[ONLYA6]

Originally Posted by aWanderlustSeoul

Unless anyone knows differently, all vehicle speedometers typically do not reflect the actual speed. All manufacturer could also calibrate it in a way so it's actually lower possibly due to liability issues if in an accident, speeding, etc. (e.g vehicle displays you are going 70 mph but are actually going 80 mph).

Also the speedometers in vehicle determine the speed by measuring how fast the wheels are spinning using the speed sensor so the speed will be different than what a GPS would be calculating.

Also there's dependencies on the diameter of the wheels, tire size, pressure, wear so that's a factor in the accuracy of the speedometer.

My motorcycle is the same way and is off 4-5 mph lower than the actual speed. On motorcycles, the speed sensor is on the rear tire but I'm not sure where the speed sensor is typically on cars.

Vehicles speedometers reflect actual speed.

I have a GPS radar detector that has been in a dozen vehicles I've owned. All accurate within 1-2 MPH from tire wear.

[chris719]

Originally Posted by ONLYA6

Vehicles speedometers reflect actual speed.

I have a GPS radar detector that has been in a dozen vehicles I've owned. All accurate within 1-2 MPH.

Maybe you haven't gone very fast then? I have never seen a German car where there wasn't a few percent difference above 100 mph.

[srwatters]

Originally Posted by ONLYA6

Vehicles speedometers reflect actual speed.

I have a GPS radar detector that has been in a dozen vehicles I've owned. All accurate within 1-2 MPH from tire wear.

Sorry, but I have evidence to the contrary. My current 335i is my 5th BMW and not one has been within your mentioned tolerance. And I'm not always using smart phones. I have access to high accuracy gps receivers used in mapping applications. If your evidence is documented, consider yourself in the minority at the edge of manufactured tolerances.

[orangeglim]

My M235i always showed 2mph faster than I was actually going, which I suspect is pretty much the norm to account for wheel diameter differences, etc. So, if it said I was going 70, I was actually going 68. I haven't tested my M2C yet.

[808elise]

Wonder what STG2 does.

[Reid]

My former M4 and M2 did an indicated 167 mph on the speedometer, sitting on the speed limiter. I had many opportunities to experience this on the autobahn and each time the results were the same.

Due to the worst traffic I've ever experienced on the autobahn, I was only able to get the M2C up to 174 mph (indicated via phone GPS). Of course, once I dropped the car off, I never saw traffic again.

[aWanderlustSeoul]

Originally Posted by ONLYA6

Vehicles speedometers reflect actual speed.

I have a GPS radar detector that has been in a dozen vehicles I've owned. All accurate within 1-2 MPH from tire wear.

I'm not sure how you can make this generalized statement since you are implying all vehicles speedometers will reflect the actual speed regardless of the type of vehicle (e.g. cars, motorcycles, boats, or any motorized vehicles). Do you have data from each manufacturer that supports your claim?

If cars/motorcycles use the wheels to determine the speed, there are too many factors/variables that will impact the speed calculation that I mentioned in my previous post you commented on.

Also the speed from a GPS is not exactly correct since there's also inaccuracy but I believe the consensus is it that it's more accurate than a vehicle’s speedometer.

So unless I'm mistaken, neither are completely 100% accurate.

Just do some google searches. I found this info about GPS calculating speed.

Step 1: Using GPS to calculate speed
The formula for calculating speed is speed equals distance covered divided by the time taken often represented as x = d/t.

By using two GPS points (locations) we can calculate the distance covered. We can use the clock inside the GPS receiver (a very accurate clock that synchronizes regularly with the atomic clocks aboard the GPS satellites) to measure how long it took the vehicle to travel between those two points.

In the example below the GPS receiver within the truck records its location (latitude and longitude, or lat/lon) at Point A. It takes note of the time as well. A short while later, say two minutes, it records its location again (Point B) - see below*. The GPS receiver can then perform a calculation using these numbers and determine the speed of the vehicle.

*GPS satellites send their positions to receivers on the ground every second. For the purpose of this example, we are comparing position difference over a longer period of time.

In a split second the GPS receiver will generally perform the following tasks to determine speed:

Convert the difference between the two latitudinal/longitudinal positions into a unit of measurement (you can use online calculators to try this yourself).
Determine the difference between the two timestamps to calculate how long it took to get from Point A to Point B.

Calculate the average speed based on these results. For example, if the distance was three miles and the time taken was 2 minutes, then the average speed across that distance would be 90mph.
Generally, the longer the journey and the more measurements that are taken result in a more accurate, overall speed reading.

While some may argue that the speed returned by a GPS receiver is higher than the speedometer in the vehicle, most modern GPS receivers can collect speedometer readings using the OBDII port. This provides a method of verifying the vehicle’s speed.

[kpaso]

Originally Posted by ContactPatch

Where does one drive at 170mph?

Dallas North Tollway.

[aWanderlustSeoul]

Originally Posted by Poochie

It's a technicality you write in, when posting YouTube videos of illegal street racing, so to possibly circumvent the state of said event from prosecuting you.

I sincerely doubt anyone actually crosses the border to get their kicks..

I would love the idea of an unenforced speed limit like in Mexico. But I don't think my ObamaCare insurance kicks in over there, so if I crash, I'll probably end up dying in the barrios.

Ok this makes much more sense to me. Prior to responding to your other post, I was thinking would anyone in the US ever take their brand new car across the border and what if something happens to the car on foreign soil (e.g. accident, stolen, etc.). I also thought, how difficult or how long would it take to cross back over to the US.

I've only driven to Mexico once with some friends but we were in a very old Jeep Wrangler and did not enjoy the wait to cross back over to the US...waited over 2 hours which sucked. Much more convenient and easier to get and out by flying...

[TURBO8]

On the BMW website, they claim it will go 250mph and 280mph. I know it's a typo, thought it was funny.

[Poochie]

Originally Posted by TURBO8

On the BMW website, they claim it will go 250mph and 280mph. I know it's a typo, thought it was funny.

You would have to upgrade your Flux Capacitor to hit those speeds.

Typo; they meant KLM not MPH probably because the person typing it hates the US-only imperial system of measurement.

[srwatters]

For a primer on how GPS works:

https://timeandnavigation.si.edu/mul...-does-gps-work

Originally Posted by aWanderlustSeoul

*GPS satellites send their positions to receivers on the ground every second. For the purpose of this example, we are comparing position difference over a longer period of time.

This is incorrect. Multiple GPS Satellites are sending a constant stream of data far in excess of once per second. The receiver is decoding and making calculations based on a constellation of some number of satellite streams.

https://en.wikipedia.org/wiki/GPS_signals

The GPS receiver chip may be sending NMEA sentences to the CPU at 1 Hz, but often times now that can be 5, 10, or even 20 Hz. It depends on the application and how they program the positioning receiver chipset. uBLOX makes some great low-cost GPS/GNSS receivers.

https://www.u-blox.com/en/product/neo-m8u-module

And they can be VERY accurate in both position and speed depending on the type of receiver and the software used to interpret the data.

[JustDrifting]

Originally Posted by srwatters

For a primer on how GPS works:

https://timeandnavigation.si.edu/mul...-does-gps-work

This is incorrect. Multiple GPS Satellites are sending a constant stream of data far in excess of once per second. The receiver is decoding and making calculations based on a constellation of some number of satellite streams.

https://en.wikipedia.org/wiki/GPS_signals

The GPS receiver chip may be sending NMEA sentences to the CPU at 1 Hz, but often times now that can be 5, 10, or even 20 Hz. It depends on the application and how they program the positioning receiver chipset. uBLOX makes some great low-cost GPS/GNSS receivers.

https://www.u-blox.com/en/product/neo-m8u-module

And they can be VERY accurate in both position and speed depending on the type of receiver and the software used to interpret the data.

Old thread but on the autobahn for the first time since buying my M2C (2.5 years ago, thanks to Covid!).

Soft limiter at 264 kph and the car was pulling strong until that point. It's a UK spec car and I didn't opt for the pack to remove the 155mph limit…

[Brandt51]

A friend of mine has a stock M2C comp without the divers package. I think it pulled to 163mpg on GPS before the governor kicked in. I can't remember what track but sounds close enough to the 155 number.

Our X5M's Speedo reads faster for sure. Our M2 is pretty close and the big F-350 is dead on (only with 35x12.5x20 tires mounted). The manual for some Ducati's back in the day stated the speedo was 8% faster than actual speed. Hahah. Weird.

[DelGriffith]

I know a guy, drives an M2 Comp with Bootmod 93 tune and cat delete, who touched 180 mph. Somewhere out Western US with no other vehicles within miles... Lived to tell the story but doesn't need to do that again

[Ratcher]

I don't have M Drivers Package and my car is limited at 266 kph tacho, 264 GPS. Please say I can't be right so I can share my Vbox screenshot I know its nuts, but what can I do.

Stock software without limiter should be 296 kph. Won't reach 300 kph.

With a tune it can reach speeds of over 310 kph/190mph without too much difficulty