Speedo replacement

[michaeljclark]

I have just replaced the instrument panel in my car as the speedo was developing a nasty habit of jumping from whatever speed I was doing, to display 46MPH - and I didn't want to get gatso'd etc

I have visited the scrap yard (it's a 11 year old car) and parted with £35 for a replacement unit

Short of using a GPS or finding a friendly BiB with a laser speed gun, where can I go to see how well the thing is calibrated? It came from the same model of car - just a different trim spec. I went for a trundle down the A2 and as I went past the various cameras (those which weren't fire bombed) I was being passed by other cars (and I was at the posted limit according to the speedo).

Oh and the car the unit has come out of has done 4,500 miles LESS than my car has actually done - am I required to tell someone (DVLA, VOSA etc) about the change as the next MOT could prove interesting when they check the previous certificated mileage to the displayed (cos it's going to be less, unless I do some serious miles)

Any thoughts any one?? - PS not going to be on line for a few days so sorry if I'm delayed answering any replies/queries

Cheers

Mike

[Hooli]

unless you have a fetish for history on the car dont worry about the mileage.
rev coutner? are the revs the same for speeds as the old unit?
normally if it looks like the same speedo as the old one then it will be & will display the same. does the speed it shows feel right?

or find someone with a handheld GPS just to make sure.

[michaeljclark]

Hooli said:

rev coutner? are the revs the same for speeds as the old unit?
normally if it looks like the same speedo as the old one then it will be & will display the same. does the speed it shows feel right?

Rev counter never worked from when I had the car (2nd hand you see) but yes the speed "feels" right

Mike

[NobleGuy]

Drive past a 30 limit gatso at what the speedo thinks is 30 and see if it flashes.

[Flat in Fifth]

have a word with either your local county surveyor's office or your local plod traffic unit, they won't bite. Explain that you want to check your speedo as it's been changed and you want to be sure it's correct.

They should advise you of road, location, distinguishing marks at start and end. Make a run along road at steady speed, helpful if you have an observer and stopwatch.

Otherwise a lot of GPS units have speed displays as previously mentioned.

[tigger1]

Do you know what the max speed in any gear was in your old car?

(Like would it max at 30 in 1st, 55 in 2nd etc?)

Possibly not the kindest way to check

[banzai_dan]

You could try using the emergancy phones located by the side of the motorway. They are placed exactly 1 mile apart, so just get a stopwatch and time how long it takes to travel between two of them. Not the most scientific of methods, but should be acurate enough as most speedos are about 5-7% out anyway.

(At a steady 70 miles an hour it will take 51.4 seconds to travel between two emergancy phones)

Hope this helps

[tigger1]

banzai_dan said:

You could try using the emergancy phones located by the side of the motorway. They are placed exactly 1 mile apart, so just get a stopwatch and time how long it takes to travel between two of them. Not the most scientific of methods, but should be acurate enough as most speedos are about 5-7% out anyway.

(At a steady 70 miles an hour it will take 51.4 seconds to travel between two emergancy phones)

Hope this helps

As great as that calc' is - wouldn't just suggesting 60mph for a minute be easier

[Dracoro]

You need to declare the mileage change to DVLA (motor traders have to, by law I think).

This makes it easy to explain when you sell up (i.e at 90,000 miles you went down to 85,000 miles etc.).

Otherwise, everyone will - understandably - think the car has been clocked and it actually had 250,000 miles or whatever on it.

[Jules360]

Flat in Fifth said:

have a word with either your local county surveyor's office or your local plod traffic unit, they won't bite. Explain that you want to check your speedo as it's been changed and you want to be sure it's correct.

They should advise you of road, location, distinguishing marks at start and end. Make a run along road at steady speed, helpful if you have an observer and stopwatch.

Otherwise a lot of GPS units have speed displays as previously mentioned.

Yes, and since by your own admission you are uncertain of your speed, plod will claim you were doing 34 and nick you. Try proving your innocense then !!!