The car feels slower than indicated on Speedometer

I used to pass everyone at 70mph. And now I am in the slow lane keeping up with traffic at 70 mph.

Has anyone checked the accuracy?

I am on stock 16" wheels and tires inflated properly.

 

GPS, highway mile markers or a friendly LEO willing to time you? You gotta have an external benchmark to start from.
OR, everybody else is just now going faster in defiance.
AND, everybody should know by now about the 3MPH speedo error built in but I don't think that's an issue.

 

I checked mine with a Garman GPS. My speedometer is 2.5 miles an hour off and it doesn't matter whether it's a lower speeds or higher speeds.

 

Mine's about 5% slow. I read somewhere that it's done on purpose. I used a GPS.

You can adjust things in the hidden menu and I think there's another speed measurement if you have an OBDII reader.

 

Thanks. I will have to add a few mph..

 

When I set the cruise out on the hiway it's always 5 MPH over the posted speed, i.e. 65 posted and indicating turns for 70. Never been looked at twice by LEO.
And don't worry about other people going slower or passing you. Georgeorgeor... Carlin said it best: "Have you ever noticed that anyone driving slower than you is an idiot, and anyone going faster than you is a maniac?"
I especially like those going faster. I consider them LEO bait.

 

Anyone quoting George Carlin gets an automatic ! He was one of the funniest, most observation guys ever.

 

Checked mine against GPS too - and it's about 4-5 mph off.

 

Please expound upon this a little bit.

 

BMWs and MINIs have a built in overestimation of the speed. It's usually about 3mph, but it can be as much as 3 mph + 10% of your current speed and still considered "normal" by techs.

You can either rely on a GPS device for accurate measurement, find out exactly how much the estimation is (mine is always 3 mph), or code the overestimation out using ESYS or NCS Expert (what I did - the tool will depend on whether your MINI is an R-series or F-series).

 

FWIW - Fiat's 500 speedo's are also not accurate.

 

OBDII. I have a GoPoint BT-1. If I remember correctly, the VSS Vehicle Speed Sensor PID shows the actual speed and not what is shown on the speedometer. There is also an option to use a calculation from the RPM.

The hidden menu. From the instructions on this page:

https://www.northamericanmotoring.co...e-success.html

You scroll through the options using the tripometer reset button. One option is to unlock more options, the number to unlock the options is the sum of the last five digits of your VIN.

I thought there was an adjustment for the speedometer, but I don't see it.

 

How would a speed sensor know what the actual speed is without knowing the current tire diameter which changes with wear and replacement tires?

 

O.K. so if I am reading you correctly the "secret menu" does not have a way to correct the speedo?
But if I am also reading you correctly this OBDII reader you have will correct it, or no?

I have a Smarty tuner for the Diesel truck I had (best tuner on the market BTW. Not VIN locked so if anyone is in the market for a SMARTY for the 03 to 06 common rail cummins, P.M. me) it had a program to adjust the speedo. Measure the hight of your tire and plug in the number and bingo, your speedo is ***** on accurate.

 

I went on the freeway and used the mile markers and set cruise and timed myself.

At 70 mph, it took 54,6 sec
At 75 mph it took 50.8 sec

70 mph = 66 mph
75 mph = 71 mph

I will add 4mph

 

No I don't see the adjustment in the hidden menu.

The OBDII reader displays the correct speed, but doesn't correct the reading on the speedometer.

Coding seems to be the way to go.

 

It seems to be more correct than the speedo.

It has parameters for wheel size. You can enter a correction, I put in 1.053 to get it to match the speedometer.

It can also try to calculate the speed from the RPM if you put in the gear ratios.

That's using the DashCommand app.

 

Almost ALL cars have had speedos that over-estimated speeds. If you could find a 50 year old car magazine that showed actual versus speedo, you'd see that 5-7% high was not unusual. Of course, tire wear and inflation are factors.

 

If the speed is overestimated on the speedometer then the mileage shown on the odometer is also over-reported, right? Or is the odometer reading accurate?

It seems like there would be legal issues for a manufacturer to sell cars knowingly and artificially boosting the car's odometer reading. Warranties that end 3% too soon.

 

But it would be far worse to underestimate and get hit with hundreds of thousands of small lawsuits from people regarding speeding tickets. Imagine if you were 3 percent the other way, how many people go 9 over, that would equate to actually going 12 over and may get you a ticket when you otherwise wouldn't have. Also. Mileage and speed are measured by different devices AND most dealers i have seen would still warranty a claim if you were within 3 percent of your warranty mileage.

 

From my experiences with GM in the mid 2000's, they won't.

 

All the speculation in the world won't change one glaring fact about this issue. That is, the European Union in it's infinite wisdom has mandated that speedometers show a 3 to 4 MPH difference from actual. It's there so we just have to deal with it.

 

Its not the EU. Ive had Kawasaki Motorcycles that did it. You can get a speedometer correction device for them. I have a Harley that does it. My dodge P/U did it. I got a programmer that had a setting to correct the discrepancy for that. It isn't that hard to do. I wish someone would build one for these cars.

 

A few things worth noting... There is a hidden menu in the odometer cluster and one of them allows the user to edit a ratio number like 1.021 to make the estimated MPG figure more accurate. I wonder if there's something similar for MPH.

I've played with NCS Expert and was able to remove the correction from the analog speedometer I believe, but couldn't get the digital speedometer to match. Also, the digital speedometer would show 2 different speeds, the instantaneous cruise control set speed for a couple seconds after setting my cruise controlled speed, and the standard continuous digital speed. The Carly app shows the same correction removal but says it's not for North America or something. It bugged me more having the digital and analog speedometers mismatched so I put them back the way they were.

The factory tire size on my R55 is 195/55 R16. The speedometer overestimated by about 2 or 3 MPH at 60. When I installed 215/45 R17 the speedometer accuracy did not change. Now with 205/55 R16 the speedometer overestimates by only 1 or 2 MPH at 60. That's close enough for me.

The factory should allow the owner to correct the speedometer so it's 100% accurate to account for tire wear or alternate tire sizes.

I still don't have clarity around the odometer accuracy. I guess I need to test it myself.

 

No, it isn't mandated. Please give your source.

The auto manufacturers do it by choice for business and legal reasons, but they won't state publicly that they purposely made the speedometer inaccurate.