Speedo inaccurate ?????

Hi guys,
Drove past an automatic radar "your speed is (whatever)" boxes today and it significantly disagreed with my speedo. my speedo read 70 the box read 64. 10% out !!!

I've just bought this old GQ y20 safari.
Could someone in the past have...
1/ put in the wrong instrument cluster?
2/ put in the wrong auto transmission?
3/ put in the wrong diffy?
4/ put in the wrong transfer case?
5/ put on the wrong tyres?
6/ All of the above?
From my basic understanding of the speedo I doubt if it would read high. Low perhaps, but not high.

Any comments please.

Thanks
Dave

I wouldnt trust the box thingy mate ive had the same type of thing before. best bet is use (if ya have1 or borrow) a GPS should set ya straight

speaking of gps has anyone had experence with hema gps or iphone vms gps

Quote:

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Originally Posted by CptClinac

Hi guys,
Drove past an automatic radar "your speed is (whatever)" boxes today and it significantly disagreed with my speedo. my speedo read 70 the box read 64. 10% out !!!

I've just bought this old GQ y20 safari.
Could someone in the past have...
1/ put in the wrong instrument cluster?
2/ put in the wrong auto transmission?
3/ put in the wrong diffy?
4/ put in the wrong transfer case?
5/ put on the wrong tyres?
6/ All of the above?
From my basic understanding of the speedo I doubt if it would read high. Low perhaps, but not high.

Any comments please.

Thanks
Dave

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Hi Dave, It may be the tyre size. There is a thread with a few links to tyre calculating sites. http://www.nissanpatrol.com.au/forum...onversion-Tool
Lets you calculate how much your speedo is out when you change tyre sizes

Quote:

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Originally Posted by growlers71gq

I wouldnt trust the box thingy mate ive had the same type of thing before. best bet is use (if ya have1 or borrow) a GPS should set ya straight

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I went past one of those things I was doing 100 and it said I was doing 14....... no joke

Quote:

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Originally Posted by Ben-e-boy

I went past one of those things I was doing 100 and it said I was doing 14....... no joke

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That happens with 16" tyres!!!! LMFAO

There is a fudge factor built into speedos - commonly 5% to help us stay legal.

Change tyre diametre and things get interesting :-) I've checked mine against a few GPS units, and its out by the same as yours - Mav on 10Rs.

You can mentally adjust for it if you can be bothered - but beware swapping cars - The Cook's Camry is much closer to the mark with it's current boots.

Not sure of the actual percentage, but certainly all new vehicles sold in Australia MUST overstate speed - that is, the speedo tells you you're doing 100, when you're actually doing less. That legislation came into affect some years back - id say it's probably the same guidelines companies use who can adjust/recalibrate speedos, but that part is only an assumption ... based on logic, but when does that ever apply when it comes to legislation??

Mate you will find that the radar is probably only slightly inaccurate.
You may find tyres are wrong size, should be sticker in glovebox with recommended size.
The fellah who said doing 100 and radar 14 or something, these things look for vehicles speeding it had moved on looking for the next one. And when multiple lanes are there they scans alot, and alot of shadows created.
moving vehicles create shadows/blocking a reading at times for the next vechile and so you can see a funny display before it's locked in on actual speed or completely shadowed.
fairly accurate a great deal of time testing em before they are allowed on site.
but a warning only to guilt people into slowing, but sooner or later a bit further down the Rd a radar that does matter will be waiting for ya.
If ya cause an accident, their more likely to throw the book at ya instead of a lesser penalty as you had possibly been warned about going to fast, food for thought.

Quote:

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Originally Posted by CptClinac

Hi guys,
Drove past an automatic radar "your speed is (whatever)" boxes today and it significantly disagreed with my speedo. my speedo read 70 the box read 64. 10% out !!!

I've just bought this old GQ y20 safari.
Could someone in the past have...
1/ put in the wrong instrument cluster?
2/ put in the wrong auto transmission?
3/ put in the wrong diffy?
4/ put in the wrong transfer case?
5/ put on the wrong tyres?
6/ All of the above?
From my basic understanding of the speedo I doubt if it would read high. Low perhaps, but not high.

Any comments please.

Thanks
Dave

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you forgot option 7) Perfectly normal.

For about 30 years now ADR's require that a Speedo overeads by 0 to 10% of the actual speed plus 4 KPH. Speedos are not allowed to underead by even 1/10th of a KPH... so that means if your vehicle is doing 64 KPH the speedo must read between 64 and 74 KPH (IE actual speed or up to 10% of 64 plus 4)

Ex factory... most vehicles will be around 3 to 4 KPH under IE 100 KPH indicated is about 96 to 97 KPH actual.

If you want to look at it the other way... if your speedo says 100 KPH the vehicle must be doing more than 86 (approx) and not one iota above 100 KPH.

You can by different sized cogs for the gearbox speed sensor to calibrate the speedo if you wish (Nissan have 4 sizes each 1 tooth larger than the prev) OR you can use GPS derived speed