What speed am I doing

Notmyrealname

George_Michael wrote: »

This is one of those urban myths that people still keep saying is fact, yet those same people still keep failing to post anything other than their opinion to back it up.

Its not urban myth at all.

The Road Vehicles (Construction and Use) Regulations 1986
1986 No. 1078PART IIFRegulation 35
Speedometers

Fitting

Regulation 35 Road Vehicles (Construction and Use) Regulations 1986 states that every motor vehicle shall be fitted with a speedometer except:

a vehicle having a maximum speed not exceeding 25 m.p.h.,
a vehicle which, at all times, is unlawful to drive at more than 25 m.p.h.,
an agricultural motor vehicle driven at not more than 20 m.p.h.,
a motor cycle not exceeding 100cc first used before 1st April 1984,
an invalid carriage first used before 1st April 1984,
a works truck first used before 1st April 1984,
any vehicle first used before 1st October 1937,
a vehicle fitted with an approved tachograph which is required or not.

Vehicles first used on or after 1st April 1984 the speedometer should be capable of indicating the speed in miles per hour and kilometres per hour. Vehicles may instead comply with EC Regulation (Community Directive) 97/39 or ECE Reg 39.
These directives stipulate the markings, graduations of the speedometer and refer to 75/443/EEC which specifies the tolerances.

The indicated speed must never be less than the true speed (it must read exact or high) and between 40km/h and 120km/h the error must not exceed 10% + 2.5 m.p.h. high (true speed/10 + 4kph).
This means at a true speed of 25mph or 40km/h the speedometer may read 40/10+4 = 8km/h or 5mph high = 30mph indicated.

Maintenance

Regulation 36 Road Vehicles (Construction and Use) Regulations 1986 states that the speedometer fitted to a vehicle must be kept free from any obstruction which may prevent it from being easily read and shall at all times it is used on a road be maintained in good working order except if:

the speedometer became defective during the journey being undertaken, or
steps have been taken to have the defect remedied by replacement or repair with all reasonable expedition, or
the vehicle is fitted with an approved tachograph which is required to be fitted under the Community Recording Equipment Regulation (offence is under that regulation).



The Road Vehicles (Construction and Use) Regulations 1986, as amended, allows the use of speedometers that meet the requirements of EC Community Directive 75/443(97/39) or ECE Regulation 39. Both the EC Directive and the ECE Regulation lay down accuracy requirements to be applied at the time of vehicle approval for speedometers. These requirements are that the indicated speed must not be more than 10 per cent of the true speed plus 4 km/h.

mikey72

That's wrong. Look at the correct specs in the link above.

Rover_Driver

mikey72 wrote: »

That's wrong. Look at the correct specs in the link above.

It's not wrong, see the last paragraph.

The Construction and Use regulations, as amended, allows the use of speedometers to 75/443(97/39)

George_Michael

The Construction and Use regulations, as amended, allows the use of speedometers to 75/443(97/39)

Exactly.
Your speedometers accuracy can be in accordance with that particular regulation, but they do not have to be.
They can also be within the tolerance allowed by "The Motor Vehicles (Approval) Regulations 2001" and these reg's allow the speedo to overread by 10% + 6.25mph.

So stating that a speedometer can only over read by a maximum of 10% is a falacy.

Rover_Driver

The Type Approval 75/443(97/39) for speedometers was introduced in 1975.

Speedometers complying with that type approval can use the accuracy figures in it.

Earlier speedometers, and those which don't comply, must use the accuracy figures in the 1968 Construction and Use regulations, which are lower.

mikey72

George_Michael wrote: »

Exactly.
Your speedometers accuracy can be in accordance with that particular regulation, but they do not have to be.
They can also be within the tolerance allowed by "The Motor Vehicles (Approval) Regulations 2001" and these reg's allow the speedo to overread by 10% + 6.25mph.

So stating that a speedometer can only over read by a maximum of 10% is a falacy.

That's the correct figure. I'm building a car that will need SVA approval, and that's the spec I need to comply to for the speedometer.

Lum

The one on my car is out by way more than that. When you're doing 50mph the needle points at 80 . They didn't even bother to check when I imported and registered it as it was over 10 years old.

Don't worry though, I have a second speedo as a little HUD unit that displays correctly, but that got fitted after registration.

Notmyrealname

Lum wrote: »

The one on my car is out by way more than that. When you're doing 50mph the needle points at 80 . They didn't even bother to check when I imported and registered it as it was over 10 years old.

Are you sure that wasn't 80kph, Lum?

Lum

I'm quite sure that it is 80kph

There is no mph on there at all.

e999sam

I certainly wouldn't trust a sat nav or GPS phone to track my speed. On a recent cycle ride it clocked me doing something like 60mph and on a hike at 16mph. If you go to sports tracker you may be able to see my log (same user name) and you will see from the the ride/walk plotted on the map how inacurate they are.