Why Your Speedo is Lying to You
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- čas přidán 18. 04. 2024
- Look at this, I’ve got my cruise control set at 70mph but my phone and this GPS box both say something different. Is my speedo lying to me?
Now I’m not normally one for conspiracies - but there is NO WAY that the car is just ‘accidentally’ off with it’s speedo reading. VW can’t just be making up the numbers displayed on the dash of my car - oh hang on…
But still, what’s going on here? Why do speedos over-read by so much?
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Right, let me know! Set your cruise control to 70mph in your car, and let me know what your phone reads! Also, let us know what car you have!
My Volvo v50 is spot on waze goes between 70 and 71
What is the point of this video? People have known about this for years and years.
My Audi A7 (2015) is usually spot on or only off by 1mph. I used to have an Audi A6 (also 2015) and that was off by 2-3mph.
@@davidt8087 What is the point of your life ? We already have billions of people and you can't provide anything the other billions won't. Replicate whatever answer you choose for yourself to the question you asked.
I remember a few years ago, where a group of taxi drivers mounted illegally small tyres on their cars, so that the system would overcharge the customer, since it relied on the car's speed to calculate distance driven.
You've missed out a very important part here. Your speedo might be lying, but the car's speed sensor is usually very accurate. Hook a reader up to your car's diagnostic port and access the output from the speed sensor and you will find it is usually very close to the GPS readout (also proving that the speedo is being artificially set to over estimate speed).
The whole thing with the speedo over estimating your speed in the UK and Europe is because there are significant fines for manufacturers that issue a speedo that reads a lower speed than the car is actually doing. They don't do it to protect you from speed cameras/limits; they do it to protect themselves.
As a slight aside, cars over estimating speed by significant values is not really a good thing, especially if you have a driver that doesn't understand their speedo isn't accurate. A lot of people get this idea that because their speedo says they are doing the speed limit, anybody passing them is speeding. This in turn leads to certain drivers taking it upon themselves to attempt to control other drivers speed. Or you end up with drivers angry at the people they perceive to be speeding, or angry drivers being held up by drivers who are going dangerously below the speed limit.
Vehicle technology allows for highly accurate speedo readouts. Let's stop this pandering to manufacturers, pretending that over reporting speed is a good, or even acceptable state. If Mazda can confidently set their speedos to report very close to the correct speed, none of the other main manufacturers have any excuse.
Honestly Mazda is doing a lot of things differently to other manufacturers.. while VW and its brands went the way of 1.0 3 cylinder engines with a turbo (for the low and mid end cars, you can still get a 2l min something more expensive), you have to turn all the assists off every time you start the car, many of them are quite understeery and heavy. Mazda went with 2.0-2.5l 4 cylinder atmospheric engines even for its base models, push one button and all the lane keep etc. shit assists are off until you turn them on again yourself. In Mazda you dont need an automatic gearbox to get 4x4..Even the whole infotainment is done completely differently to the whole industry.. all car manufacturers talk about how its impossible to make "good old cars" anymore while its somehow possible for Mazda. Im not saying their cars are perfect, driving a car with no turbo after driving with it for a while will feel a bit slow but the nice throttle adjustment mid corner is something I personally cant let go of.
From that I would assume that overestimating the speed is just a safe bet, simpler and possibly cheaper way to do it..just like with small turbo engines and everything else. Maybe thats the one thing every manufacturer should copy. It would certainly made roads safer if I didnt have to pass moms in their SUVs when theyre doing 40km/h all the time.
@@MisoElEven Something that could be interesting to note about the choice of engines for given market are the taxes.
In many country (including in Belgium where i live), you have a yearly taxe to pay depending on your engine displacement.
So people tend to go for smaller engines with turbo in order to pay less. And Belgium is quite expensive in that area (More than France).
Which could explain why i don't see a lot of Mazda on the road in Belgium.
That is very interesting. That means the over read could be a constant and not linear with speed.
So you would always be 5 kph above irrelevant of speed (appart for when you are at a stop or very slow i assume).
I used to think that if you have +5 at 100kph, you might have +10 at 200. Which would make sense if the overread is from the system inaccuracies instead of an electronic margin.
@@guilemaigre14 the over estimating being a fixed amount, or a percentage likely varies by manufacturer and how they are achieving the result. My past couple of vehicles have been a percentage difference.
For example, my current main vehicle (an older Nissan X-Trail (T30 model)) reads 33mph on the speedo when the sensor reads 30mph. The speedo reads 78mph when the speed sensor reads 70mph.
Would be quite interesting to have details from a range of makes and models to see the difference in how big the speed variance between the on-board computer and the speedo is; and how many are a percentage of speed difference Vs a set speed difference.
This is exactly right. My old Ford Ka reported insanely accurate speeds through the OBD port (+/- 0.3-0.5 km/h) but chose to move the needle less than it was reading.
actually, as a delivery man, i'm quite familiar with this system here in Hungary. our fiats overread by around 6km/h, and fixed cameras have a given tolerance (by law) depending on speed, in 50km/h areas its 62km/h. so in theory you could pass the camera in a 50 zone at 67, and not get a ticket. I usually play it safe as you say in the video, and never exceed 60. and it's working, I haven't gotten any tickets so far. at least not from fixed cameras.
I stick to the 10% rule.. if Im supposed to go 50 Im going 55 on the speedometer and so on. But when I go through a route that I know very well (where the straights are, where it is possible to safely ovetake, where the holes are in the road, where the cops like to measure the speed etc.), I will push the car. Theres no reason to go 90 on a road that I can perfectly travel at 150 without endangering myself nor anyone else and also without the risk of getting a ticket.
@@alunesh12345 Off point, but yes. Is speeding a sin though? I'd say it is.
@@MisoElEven If something changes you're going an extra 60kmh faster though. And what if someone doesnt realise you're going that much faster and pulls out in front of you?
@@Noreceipts400 Theres nothing that can change on that particular road and I can see several km ahead..the faster the overtaking manouver is over the safer it is. What if the driver doesnt see you when youre going the legal 90km/h while the other one is doing 80? Nothing changes, you will crash if he moves to that lane or a car flies into my face from the other side. Seriously, unless the car in front explodes theres nothing that can happen on that particular road. Lets not forget theres not much traffic anyway. If anything I would be more afraid of gypsies crossing the road with their tons of copper and other scrap metal etc. XD in the city where I was born (Košice) theyre aparently going to lower the speed limit on the highway from 130 to 90 and install traffic lights just so they can move the trash they have stolen from one side to the other because if we built a wall again then the EU could sanction us for racism/segregation. Thankfully I dont have to ride through that piece of road anymore.
Edit: also you always have to let the car in the left lane go, even if its speeding and youre just moving to the left to avoid a colission with lets say a bus.
@@alunesh12345 leave it out
wheel speed sensors are usually used for abs and esc. 99% of the time most cars use a speed sensor from the gearbox for the speedo. just FYI. Also the faster you go the futher out your speedo will read
Glad to see someone here actually knows the truth lol
Unless you have an old VW beetle with a hub reading
Lincoln mark 8 uses wheel speed sensor. I was suprised to see that my speedo worked after i swaped trannys
All the cars I have owned show speedo is off by the same absolute amount regardless of speed. The computer reads the speed from sensors and subtracts a given amount…50kph is really 46, 100 is really 96. 120 is really 116. Not a percentage amount, but a fixed amount regardless of speed.
Except most japanese cars? Which use the wheel speed sensor in the wheel hub.
In many parts of the US, speed cameras can't give automatic tickets. Making this a none issue, following the flow of traffic is generally the only thing to think about
in louisiana (where i am), often the posted limit is 35, but traffic is moving at 55, so if you do 35 you WILL cause an accident. in the US, it's ALWAYS better to follow traffic rather than the speed limit.
@@staterafukumoto in new york, the highway speeds are 55 but you won't catch a single car in the left/middle lanes going below 70. you can also be driving alongside cops doing that speed
@@staterafukumoto In Miami if youre not doing at least 85 in the left lanes which normally at 85-100mph sometimes 105 you getting yelled at with horns blazing that's including the coop excluding State boys
WA school zone cameras can send automatic tickets. I don't know of any other automatic ticket cameras tho.
In Oklahoma, the speed limits are anywhere from 60 to 80 on highways. Usually add 5-10 to that and you're safe. My wife and I were recently in Philadelphia and the 55 mph speed limit is more of a suggestion than the law. Go 70-80 or get rear ended. We learned that real quick when I was doing 60 on I-95. I learned then that even the worst drivers in Oklahoma are pretty tame.
I don't have cruise control, but a steady foot. My old ass VW Vento (Jetta 3) overreads by like 3km/h on winter tires and it's pretty much spot on with my summer setup
Yeah
As another separate comment, I also want to note the effect of the wheel circumference. Back in the early 2000s both myself and my sister owned an E110 Corolla. Mine had the stock 175/65/14 wheels. Hers was modified by the previous owner to run 185/60/14. That's a difference in sidewall height of 2.75mm, or 5.5mm in circumference. On a long-haul trip from Namibia to South Africa we were driving together, and I asked her why she was driving 5km/h below the speed limit. She said she wasn't...
"modified" bruh that's just changing tires lol
@@Nibblerrare your 12? That’s exactly how the verb modify is used.
@@mahadali619 25 actually. And no, no one calls changing tires "modifying".
@@Nibblerr that’s literally what the word means, if you’ve changed something, you’ve modified it, be it tires or an engine
@@mahadali619 something tells me you've never worked on anything.
When I’m doing the legal speed limit of 120km/h in my Lexus, Waze says I’m doing 114km/h, what I find interesting is that the Lexus CT is limited to 180km/h but on the speedometer I’ve reached 190km/h which with Waze is 180km/h so I almost wonder if Lexus knows by how much their speedos are of, limiting to the actual speed and not the speedometer
Yeah my ct is like that too and so is my Toyota
Probably adjusted for max error at certain tire thread depth. If you got a slightly larger in radius wheel, you could go faster
That is exactly how it works. Example: my e36 M3 is Limited to 250kmh but the limiter doesn’t kick in until 268kmh on the speedo
@@geraldkottler3014 yup, that's how it works in modern amgs as well
of course toyota know the speedo is out. in this day and age, if they wanted to, they can make speedos 99% if they want.
Yeah, that's why it's OK to be slightly speeding most of the time, cause you're actually not speeding at all. But I agree with the regulations - it is far more convenient to drive just a bit slower, without even noticing, than to get a ticket while thinking that the speed was under the limit.
My E39 528i is exactly 5 kmh over the real speed. The funny thing is that in the hidden menu on the bord computer there is a real speed option which is spot on but must be turned on every time you start the car if you want to use it.
My e46 touring shows exactly the same 5 km/h over the actual speed. Hidden menu is awesome
How do you turn it on? I would love to try that out on my E39.
@@xJustInTime it depends on the version of obc you have (big or small screen in the cluster) but there are a lot of tutorials on CZcams. Normally on all BMWs it's turned on by holding the button to reset the trip odometer for around 10-20 seconds. You have to unlock it as well after you get in, so better check a CZcams tutorial as it's a but too much to type in a comment.
Why would they lie about it in the first place?
5:11 Of course, timing for record speed attempts is generally done with external equipment (though I'm sure it's useful for the driver to have an accurate indication too!).
I've been using the 10% rule for ages. I regularly drive 10% over the speed limit while going through speed cameras and I've yet to get a ticket (other than when I've not known I'm going past a camera).
Yeah for 20 years
in maryland, where i live, the fixed speed cameras allow you to go up to 12 miles an hour over the limit, so 37 in a 25 etc... Of course most people dont know this so they slam on the brakes right at the camera and go 10 under the limit then floor it afterwards cuz idiots ...
I learnt about this when I was still in high school, when I got my first car I already knew that 129km on my Speedo was 125km in reality but I also noticed that the accuracy varies depending on how fast you're going.
My BMW shows 4 MPH on the speedometer over GPS speed indicators. I always suspected this was intentionally done so that the car warranty would be voided sooner than it should have otherwise been.
I can tell that at least an NB MX-5 does use the sensors from a gearbox. Changing the differential to a bigger torsen model caused it to actually underread by about 10%. I did get used to it quickly though.
My mate and i actually figured this one out pretty recently, got a 2010 VE Holden Commodore SV6 and when the dash is spot on 110km/h, phone GPS only shows 105km/h. On a 7 hour drive in Western Australia that 5km/h does add up!!
that's a 20mn difference if you drive 100% on cruise control, less if you have some slowdowns
Having driven many cars both in the US and Europe, I can confirm, almost all cars consistently overread in Europe, but in USA it's much closer. I've heard carmakers do this to make the car feel "faster", as you seemingly reach a higher number sooner than if the speedo was accurate, whilst still staying within the lawful limit.
Can confirm, Mazdas are accurate even in Europe.
I kinda knew this already since i noticed that gps speed is usually less than the car speed. My dilema is: what about the car odometer? If your car overreads in 99% of the cases, then that means the car odometer is higher than it should be. Also the mileage is worse than the car reports. So, if the car overreports by 5% then for a 60mpg car means 57, not a huge difference, but its a difference
For the odometer it's not particularly important because it's only a general indication rather than a datum point for specific tasks. If you were buying a second hand car a 90000 mile car that has done 85% of those miles on the motorway could be in better mechanical order than a 25000 mile car of the same age that has been used as a courtesy car and ragged every day of its life, also if you're due a service/belt change at 20K it's not likely to matter within +/-15%. Indicated mpg is again never particularly accurate, it's an estimation designed to highlight optimal engine conditions rather than an actual indicator of consumption.
From what i gathered on other comments, the odometer is usually very accurate. It is only when displaying the speed that they add a margin. Now i lack soucres to confirm, but others seems to says so.
My old passat b5 overread 10km/h but odometer showed less km. It was strange but that meant that car used less fuel than calculated or indicated😁
I can't say for all odometers of course, but I can tell you for my last couple of vehicles the odometer is not connected to the speedo output.
I have mentioned in a comment below that whilst the speedo is often quite inaccurate, the speed sensor on onboard computer monitoring speed in a vehicle is usually very accurate. If you connect to the diagnostic port on relatively modern vehicles, and check the speed sensor output, you will find it is different to the vehicle's speedo output. Odometer figures are based on using that speed sensor.
So, for example, when my vehicle's onboard computer reports the speed sensor as running at 70mph (using the EODB (equivalent of the OBD-II port used in North America) port to read data), my speedo with display 78mph. But if I was to run constantly for an hour at that speed, my odometer would increase by 70 miles.
@@damionlee7658 guess overreporting is so bad that they artificially reduce the value. I usually set my cruise control to the gps speed, sometimes 5-10km above it, but it seems really strange. Also modern cars should be able to auto adjust for wheel, since they have a gps internally and they can compare the gps speed to the wheel speed. Tesla can detect wheel uneven wear, this should be easier to do
My Mitsubishi Eclipse GT v6 from 2008 reads 10% under. I actually noticed just because 120kmh didn’t feel remotely as fast as it did in my Santa Fe and when tested found that I was completely correct. Living in Ontario Canada, and the car has 150k clicks on it. It’s really neat to know it’s not just a my car problem
When I got my first car - a Honda CR-Z - a few months ago at 18, naturally I was super hesitant with my speed & I've actually been wondering ever since why Google maps reads my speed 3mph less than the car does (I assumed it was an inaccuracy on my phone's part). This video's been an awesome help, cheers!!
I've got a CR-V, and the speedo always ready at about 1.5 - 2mph faster than what google maps reads
That’s interesting. Adds another level to how fast people drive now. Really tempted to test this out now 😂
Edit: tested the theory and yes, my dads 2018 BMW 5-Series does it too, the car was 2 mph above the what the GPS was telling me.
I used to have an E36 and I currently have an E60. Both would consistently show 2mph faster than the GPS showed I was going. The E60 is a little more odd though. I've coded the cluster to show a digital reading of the current speed. If I set my cruise to 72mph, the GPS speedometer on my phone will show 70mph, but the digital reading in my gauge cluster will show 69mph.
In Australia, regulations (ADR18) required a car built before July 2006 to have a speedo read the actual speed +/- 10%. The vast majority of manufacturers, of course, tried to make the speedo as accurate as possible.
In July 2006 that regulation changed, so that a speedo can NEVER read a lower speed than what the vehicle is actually doing, but MAY read up to 10% + 4km/h over the actual speed.
So not really a significant change. Except, the national transport authority in Oz ... err ... actively 'encourages' manufacturers to make maximum use of the allowed tolerance. Put simply, it is a strategy to make the speedos in all cars (made after 2006) read high, thereby slowing traffic. So the same result as reducing ALL speed limits across the country by 10% + 4km/h , without the political backlash of doing so.
And before you say "but my car here in Australia is made in Europe, so it will be more accurate", let me add a minor detail that was missed in the video. Basically all modern cars get an extremely accurate speed reading from the relevant sensor, and that is what is supplied to the ECU etc. But the ECU then hands that input to the dash display unit, which displays the speed etc. It is in this unit that the speed is 'modified' to read 10% + 4km/h higher than the actual speed. This allows for the odometer to remain accurate, as the 'correction' is not applied to that element of the display. So all the European manufacturers have to do, is a simple software update to the cars coming to Australia, to make the speedo read high, as is required.
So to put this in more practical terms. When you are in the Righthand lane of a multilane motorway, trying to overtake at the actual 110km/h speed limit, and there is a car sitting in front of you, slowing you down ... say doing 96km/h (by your accurate speedo or GPS)? Well, his speedo says he is doing 110. Just as the authorities want.
And people still complain when they get snapped by a speed camera and the speed camera even has a warning sign ahead of it lol
I got called out :D I am definitely doing the math - Waze speed readout + 5km/h tolerance on measuring equipment so in 50km/h I will be usually doing 58km/h on the speedometer and 55km/h on GPS... but I noticed the car having different margins at different speeds and that a GPS speed read-out is wrong if you are going up or down a hill -- so I have to account for that too
Congrats on 100k subscribers!🎉🎉🥳
I had a Golf. It showed me digitally to which speed the cruise control was set. The speedometer showed 100km/h when the cruise was set to 106. The GPS reading was 104.
Unusual usually golfs read high
Yeah, been aware of this for more than ten years. In my Jetta, I've noticed 33 is 30mph; 44 is 40mph, 54 is 50mph and 66 is 60mph. Have driven past speed cameras hundreds of times at these speeds and not gotten a single ticket.
I have noticed that in my 2 VWs as well (Golf and Touareg) The faster I go, the more the car would over-read. Phone GPS would say 80, car might say 85
My last car was a Chevy Sonic, and I remember that I felt the speed sensation was a little off, so I checked with my phone and it was 10km/h less than speedometer's velocity.
This is important to know when doing regularity rallies....
(When I did them, I built a table with a GPS, my dad used to use a stopwatch and a measured kilometer (there are / were some of them on some roads around here at a time) in the 90s) (The other option in South Africa is the blue signs next to some freeways, which are spaced 200m apart (they are not always accurate though))
Yes SSC and the Tuatara.. 🤔💭301 Mph, Let Alone 331 Mph!🤥 A record run requires reliable data.. 🚗💨💨💨
Believe in JESUS today, confess and repent of your sins. No one goes to heaven for doing good but by believing in JESUS who died for our sins. GOD loves you soo much unconditionally.😍😚☺🤗❤😇
@@alunesh12345 UwU
Typically I found my speedos to between 5-7% out but my BMW is alarmingly accurate I think it uses gps via the nav system . My wife’s Prius was about 10% out so 70 was 63 at best , I wonder if that was deliberate
Believe in JESUS today, confess and repent of your sins. No one goes to heaven for doing good but by believing in JESUS who died for our sins. GOD loves you soo much unconditionally.😍😚☺🤗❤😇
There's a setting (accessed via the ODB2 connector) where you can set it to be an accurate reading. I suspect that one of the previous owners has adjusted this setting.
@@alunesh12345 go away
@@igniteED No previous owners on my g82 im the first
Have a 2002 subaru liberty and it used to overread by about 5% on factory rims. So bought bigger rims and low profile tyres. Because of the adjustment it now reads spot on with gps 👌
Here in Italy the regulation states that speedometers have to overread by at least 4km/h, with a maximum of +10%. My car is a Hyundai Tucson 2016, and testing it I found out that it overreads by exactly 4km/h consistently, when going over 40.
Speed traps also have a tolerance of 10% (some sources say 15% but it's better to be on the safe side), so it's pretty easy to calculate that on a highway I can go at 143km/h, so in my car at an indicated 147km/h. Easy enough to calculate!
I usually keep a GPS speedometer on my phone that tells me the average speed, so I can speed up a bit for fun when the road is empty, and still stay under 143 on average.
In germany most people just drive at least 10% above the speed limit because of techometer inaccuracy and the tolerance of speedtraps.. If you're driving exactly 100 on a normal road people will pile up behind you pretty fast unless they can overtake. 😁My 2021 Focus ST is about 5km/h off at 100km/h, gps displays 100 when the dash shows 104-105.
I'm German too and usually overtake with exactly 5km/h over the limit when I'm driving with GPS. It's surprisingly useful in 130 roads where people stick exactly to the limit. I may not be overtaking fast but I only have 1 or 2 people tailgating me at best 😆
Does that mean normal Focus drivers in Germany routinely go at least 115kph? (105+10%)
Will insurance cover damage to their own car if they have a crash no matter the speed or is there a cutoff? (say 140kph)
I’ve noticed my Porsche 944 seems to be consistently 2-3mph out across the entire speedo, not a percentage. Whereas my Mini Cooper seems to be about 5% out.
Believe in JESUS today, confess and repent of your sins. No one goes to heaven for doing good but by believing in JESUS who died for our sins. GOD loves you soo much unconditionally.😍😚☺🤗❤😇
@@alunesh12345 this has nothing to do with cars
On BMW's (I have no knowledge regarding other brands) you're able to go into the vehicle settings using the OBD2 connection, and set your speedometer to normal or a more accurate reading.
VW Touareg 2005 3.0 TDI, spot on with both 18" summer tire and 17" winters. I just love it!
When I got my BMW I noticed the speedometer was always reading faster than I was actually going so I researched it and apparently German cars must always over read and never under read the speed. There’s a setting in BMWs that lets you make the speedometer display the actual speed but that’s turned off in the United States. I used an online calculator to figure out what tire size I needed to install to get the true speed reading on my speedometer and installed that size of tires now. They were very close to the original size but made just a small difference in my speedometer and now it’s spot on.
Thats right. Im in europe and my BMW have submenu where you can read actual speed. It is always few km/h lower than reading speedometer is displaying.
You missed a key point: If the speedo is always +10% then your cars mileage reading is wrong. When your car's odometer indicates it's travelled 100,000 miles it will have actually only covered 90,909 miles in reality.
Unless it's a Mazda mx5 of course.
Most vehicles read ( sense ) the speed and distance incredibly accurately , but, they deliberately display the speed as lower than real to conform with law. So mileage with come from the accurate reading.
@@nobodyimportant7380 that's not true. They don't display the speed as lower, they display the speed as HIGHER than it really is.
Secondly there are not 2 streams of information the mileage is based entirely from the speed sensor readings, so yes the mileage will be wrong like I first explained.
Maybe rename yourself to "NobodyIntelligent"
@@steve0680657 oh I'm sorry, I used the wrong word by mistake. As the ECU reads the information accurately then displays it deliberately wrong, it can be seen as 2 streams of information when read at the ECU.
Displaying the speed incorrectly deliberately higher than actual, will never get the manufacturers in trouble, displaying the mileage incorrectly ( higher than actual ) would have them sued as it could be used as a way for them getting out of a mileage limited warranty repair.
@@nobodyimportant7380 there are not 2 streams of information the mileage correlates to the speed.
@@steve0680657 one in (accurate) and one out (altered) to go to display, is two streams. But if have actual ECU data to confirm what you are saying then show me, I am happy to be incorrect with evidence showing that fact.
Legitimately one of the first things I do when I get a new car (well, new to me) is check the speedo against my phone GPS to get an idea how the actual speed compares. In my '98 firefly the speedo overread by about 5%, but around a year before selling it I acquired a set of 14 inch wheels (as opposed to the stock 13s), which I measured the outside of the tires to be about 5% larger circumference than the 13s, and sure enough the speedo was roughly spot on running those wheels.
My '93 civic also overread by around 5% if I recall.
My '06 Swift is I believe 1-2% over.
Thats really nice actually, i love this!
It's good the speedo over reads. That saved me a few times from speed cameras.
I once bought a used motorcycle 5h away, rode back on it. it took me a little while to realize the speedo was completely off, undereading by at least 30kmh, I was around 110kmh and passing all the traffic.
My hands and butt going numb were not lying though, measuring the vibrations of the big 650cc single doing 140-150. I was slightly relieved to see that doing more reasonable speeds wasn't as uncomfortable.
Literally been wondering about this; our 2016 minivan (standard wheels / tires) always reads 5-8mph lower than phone gps, and I guess it's to err on the side of safety. THANK YOU for this video, great work!
Two completely different Ford vehicles, a 2014 Cmax plug-in hybrid and a 2016 F150 with 4WD, they both have the same error from actual speed versus both GPS and radar (which both agree). There's a static deviation of about one mile per hour, plus a very slight proportional deviation. To go an actual 40mph, I have the speedo at 41. To go an actual 70mph, I put the speedo (and cruise control, etc) on 72. Strange that it's the same with such different vehicles and drivetrains -- makes it seem intentional.
My 2017 Kia Sportage SX-T (US market) is accurate within 1~2 MPH - regardless of the actual speed driven. I have checked it against the speed readout in Google Maps, the GPS based speedometer in my radar detector, and free-standing radar speed cautions.
As you noted i the video, in the US market the rules on this is within roughly 2.5% in either direction.
A vehicle-mounted non-contact ground speed sensor, such as those which rely on Doppler radar, are pretty much the ideal for this purpose. They can achieve very high accuracy and refresh rates, and obviously aren’t affected by wheel/tyre circumference. If one seeks to use one of these sensors with a factory speedometer though, it would likely require a bespoke (usually rudimentary) electronic interface.
Found this out when I was driving down the high way side by side with my cousin while we were on the phone together and I told him to set the cruise control to 75 mph so we both set it and next thing you know he starts leaving me behind, did a bit of research and I found out that North American cars don’t do this while most other places do
We in the Netherlands have something called FlitsMeister. This warns for speedtraps, average speed checks and all sort of other stuff. If I do 80 (kmh, because duh) on FlitsMeister, I'm driving 84 on my speedo. At almost every speed, it's 4 or 5 off.
The car I'm talking about:
2018 VW Polo 1.6TDI with manual transmission. Not my car, but still drive it every day.
Our -17 Mazda 6 over reads by like 2km/h when going 80, which I find really accurate!
I recently realised this when bought an Audi A3. Overreading with the 17 inch wheels. I put on 19 inches from the rs3 and the Speedo is almost spot on, 1kmh off instead of 5-6 that it was. My guess is that the manufacturer will do one speed Reading system for that particular car and will do it more accurately for the top performing version of that car as it will likely have bigger wheels. Otherwise if done in reverse it will under read in the performance trim.
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I have a T-Cross (but in Brazil) and the speedometer reading is very spot on. Most of the times, the difference is in the scale of one kilometer.
I remember my old M2, speed was bang on at all speeds. My 435d I had before that had a fairly significant under read
Believe in JESUS today, confess and repent of your sins. No one goes to heaven for doing good but by believing in JESUS who died for our sins. GOD loves you soo much unconditionally.😍😚☺🤗❤😇
I've got a Volvo-v70 from 1998. At lower speeds 0-50 km/h it's spot on. But when the speedo gets up to 70-130 km/h the car is roughly traveling 5-7 km/h slower
1 thing that works out well with wheel speed sensors, unless the sensor system can take wheelspin into account for mileage, is if you do lots of burnouts it'll age your mileage faster than no slip, which is fair enough really!
I had a 2011 Holden Commodore SS-V In the settings menu was a tyre size section, if you put bigger wheels on you can enter the size of the tyre to allow the computer to re-calibrate the speedo.
Even changing tires can make a differece. You can adjust that through a tuner box though. I put larger tires on my Jeep and used my tuner to tell it how tall the tires are. My GPS and speedometer are actually very close.
I'm in the USA. My VW id4 is +1mph, but my e90 BMW 3 series is interesting. It is +2.5mph on the speedo, but I turned on the the digital display without a "correction" and it is spot on.
Had a 2015 Mini Cooper S and it was just like your VW. Have now a 21 Hyundai Elantra N line and it is spot on with all the radar gun signs. Or with the photo radar van.
Trivia: In Japan we have misdemeanor speeding (
In the US we mostly catch speeders the old fashioned way: a cop with a radar gun.
@@slowanddeliberate6893 our cops do the job in an ever older fashioned way: follow you and keep the same speed with you and hit the record button on their speedometer
It is also required by law for them to turn on the red strobe light when doing this. So if your situation awareness skill is good enough you can just hit the brakes when you spot a cop following you and you'll be good to go.
But most people get caught in a so called mouse trap: a hidden radar and pull you over later
My GPS sat nav screen was always showing a few KMH over the indicated speed and it annoyed the hell out of me, so I recalibrated mine on my E46 M3 by opeing up the speedo cluster and readjusting the needle.
I have been wondering this bc when my gf and I are on cruise at the same Speedo speed, my car goes faster, but her car goes slower than all of the other cars as well. I wonder if this has come out of so many people going 5-10mph over?
In my country there are sometimes speedtraps that don't ticket you, but instead display your speed. So there will be a sign saying "You are going 50 km/h" followed by a smiling or a frowning smilie depending on whether you are too fast or within the speed limit. I always use these to check how much my speedometer is lying to me, it is usually around around 5-8 km/h higher than my actual speed. Depending on the speed i am going at, 5kmh at 50 and 8kmh at 100.
My country has a 4% tollerance in speed traps, however tickets are only given when more than 10km/h above the speed limit. So i usually go speedlimit + 10km/h and never gotten any tickets with that
Good video. My 2012 Audi S5 reads high by 1 mph; at 70 I'm actually doing 69. My 2001 Porsche Turbo reads high by 5 mph; at 70 I'm doing 65. It surprised me that the Porsche was off by that much, given how well the car is made. Both are running stock size tires and wheels. FYI, I've run through many speed traps in the US in my Audi and never been pulled over with the cruise set at 10 over. However, when driving in areas with known speed cameras like DC and MD I don't take a chance and set it at the posted limit.
I estimate my speedometer's accuracy by comparing its reading when I pass by a speed check sign. I find it's usually 2-3 MPH higher than my actual speed, assuming all speed check cameras are accurate.
I'm convinced it's so the odometer is fast and the warranty ends quicker. Your speedo may be way off, but plug into the onboard diagnostics and you'll find they are pretty bang on and they are both getting info from the same sensors!
I've done similar tests with phones and my cars are always showing nearly exactly 5 km/h faster. I'm in South Africa.
I can't exactly remember the cars I used, but we've owned mostly German cars like '04 Polo (this one I do remember testing), a variety of Porsches - some of which I definitely tested, some Mercs and Audis. I do remember testing it on a +/- 2010 Ford Ranger and also getting about a 5 km/h increase on the car's speedo.
Speedo means something different here. The title just cracked me up and hearing it was hilarious. Very informative though.
My 2006 honda accord is spot on with most of the apps, and almost all the electronic speed bumbs with wires on the floor to get the measurements
My 2012 Honda Civic reads pretty accurately. I've noticed that if I'm indicating 70 on the speedometer, the GPS usually indicates within 1 mile an hour. I'm on super cheap Douglas tires from Walmart that are probably well past due for a rotation.
2005 Subaru Impreza STI imported from Japan. Even though the speedo's been converted to indicate MPH instead of KPH it's still extremely accurate and agrees with the GPS exactly
The car I did my test in - fiat Siecento - over read by 10 mph...going round on my test knowing I was doing 20mph because the satnav said the gps speed but not going quicker otherwise my cars speedo would say I was speeding was almost painful!
Interestingly one time I put larger sidewall tyres on the car and the speedo became almost perfect. I knew the difference wold be less but it was spot on at 70mph! the rpms sat lower as well so it was much more comfortable for distance :)
In NZ on some motorways we have speedo checks using markers on the side of the motorway, poles marked from 0 to 5 km distance, as you pass the 0 marker reset your odometer and then check again at the 5km mark, this will tell you if your odometer is out, have found out on my last 5 cars that the odometer has been very accurate.
But all my speedos have generally been out by up to 5 %
The odometer runs on a different system to the speedo.
My new car was out by 2% when new and 5% out after 60000km, put that down to lower tyre circumference due to wear, as soon as I replaced with new tyres back to 2% again.
After driving numerous different brands of cars, my '19 Acura RDX's speedometer was almost the same as the "GPS" speed when cruising around 75 MPH. Other cars tend to differ anywhere from 3MPH - 8 MPH.
Glad to see this. Thought my Forte Koup was buggin
Opel Astra F did over read quite a bit if you were doing the city speed limit on the speedo which is 50 kmh you would actually be going 40, and the overread grew along with the gain of speed, it showed 140 when you were actually going 120, but the overread was within the tolerance required by the law. It was a cable speedometer and this car was from 2001!!!!! Even my Audi 80 from 1989 has an electronic speedometer with an inductive sensor on the gearbox's left axle output.
Does GPS no longer have the issues with unflat elevation leading to underreading speeds. If you are going up, or down, a steep hill, from a birds eye perspective you have a slower apparent speed than you actually have due to perspective. Im not sure if this is a thing that is or isnt accounted for in most GPS speedos.
I remember about 6 or 7 years ago my mum asking some car guy about why her speedo in her car and her speedo on her GPS were so different and the guy had said that it was likely to do with this issue, this was at a point where I was living in Australia so I dont know how their laws on in-car speedo accuracy works and if its similar to the uk.
With GPS reading does it account on the terrain or assume you are driving on a flat 2d plane at all times?
If the roads are very undulating then that can affect the length it's measured?
GPS operates by measuring the distance to multiple satellites then determining your position via triangulation. The raw data from that would indicate height as well. So I would hazard an educated guess that vertical velocity is taken into account as well. Not to mention that GPS watches also measure height and stairs climbed.
I already know this because in my country there are some electronic boards that shows speed when your car is travelling on the highway, it's usually 4-5 kilometers less than car reading.
There are also the cars that have two speed readings, one for the ECU ( accurate ) and one for the speedo display ( showing higher speed ).
General GPS is accurate to 10m at best, I am not aware of any publicly available GPS with better accuracy, Hence the reason many young drivers have been accused of speeding with their insurance black box, because they were on a Dual carriage way which was alongside and parallel to a 30mph limited local road. The GPS was showing them as on the 30MPH local road.
This is absolutely true!! I own a 2014 Cayenne GTS and a 2018 Macan S and BOTH Read exactly 5MPH over. I asked Porsche about and they told me all their cars do this. My mom’s 2018 Audi Q5 equipped with 20” wheels is almost spot on accurate but my 2009 E63 AMG was about 3MPH over.
I once had a set of tires on my Subaru that was slightly to big (I think one size bigger than recommend) an it made the speedometer pin point accurate 😅
Thanks. I’ll check it out
In Australia a speedo is allowed to be 10% inaccurate. In the past most cars were fairly accurate, but that changed in 2008.
Starting in October 2008 car manufactures had to list on the windscreen of a new car its fuel consumption rating. Manufactures soon worked out that they could improve their fuel ratings by making the cars speedos inaccurate. My 2012 Subaru was so inaccurate ( 8% higher ) that I used to have a old phone sitting on my dash that I used as a GPS speedo.
No need for the GPS speedo anymore as my current Mercedes is 100% accurate. As a result my Mercedes fuel consumption reading is 100% accurate, not reduced by a false 8% like in my Subaru.
As an aside, you can modify your 0hone settings on Android both in the developer menu (such as by preventing the phone from having rest periods on GPS timing) as well as through secondary apps (in particular through rooted devices with unlocked bootloaders) that enable for vastly increased update times for the system. Downside is that it will HUGELY increase the battery drain on your phone. Not sure how much more it can improve accuracy via increases time measurements, but it does offer at least *some* options.
I discovered this on longer journeys in both my cars, I have two Audis and they seem to be off for the same amount, even tho they are like 10 years apart from each other. And also, at different speeds they underspeed for different amounts. When I'm going under like 110 KM/H the real speed seems to be 105, when having the navigation on my phone, and when going something like 140 KM/H the real speed is 130.
I'm curious if other Audi, Volkswagen, Skoda owners actually get the same readings.
BMWs E9x series know exactly how fast you are going, and then add an offset, whereas the older E46 series was dead on. You can actually turn it off for the digital readout, but fixing the gauge is more difficult. I read that it is due to TUV regulation requiring that is doesn't under-read even if slightly over-sized tyres are fitted.
Peugeot 508 2013, cruise set to 70 mph, sat nav and phone show 67 ( sat-nav) 64 Phone, I have always suspected the difference was because of the time a signal took to travel the 250,000 miles to any given satellite, I did know that the speedo in most cars tend to under read too, I had a motor bike which broke the cable ( from the front wheel hub) and being an old ( 50 years old) the cable was a non stock item, so replaced it with one of those computerised ones you can get for bicycles ( they read up to 99 MPH) this you have to set up giving the wheel/tyre size, and that was pretty close with less than a 2mph speed difference when checked against a sat-nav, but as you stated as the tyre wore down it became less reliable, also I found that hot and cold conditions caused fluctuations in the average speed displayed too, the most accurate speedometer I have come across was on my ex police bike ( BMW K1100 LT ) but that speedo was not an OEM part it was recalibrated by a company that the police use, and that was accurate to within 0.5 mph
Two true stories that both made the news regarding speed cameras in Virginia.
First was a guy that got sent a ticket with a picture of his tag and a pic of the windshield view. He sent in a picture of the money. Someone at the office sent him a pic of handcuffs. Second story was a congressman getting sent a ticket but the wife opened it and the guys side piece was clearly seen in the passenger seat when he was supposed to be out of town. He complained and that ended the speed cameras on I66 inside the Beltway. Thanks Congress guy as I drive there a lot.
I tested this many times on my 2005 Focus. So at the city speed limit here - 50km/h I am usually at around 55-57 on the car. But the faster I go the bigger the difference. So let's say on a highway the limit is 130km/h. On Google maps if it says 130, my car is above 140. I tested this in Germany at even higher speeds and the difference still grows.
I have seen this in all the cars I have driven when using sat nav. From big vans to small compact cars, it's usually between 3 to 7 kmh slower
This video is very helpful
Well even in older European cars this holds true.
In a Renault Clio of 1992 (1.1) I was doing 140km/h on the highway accordingly to the speedometer, but according to Waze or Google Maps I was doing 125km/h
So this is what this thing is showing! 😳
I always thought you just have to get both needles to the other end 🤔
In Germany, cars fail their biennial technical inspection (TÜV) if the speedo reads under. It can read up to 10% plus 4kph over tho. So it is usually adjusted 3-5% over (showing 103-105kph when the car is really doing 100) so that even if it‘s warmer during the inspection (=> more tyre pressure => bigger diameter = car goes further per rev => higher real speed) or something like that, it definitely won‘t read under, since failing the inspection means the car has to stay at the garage until the next possible appointment and it will cost another good 100€. No garage wants to have to tell their customer those news.
I have checked many cars on this. A D40 Nissan Navara used to read about 10% over up to about 70mph, so 33mph indicated was 30 actual speed and 66 indicated was actually 60. My D23/NP300 Navara read 5mph over all the time. My new Discovery reads 3mph over. My Mum had a Hyundai ix20 that used to read about 2mph over.
hello nice vids keep it up 😁👍
In Australia the Design Regulation 18/03 specify for cars:
_The production shall be deemed to conform to this Regulation if the following relationship between the speed indicated on the display of the speedometer (V1) and the actual speed (V2) is observed:
In the case of vehicles of categories M and N:_ (Cars are in class M)
0 ≤ (V1 - V2) ≤ 0.1 V2 + 6 km/h
So in short the speedo can read up to, 10%+6kph over the actual speed, but not under at all.
My Honda bike is a consistent 10% higher than actual, my old Toyota also over read, but my Jeep is reasonably accurate from factory. (It is more so now that I recalibrated it against GPS via OBD2 by updating the wheel size recorded in which ever one of the computers stores that data.)
10mph is really extreme, ive seen it for years on different cars and the deviation is usually 4-5 km/h on standard tires, and here in Germany if you change the circumference of the tires you need to recalibrate the speedometer in order to pass TÜV inspection. My mini cooper s r53 has 4kmh deviation, other cars tested are golf 3, golf 4, volvo V40 all in the same range, GPS and speed trap tested
50€ on the dashboard and any car will pass :D
@@MisoElEven XD I'd love to know where that is, would have saved me around 700€ last month for the inspection lol
I've actually been in a car that had a perfectly accurate speedometer. My old work van with brand new winter tires read exactly 80kmh while GPS said i was going 80kmh.
It just comes down to tire wear and speedo calibration mainly, i think.
one thing I found in my cars is that if you have an obd reader and plug it in. it shows a different speed than the speedo