Speedo Accuracy

[mike-s]

Hey guys,

I took the GPS to work with me yesterday and today and found that the speedo in my car is spot on up until 120 (i didnt go faster ).

However i discovered this morning that the speedo on my bike is running about 12% slow, i.e. at an indicated 60 i'll be doing a real 53km/h and at 110 i'll be doing a real 98km/h. I know the gps is pretty spot on too. Has anyone else tried to compare gps speeds to the speedometer & how far out were they running?

[Stereo]

Hey guys,

I took the GPS to work with me yesterday and today and found that the speedo in my car is spot on up until 120 (i didnt go faster ).

However i discovered this morning that the speedo on my bike is running about 12% slow, i.e. at an indicated 60 i'll be doing a real 53km/h and at 110 i'll be doing a real 98km/h. I know the gps is pretty spot on too. Has anyone else tried to compare gps speeds to the speedometer & how far out were they running?

The closest I have come is comparing the speed of two bikes..... both my wife and I sat on exactly a hundred.... I then maintained speed and held my thumb up.... her bike indicated 102 at the same speed....

The speed check thingee on the way back from geelong doesnt seem to work on my bike

[mike-s]

well heres my excel spreadsheel & graph. basically i drew a line along both of the "paths" where the points for real speed would be and tweaked the figures until they lined up, the numbers in red are the actual numbers that i used to get the sample..

[MickLC]

Yeah borrowed a GPS of a mate when I bought my speedohealer after putting a 16t front sprocket on. It was about 9% out.

[javaman]

240 indicated is 211 in my GPS terms.

[MadKaw]

Good post Mike...

Next time your mates brag about hitting some insane top speed, just subtract about 10 percent..

I had a bicycle speedo on my 9, as it had no speedo, and that is more accurate than the std ones.. You can't read it while moving too well as the numbers don't change fast enough but it records top speed for later viewing..

[Rusty]

Real vs indicated with my current tyre selection:

40 = 44
50 = 53
60 = 63
70 = 72
80 = 82
100 = 104
110 = 116

[Smitty]

Hey guys,

I took the GPS to work with me yesterday and today and found that the speedo in my car is spot on up until 120 (i didnt go faster ).

However i discovered this morning that the speedo on my bike is running about 12% slow,

Mike
I found the speedo on my GPx was out too...an indicated '100'
was in fact 95kmh and I got that from one of those freeway speed testers
we have in Vic

one of the reasons no-one EVER got booked for speeding when I was ride leader I reckon

and another reason why I disbelieved the speedo at PI..it was off the clock
at the end of the straight

cheers

[mohawk miss]

Apparently my speedo is out by 10k's. This was determined by 2 things:

1- the BF sitting at 110 on the freeway coming back from Canberra and mine saying 120 just to sit even.

2- the radar cop then watching me go past at 120km/h on a double fly buy weekend and being more interested in my mohawk.

[Flakey]

I've gone through a 40kph roadworks zone wif a speed display running, and with the speedo reading dead on 40, it showed 33. I am one down on the front tho.

Prolly explains how I've only gotten 3 tickets in 12 years of m/c riding...

All the speedos are crap...

[Glen]

The Aus standard for speed measuring devices apparently allows for a 10% discrepancy either way, which I think is why you get some buffer on radar detected speeding offences also.

[mike-s]

also explains why i've gone past many many cameras dead "on" or just over the limit and never ever been gotten, i was still UNDER the limit *grin*.

[Maty10]

100 indicated is around 95 real road speed on my thing according to my GPS.

[Smitty]

The Aus standard for speed measuring devices apparently allows for a 10% discrepancy either way, which I think is why you get some buffer on radar detected speeding offences also.

do NOT try that in Victoria
its one of our big beefs with 'greed' cameras

here....
do more than 62 in a sixty zone....and you contribute $125
to the Victorian Treasury
and when you approach 100..don't even think about a 10% variance
103 will have you contributing

[Glen]

The Aus standard for speed measuring devices apparently allows for a 10% discrepancy either way, which I think is why you get some buffer on radar detected speeding offences also.

do NOT try that in Victoria
its one of our big beefs with 'greed' cameras

here....
do more than 62 in a sixty zone....and you contribute $125
to the Victorian Treasury
and when you approach 100..don't even think about a 10% variance
103 will have you contributing

Bastards