What's the "real" speed?
 

When Im on the highway I can see the difference between the speed in the tach (Digital Speed) and the speed in the center speedometer (needle).

I'm running at 130KM/H (digital speed) while the needle is saying 140KM/H (+10KM/H).
I'm running JCW 17' wheels with Bridgestone Potenza 215/45.

Is there any way to match this two speed sources?
And which is the more accurate source?

And which is the more accurate source?
Can you compare them to your GPS's speed?
-Mike

The MINI comes preset to overstate the actual speed (odometer is correct).

There is a config setting that will display the actual speed in the tach, but the center speedo will still be off. Looks like your car has this configuration.

This is based on the other numerous threads on this forum discussing the same thing.

Note that even the "actual" speed is based upon the OE wheels and tires.

If my GPS speed displayed is different to the displayed on the speedometer and different too to the displayed on the tach: which I should take as the reliable value?


On the odometer you just can see the distance traveled (right?).
I have another problem with that but it is not related (I think my Mini is overstating the distance traveled).

And yes, the OE wheels were 15' (moved to 17') so I know there is affecting the value.
My question is, if I should take the digital speed or the center speedo speed as the reliable value.
Today I'm taking the digital speed since it is the lower value (it is good for avoing tickets)

gps speed is most accurate.

Typically the GPS speed is more accurate, but not always. I've noticed that my GPS speed can go up and down a fair bit when I am holding a steady speed. (And RPM, as shown by the tach and by my ears.)

Remember that the speed readout in the tach and the reading on the speedo dial are only counting revolutions of the road wheels. If you change the overall diameter of the wheel/tire package, you will change your actual speed traveled versus the speed the wheels are turning, and therefore versus the reading of your instruments.

Funny enough, the speedo readings actually change as your tires wear! The change in overall diameter is small, but it adds up to a noticeable (small) amount over the lifespan of a set of tires.

I have confirmed that my digital speed reading is certainly overstated. My Bluetooth OBDlink provides an accurate reading which is always in sync with various GPS sources I've compared against. Several weeks ago while driving on the freeway I looked over at a Honda Civic, which has a large and bright digital speedometer, showing that it was traveling 74mph. He was driving slightly faster than I but my readout was 78mph.

I'm on factory 17"s with OEM sized tires.

I've been told that one of the many laws that auto manufacturers have to adhere to is that the speedometer can not read slower than the actual speed the car is traveling but it can be as much as 10% off in the other direction. If true it's not too hard to understand why speedometers are off the way they are.

If you want to avoid tickets, use the HIGHER value, your actual speed will be less. I have to manually convert my speedo values in my head while driving. 65mph displayed is actually 60mph, 87mph displayed is actually 80mph. My odometer is correct and I'm on factory size 15" wheels.

Until you know how yours stacks up by comparing it to a GPS value at various speeds and in various locations (just to be sure), just be careful. R56 speedos seem to have a LOT more variation than other makes. I'm not sure why this is, but the dealer considers it "accurate" as long as it's less than 10% +2mph over the actual speed.

Trouble is, knowing its way high you may overcompensate.
The worst part is having to explain to passengers were not really going 83.

83 is easy to explain. Explaining to the boy's mother (he sits in a car seat in back) why he was all excited over seeing it hit 100 is a bit more problematic. "Honey, honest, 100 is really only 90 in this car."

This is why I don't really need a Cooper S. I get in enough trouble.

This subject does come up all the time.

You can disable the overestimation for the digital speed using either NCS Expert or the Carly app.

I prefer to have an accurate gauge.

Try a gps. check the indicated speed from that compared to speedo. gps is very accurate.

New owner here and I've noticed mine is off by at least 5-6 mph. Both my digital and center speedo. I've tested it several times against some digital MPH speed signs in a local city. When I set my cruise at 52-53, the city speed signs say I'm going 47. It doesn't bother me much, especially if I know what I am really going. What does bother me is that if the speed signs are correct, and my car says I am going faster than I really am, isn't it logging more miles on the car than what is realistic? Right now I have a little more than 58K on the car. being almost 10% off, doesn't that mean my car really has a little over 52K? This seems like it can be a problem for warranty issues or even resale.

I had the same issue a while ago. Bought a Garmin Nuvi GPS to get my true speed. I still have no idea how the odometer is registering correct mileage with incorrect speedometer readings. Just to complicate things further, I recently bought and plugged in a Scangauge 2. I now have 4 different speed readings....the digital in the tach, the actual dial speedo, my Garmin, and the Scangauge 2. Most times, they are with 4 MPH at 50 or so. I still fail to see how the odometer reads correctly, while the car's internal computer thinks I am traveling faster than actual ground speed. Isn't this all read by the VSS? (vehicle speed sensor) And, yes, this existed even with stock tires. I know how many miles I racked up on my previous daily driver per year, (same job, same drive) and I have taken some road-trips in my MINI. Disregarding those trips, my MINI is racking the miles up more quickly than my previous DD did. And, yes, I have taken into account the tire-size change that I made. As I said previously, this issue existed even with the stock-sized tires. Can anyone tell me WHY they think that the odometer reads accurately even if the ground speed does not? Is there another sensor that somehow reads miles traveled versus ground speed over distance covered? I figure to keep my MINI for a long time, so those "extra miles" don't really matter that much, I guess. Until it comes time to sell. An 8 or 10 percent difference over 100k miles makes quite a bit of change in resale value. Or maybe not. Not like these MINI's hold value well. Smiles per gallon! The way I maintain mine, someone is going to get a VERY nice used 2011 MCS at 160k or so in a few years....

You are correct, of course, if the odometer reads correctly then there is no good reason why the speedometer can not be made accurate as well. And yet clearly MINI has failed to do this.

I've tested my car with various accurate methods (GPS was easiest) and the odometer is quite accurate with stock tires but the speedometers are inaccurate, as most people report. You can program a Scangauge to display a fixed fraction of the car's digital speed. I don't recall the correction factor I'm using but it's something like 95%, which turns out to be pretty accurate at all speeds from 30-75 mph.

Well, there is a damn good reason for this. The subject has been covered on this forum ad infinitum (nauseum). The MINI comes from Europe and the European Union dictates how these machines will operate. Operating with a +2 to +3 MPH (KPH) or thereabouts adjustment is part of that dictate. It's like a lot of other things in life. Get used to it.

Wow, this topic comes up a lot.

However I do like the link posted above to the UNECE document.

However to be fair, and if I read the document correctly; it only states that the speedometer must have an accuracy of from "spot on" to 0.1 of actual speed plus 4km/h.

Or in other words if your true speed is 70km/h the speedometer can read anywhere from 70-81.

The document does not state that the speedo must overstate true speed by "X" amount.

All manufacturers overstate the true speed. I still maintain this is primarily to prevent lawsuits. You won't get in legal trouble for overstating speed, but imagine all of the class action litigation you would be in if you reported a speed that was to low.

So where does this leave things with your MINI?

1. The odometer is correct when you use the OE tires.
2. The speedometer overstates your actual speed.
3. Using NCSExpert or BMWWhat/Carly you can configure your car to display the "non-corrected" speed on the digital display, but the "corrected" speed is always displayed on the center dial.

Just to put things to rest in my mind I did the following test today.

I found a stretch of road that was mostly flat and set my cruise control to 55mph. And then drove for 15 minutes. I also had the Torque app and a bluetooth OBDII dongle setup.

Speedometer stated I was going 55mph
Torque stated I was going 53mph by the OBDII reading
Torque stated I was going 52.6mph by my phones GPS

After 15 minutes I checked how far I had driven (via the trip meter) and multiplied by 4; and got a hair under 53 miles.

Given the rounding I am sure the MINI performs and the inaccuracy of my phones GPS I consider this exactly what I would have expected. Odometer is correct and at 55 my speedo overstates my speed by 2-3 mph.

BTW the speedo inaccuracy is relative to your true speed. The faster you go the more inaccurate it is; at least in my experience from the highway "your going X MPH, slow down..." signs.

The document simply states the requirements of speed readings and the accuracy of such, not odometer readings. I still feel that with over-estimated speed readings, the odometer will rack up miles more quickly. At an 8% over-estimate, my MINI at 100k would register 108k miles. No biggie, I guess. It's just "one of those things" that drive me nuts. I will stop now. It has been fun. Since nobody else is worried about racking up un-driven miles, I will only say that it may just matter to folks on a purchased warranty that includes mileage limitations. Or folks on a lease.

Rench, the odometer is accurate, it's the SPEEDometer that shows the exaggerated difference between indicated and actual. I wish, with all the years of postings, thousands of threads, more research was done before asking questions that have been answered a multitude of times.

PS: I just spent a few minutes reviewing all the threads I've responded to over the years and found 14 asking this very same question each containing variations on the same responses.

Sorry to be a pain in the rear. I will find out elsewhere how the odometer gets it's info from another source than the speedometer.

The source is the same (counting final drivetrain revolutions via sensors). The ECU adds speed to the speedometer, but not the odometer. Via software editing you can eliminate the adder to the digital speed readout in the tach but not to the analog big dish speedo.

Bear in mind that they are both digital so the odometer is not 'driven' by the speedometer. Both get their information about how fast the wheels are turning from the car's ECU and then the speedometer reading is 'corrected' before being displayed, so that it read high. But the odometer got its information before that.

Thanks for the further explanations. I understand the situation now.