Speedo Error

[OSSI]

Hi guys
I have read here in several posts about the Speedo error.
I understand that the speedo is out about 10 ks

What I would like to know is the effective speed 10 ks more or less then the speedo shows

I have Toyo AT 255 /70/16

Thanks for your help

 

[Old.Tony]

It's not a flat 10km/h, generally it's a percentage and seems to read - on standard-sized tyres like yours - about 10% higher than you're actually travelling. Your odometer and tripmeter will be very close to accurate (on those tyres).

For fairly accurate speed indication, just use a GPS.

 

[OSSI]

It's not a flat 10km/h, generally it's a percentage and seems to read - on standard-sized tyres like yours - about 10% higher than you're actually travelling. Your odometer and tripmeter will be very close to accurate (on those tyres).

For fairly accurate speed indication, just use a GPS.

I use a GPS every day, even on way to work. So you would trust the GPS over the Speedo ??

 

[OSSI]

At the moment the difference between the Speedo and the GPS is about 4 to 5 ks

 

[Old.Tony]

Absolutely. The GPS is a computerised device calculating your rate of motion based on your position sampled about every second. It is accurate to within 1%.

I have had 3 GPS devices in my car (one in dash, two on the windscreen) to compare them and have driven through a radar trap. Each device indicated the same speed as the radar equipment (which is also calibrated to within a 1% margin of error).

 

[Krankin]

So you would trust the GPS over the Speedo ??

Big fat YES

 

[OSSI]

Thanks guys
From now I gonna set my cruise control at the GPS Speed

Thanks four your help

 

[OSSI]

By the way, my Avatar doesn't really show it (too small)

 

[KraftyPg]

For those who don't use a GPS all the time things like a Scangauge (or the many other tools you can get for an OBD port) will give you accurate speedo readings also.

 

[Krankin]

For those who don't use a GPS all the time things like a Scangauge (or the many other tools you can get for an OBD port) will give you accurate speedo readings also.

Yes,
my SG shows 2-3 klm/h higher than true but that is what I would like my Fn $35,000 speedo to read.
Gives you a little bit of margin out on the road.





.

 

[KraftyPg]

My SG isn't that far out, it's within about 1k of my GPS.

 

[Krankin]

might be just the different vehicle??????

 

[KraftyPg]

Yeah your vehicle is different to mine

 

[Krankin]

Yeah your vehicle is different to mine

bloody 'cow cocky mobile'

 

[KraftyPg]

Yeah and this cow cocky (with his mobile) is off to the farm with about 1.5 tones of **** wood in the back, just how I managed to collect so much crappy wood at home is beyond me but it's going to be a rip roaring bonnie out there this arvo....marshmallows at the ready.

 

[Old.Tony]

For everyone reading about the ScanGauge's accuracy: this is only with standard tyres. The ECU is programmed with the standard tyre in mind - one revolution does 2398mm of travel.

Larger tyres will travel further for each revolution and thus even the ScanGauge will be inaccurate.

No matter what tyres you have, your GPS unit will be within 1% of your actual speed except in the following conditions:

* You are in a deep valley or at the foot of a south-facing cliff

* You are underground

* You are in the middle of an area with many tall buildings

* Military activities have caused the bulk of the geostationary satellites' bandwidth to be allocated to the armed forces. This may not be the case now, but in the early days we'd see accuracy to within 10m, but when the military had certain exercises or had gone into high alert (eg post 9/11) your GPS accuracy was within 100m.

Sometimes we've had ours upset by big storms too.

 

[OSSI]

But generally speaking always trust your GPS over your Speedo ???

 

[KraftyPg]

Well yeah generally, but like all technology it can be wrong, as opposed to a speedo that is always wrong.

 

[Rich64]

I too have discovered that my speedo is about 8% out, ( reading high) I intend to try and rectify that when I next change tyres, until then there is always the GPS..

 

[Aussie Frontier]

Actually Tony you can adjust the reading on Scangauge to allow for changed tyres.I have my scangauge reading pretty much same as GPS .I just have to remember my 17" wheels are a 6% variation and my 16" are 5% variation