mean over not under the rest of the text is right though.

There no rule so long as it reals the speed or faster as said in the text that ok there a legal limit when new.

 

[BigChris]

interesting point made... it had a new gearbox at around 8,000 miles... so maybe thats the problem.

 

[GordonD]

GPSs should be within plus or minus one (mph or km/h) if you are driving at a steady speed. They will give a lagging reading - low if you are acceleratying, high if you are braking - if your are changing speed because they give you the average speed over the last second not the current speed.

Speedos should always read high from the factory. Mine reads high by 4 km/h + 4% of the actual speed.

 

[domjolly]

no no no dont worry fella if an old gatso flashes when it is going towards you it means one of two things it is broken or it is not setup properly i got one by mine and i get flashed all the time but nothing happens and my old mans been doing the same thing (getting it to flash when someone is on the other side of the road)all the time as longs as you where going towards it ya safe