How much is your speedo out by?

[raf_gti]

I've always known speedo's to over-read but for my iPhone GPS to show 73 whilst speedo shows 80 is taking the piss a little!

FWIW the car is a Puma with correct tyres on.

[kambites]

That's about the same as my Elise.

[Dracoro]

Not tested over 80mph but the speedo on my S2000 is within 1 - 3 mph up to 80. IIRC 77 was an actual 75/74 when I last tested.

That's assuming iPhone GPS and speed camera app (that shows speed as well) are both accurate.

I think my Omega is more inaccurate, as is my wife's 06 Focus. Understandable as both cars are more cheaply made and less well engineered etc.....

Edited by Dracoro on Friday 30th July 10:04

[Robatr0n]

The speedo on the Audi reads 70mph when we're actually doing 62mph.

The speedo on the TVR reads 70mph when we're actually doing 69mph.

[anonymous-user]

My old focus and e46 used to over read by about 4mph at 70+, and about 2-3 mph at around 30 mph.

I'm yet to test my audi.

[mrmr96]

I think it varies from car to car....

[Robatr0n]

mrmr96 said:

I think it varies from car to car....

I think that's the whole point of this thread....

[sday12]

About one and a half foot.

Then I drive an Mini

[extvr]

My TVR Chim 500 speedo read 169 sat nav read 167, not to bad.

[PIGINAWIG]

1 mph over reading at 70mph.

[OMNIO]

Indicated 80mph was 75mph on the tom tom and indicated 30mph was 25mph so mines out by 5mph up to an indicated 80mph

After this the innacuracy increases and an indicated 100mph is actually 92 on the tom tom.

Not too bad on a 12 year old car.


My uncles Cavalier SRi had a speedo innacuracy of 25mph haha!

[raf_gti]

extvr said:

My TVR Chim 500 speedo read 169 sat nav read 167, not to bad.

Very similar to the Puma when I took it on to an airfield

[PIGINAWIG]

extvr said:

My TVR Chim 500 speedo read 169 sat nav read 167, not to bad.

On the same bridge as tallbutbux..........

[extvr]

raf_gti said:

extvr said:

My TVR Chim 500 speedo read 169 sat nav read 167, not to bad.

Very similar to the Puma when I took it on to an airfield

Of course forgot to mention it was an airfield

[CraigyMc]

On my 2.0 TT with standard wheels, speedo ays 73mph, GPS says 70mph.

At 149mph indicated, GPS reads 144mph.

I think wheels/tyres have a lot to do with the inaccuracies. Bigger wheels, with smaller sidewalled tyres, arent always exactly the same circumference as the smaller ones. There will always be variation because of that.

Incidentally, GPS is quite accurate but it doesn't often take hills into account properly.
I see variation when my car has cruise control turned on - the same revs and speedo readout can have varying GPS speeds listed for it if there are hills on the route.

Hands up who can be bothered to hire/purchase some proper datron gear? (nobody? ok.)

C

[Shropshiremike]

CraigyMc said:

Incidentally, GPS is quite accurate but it doesn't often take hills into account properly.
I see variation when my car has cruise control turned on - the same revs and speedo readout can have varying GPS speeds listed for it if there are hills on the route.

Hands up who can be bothered to hire/purchase some proper datron gear? (nobody? ok.)

C

That's the important point though - is GPS on Tomtoms, I-phones etc accurate? I presume it's more accurate than a lot of speedos.

Garage 419 tested the Dynolicious I-phone app against 'proper' timing gear but it would be good to see a UK mag like EVO do the same thing with their V-box or whatever

[10JH]

I reckon a mag doing a proper test with a v-box would be quite interesting. Probably not to most people though....

[y2blade]

my D5 and T5 both show 130 when the GPS is showing 127

all my Volvos speedos have been very accurate
the least accurate I've had were the Vauxhalls (surprise surprise)..I didn't have GPS back then but there was no was a Mk3 Cavalier 2litre CDI was really able to do 140 ditto Mk2 Cavalier SRI130 seeing the same sort of speeds


edit for spelling

Edited by y2blade on Friday 30th July 10:44

[Shropshiremike]

10JH said:

I reckon a mag doing a proper test with a v-box would be quite interesting. Probably not to most people though....

I would imagine one of the journos at EVO would have an I-phone and could clamp it in a cradle whilst figuring a car with proper timing gear.
Doesn't have to be an article in itself....just a little 1/4 page column as an add-on

[sebhaque]

I got the gauges recalibrated in my Impreza as originally 70mph indicated was 62mph. For a little while I did wonder why everybody was travelling so fast. They're now 1-2mph under until >100 leptons, where they start to under-read further (~5mph).