I had a thought.....

I was thinking (don't like to make a habit of it) about the speedo inaccuracy in our cars, and saw a post in the tyre section how someones fuel economy got worse when putting bigger tyres on.

Lets do an experiment....

If our speedo from standard was say 10% out, maybe a bit extreme but lets stick to nice round figures. If we are getting 10L/100kms by the odometer, we are really only doing 90kms so the fuel economy should be 10l/90kms or 11.1L/100kms. If we changed to a bigger tyre and corrected the speedo innacurracy, anything under 11.1L/100kms by the odometer is actually a gain in fuel economy? So if your fuel economy went up by 2L/100km when you put bigger tyres on, it has really gone up bugger all.

Am I correct or full of shit as usual?

In my case, the speedo is now correct with the 265/75's, but the odometer is out by 10%, not sure what the difference was as I never checked on standard rubber.
I don't think everyone who posts their fuel figures factor in the odometer accuracy when calculating their MpG.

The bigger tyres require more grunt to turn, have more frontal area, so will use more fuel, but you use less revs at the same road speed

In summary I didn't notice any significant difference in fuel useage. I think my roof rack had a much larger influence.

i just upgraded from 235/70 to 265/70 and the revs stayed exactly the same at 100km/h (2000rpm) 6th gear which i thought the revs should be lower..

nismo4x4 said:

i just upgraded from 235/70 to 265/70 and the revs stayed exactly the same at 100km/h (2000rpm) 6th gear which i thought the revs should be lower..

Click to expand...

Your speedo still thinks you are doing 100km/h at the same revs, and indicate as such, your actual speed will be different though.

Matt76 said:

I was thinking (don't like to make a habit of it) about the speedo inaccuracy in our cars, and saw a post in the tyre section how someones fuel economy got worse when putting bigger tyres on.

Lets do an experiment....

If our speedo from standard was say 10% out, maybe a bit extreme but lets stick to nice round figures. If we are getting 10L/100kms by the odometer, we are really only doing 90kms so the fuel economy should be 10l/90kms or 11.1L/100kms. If we changed to a bigger tyre and corrected the speedo innacurracy, anything under 11.1L/100kms by the odometer is actually a gain in fuel economy? So if your fuel economy went up by 2L/100km when you put bigger tyres on, it has really gone up bugger all.

Am I correct or full of shit as usual?

Click to expand...

You might be FOS but then well all know it's the S that makes the world go round.

For anyone who wants 100% accuracy in their figures they should have taken any speedo/odo error into their equations, just like if they added bigger tyres and everything was exact they should take into the equation that the bigger tyres have made an error. But given that most of us are only playing with figures and not using them for any scientific data (unless there is a pissing contest to win) then some errors are just going to have to be acceptable.

Despite the ECU reading closer to true spped and distance even it can only record averages in fuel usage so unless you can do one entire tank without stopping or turning the engine off (and even thats not 100% accurate) then any computerised calculation by the car will have a degree of error in it as well.

I think this is why we should all remember that while there are high figures quoted and there are low figures quoted there is still never going to be a right or wrong figure. But there will always be figures you want to improve.

Hi Guys,

I spoke to a guy who supplies a little electronic gizmo which you can wire into your car which will correct the speedo, problem is, the ODO is correct and your speedo is out, so fixing the speedo will then put your ODO out of whack.

Apparently the gizmo works on the Hilux's and fixes both, but the Nav's have a different setup.

This would indicate that Nissan know of the issue and deliberately over read their speedo's, but the ODO's are correct and is more critical for service intervals etc.

Bummer eh? Looks like we're stuck with over reading speedo's.

DJ

I'll confirm the above observation: my speedometer is inaccurate: it reads higher by about 10%.

However, my odometer is near enough spot on. I will not be putting any adjuster in place to correct the display of the vehicle speed while the odometer is reading accurately.

If I changed my tyre size, I'd be facing a different problem. Because the outside of the tyre covers a different distance to what the odometer is expecting, the odometer will be inaccurate and I do not want that at all. This is when I would consider an "adjuster" like Jaycar sells, but only to correct the distance travelled.

For monitoring speed, I can either mentally give myself 10km over the speed limit, or I can (as I normally do) rely on the satellite navigation device to provide a more accurate (within 1%, they say) reading of my current speed.

My ODO is out exactly the same as the speedo and I've tested it with two GPS's, Scangauge and one of those measuring wheels.

I'm not overly worried about any of the inaccuracies though, so my economy could be a different to what I'm calculating the bottom line is that this tanks economy is going to be calculated with the same errors the last tank was and therefore I'll still be able to tell if getting better or worse.

ODO's aren't even crucial for service intervals, people service their cars at different intervals these days, some go by the book, some do it more than the book, some even do it by the date because they don't go anywhere near clocking up the k's required. A mate of mine even drove his 07 Prado 130,000ks and the only service it every got as the 1000k look over, obviously that's not recommended (but if you knew the guy you'd understand) but it proves that even Toyota can make an engine that goes over 100,000k's without an oil change.

Just cause my speedo says 20,000K's doesn't always mean it's going to be due for a service, and how many people actually get their cars in at exactly 20,000k for the service anyway, my 10,000 didn't get done till the ODO was reading 10,960, it's still a 10K service.

my speedo reads 100km/h and my navman reads 100km/h does that mean my speedo is correct,i thought it did but was never 100% sure.

ive just put on 265/70/16 bfg a/ts and the speedo is now only out by bt 2-3ks!

If your speedo is accurate, stop by the start sign of one of those odometer check lengths, note the tripmeter kms, then stop by the last one and compare. Mine's out by less than 100m over 5km (under 2%).

Deejay said:

This would indicate that Nissan know of the issue and deliberately over read their speedo's, but the ODO's are correct and is more critical for service intervals etc.



DJ

Click to expand...

Yes Nissan know about this, but its not an issue as such for them as they purposely program the cluster that way.
According to an Australian piece of legislation/law (which i have posted in another thread) the
"customer can request that their speedo show true speed".

Krankin said:

Yes Nissan know about this, but its not an issue as such for them as they purposely program the cluster that way.
According to an Australian piece of legislation/law (which i have posted in another thread) the
"customer can request that their speedo show true speed".

Click to expand...

And as I discovered, Nissan don't want to play ball on this one if the speedo is within the spec provided by ADR, which is (from memory): "the speedo must never indicate a speed lower than is actually being traveled but may indicate up to 10% higher". Nissan are happy enough to use this to support their "don't wanna touch it" ethos.

Something tells me that the wheel size variations allowed (remember the discussions about whether going to this tyre or that tyre is legal?) is closely related with this issue as well. My guess is that sticking within the variations allowed keeps the speedo within a tolerance range that the authorities aren't unhappy with.

I would also imagine that venturing beyond the standard tyre size would need to be accompanied by a calibration of the speed & distance measuring equipment to keep the engineer happy.

Old.Tony said:

And as I discovered, Nissan don't want to play ball on this one if the speedo is within the spec provided by ADR, which is (from memory): "the speedo must never indicate a speed lower than is actually being traveled but may indicate up to 10% higher". Nissan are happy enough to use this to support their "don't wanna touch it" ethos.

Something tells me that the wheel size variations allowed (remember the discussions about whether going to this tyre or that tyre is legal?) is closely related with this issue as well. My guess is that sticking within the variations allowed keeps the speedo within a tolerance range that the authorities aren't unhappy with.

I would also imagine that venturing beyond the standard tyre size would need to be accompanied by a calibration of the speed & distance measuring equipment to keep the engineer happy.

Click to expand...

Yes i know nissan dont want to play ball on this one.
Its more the fact they dont want too many owners finding out the truth of the matter.
As told by the relevant body, the speedo reading i get
"is in the upper limits" which the ADR does not mandate and that Nissans QC should be reviewed.
You really need to go through the post i entered on the matter i think way back about Nov last year.
I put it in for the hope a lot of owners would jump onboard and do something about it as many hands make light work.
Its not something i made up, but the facts given to me by the Gov body's.

If you cant find the post, I'll look for the emails sent to me on the matter and post them but they are explained as i said in the forum allready.



As far as i got with Nissan and its still open,
is after sending Niss Aust the emails, they returned with take it to your dealer , have them test the truck and deal with the matter accordingly.
After several phone calls to and fro the service manager told me that he should'nt have to wear the cost to repair the problem and i argued that its nissan aust's cost not his, but that he is just playing games with me.
Then he rang back and said he cant find any guru's that are capable/willing to alter the cluster.
What next?
I left it a while to regroup. What to do?
I thought, nissan have 4 speedo 'driven' gears that suit that gearbox, 18,19,20 &21 teeth why dont they try that?
Get a fix from japan, its software related, the most simple fix or
supply me with a GPS unit.
Anyway sent an email for an progress report and some weeks later was told that the service manager has left and a new one has started, FUCK FUCK FUCK.
Although a true thing I've not been in touch with them for a while.

Anyway Old mate have a look at my previous post on the matter its all there.

I still find it hard to believe that speedo's reading 10% faster than actual speed is such an issue, sure Matt's original theory that economy calculations and the like will be out has validity when the speedo is out and even when bigger tyres are added but does that up to 10% really matter in the big scheme of things.

Sure people can argue it's the principle of having a gauge read what it's suppose to and that reading true means you are getting something that does what it's meant to but by the same token reading faster than true also means that providing you don't go over the speed limit on the gauge you wont get booked for speeding because your never truly at the speed shown.

10% is always 10% and at 100ks sure that 10% is 10ks but at 60ks that 10% is back down to 6ks, is that 6ks difference in speed really going to make a difference to your trip. Sure as the numbers get larger the differences get larger but given so much of our traveling is done in stop start traffic or even moderate traffic does that 10% really impact on your life. Any one who spends their time driving in traffic is usually dictated fairly heavily by the traffic around them and the conditions not by a maximum regulated speed limit.

As far as I'm concerned (and I don't mind people trying to shoot me down in flames for thinking it) speedos being out by up to 10% is entirely acceptable and in many ways should be looked at as a safety feature to keep all those people who think 5-10ks over the speed limits is ok, and there is still plenty of people around who think that.

Economy figures and the like which this thread was originally started about are easily worked out taking any pre determined error into the equations if accuracy is needed but for most of us that isn't even an issue, we just work out things but what we see and the figures in front of us.

Krafty,
i dont care about the economy calc's or any of the other issue's bought up,
but for me personally I want my speedo to read true, well within 1or 2 k's.
Thats MY choice and by the laws, MY option.
If others dont agree, fine.
95% of my driving is HWY driving so a speedo that is 10k out is a BIG annoyance to me.
Buy a gps some say and you have your own response to the matter also.
Fine.
Well, i say why the fuck should i buy a gps after i just forked out $35k for a brand new car to put up with shit like that.Bahh
Shit, my 1989 XF reads dead spot on,
my 1966 HR reads within a couple of k.

You want it to read true but will accept a 1-2k error, that in itself is a contradiction.

So where is the 1-2 error allowed at 10ks, 50ks, or 100ks, even higher? Throw a 2 k error into the equation and you still have to look at your speedo and mentally take 2 ks off your speed limit whats the difference between 2 or 10.

Is your tacho 100% accurate? Surely accuracy in such an important gauge should also be paramount when spending $35K.

Is your temp gauge accurate? Who knows it hasn't got figures on it that relate to anything.

For the record my tacho is about 70rpm out against the scangauge but given the divisions on the tacho I also consider this error acceptable.

I'm not suggesting you are wrong or that you should just accept an inaccurate speedo but with all the other inaccuracies in our everyday life I reckon there is more things worth complaining about that a slightly out of whack speedo. And for the record nearly all my driving is also done in 100k speed limits but obviously you get a little bit more annoyed about something so many other people are happy to accept, more power to you.

I dont care about the other things you bring to the table, my concern is the speedo atm.
If you prefer then make it 100% true then.

And 10k is not slightly out, when the speedo shows 110k I want it to be traveling at 110 not 100,
and leave the problems of getting the speed right in relation to fines etc to me, thats my problem not nissans or yours.

How do you know your scangauge is reading true rpm, have you put a precision/calibrated rev counter to the crank?
And for the record i find that indescrepancy annoying in my truck/scangauge, maybe i,m fussy or just i don't like paying good money and getting ripped off also.

Did I say Scanguage was 100%? I just said my tacho was out by that figure compared to scangauge, right or wrong there is still an difference of rpm's just like the same tool reports a difference in speed and distance traveled.

I'm not even suggesting that any speeding problem you might have is a problem of mine or Nissan's, accurate or not everyone is responsible for their own actions and I don't treat you any different in that regard.

To me speedo accuracy is not an issue just like the areas in my life where I do expect accuracy could well be something you just accept as something you can't/don't need to change.

If you think your speedo needs fixing I'm all for it and once again more power to you in that regard but in the fairness of people reading this (past, present or future) the fact that this inaccuracy exists in just about every vehicle on the road isn't something that should influence them against Nissan or Navara's it's something we've all been living with for years, by different degrees or inaccuracy and in all makes of cars, some of us ignore it, some of us learn to adapt, some fix it. My aim wasn't to prove you wrong and get you all hot and bothered (someone else can do that easily enough) my aim was to point out that it's doesn't have to be a huge issue and there is options other than bagging out the manufacturer who is after all only adhering to law.

Ok.
Not getting hot here, just like to put forward a clear picture.
Though it seems some have a problem if i bring it up but not if others do.
Gets a bit clicky here does'nt it.
Sorry, not going away.

You should have noticed that i have NOT bagged the manufacturer but a specific part of a vehicle, which you may have noticed a lot of other readers here have a problem with.

You may have noticed that you yourself have a slight annoyance with nissan dealers in particular

You may also notice I didnt bring up the subject.

You will also notice that NOWHERE have i tried to stop ANYONE from purchasing a nissan navara but quite the opposite.

You will also notice that if you read the laws and legislation i mentioned earlier I am also wanting ONLY (not above or beyond) what the laws provide for the consumer,
but not what the manufacturer is willing to provide me for my hard earned.

If you are happy to take whatever is given to you right or wrong or less than acceptable, well thats up to you,
I didnt bring it up, start any threads on the subject,
just adding to something obviously others are jacked off with.

I dont accept the speedo innacuracy and some other readers here dont like it either.
some people want to do something about it and some just lie down cop it.