Speedo Accuracy

[Donut]

As I haven't yet got round to fitting a sat nav, to find out how whether the standard speedo is accurate or not, is anyone able to advise on what their speedo reads compared to their sat nav at various speeds (mph or kmh - as can easily convert your figures from what you have to what I need (mph in my case)).

 

[DeadHead]

It's not that accurate, not compared to the Tomtom. I would say at least 10%-12% out at some speeds.

eg

Display Actual
45mph 40mph
67mph 60mph
34mph 30mph

 

[Anthony]

I find most speedo's are set to about 10% under. So that 33mph you did past the police car hidden around the blind corner clocks you at 30.

 

[Ralph]

Mine is 2/3 mph fast anywhere this side of 3 figure speeds which is better
than my last Suzuki that was about 3 mph fast at 30 but 7 at 70 the mt
is 2/3 fast anywhere.

 

[Donut]

It's not that accurate, not compared to the Tomtom. I would say at least 10%-12% out at some speeds.

eg

Display Actual
45mph 40mph
67mph 60mph
34mph 30mph

While that is good in some ways (i.e. less likely to get pulled for an indicated few miles "over" the limit) it's less good if it is more than 10% as that would make the speedo illegal I believe. It always used to be the case that they may not under-read at all but may over-read by as much as 10% - so 12% would be a case for a re-call to get them sorted. Does however make my indicated 132mph (closed - private road of course) less impressive if it may not have even been a true 120mph!!!!

 

[Gaulois]

Mine is pretty accurate. At a study, flat stretch of road with 70mph on the dash, the GPS showed 68/69mph.

 

[pauljr]

Mine seems to be just about dead on, much better than my BMW which reads 5-6 mph high.

 

[addy]

Checked my garmin zumo a few times while out today and 43 mph was 40, 70 mph was 65.

So are sat nav speedo's very accurate?

 

[Donut]

Interesting that the US speedos seem to be more accurate than the UK ones. Maybe there is a different tolerance on either side of the pond. I hope to get a sat nav wired in soon to find out how good/bad mine is and then maybe get/fit a speedo healer (HealTech Electronics Ltd.) if it's too far out.

 

[Ralph]

Sat nav's are about 1/10th of a MPH out so very accurate.

 

[jeppebm]

why do you think the GPS is more precise than the speedo? - A gps has some lag and when inputs are delayed, pinpoints used to measure will calculate a speed from A to B being faster than real speed cause of the lag.

Why is the general opinion that gps is just a fact matter?

 

[sdrio]

Haven't sat-navved mine, but usually when I pass one of those smiley face things that tell you how fast you're going, it's within 1 mph.

Whether those are accurate or not I don't know.

OK, so they're more usually frowny face things when I pass them, but that's a different story.

 

[Donut]

As I haven't yet got round to fitting a sat nav, to find out how whether the standard speedo is accurate or not, is anyone able to advise on what their speedo reads compared to their sat nav at various speeds (mph or kmh - as can easily convert your figures from what you have to what I need (mph in my case)).

Looks like mine is about 8% out so seeing as I prefer to have a much more accurate speedo I'll be looking to invest in a Speedo-healer to remove most/all of the error.

Speedo Healer V4