Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Please follow the links below to help get you started!

Go Back   Bimmerfest - BMW Forums > The Best of Bimmerfest! > BMW Diesel Owners / Enthusiasts

BMW Diesel Owners / Enthusiasts
Do you own a diesel powered BMW? Maybe a 335d or a BMW x35d? Come and talk about what makes your car great!

Reply
 
Thread Tools Display Modes
  #1  
Old 02-08-2012, 03:12 PM
Runnerman2 Runnerman2 is offline
Registered User
Location: Texas
 
Join Date: Jan 2011
Posts: 30
Mein Auto: 2010 335d
Speedometer calibration

While on a recent trip to West Texas, traveling along with another car, we discussed how fast we were driving and my buddy following me said that I was driving 3-4 mph slower than my speedometer was indicating. In other words, at 80 mph indicated, i was actually traveling at 76 mph.

I thought maybe it was his speedometer that was off some, but after verifying with a very accurate GPS, on a long straight stretch of roadway, our 335d was in fact running about 4-5 miles per hour slower than indicated.

Being a stickler for accuracy, I want my speedometer to read exactly how fast I am traveling and don't want to have to constantly make a mental adjustment. Can anyone tell me what could be causing this, and more importantly, can it be easily corrected? I know it's not caused by the tire size because I am running the same size and type of tires that came originally on the car, which is a 2010 model. Thanks for any help!

Last edited by Runnerman2; 02-08-2012 at 03:13 PM.
Reply With Quote
Ads by Google
  #2  
Old 02-08-2012, 03:26 PM
ArtL's Avatar
ArtL ArtL is offline
Officially Welcomed to the 'Fest
Location: VA
 
Join Date: Nov 2011
Posts: 266
Mein Auto: 2006 750Li
I think I read some previous threads on this which indicated that BMW deliberately sets the car in this fashion. Try searching and you may find some info on a fix.
Reply With Quote
  #3  
Old 02-08-2012, 03:31 PM
floydarogers's Avatar
floydarogers floydarogers is offline
Pedant and Curmudgeon
Location: Renton, WA
 
Join Date: Oct 2010
Posts: 3,561
Mein Auto: 335d, 328d, Toyota T100
Quote:
Originally Posted by Runnerman2 View Post
...
Being a stickler for accuracy, I want my speedometer to read exactly how fast I am traveling and don't want to have to constantly make a mental adjustment. Can anyone tell me what could be causing this, and more importantly, can it be easily corrected? I know it's not caused by the tire size because I am running the same size and type of tires that came originally on the car, which is a 2010 model. Thanks for any help!
As Art mentioned, there is lots of discussion of this (mostly on the main E90 forum, probably on many others.) I think if you search for my handle and speedometer you should be able to easily find it.

It's the way it is because of an intersection of US/CA/EU laws & regulations: has to read fast, etc. There is no way to get it changed. If you have iDrive, you can somehow get the actual instantaneous readout in digital form, I believe.
Reply With Quote
  #4  
Old 02-08-2012, 03:37 PM
ArtL's Avatar
ArtL ArtL is offline
Officially Welcomed to the 'Fest
Location: VA
 
Join Date: Nov 2011
Posts: 266
Mein Auto: 2006 750Li
Here is the one I was thinking of. http://www.bimmerfest.com/forums/sho...d.php?t=579643
Reply With Quote
  #5  
Old 02-08-2012, 04:47 PM
4pipes 4pipes is offline
Registered User
Location: Bay Area, California
 
Join Date: Aug 2006
Posts: 77
Mein Auto: 2011 335d Alpine White
All BMW's are 3mph fast.....when indicating 65mph, you're really doing 62. I've verified mine with GPS and radar.
__________________
Previous BMW's:
'79 530i, '93 325iC, '97 740i, '99 540i, '00 M5, '03 X5, '05 645i, '09 335d, '11 335d
Reply With Quote
  #6  
Old 02-08-2012, 05:16 PM
floydarogers's Avatar
floydarogers floydarogers is offline
Pedant and Curmudgeon
Location: Renton, WA
 
Join Date: Oct 2010
Posts: 3,561
Mein Auto: 335d, 328d, Toyota T100
http://forums.bimmerforums.com/forum...1266637&page=2

Has the service bulletin text.
Reply With Quote
  #7  
Old 02-08-2012, 05:34 PM
listerone listerone is offline
Officially Welcomed to the 'Fest
Location: Connecticut
 
Join Date: Jul 2009
Posts: 832
Mein Auto: 2014 328d
My speedometer ran about 3-4 mph fast.I've read that it's because there's a German (or European) law which heavily fines a car maker which builds a car featuring a speedometer that's even a tiny bit slow so,to avoid the fines,they deliberately set them a bit fast.
__________________
Currently: 2014 328d / Mineral Grey Metallic / Nav / Apps / Backup Camera
Formerly:2011 MB E350 Bluetec / Palladium Silver / Nav / Active Cruise / HarmonKardon Logic7
Formerly:2009 335d / Monaco Blue / Beige Leather / Nav / iDrive / Xenon / Sirius / HD Radio

Fuelly

Last edited by listerone; 02-08-2012 at 05:37 PM.
Reply With Quote
  #8  
Old 02-08-2012, 11:11 PM
chetah45 chetah45 is offline
Registered User
Location: brentwood, ca norcal
 
Join Date: Dec 2011
Posts: 40
Mein Auto: 335d
Runnerman2: Same here for my 335d...seems to be off 3-4 mph, but in my testing it seems the odometer is pretty much dead on. If you change your tire diameter, then you will mostly likely throw the odometer off( in your favor, for once).
Reply With Quote
  #9  
Old 02-09-2012, 03:38 AM
Flyingman's Avatar
Flyingman Flyingman is offline
hang up and drive!
Location: Miami
 
Join Date: Sep 2009
Posts: 1,945
Mein Auto: 335d
Ditto, well documented.

There is something you can do, install slightly larger diameter tires. I changed my tires recently and now I'm just a little bit closer to actial. Diameter (circumference) was slightly greater on the newer tires.

I usually go by my GPS any way.
__________________

2010 Black 335D Sport/Premium, Michelin PSS 235/265
2000 Silver Z3 3.0i (Ret)
1999 Silver R1200C (Ret)
1968 Black 1600 Coupe (Ret)
Reply With Quote
  #10  
Old 02-09-2012, 06:30 AM
Runnerman2 Runnerman2 is offline
Registered User
Location: Texas
 
Join Date: Jan 2011
Posts: 30
Mein Auto: 2010 335d
Thanks guys for all the input! Sounds like I will just need to keep the difference in indicated vs. actual speed in mind in the future. We do have iDrive, but haven't looked at that to see if there's a way to show current speed all the time on the screen. May be a possibility as well.
Reply With Quote
  #11  
Old 02-09-2012, 08:02 AM
BMWTurboDzl BMWTurboDzl is offline
Officially Welcomed to the 'Fest
Location: SE United States
 
Join Date: Jul 2010
Posts: 1,136
Mein Auto: 335D, 435i (Ordered)
Quote:
Originally Posted by Flyingman View Post
Ditto, well documented.

There is something you can do, install slightly larger diameter tires. I changed my tires recently and now I'm just a little bit closer to actial. Diameter (circumference) was slightly greater on the newer tires.

I usually go by my GPS any way.
What size did u move up to?

Sent from my MB525 using Bimmer App
__________________
Reply With Quote
  #12  
Old 02-09-2012, 09:15 AM
Snipe656 Snipe656 is offline
Officially Welcomed to the 'Fest
Location: Humble, Tx
 
Join Date: Oct 2009
Posts: 4,032
Mein Auto: 2009 335d
Of course if you change tires to "fix" the speedo reading now your odometer readings will be off (not that I'd care but I do not care about the speedo either).
__________________
--Admiral Aaron Rouse
Reply With Quote
  #13  
Old 02-09-2012, 11:31 AM
JŠnos's Avatar
JŠnos JŠnos is offline
Officially Welcomed to the 'Fest
Location: Pacific Depths
 
Join Date: Jun 2010
Posts: 429
Mein Auto: 335d, FIAT 500 Abarth
Quote:
Originally Posted by Runnerman2 View Post
Being a stickler for accuracy, I want my speedometer to read exactly how fast I am traveling and don't want to have to constantly make a mental adjustment.
I'm just accustomed to doing the 'mental adjustment' now.

For example, if the speed limit says "55" I set my cruise control to "65", then bump it down one MPH. That is really close to the maximum legal speed. If you are feeling particularly feisty you could leave it at 10 MPH above the speed limit.
Reply With Quote
  #14  
Old 02-09-2012, 11:40 AM
Snipe656 Snipe656 is offline
Officially Welcomed to the 'Fest
Location: Humble, Tx
 
Join Date: Oct 2009
Posts: 4,032
Mein Auto: 2009 335d
I just tend to always speed and if my radar detector goes off then I hit the brakes to whatever point on the speedo is the speed limit. I am not going to worry about if I am truly doing something like 77 in a 65 instead of what I think is 80 in a 65.
__________________
--Admiral Aaron Rouse
Reply With Quote
  #15  
Old 02-09-2012, 02:53 PM
Runnerman2 Runnerman2 is offline
Registered User
Location: Texas
 
Join Date: Jan 2011
Posts: 30
Mein Auto: 2010 335d
What really bugged me was on the West Texas run I mentioned, set it on 120 for about 40 miles (wide open spaces, you know). Just kills me to know now that I was "only" going 116. Will have to go back and do it again.
Reply With Quote
  #16  
Old 02-09-2012, 05:51 PM
A8540TDI A8540TDI is offline
Officially Welcomed to the 'Fest
Location: South Florida
 
Join Date: Jan 2011
Posts: 218
Mein Auto: 335d, 540i, M Roadster
On a non sport 335d, go to 245/45 - 17 and your speedo will be very close to dead on. Your odometer will be about 3% under.
__________________
Reply With Quote
  #17  
Old 02-10-2012, 03:43 AM
Flyingman's Avatar
Flyingman Flyingman is offline
hang up and drive!
Location: Miami
 
Join Date: Sep 2009
Posts: 1,945
Mein Auto: 335d
Quote:
Originally Posted by BMWTurboDzl View Post
What size did u move up to?

Sent from my MB525 using Bimmer App
I have the 18" Sport, changed from the OEM RFTs B/S to the Michelin Pilot Super Sport, but went slightly wider up front, from a 225 to a 235. Rears are still 255. Turns out the diameter of that size is just slightly larger.

Now comes the question: Are the front wheels or the rear wheels driving the speedometer/odometer? I suspect the rear wheels as Odometer is usually driven off the Transmission, but since I changed tires my indicated speed seems to be closer to my GPS.
__________________

2010 Black 335D Sport/Premium, Michelin PSS 235/265
2000 Silver Z3 3.0i (Ret)
1999 Silver R1200C (Ret)
1968 Black 1600 Coupe (Ret)
Reply With Quote
  #18  
Old 02-10-2012, 05:19 AM
Runnerman2 Runnerman2 is offline
Registered User
Location: Texas
 
Join Date: Jan 2011
Posts: 30
Mein Auto: 2010 335d
Regarding swapping to a different size tire, thanks for the suggestions. But having just purchased a new set of "non-run-flats", that's not an option for at least another few thousand miles. I'll just live with knowing there's a difference in actual vs indicated speed. Thanks all!
Reply With Quote
  #19  
Old 02-10-2012, 06:30 AM
floydarogers's Avatar
floydarogers floydarogers is offline
Pedant and Curmudgeon
Location: Renton, WA
 
Join Date: Oct 2010
Posts: 3,561
Mein Auto: 335d, 328d, Toyota T100
Quote:
Originally Posted by Flyingman View Post
Now comes the question: Are the front wheels or the rear wheels driving the speedometer/odometer? I suspect the rear wheels as Odometer is usually driven off the Transmission, but since I changed tires my indicated speed seems to be closer to my GPS.
Neither. The ABS/DCT computer uses the wheelspeed sensors to derive it.
Reply With Quote
  #20  
Old 02-10-2012, 01:45 PM
TXPearl's Avatar
TXPearl TXPearl is offline
Officially Welcomed to the 'Fest
Location: Texas
 
Join Date: Apr 2010
Posts: 551
Mein Auto: 2014 650i Gran Coupe
Quote:
Originally Posted by floydarogers View Post
Neither. The ABS/DCT computer uses the wheelspeed sensors to derive it.
So some sort of average of the indicated speed of all 4 wheels?

That would help explain Flyingman's observation.
Reply With Quote
  #21  
Old 02-10-2012, 02:58 PM
Flyingman's Avatar
Flyingman Flyingman is offline
hang up and drive!
Location: Miami
 
Join Date: Sep 2009
Posts: 1,945
Mein Auto: 335d
Quote:
Originally Posted by Runnerman2 View Post
Regarding swapping to a different size tire, thanks for the suggestions. But having just purchased a new set of "non-run-flats", that's not an option for at least another few thousand miles. I'll just live with knowing there's a difference in actual vs indicated speed. Thanks all!
Hey, compare the specs on your original tires vs the new ones, maybe they new ones have a larger diameter. It really can affect your speed/miles reading.
__________________

2010 Black 335D Sport/Premium, Michelin PSS 235/265
2000 Silver Z3 3.0i (Ret)
1999 Silver R1200C (Ret)
1968 Black 1600 Coupe (Ret)
Reply With Quote
  #22  
Old 02-10-2012, 03:04 PM
Flyingman's Avatar
Flyingman Flyingman is offline
hang up and drive!
Location: Miami
 
Join Date: Sep 2009
Posts: 1,945
Mein Auto: 335d
Quote:
Originally Posted by TXPearl View Post
So some sort of average of the indicated speed of all 4 wheels?

That would help explain Flyingman's observation.
This is just too high tech for me! But explains why I'm seeing a slight closing of the gap between indicated and actual.

So why would speedometer and odometer read different? i.e. if I go down the highway at 60mph and the odometer says I actually did 63 miles in an hour.

My OBC is notorious for saying my mpg is around 27-28mpg but when I calculate my actual fuel consumed vs miles driven (odometer), I always get the fuelly value below, which is some 1-1.5mpg better.

Regardless, after over two years and some 34k miles, my smiles/miles are still up there!
__________________

2010 Black 335D Sport/Premium, Michelin PSS 235/265
2000 Silver Z3 3.0i (Ret)
1999 Silver R1200C (Ret)
1968 Black 1600 Coupe (Ret)
Reply With Quote
  #23  
Old 02-10-2012, 06:47 PM
Penguin Penguin is offline
Officially Welcomed to the 'Fest
Location: Illinois
 
Join Date: Aug 2003
Posts: 1,915
Mein Auto: Z4 and X5 Diesel
Quote:
Originally Posted by Flyingman View Post
if I go down the highway at 60mph and the odometer says I actually did 63 miles in an hour.
The easiest comparison which is accurate is to borrow someone's portable GPS unit and use it's speed measurement. GPS speeds are typically extremely accurate.
Reply With Quote
  #24  
Old 02-10-2012, 08:07 PM
ProRail ProRail is offline
"Clunker" *****
Location: Columbia MD
 
Join Date: May 2006
Posts: 4,602
Mein Auto: 1999 BMW 528A--165K
Quote:
Originally Posted by Flyingman View Post
This is just too high tech for me! But explains why I'm seeing a slight closing of the gap between indicated and actual.

So why would speedometer and odometer read different? i.e. if I go down the highway at 60mph and the odometer says I actually did 63 miles in an hour.

My OBC is notorious for saying my mpg is around 27-28mpg but when I calculate my actual fuel consumed vs miles driven (odometer), I always get the fuelly value below, which is some 1-1.5mpg better.

Regardless, after over two years and some 34k miles, my smiles/miles are still up there!
Different systems.
Reply With Quote
  #25  
Old 02-10-2012, 08:19 PM
Penguin Penguin is offline
Officially Welcomed to the 'Fest
Location: Illinois
 
Join Date: Aug 2003
Posts: 1,915
Mein Auto: Z4 and X5 Diesel
Quote:
Originally Posted by Flyingman View Post
My OBC is notorious for saying my mpg is around 27-28mpg but when I calculate my actual fuel consumed vs miles driven (odometer), I always get the fuelly value below, which is some 1-1.5mpg better.
Most MPG computers are not that accurate. While the fuel measurement is quite precise over small intervals for the purpose of controlling combustion, when the data is integrated over time to provide the volume of fuel used over a long period, a fair amount of error can creep in.

To a certain extend the ECM does not have to really know precisely the absolute volume of fuel it is injecting, as it simply uses feedback from the exhaust gases measurement to adjust the fuel trims to provide the right amount... a little bit like nudging the water faucet a little bit to increase or decrease the flow of water out of the garden hose without actually knowing the precise flow rate. If the "nudging" required to get the correct sensor readings gets to be too great, you get a MIL and an error code for fuel trim out of range or at the limit.
Reply With Quote
Reply

Bookmarks


Forum Navigation
Go Back   Bimmerfest - BMW Forums > The Best of Bimmerfest! > BMW Diesel Owners / Enthusiasts
Today's Posts Search
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



Forum Jump


All times are GMT -7. The time now is 03:50 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
© 2001-2011 performanceIX, Inc. All Rights Reserved .: guidelines .:. privacy .:. terms