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Not the flattering swimwear.
Just got myself a new (to me) motor and a big change from the previous 11-year old Mondeo; lots of toys and gadgets, including a digital speedo. Cool! But why is this not accurate, always 3-4 mph under? Car has satnav so 'knows' exactly where it is at all times so why can't the speed displayed be accurate?
Every car ever is about 10% low. It's intentional.
They all do that.
Cars cannot underread, and a small change in the tyre circumference due to wear/underinflation would mean if it read 100% correctly when new, it'd underread and you'd be doing 73 when doing an indicated 70.
Better to have it show an indicated 70 and be doing 67.
Not hard to remember, I set my cruise to 52/53 in 50 zones, and 42/43 in 40 zones and *touches wood* never had a ticket.
But why is this not accurate, always 3-4 mph under?
Do you not mean 3-4 mph higher than GPS speed?
Yes, I put that badly, display shows 73mph at an exact 70
Ignoring the tyres why can't the speedo be linked to the GPS? The car turns it lights on and off on its own, dips the headlights, has collision protection so lots of electronic 'awareness'
I set the cruise the same way, the missus struggles though
why can’t the speedo be linked to the GPS?
there my be some legislation requiring an input local to the vehicle from the final drive? At least the Speedo would then work if gps signal lost?
Not the flattering swimwear.
...and I was about to share my holiday snaps - is disappointed! 😕
Ignoring the tyres why can’t the speedo be linked to the GPS?
Because you would have no speedo passing through underpasses and tunnels.
Also, the fact you have GPS at all is basically down to the US allowing anyone to use it. They could in theory switch it off at anytime. (I know that other systems are available).
Speedos will always read zero if the car is driving on a conveyer belt.
Fact.
Every car ever is about 10% low. It’s intentional.
Take care with that assumption of 10%. The only thing the law requires is that the speedo doesn’t under read.
My current car (Tesla), and my last one (Jaguar), were pretty much bang on the same as GPS speed at all times.
If I set cruise at 70mph (digital display), my analogue speedo needle reads about 67mph.
At this point, lots of people are used to going "Oh it says 70 but it underreads" and it's been true of every car they've driven ever, so if their new car was perfectly accurate and they don't realise, they might accidentally speed.
I have an oversize teaspoon, I've been using it for years to make coffee, if I use a proper accurate teaspoon- absolute carnage
I have an oversize teaspoon, I’ve been using it for years to make coffee, if I use a proper accurate teaspoon- absolute carnage
Isn't that a called a tablespoon? And if so, you may have a caffeine addiction... 🤣🤣
I set the cruise the same way, the missus struggles though
Good - she's the adult in control of the moving vehicle so she should drive it how she sees fit. If she wants to drive at an actual 67mph with 70mph on the display no baby robins were hurt and she's probably burning marginally less fuel. Even if she is making a 150-mile journey that is 5 minutes difference. FWIW if you do drive at a true 70mph you'll often find you have to keep leap frogging traffic because other cars are sitting at what they think is 70mph, or your active cruise control will tuck in behind someone at 67 mph anyway, drive at 67 and you can often have a less taxing drive.
ta11pau1
Full MemberIsn’t that a called a tablespoon? And if so, you may have a caffeine addiction… 🤣🤣
It's pretty old, it may be whitworth
Your speedo will generally say you're going faster than you are and you'll have done a shorter distance than your odometer says. There's parameters car companies work to and doing it that way means you get a better mpg calculation and a bit more lee-way when you pass a speed camera.
Personally I just go on what the speedo says, a couple of mph isn't going to get me there noticeably quicker and I can't be arsed with the stress of it. Radar cruise control FTW!
Speedos will always read zero if the car is driving on a conveyer belt.
Fact.
Except when the Speedo is reading 100mph in reverse and the car isn’t moving
there my be some legislation requiring an input local to the vehicle from the final drive? At least the Speedo would then work if gps signal lost?
Construction and use ... How ever you do not need a working Speedo to pass an MOT......it must be present and legible but it doesn't need to physically tell the speed.
While it's written in the guidelines....there is no specific test that confirms the speed it's showing.
As such I've put in for MOT without a Speedo cable fitted (I use a GPS) 2 years in a row and no mention
At this point, lots of people are used to going “Oh it says 70 but it underreads” and it’s been true of every car they’ve driven ever, so if their new car was perfectly accurate and they don’t realise, they might accidentally speed.
They can over-read by 10% but not under-read at all, manufacturers generally set them to be 4-5% over but some do play around with it digitally so that it's not 5mph too high at 100 for example. The one on my Fabia is 2mph over at 30, 50 and 70 compared to GPS. Oh and GPS is legal, it is used in many kit cars and track day cars for example but manufacturers never fit just GPS (some have GPS and wheel speed ones that self-calibrate) as loss of signal is a real issue in large parts of the world eg tunnels, steep valleys etc. Current speedos are miles better than old ones though, the one on my Mini is 'an indication' at best, a local radar speed sign will say I'm doing 30 but the old mechanical speedo can say anything from 30-36, that's if it's not wobbling!
EDIT: and don't forget the 10% +2 leeway you normally get here in the UK so if you're caught speeding on the motorway at 79mph then your speedo could well have been showing around 85+, very naughty.
and don’t forget the 10% +2 leeway you normally get here in the UK
Urban legend.
why can’t the speedo be linked to the GPS?
I've often thought you could have a GPS speed and a traditional speed with a little green GPS symbol showing green or red depending on status. Or the needle colour could change or something.
Sounds like some cars are already doing similar.
Oops, got over and under the wrong way round!
No dear, if it says 79 the actual speed is 75.5. She has the 33 in a 30 fine, I don't.
Still got the phone mount on the screen. I'm happy with Android Auto and Spotify+Waze/Maps/Co-pilot - with accurate current speed shown - but can't use Radio at same time so end up with car satnav - no speed! - and radio plus phone speedo app.
Unless I'm understanding the last point wrong, you can set Google maps to shout directions from the phone, even when it's Bluetooth'd to the vehicle so you get radio/music/whatever uninterrupted, but still have the directions.
I like the Satnav for the advance hazard warnings but I guess there are Radio apps for Android? All new to me. The BBC Sounds app offers BBC main channels and works with Android Auto, apparently, might keep her happy. Any Android app recommendations?
Urban legend.
FOI Request says otherwise.
It was Association of Chief Police Officers guidance for years and many forces worked to it. ACPO doesn't exist now and it was only ever guidance.
There's useful info here... https://www.roadlawbarristers.co.uk/speeding-what-is-the-10-plus-2-rule-and-what-does-it-mean/
Bottom line; tech is so good that a margin isn't needed for certain detection systems and your speedo will over-read, protecting you
Any Android app recommendations?
No sorry, not got that in the van. Its either the built in DAB radio or YouTube music via Bluetooth from the phone. In either case the audio directions from Google Maps come from the phone without interrupting the music. This option isn't difficult to find in Google Maps app.
FWIW if you do drive at a true 70mph you’ll often find you have to keep leap frogging traffic because other cars are sitting at what they think is 70mph, or your active cruise control will tuck in behind someone at 67 mph anyway, drive at 67 and you can often have a less taxing drive.
Can’t say that’s ever been an issue on a motorway, which is the only time I ever use cruise-control/limiter. I usually set the cruise for around 75, but if there’s a stretch of average speed camera-controlled road, I use the limiter set to 52. Like many cars, mine doesn’t have active cruise control, that’s mostly VAG cars.
Oh, and regarding speed displays, my original Ford Puma had a digital odometer display that could be switched to an active digital display on start-up, which allowed speed, tacho, and some diagnostic data, I used to have the speed display on, which showed my analogue speedo was exactly 10% out, and I quickly learned to drive by what gear I was in and what revs were showing.
Which was fine with a five-speed ‘box; when I later got to drive a new Audi diesel with a 6-speed ‘box, I discovered that 1200 rpm in top wasn’t 60 mph, it was 95…