![]() |
![]() |
![]() |
![]() |
![]() ![]() |
![]() |
BMW Garage | BMW Meets | Register | Today's Posts | Search |
![]() |
![]() ![]() |
BMW 3-Series (E90 E92) Forum
>
Speedometer slightly off??
![]() |
![]() |
08-07-2013, 10:34 PM | #24 |
Brigadier General
![]() ![]() 1560
Rep 3,475
Posts
Drives: E90 6MT FBO; '18 F150 Platinum
Join Date: Jul 2013
Location: WI
|
It's 5% off as many have said... I have the "true speed" coded into my dash with my mpg, range, etc. and it matches perfectly with my gps and police radar things on the side of the road.
__________________
![]() 2008 335xi 6MT | VRSF Catless DP | VRSF 7" FMIC | VRSF CP | TIAL BOV | DCI | MHD 2+ BC Racing BR | Stoptech 600 | Firehawk Indy 500 255 Square | Atric Altimax 225 Sq. 2018 F-150 Platinum 701A | FX4 | 3.5 EcoBeast |
Appreciate
0
|
08-08-2013, 08:31 AM | #25 |
Private
![]() 2
Rep 51
Posts |
I've decided I'm going to get into this coding nonsense.... anyone know where a cheap and capable cable can be purchased?
The thread I posted earlier did say though, that you can't actually code out the skew in the needle, just that the work around was to add that V= thinger. Was that tough at all for those who did it? I just cant stand being in the "flow" of traffic, and my car telling me I'm going 80mph....There's no way that jalopy next to me can even go that fast! |
Appreciate
0
|
08-09-2013, 12:26 PM | #26 |
Brigadier General
![]() ![]() 693
Rep 3,696
Posts |
|
Appreciate
0
|
08-09-2013, 12:30 PM | #27 |
Brigadier General
![]() ![]() 693
Rep 3,696
Posts |
If you change your wheels to a different overall rolling diameter, then you are going to throw off a lot of stuff. The car expects the rolling diameter to be the stock height. Usually because of wheel well clearances you can't change it too much tho. But it would be nice if cars actually used the built in GPS to "auto correct" the land speed or a way to code the the rim size and tire size for each wheel into the car so it can help compensate.
|
Appreciate
0
|
08-09-2013, 04:17 PM | #28 |
Curmudgeon and Pedant
![]() 695
Rep 3,488
Posts |
No (as already stated). My winter tires are 225/45R18 rather than the OEM 225/40R18. They "corrected" the speedo error from the 3-4 mph range (70 mph) to only 1 mph fast.
|
Appreciate
0
|
11-21-2013, 03:27 AM | #30 | |
Private First Class
![]() 9
Rep 152
Posts |
[QUOTE=Rossland;14460631]
Quote:
If there's a reason for me not to get a BMW again this would be it. Anybody know if M-B or Audi has the same problem? |
|
Appreciate
0
|
11-21-2013, 04:16 AM | #31 | |
Private First Class
![]() ![]() 6
Rep 180
Posts
Drives: BMW E90 M3 ZCP
Join Date: Mar 2012
Location: Sweden
|
Quote:
At least in Sweden it is not allowed to have more than 5% difference (+/-) in roll circumference from OEM specification.
__________________
E90 M3 ZCP 2010
E92 335i 2007 black edition |
|
Appreciate
0
|
11-21-2013, 11:31 AM | #32 |
Curmudgeon and Pedant
![]() 695
Rep 3,488
Posts |
|
Appreciate
0
|
11-21-2013, 12:02 PM | #33 | |
Captain
![]() ![]() ![]() ![]() ![]() 32
Rep 644
Posts |
Quote:
|
|
Appreciate
0
|
11-21-2013, 12:18 PM | #34 |
Lieutenant Colonel
![]() ![]() 289
Rep 1,710
Posts |
Anybody running large wheels? That contributes to a loss too.
__________________
DONE: Seibon CF Hood, M3 Rep, MSport rear w/DD CF Diffuser, M3 Rep Skirts, Seibon CSL trunklid, Forgestar F14 18s w/Michelin PSS, Eisenmann catback, AA Headers, BPC Stage 2, Charcoal Delete+revMotor+AFE Drop In filter
FUTURE MODS: LED headlights, CF rooftop, M3 Suspension Conversion, Dinan CAI Mod |
Appreciate
0
|
11-21-2013, 12:23 PM | #35 |
Second Lieutenant
![]() 21
Rep 224
Posts |
My W204 MB C350 was pretty bang on.. Didnt even take notice in my e92.....after the water pump gets replaced by BMW this weekend ill be sure to look out for it...
|
Appreciate
0
|
11-21-2013, 08:59 PM | #36 | |
Lieutenant Colonel
![]() 119
Rep 1,951
Posts |
Everybody have a good read:
This wikipedia entry is very enlightning: http://en.wikipedia.org/wiki/Speedometer#Error In short, when you sum up all the sources of error between the road and the needle (including tire under/over inflation, actual installed tire diameter which may be different from factory fitted wheels, actual measurement error inherent to the system used and its construction tolerances, etc), the overall measurement uncertainty is pretty significant. Various regulations govern how this uncertainty must be handled, but in the EU in particular: Quote:
tl;dr, every system has measurement uncertainty and therefore, by various laws depending on jurisdiction, a car may be legally required to overreport your speed.
__________________
![]() |
|
Appreciate
0
|
11-21-2013, 09:03 PM | #37 |
Lieutenant Colonel
![]() 119
Rep 1,951
Posts |
If your running radius is larger than factory spec, the speedo will UNDERreport your speed. Larger wheel means lower RPM for the same linear speed.
And this is sort of the point. If you install larger wheels on the car, per legalese it still shouldn't ever report that you're going slower than you really are.
__________________
![]() |
Appreciate
0
|
11-22-2013, 10:22 AM | #38 | |
First Lieutenant
![]() ![]() ![]() 78
Rep 375
Posts |
Quote:
This makes a lot of sense. A while ago I had a e90 328i as a loaner from the dealer, and that thing's speedo was so far off I could notice it without a GPS. I couldn't tell exactly how far off, but cruising around left lane on the highway following the flow of traffic, the speedo would indicate nearly 90mph. And going by the speed sign near my house, speedo would indicate 35, sign would say 25. But that was the only car that I've noticed that's been off so much. My old E46 felt somewhat accurate (going with flow of traffic speedo would say 82-85), same with my new E92. I remember seeing an article a long time ago that compared how accurate the speedos of different manufacturers were, and Chevys ended up being the most accurate or something. Found it. http://www.caranddriver.com/features...ometer-scandal |
|
Appreciate
0
|
02-16-2014, 11:33 PM | #39 |
I Can't Drive 55
![]() 132
Rep 887
Posts
Drives: 2008 BMW 335i (E90)
Join Date: Dec 2013
Location: SF Bay Area
iTrader: (4)
Garage List 2023 VW ID4 Pro [0.00]
2002 Ford F250 7.3L ... [9.50] 2008 BMW 335i [0.00] 2012 Mercedes ML350 [0.00] 2002 Toyota MR2 Spyder [0.00] |
Based on speed readings made with my Cobb AP3, the speedo in my 335i runs about 5 mph "fast" at 70+ mph.
I've read threads that say that there is no software fix for this and that you just have to accept it. HOWEVER, I use a SuperChips tuner in my Ford F250 which has a speed adjustment function that allows you to correct the speedometer reading in the truck based on the measured tire diameter. So, if the SuperChips tuner can make a speed adjustment for my truck, why can't anyone (who has the necessary skills) design a simple program to make the same adjustment in our BMW's? ![]()
__________________
2008 Black Sapphire 335i E90 Sport & Premium Pkgs - Cobb Stage 1+FMIC Sport map, Mishimoto FMIC & Alpina B3 AT Flash. See: My Build Thread.
Last edited by SSW; 02-17-2014 at 01:06 PM.. |
Appreciate
0
|
02-17-2014, 12:49 AM | #40 |
Libertarian
![]() 134
Rep 1,577
Posts |
For the most part, I just pass everyone. Usually quickly. Even cops.
__________________
2011 335xi Coupe BSM (e92/N55/ZPP/ZCW, Alpina B3 Flash)
Bought 08/09/2013@53,340mi Current 3/13/2019@206,283mi Fail(s): tstat hous/water pump 89k, Chargepipe 106k, coolant tank 114k, FRM3 114k Maint: Walnut blast 101k, Trans/T-case Fluid 103k, OFHG 195k Last edited by GB-335xiCoupe; 02-17-2014 at 12:58 AM.. |
Appreciate
0
|
02-18-2014, 08:25 AM | #42 | |
Colonel
![]() 199
Rep 2,802
Posts |
Quote:
|
|
Appreciate
0
|
02-18-2014, 03:31 PM | #43 | |
I Can't Drive 55
![]() 132
Rep 887
Posts
Drives: 2008 BMW 335i (E90)
Join Date: Dec 2013
Location: SF Bay Area
iTrader: (4)
Garage List 2023 VW ID4 Pro [0.00]
2002 Ford F250 7.3L ... [9.50] 2008 BMW 335i [0.00] 2012 Mercedes ML350 [0.00] 2002 Toyota MR2 Spyder [0.00] |
Quote:
It "could" also matter legally if you are caught on radar driving at a certain speed above the limit because you inaccurately "guessed" what your speed was. For example, if you are driving at "70" on the speedo in a 65 mph zone in the expectation that the error is 5 mph but the error is actually only 3-4 mph, you could get a ticket for driving at 66-67 mph. It would be a chickensh*t ticket but you could still get one for that nonetheless. If you're using a digital speedo and it's accurate, there would be no such issue because if it shows you driving at 65 that's what it is and you don't need to worry about guessing what the degree of error in the speedo is at all.
__________________
2008 Black Sapphire 335i E90 Sport & Premium Pkgs - Cobb Stage 1+FMIC Sport map, Mishimoto FMIC & Alpina B3 AT Flash. See: My Build Thread.
|
|
Appreciate
0
|
02-19-2014, 07:59 AM | #44 | |
Colonel
![]() 199
Rep 2,802
Posts |
Quote:
|
|
Appreciate
0
|
![]() |
Bookmarks |
|
|