speedometer

[fortunehunter]

has anyone checked the accuracy of the speedo,i believe they read faster than actual speed ie: 120km/hr but really a few km/hr less gps tested,thoughts??

[Bmhdg1976]

My gps says my speedo is about by about 3klm at 100. So at 100 I am doing 97. Close enough for my like liking.

Bj.

[lufkin]

the speedos are reading higher than actual speed. my scan gauge and GPS show I’m doing 96km/h when needle is set dead on 100. was very surprised that the scan gauge and GPS were identical. Means the ECU is reading 96km/h

[Psykamaholik]

Ever since 2006 or 2007 all car speedos have been calibrated this way

[fortunehunter]

why is this?

[RALF]

why is this?

to stop you getting busted by the boys in blue for speeding.
😜

[pointlowly]

Mine is the same. The speedo reads 100 when the GPS shows I am doing 97. This for me is great as I live in the country and I am always doing long highway travels. Yes I might get there 10 - 15 minutes later but I do get there. Also I still have $400 in my pocket not the government.

[cheekydonkey]

Speedo is off! I'm doing a constant 113 kph on the freeway and the GPS speed is 110. Maybe if you shod on bigger tyres, it'll be more accurate..

[Hylife]

If your speedo does NOT display at least 4km higher reading than actual speed at 40, 80 & 120kph, then the speedometer is faulty.
ECE design specs require this.

The UN ruling is:
United Nations - Economic Commission for Europe Regulation No. 39 –
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF VEHICLES WITH REGARD TO THE
SPEEDOMETER EQUIPMENT INCLUDING ITS INSTALLATION, incorporating the 00 series of amendments.

aka, UNECE REGULATION NO 39/00

It makes pretty dry reading but for those that might be interested there is a direct copy/implementation of the UN ruling in the Australian Design Rules which you can read up on here:
http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf

Whilst there is a whole raft of details about how the testing is done for different types of vehicle and at what speeds etc, etc, etc, the basic maths formula is:-

0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h

V1 = displayed speed
V2 is actual speed

In simple English it reads,
Your displayed speed must not read less than the actual speed (considered defective)
and the difference between displayed and actual must be less than or equal to 10% of the actual speed
Plus 4kph.

[Kat]

GPS shows 110 speedo is about the 117 mark. Waiting for Toyota to get back to me regarding the gear box slipping might mention the speedo.

[Hylife]

GPS shows 110 speedo is about the 117 mark. Waiting for Toyota to get back to me regarding the gear box slipping might mention the speedo.

Still quite within legal specs though I wouldn't be too happy about the inaccuracy on a modern car.
Some GPS can be rather slow on sampling and can display inaccurate speeds worse than cars.

Legally at 110kph your speedo could read to a maximum as follows.

110 plus 10% plus 4kph
= 110 + 11 + 4
= 125

The legal minimum it must display at 110kph is 114, so you see it is only over by 3kph or 2.63%
This may be deemed by Toyota as quite reasonable.
Every vehicle is in different condition and if you don't have the OEM wheels and tyres in new condition then that is reliably the biggest contributor to inaccuracies.