Hang on a minute...

[LBD]

Reading Trihards post about speedo working but milage counter does not got my mind on a train of thought that ended with....

We know that speedometers generally read some 7 percent high....does the counter do the same?

I know in most cars the speedo is reading about 7 percent high when compared with the GPS, so.....

If you have a diesel vehical and buy road user charges based on the odometer reading and your odometer is 7 percent out, are you being ripped of by some 7% of your road user fees?

Where has my logic gone wrong...has it gone wrong?

I have not owned a diesel vehical or spent much time in NZ for many years you I may be horribly mistaken some where.

[LBD]

Reading Trihards post about speedo working but milage counter does not got my mind on a train of thought that ended with....

We know that speedometers generally read some 7 percent high....does the counter do the same?

I know in most cars the speedo is reading about 7 percent high when compared with the GPS, so.....

If you have a diesel vehical and buy road user charges based on the odometer reading and your odometer is 7 percent out, are you being ripped of by some 7% of your road user fees?

Where has my logic gone wrong...has it gone wrong?

I have not owned a diesel vehical or spent much time in NZ for many years so I may be horribly mistaken some where.

[p.dath]

The "speedo" reads around 6% higher due to European regulation. This is a deliberately engineered error. Any road going device designed to be sold in the European market will always say you are going faster than your really are as a result.

This is my recollection of the regulation, so this may not be 100% right, but will be pretty close. There is a large formula that specifies the error tolerance for speedo gauges, but basically at 100 km/h, with tyres at normal operating temperature, on a "average" temperature day, correctly inflated, with the correct aspect ratio, the error [B]has[B] to be between 0% and 12%. To play it safe, the manufacturers aim for the middle, and design the error to be 6%.

ps. You'll see a survey every year where the Police report that on average people are now travelling slower on NZ roads ... co-indicidentally the the change is almost always exactly equal to this error. In other words, people think they are travelling at 110 km/h still, but are in fact only doing about 104km/h.

The odometer is required to report the distance travelled with a very small error tolerance, and on average should report the correct results. They do not deliberately make the odometer report the wrong value.

[p.dath]

Found the info about this again, "United Nations Economic Commission for Europe (UNECE) Regulation 39[4]".

http://www.unece.org/fileadmin/DAM/t...gs/r039r1e.pdf
Section 5.3.
Which specifies this formula for the standard error:
0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h
But I'll let you read it. It's a tad complicated for me. But basically, at 100km/h it equates to a 6% error.

[FJRider]

A check with a GPS unit would confirm any error ... but most vehicles I've had ... speed reading was way out, but mileage was close.

Commercial vehicles have Hubbometers to eliminate such errors ...

[darkwolf]

Clearly you just through bigger wheels on the vehicle subject to RUCs. Plus it makes the vehicle more offroad worthy! Which is more important than being ripped off from RUCs.

Unless the odo reads from somewhere else - but I doubt that.

[Scuba_Steve]

Reading Trihards post about speedo working but milage counter does not got my mind on a train of thought that ended with....

We know that speedometers generally read some 7 percent high....does the counter do the same?

I know in most cars the speedo is reading about 7 percent high when compared with the GPS, so.....

If you have a diesel vehical and buy road user charges based on the odometer reading and your odometer is 7 percent out, are you being ripped of by some 7% of your road user fees?

Where has my logic gone wrong...has it gone wrong?

I have not owned a diesel vehical or spent much time in NZ for many years so I may be horribly mistaken some where.

Diesels odo's are taken separately from speed, so the speed difference doesn't affect the reading & the tolerance for diesel odo's is max 1% from memory.

[sil3nt]

Aston Martin Virage - 95 at indicated 100.
VW Golf GTI 35 Edition - 99 at indicated 100.
Jeep Grand Cherokee Overland - 96 at indicated 100.
VW Touareg - 96 at indicated 100.
Kia Picanto - 95.5 at indicated 100.
Holden Barina - 94.5 at indicated 100.
Porsche Panamera Diesel - 99 at indicated 100.
Audi A6 Quattro - 96 at indicated 100.

All from an Autocar magazine i had lying around.

They tested a Ducati Diavel and GSR 750 but didn't do a speedo error check on them.

[Grumph]

In my experience commercial diesel hubodometers are correct but small commercial/personal diesels are often wrong.

But WTF are you doing driving with the speedo connected on a diesel anyway ? that's what the tacho is for...
This is a motorcycle forum right ? Home of anachists whose only desire is to shaft the system.....

[Berries]

Diesels odo's are taken separately from speed, so the speed difference doesn't affect the reading & the tolerance for diesel odo's is max 1% from memory.

Is that true? My brother in law was complaining to me that his new Ford Ranger was over 10% out on speed readings, tested with a GPS, and wondered how that would affect his RUC. Followed him to test it using a calibrated tripmeter and he recorded a greater distance than I had - think it was an extra 800m over 13km. If you are paying RUC for 1000km and only actually doing 900 or whatever then you are being ripped off. Ford don't want to know about it apparently. Was told it was a known issue so thought I would Google it before I posted, but the first result when I search ford ranger speedometer site:nz is actually a KB thread. So who knows.

[p.dath]

Is that true? My brother in law was complaining to me that his new Ford Ranger was over 10% out on speed readings, tested with a GPS, and wondered how that would affect his RUC. Followed him to test it using a calibrated tripmeter and he recorded a greater distance than I had - think it was an extra 800m over 13km. If you are paying RUC for 1000km and only actually doing 900 or whatever then you are being ripped off. Ford don't want to know about it apparently. Was told it was a known issue so thought I would Google it before I posted, but the first result when I search ford ranger speedometer site:nz is actually a KB thread. So who knows.

If you have a GPS to measure the speed .... wouldn't you use it to measure the distance travelled as well?

[dangerous]

If you have a diesel vehical and buy road user charges based on the odometer reading and your odometer is 7 percent out, are you being ripped of by some 7% of your road user fees?

well in my case wearing 31/10's the speedo reads 90 but Im doing 100... so that would mean the milage is turning over slower than it should aswell... means Im saving 1 km of road users to every 10km's traveled

Diesels odo's are taken separately from speed, so the speed difference doesn't affect the reading & the tolerance for diesel odo's is max 1% from memory.

You are refering to comercial diesels yeah? cos other wise its 1 cable for speed and milage (or wire for both?)

If you have a GPS to measure the speed .... wouldn't you use it to measure the distance travelled as well?

How do you know a GPS is acurate?

[SMOKEU]

If you own a mechanically injected diesel then install a hidden yet easily accessible "economy switch" under the dash.

[Berries]

If you have a GPS to measure the speed .... wouldn't you use it to measure the distance travelled as well?

It wasn't his. He had a mate in the truck showing him what it did. They still got lost.

[dangerous]

If you own a mechanically injected diesel then install a hidden yet easily accessible "economy switch" under the dash.

ya... what?