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Speedo Calibration...

JDM_Spirit
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JDM_Spirit Community Regular

JDM_Spirit

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Ever wondering if your speedo is accurate?

So far Ive been in 2x Stagea's (mine and a mates) and both speedo's were out by 10%.

So for every 10km/h on the clock it was out by 1km/h...

Note: This was with FACTORY Spec Tyre Dimentions + Factory Alloys.

Ie: 10Km/h(clock) = 9km/h(Real Time) & 110km/h(clock) = 100km/h(Real Time)

I noticed when I used to hit Speed Cut at 180km/h.. Navman would be Register 170km/h.

Someone once told me that Nissan did this so you didnt speed? and its only till 100km/h(Real Time)

as very few free/highways exceed this speed.

Cheers, Aerron

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jrm Veteran

jrm

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Most cars speedometers - not just Nissans - will err on the side of over-reading (reading higher than the road-speed).

From what I understand, speedometer accuracy is a tricky business for car manufacters. They need to allow for things like:

* Tyre wear

* Tyre temperature

* Variations in factory-released tyre rim sizes in a single model (where all models share the same speedometer and sensor)

As soon as you start introducing non-factory components like aftermarket rims & changes in the overall diameter of the wheel (different tyre profiles, widths, etc) you introduce even more variables that may affect your speedometer accuracy. The manufacturer will typically provide a tyre placard which lists acceptable tyre rim/tyre sizes for your car - it's up to the owner to ensure that they keep the rolling diameter as close to this as possible to try and avoid upsetting the speedometer accuracy. (Though there are state-by-state laws regarding how much the rolling diameter can be too).

There are regulations under the ADRs regarding speedometer accuracy. These have since changed in - I think - 2006 to be even more stringent, but for most of us it's still under the older rule that it must be accurate within +-10%. From what I recall, the new rules prevent any under-reading, and allow for over-reading of up to 4kph + 10%.

Testing against GPS, both of my cars over-read, but even at 100kph it's only 1-2kph out - so I don't stress too much.

Anyway, hope that helps :)

JDM_Spirit Community Regular

JDM_Spirit

Posted
  • Author
Posted (edited)
Most cars speedometers - not just Nissans - will err on the side of over-reading (reading higher than the road-speed).

From what I understand, speedometer accuracy is a tricky business for car manufacters. They need to allow for things like:

* Tyre wear

* Tyre temperature

* Variations in factory-released tyre rim sizes in a single model (where all models share the same speedometer and sensor)

As soon as you start introducing non-factory components like aftermarket rims & changes in the overall diameter of the wheel (different tyre profiles, widths, etc) you introduce even more variables that may affect your speedometer accuracy. The manufacturer will typically provide a tyre placard which lists acceptable tyre rim/tyre sizes for your car - it's up to the owner to ensure that they keep the rolling diameter as close to this as possible to try and avoid upsetting the speedometer accuracy. (Though there are state-by-state laws regarding how much the rolling diameter can be too).

There are regulations under the ADRs regarding speedometer accuracy. These have since changed in - I think - 2006 to be even more stringent, but for most of us it's still under the older rule that it must be accurate within +-10%. From what I recall, the new rules prevent any under-reading, and allow for over-reading of up to 4kph + 10%.

Testing against GPS, both of my cars over-read, but even at 100kph it's only 1-2kph out - so I don't stress too much.

Anyway, hope that helps :rofl:

I wasnt so much stressing, more so curious :)

You did bring up alot of good points...

My partner works for Toyota, she was telling me recently that all staff were warned that the new Tarago's speedo can be inaccurate by Approx 20km/h :) ... I was rather shocked.

Toyota... a leading manufacturer could be that far off. Fresh out of the box even?

But it is a Luck the Draw so 1-2% of the production could be wrong.

I bring this subject up as I went for a VERY EARLY Sunday Morning blat to stretch the Stag's legs out.

(Yes I know its dangerous to me and others etc... so smack me down if you will)

I was reading Navman's Speed as I did so, noticed that the Stags needle was above the Odometer(roughly 5 o'clock) and the Navman only said 190km/h... So I continued onto 205km/h.

I know using Nissan Consult you can re-calibrate a R33's Spedometer. Is it possible in the 34's/Stagea?

Cheers

Edited by JDM_Spirit
32TAXI Experienced

32TAXI

Posted
Posted

Mines out and over, 245/40R18 on 18x9.5' on RS4S (max std 215/50R17)

IE: needle - 110kmh pfc - 106kmh gps - 105kmh,

needle - 120kmh pfc - 114kmh gps - 113kmh

Power FC display is even different to needle but more accurate.

pixel8r Mentor

pixel8r

Posted
Posted

both of my stageas have over-read the speed. When the GPS reads 100km/h the speedo usually says about 108km/h.

Its a bit less than 10% but it means if I sit at 65km/h via the needle I'm actually doing about ~60km/h - most of the time i sit closer to 60...but the extra leeway has saved me from a fine more than once.

JDM_Spirit Community Regular

JDM_Spirit

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Posted
^^^^ This was on a private road... Right?
I should bloody well hope so!

:P ... Well.... technically I drove on a piece of My Road as part of my Tax and Rego paid for it.

Im running 17's with 500km old 235/45R17's.

GPS : 110km/h Needle = 117km/h ish

RBPOWA-(TJ) Grand Master

RBPOWA-(TJ)

Posted
Posted

i would sit at

50 speedo , 45 real time.

90 speedo, 80 real time.

116 speedo , 100 real time.

so i couldnt work it out haha, sold the car the new owner put 20's on it and said its only like 3ks off now all round, according to his GPS

Big Fella Mentor

Big Fella

Posted
Posted

Pretty much all cars are set up to be out. Brand new camry's have the correct reading at the ECU but then change it for the speedo to be 10% out, don't ask me why, they just do. but it explains why camry drivers always seem to go so slow.

GoldZilla Grand Master

GoldZilla

Posted
Posted
Mines out and over, 245/40R18 on 18x9.5' on RS4S (max std 215/50R17)

IE: needle - 110kmh pfc - 106kmh gps - 105kmh,

needle - 120kmh pfc - 114kmh gps - 113kmh

Power FC display is even different to needle but more accurate.

That's probably due to the extra stretch your tyres have made to go over the 9.5"rims, as I have exactly the same size tyres on my car, but on 18x8" rims, and it's only aout 1km/h out.

My PowerFC is way off both the speedo and actual real-time speed my car is travelling at.

pipster11 Grand Master

pipster11

Posted
Posted

with my ecutalk and gps i get 3 different speeds

the ecutalk over reads the ground speed and the dash shows more than that again

and as somone said, its pretty accurate up to about 80 (both dash and ecu are in sync) then they start to separate

anyone used the jaycar speed corrector kit?

rosella Community Regular

rosella

Posted
Posted
8-10% over-read. Means it has more kms on the clock than it has done!

Mines out about 7%. Trip to work in my Magna is 114km and the Stagea is 122km. 18" Advant T7s with 225/45 with rolling diameter of 2072.5mm whereas standard is 215/55x17" so rolling diameter is 2099.5mm. So smaller by 27mm hence more km on the odometer.

Daleo Grand Master

Daleo

Posted
Posted
Mines out about 7%. Trip to work in my Magna is 114km and the Stagea is 122km. 18" Advant T7s with 225/45 with rolling diameter of 2072.5mm whereas standard is 215/55x17"

I run 245/45/18 and my error is approx 3% against GPS, which I'm quite happy with. Where in the mountains are you Rosella? I'm at Faulconbridge, I'll have to keep my eyes peeled.

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