Speedo Accuracy

[Mr Tidy]

I visit my Mum at least once a week, and regularly use a road near where she lives that has road signs on both sides that flag up your speed.

I've noticed that all of my BMWs (E86, E46 & E91) seem to read 27 mph on the signs when my speedo is reading a steady 30 mph, so was just curious to know if this is typical - if so I could at least do 33 without getting nicked!

[Brainpox]

Not having a pop but I thought it was very common knowledge that speedos in any car will over-read, often about 10% over.

So yes, you could do an indicated 33 in a 30 and be absolutely fine.

[abzmike]

Yep, my 430 reads 33 when I go past the sign in the village reading me at 30. Better reading 10% too quick than too slow.

[Mr Tidy]

Thanks, I was used to it when I had 60s, 70s and 80s Fords - I assumed it was to make them seem faster than they really were!

But when I had Stuttgart 80s and 90s products they were pretty much bang on so I thought things had moved on, but clearly not.

Brainpox said:

Not having a pop but I thought it was very common knowledge that speedos in any car will over-read, often about 10% over.

So yes, you could do an indicated 33 in a 30 and be absolutely fine.

Good to know though - when there are cameras it seems safe to set cruise a bit higher!

[FurtiveFreddy]

You can code recent BMWs to read true speed if you want to. Otherwise, they'll over-read but only by a few mph at all speeds.

[helix402]

Mr Tidy said:

I visit my Mum at least once a week, and regularly use a road near where she lives that has road signs on both sides that flag up your speed.

I've noticed that all of my BMWs (E86, E46 & E91) seem to read 27 mph on the signs when my speedo is reading a steady 30 mph, so was just curious to know if this is typical - if so I could at least do 33 without getting nicked!

The “flash your speed up signs” are usually inaccurate (over reading) in my experience-based on GPS comparison. E46 speedos are pretty accurate, they only marginally over read by approx 1 mph. (Unlike some manufacturers such as Vauxhall who often set their speedos to hugely over read).

As mentioned BMW speedos can be reprogrammed to display the actual speed, it’s easy on E90 onwards with Carly, a little trickier on E46s with different software.

[Wills2]

I was caught at 90mph (indicated) and was given a SAC, the speedos over read.

Thank God.

[anonymous-user]

Using GPS my E46 is more or less bang on at everything up to motorway speeds but my mates E90 shows under by a good margin, 80 on the clocks is about 74 I think.

[4rephill]

helix402 said:

.........E46 speedos are pretty accurate, they only marginally over read by approx 1 mph.......

My 2001 BMW E46 330ci reads @ 111mph on the speedometer (the needle is just a smidge past the 110mph line), when My sat nav reads 110mph - Verified by the Police officers who pulled Me over on the M1 who had Me recorded as doing 110mph at the time!

[cuprabob]

4rephill said:

My 2001 BMW E46 330ci reads @ 111mph on the speedometer (the needle is just a smidge past the 110mph line), when My sat nav reads 110mph - Verified by the Police officers who pulled Me over on the M1 who had Me recorded as doing 110mph at the time!

Nice of them to verify it for you

[Simes205]

Our e91 is bang on GPS.