Limited at 155MPH? Not with 6MT...

[M6-Coupe]

Originally Posted by Boss330

I think you misunderstood what I was trying to say

Of course a "flat spot" doesn't account for 5% difference. My point was that ETRO use a variable pi factor depending on tire dimensions (as it logically should since the relative size of the "flat spot" will vary between large and small tires etc). This means that you can't just use pi=3,14 or pi=3,05 (as an example) for all tires...

We are still not talking about a difference of 5% in the above calculations, but I have seen examples where a generic online tire calculator says the tire is just over 5% larger than stock tire, but where the ETRO tables list the same tire size as being 4,8% larger than the stock tire. This is due to the fact that ETRO uses a tire specific "pi" factor, whereas most online tire calculators just use the same generic factor for pi (in fact some use 3,14) for ALL tire dimensions.

But these are the exceptions to the norm

The point is that the speedo has a tolerance and that it needs to allow for aftermarket tires with as much as +5% rolling circumference and still not show less than actual speed.

Maybe you guys in Europe are restricted with those organizations, but we are not in US (Just kidding buddy)
Anyways, it was a good discussion and thanks for your time and explanation; however I'm not convinced about 5-10% deviation.. still I assume 2-3% (I respected you and increased 1%)

[Boss330]

Originally Posted by M6-Coupe

Maybe you guys in Europe are restricted with those organizations, but we are not in US (Just kidding buddy)
Anyways, it was a good discussion and thanks for your time and explanation; however I'm not convinced about 5-10% deviation.. still I assume 2-3% (I respected you and increased 1%)

Yeah, speedo calibration might be different between the US and Europe (but if you aren't "restricted" by any legislation, then they might have even larger tolerances to keep up with US style 26" rims JK ).

AFAIK, several M5 owners have verified their 167-172MPH speedo readings with GPS as being around 155MPH true speed.

I assume their GPS' speed is correct and that the speedo deviation is accordingly

All in good fun and good clean discussion with you mate

[Mbdurham17]

Seems like one of these posts a week

[gmd2003]

Originally Posted by M6-Coupe

Maybe you guys in Europe are restricted with those organizations, but we are not in US (Just kidding buddy)
Anyways, it was a good discussion and thanks for your time and explanation; however I'm not convinced about 5-10% deviation.. still I assume 2-3% (I respected you and increased 1%)

My 2014 US M6 CP shows a error of ~ 5% with the stock 20's and tires. So it shows 84 when GPS shows 80 . And 164 when GPS shows 155 . My limiter actually kicked in at 155 but it made it to 156 . This verified by a 20hz Vbox sport so I know it's accurate . I think 5-10% is def the norm in the US as well . Few people actually look at their true GPS speed

[Penguino]

There is no speed governor on 5th gear. My DCT showed 165mph on 6th gear while it hit the limiter at 155mph on 7th.

So, no, there is speedo error.

[gmd2003]

Originally Posted by carlitosz

There is no speed governor on 5th gear. My DCT showed 165mph on 6th gear while it hit the limiter at 155mph on 7th.

So, no, there is speedo error.

If you don't have GPS data then you don't know what the error is

[Penguino]

Originally Posted by gmd2003

If you don't have GPS data then you don't know what the error is

The OP is not trying to say he hit actual 155mph GPS-based. What he is trying to say is that the vehicle speedometer is not limited to 155mph in lower gears, since his speedometer marked +165mph.

[M-bitious]

Originally Posted by Boss330

Which tires and tire dimension did you have on that run?

I thought you had 21" wheels, correct?

265/30 and 295/25/21

[Igor_M5]

So reviewed the dash cam footage and the GPS is in fact saying... 159MPH, so... w/ that being said, we're limited at 159? not 155? I shoulda tried shifting to 6th lol.

[Boss330]

Originally Posted by carlitosz

The OP is not trying to say he hit actual 155mph GPS-based. What he is trying to say is that the vehicle speedometer is not limited to 155mph in lower gears, since his speedometer marked +165mph.

[Boss330]

Originally Posted by Igor@ONEighty

So reviewed the dash cam footage and the GPS is in fact saying... 159MPH, so... w/ that being said, we're limited at 159? not 155? I shoulda tried shifting to 6th lol.

Interesting

gmd2003 said the limiter set in at 155MPH (GPS) but that he managed to get 156MPH (GPS). You did 159MPH.

Do you and gmd2003 have the same tire size? That can account for some variation and possibly also a slight deviation in speed limiter tolerance as well?

[Boss330]

Posted today on a thread over at the F8x Boards:

http://f80.bimmerpost.com/forums/sho...postcount=1112

Originally Posted by neverbeentoofast

Ok guys, here are some very fresh data, while I am still standing on the road, to give you a feeling for the speed of the new M and maybe also the convertible compared to my N55 stock.

My countryroad is about 2400m long, dense bushes right and left...so not much wind to think about. There is a decent of 14m over the 2400m distance. I gathered the data in both directions.

Weather is 14 degrees celsius, 100% sunny, altitude some 150m.

I went to a weightscale before. The 335i Vert is 1880 kg inkl. me, 19" 313 wheels with hankook v12. Tank holds about 30 liters.

I do not know why, but the vbox does not log 0-100, only 0-70 and 0-130.

Resultsi did not use the launch. Only dct on sport and go)

0-70: 3,99 and 3,92
0-130: 9,45 and 9,32
Top speed after about 2000m: 228,4 and 228,1
The speedometer was showing 240 as topspeed(!)

So much for now:

Vbox did not work at the screen, had to put it to the side window.
The scale was a truckscale. Weight is +- 20kg

If you want to campare to speedovideos:
My speedo is off about +3,5kmh till 100. after the gap widens.
Time to reach top speed was 30,7 and 32,1

At 228km/h (VBox) the speedo had a 12km/h deviation and shows 240km/h, which is just around 5%.

[Penguino]

Originally Posted by Boss330

[Boss330]

Originally Posted by carlitosz

My confused sign was because I didn't understand your post

I understood the OP to say that the M5 with MT6 wasn't limited at 155MPH, not that his speedo wasn't limited... Not sure if there are cars with a limited speedo

Here is what the OP wrote:

I know the word on the street is that stock F10 M5s are limited at 155, but no say about 6MT.

Aside from BMS Stage 1 tune (which doesn't de-limit our cars), resonator delete and charcoal filter delete... the car is completely stock. Didn't get a chance to go into 6th gear either, that was at top of 5th (as you can tell the car is telling me to go into 6th).

To me that is a clear reference to the 155MPH speed limiter...

[M6-Coupe]

Originally Posted by Igor@ONEighty

So reviewed the dash cam footage and the GPS is in fact saying... 159MPH, so... w/ that being said, we're limited at 159? not 155? I shoulda tried shifting to 6th lol.

It means your GSP has error. you need to throw it away and get the new one that does not show more than 155 (JK)

[DrewM5]

This has been addressed here before but I am too lazy to search for the thread. There is a fixed formula for the "error margin" which is a percentage plus a fixed amount. I think it was something like 3% plus 2mph (don't quote me on the 3 and the 2 as those are just guesses from memory). So there won't be a fixed percentage over.

And there is only one reason that BMW does this - to avoid any potential liability. Nothing more; nothing less.

[Ex_Stig]

Originally Posted by DrewM5

This has been addressed here before but I am too lazy to search for the thread. There is a fixed formula for the "error margin" which is a percentage plus a fixed amount. I think it was something like 3% plus 2mph (don't quote me on the 3 and the 2 as those are just guesses from memory). So there won't be a fixed percentage over.

And there is only one reason that BMW does this - to avoid any potential liability. Nothing more; nothing less.

10% + 2.2mph.

[DrewM5]

I have no factual basis to argue, but the 10% seems high to me. That means when I am running 60 the speedo would read 68.2. In my experience, the margin of error has not been that great.

But I guess it is consistent with the 155 reading 172. Looks like I can drive even faster now!

[Boss330]

Originally Posted by DrewM5

This has been addressed here before but I am too lazy to search for the thread. There is a fixed formula for the "error margin" which is a percentage plus a fixed amount. I think it was something like 3% plus 2mph (don't quote me on the 3 and the 2 as those are just guesses from memory). So there won't be a fixed percentage over.

And there is only one reason that BMW does this - to avoid any potential liability. Nothing more; nothing less.

Originally Posted by GNALUZU

10% + 2.2mph.

It's definitely not 10% + 2,2MPH when driving at 60km/h over here... We have some speed info signs where your true speed comes up (as per radar) so you can check your speedo as well as be urged to drive within the speed limits

When driving in 60km/h my speedo only has a error of 2-3km/h (as per digital speed display). That's a 5% deviation. However the deviation is larger than 5% at higher speeds for some reason...

[M6-Coupe]

Originally Posted by GNALUZU

10% + 2.2mph.

Sir, would you please address me the source of this formula?
The reason I'm asking is because most of the time I am driving in Freeway and I want to know the safe speed before I get pulled over

[Ex_Stig]

The formula isn't saying that all speedometers are overstated by 10% + 2.2mph. It is saying they unless your speedo is reading HIGHER than that amount it will just be considered to be within the acceptable tolerance.

Not all speedo are going to read the same margin of error. Some could be extremely accurate, some could be off by 2% and some off by 10%.

All BMW has said is that they could possibly be off by 10% + 2.2mph.

[Ex_Stig]

Originally Posted by M6-Coupe

Sir, would you please address me the source of this formula?
The reason I'm asking is because most of the time I am driving in Freeway and I want to know the safe speed before I get pulled over

Your speedo should never indicate that you are going slower than actual speed. There is no allowable tolerance for that.

It's probably why the speedos overstate actual speed. If they were understating them they would all have to be addressed every time.