BMW 1 Series Coupe Forum / 1 Series Convertible Forum (1M / tii / 135i / 128i / Coupe / Cabrio / Hatchback) (BMW E82 E88 128i 130i 135i)
 





 

Post Reply
 
Thread Tools Search this Thread
      07-05-2013, 07:55 AM   #1
pj.rodriguez
Major
 
pj.rodriguez's Avatar
 
Drives: Alpine White 128i Cabrio
Join Date: Jun 2013
Location: Toronto, Ontario, Canada

Posts: 1,027
iTrader: (6)

Garage List
Speedometer accuracy?

So, I was driving along the highway with cruise control on at 135 km/h and the digital speed agreed with the gauge speed. But a Honda civic passed me and I saw his digital speedometer reading at 130 km/h. I immediately thought, "am I going slower than I think I am?"

I know it is just a Honda, and how accurate could their speedometer be, but are ours accurate?

I know that hooking up a sat nav or GPS would tell me a speed, but I just don't have one.

Anyone have any similar experiences or knows what is going on? Is it a computer thing that can be calibrated? I don't have any mods and I also have the stock 18" sport rims FYI.

Thanks all!
pj.rodriguez is offline   Canada
0
Reply With Quote
      07-05-2013, 08:03 AM   #2
MightyMouseTech
Captain
 
MightyMouseTech's Avatar
 
Drives: 13 135i 6MT LeMans Blue MSport
Join Date: Feb 2013
Location: Ottawa, Canada

Posts: 796
iTrader: (0)

All speedos are pretty inaccurate. Always check them against a good GPS.
MightyMouseTech is offline  
0
Reply With Quote
      07-05-2013, 08:16 AM   #3
135-dmc
Private First Class
 
Drives: 2013 135
Join Date: Nov 2010
Location: Sanford, FL

Posts: 131
iTrader: (0)

Quote:
Originally Posted by pj.rodriguez View Post
So, I was driving along the highway with cruise control on at 135 km/h and the digital speed agreed with the gauge speed. But a Honda civic passed me and I saw his digital speedometer reading at 130 km/h. I immediately thought, "am I going slower than I think I am?"

I know it is just a Honda, and how accurate could their speedometer be, but are ours accurate?

I know that hooking up a sat nav or GPS would tell me a speed, but I just don't have one.

Anyone have any similar experiences or knows what is going on? Is it a computer thing that can be calibrated? I don't have any mods and I also have the stock 18" sport rims FYI.

Thanks all!
Mine reads 2 MPH lower than my GPS. The E46 M3 I had also read 2 MPH lower than the GPS.
135-dmc is online now   United_States
0
Reply With Quote
      07-05-2013, 08:28 AM   #4
pj.rodriguez
Major
 
pj.rodriguez's Avatar
 
Drives: Alpine White 128i Cabrio
Join Date: Jun 2013
Location: Toronto, Ontario, Canada

Posts: 1,027
iTrader: (6)

Garage List
Hmm. So you are going faster than you think? That's interesting. I was just concerned because apparently I was going 135 and the civic passed me at least 10 kmh faster and his was reading 130. So that must mean I am going 15 kmh slower than it reads?
pj.rodriguez is offline   Canada
0
Reply With Quote
      07-05-2013, 09:18 AM   #5
abirmaher
Captain
 
abirmaher's Avatar
 
Drives: 2011 135i Coupé Jet Black, Red
Join Date: Feb 2010
Location: Miami/ Orlando, Florida

Posts: 642
iTrader: (6)

Garage List
From what I've found it is a 5% exageration. That is if my Radar's GPS speed reading is accurate. I set my cruise control to around 100 and played with it until my GPS was reading 100 which according to the car was 105. So by that logic im pretty confident in saying 5%. Also due to the fact that the gap between GPS and car speed gets larger the faster I'm going.
__________________
abirmaher is offline   United_States
0
Reply With Quote
      07-05-2013, 09:49 AM   #6
jkoral
Captain
 
Drives: '09 135i MSport 6MT
Join Date: Oct 2007
Location: MA

Posts: 778
iTrader: (5)

2.4 mph + 10% as a maximum is within spec. It can never read lower than the actual speed, otherwise it's a violation of European regulation, ECE-R 39, which states indicated speed must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour.

This is a US service bulletin, but I assume it applies to all markets.


--------------
SI1996-620296 SUBJECT:
Maximum Permissible Speedometer Error

MODELS:
All

General Information:
A certain amount of "speedometer advance" is necessary to compensate for negative tolerances in tire diameter, electronic controls, and other factors. This advance reduces the risk of the speedometer displaying a speed that is less than the vehicle's actual speed.

The amount of speedometer advance can be calculated by inputting a frequency (using the DIS Tester, "Kombi Test Schedule") that corresponds to a given speed and noting the speed that is indicated by the speedometer. The maximum permitted speedometer advance is 10% of the actual (input) speed plus 2.4 mph.

Example:

Actual Speed = 50 mph

50 mph x 10% = 5 mph; 5 mph + 2.4 mph = 7.4 mph

Therefore, the permissible displayed speed is 50 to 57.4 mph.

(Note: The displayed speed must never be less than the actual speed).

No repairs should be attempted if the speedometer advance is within 10% + 2.4 mph.

NOTE: The amount of speedometer advance has no effect on recording of accumulated mileage in the odometer display. The odometer records total mileage digitally and does not incorporate any "advance" tolerances.

Warranty Status:
Information Only.
jkoral is online now   United_States
0
Reply With Quote
      07-05-2013, 09:52 AM   #7
miiipilot
Captain
 
miiipilot's Avatar
 
Drives: 2011 TiAg 135i 6mt M-Sport
Join Date: Jun 2010
Location: Cleveland, OH

Posts: 737
iTrader: (0)

Mine is b/w 2-3 mph higher than actual.
__________________
miiipilot 2011 135i TiAg w/Black Boston 6mt M-Sport, Premium Pkg, Value Pkg
miiipilot is offline   United_States
0
Reply With Quote
      07-05-2013, 09:55 AM   #8
jkoral
Captain
 
Drives: '09 135i MSport 6MT
Join Date: Oct 2007
Location: MA

Posts: 778
iTrader: (5)

On a related subject, you can get the actual uncorrected digital speed displayed in the cluster (through coding) or through the P3 Boost Gauge, which it pulls from the OBD2 port.

The only time I check the uncorrected speed is on the highway when I have cruise set to ~80mph. It usually reads ~79mph.
jkoral is online now   United_States
0
Reply With Quote
      07-05-2013, 10:16 AM   #9
135-dmc
Private First Class
 
Drives: 2013 135
Join Date: Nov 2010
Location: Sanford, FL

Posts: 131
iTrader: (0)

Quote:
Originally Posted by pj.rodriguez View Post
Hmm. So you are going faster than you think? That's interesting. I was just concerned because apparently I was going 135 and the civic passed me at least 10 kmh faster and his was reading 130. So that must mean I am going 15 kmh slower than it reads?
No, I'm going 2 MPH slower than indicated by the speedometer. When my speedo indicates 50MPH, I'm actually (according to the GPS) going 48.
135-dmc is online now   United_States
0
Reply With Quote
      07-05-2013, 10:29 AM   #10
Stohlen
Major
 
Drives: AW 135i
Join Date: Aug 2012
Location: Waterford, Mi

Posts: 1,191
iTrader: (2)

Garage List
2008 BMW 135i  [2.83]
You must realize that if you ever changed your tire size, you speedo will be wrong. If your tires are new, your speedo will be different than if they are warn to the belts. Your speedo is most accurate at 55 mph for american cars usually. Not sure about other countries but its probably similar.

No handheld gps is going to be accurate either. You need some pretty expensive equipment to reliably be within 1 mph.
Stohlen is offline  
0
Reply With Quote
      07-05-2013, 10:36 AM   #11
TMR013
Opus Angelus
 
TMR013's Avatar
 
Drives: '09 Monaco Blue 135i coupe
Join Date: Apr 2009
Location: Chandler, AZ

Posts: 998
iTrader: (0)

Thought I read a thread here a while back that talked about the OEM's (including BMW)purposely setting their speedometers low. Mine reads consistently 3 mph faster than actual. Also think the thread talked about how you can change the code so it reads dead accurate. Might want to try a search.
__________________
TMR013 is offline   United_States
0
Reply With Quote
      07-05-2013, 11:54 AM   #12
rking117
Captain
 
Drives: Z4 3.0i & 128i
Join Date: Aug 2012
Location: Central Florida

Posts: 854
iTrader: (0)

Mine can be as far off as 50% depending on how much wheel spin is involved. LOL
__________________
Enjoying an E89 Z4, E82 128i and Fiat Pop 500 / Missing my E85 Z4 (sold)
rking117 is offline  
0
Reply With Quote
      07-05-2013, 12:05 PM   #13
renaud00
New Member
 
Drives: 135i
Join Date: Feb 2011
Location: Ottawa, Canada

Posts: 17
iTrader: (0)

Quote:
Originally Posted by abirmaher View Post
From what I've found it is a 5% exageration. That is if my Radar's GPS speed reading is accurate. I set my cruise control to around 100 and played with it until my GPS was reading 100 which according to the car was 105. So by that logic im pretty confident in saying 5%. Also due to the fact that the gap between GPS and car speed gets larger the faster I'm going.
I have the same difference with my speedometer. Dealer said it was normal.
renaud00 is offline  
0
Reply With Quote
      07-05-2013, 12:08 PM   #14
renaud00
New Member
 
Drives: 135i
Join Date: Feb 2011
Location: Ottawa, Canada

Posts: 17
iTrader: (0)

Quote:
Originally Posted by pj.rodriguez View Post
So, I was driving along the highway with cruise control on at 135 km/h and the digital speed agreed with the gauge speed. But a Honda civic passed me and I saw his digital speedometer reading at 130 km/h. I immediately thought, "am I going slower than I think I am?"

I know it is just a Honda, and how accurate could their speedometer be, but are ours accurate?

I know that hooking up a sat nav or GPS would tell me a speed, but I just don't have one.

Anyone have any similar experiences or knows what is going on? Is it a computer thing that can be calibrated? I don't have any mods and I also have the stock 18" sport rims FYI.

Thanks all!
You can use a smartphone with an app like "GPS Status and toolbox" https://play.google.com/store/apps/d...sim.gpsstatus2 to help you verified your speed.
renaud00 is offline  
0
Reply With Quote
      07-05-2013, 12:57 PM   #15
Zebra M3
Second Lieutenant
 
Drives: e90 M3
Join Date: Apr 2013
Location: San Deigo

Posts: 264
iTrader: (1)

Quote:
Originally Posted by pj.rodriguez View Post
So, I was driving along the highway with cruise control on at 135 km/h and the digital speed agreed with the gauge speed. But a Honda civic passed me and I saw his digital speedometer reading at 130 km/h. I immediately thought, "am I going slower than I think I am?"

I know it is just a Honda, and how accurate could their speedometer be, but are ours accurate?

I know that hooking up a sat nav or GPS would tell me a speed, but I just don't have one.

Anyone have any similar experiences or knows what is going on? Is it a computer thing that can be calibrated? I don't have any mods and I also have the stock 18" sport rims FYI.

Thanks all!
Wouldnt you assume the CIVICs speedo is wrong. Not your BMW?
Zebra M3 is offline  
0
Reply With Quote
      07-05-2013, 01:05 PM   #16
cjof2003
BMW Newbie
 
Drives: '08 135i
Join Date: Jan 2011
Location: Georgia

Posts: 183
iTrader: (0)

Quote:
Originally Posted by ARO6ANT View Post
Wouldnt you assume the CIVICs speedo is wrong. Not your BMW?
I can see why you would make such an assumption, but you would be wrong. All recent BMWs read 5% high. You can have a coder disable this setting for a more accurate speed reading if you like.

So when the BMW speedo says 40 you are realky doing about 38.
55 you are really doing about 52 or 53.
At 80, you are only doing 76 or 77 etc.

Quote:
Originally Posted by 135-dmc View Post
No, I'm going 2 MPH slower than indicated by the speedometer. When my speedo indicates 50MPH, I'm actually (according to the GPS) going 48.
right at 5% high

Last edited by cjof2003; 07-05-2013 at 01:12 PM.
cjof2003 is offline  
0
Reply With Quote
      07-05-2013, 01:10 PM   #17
MightyMouseTech
Captain
 
MightyMouseTech's Avatar
 
Drives: 13 135i 6MT LeMans Blue MSport
Join Date: Feb 2013
Location: Ottawa, Canada

Posts: 796
iTrader: (0)

Quote:
Originally Posted by ARO6ANT View Post
Wouldnt you assume the CIVICs speedo is wrong. Not your BMW?
My Civic speedo and the 1er speedo have about the same accuracy. Actually, when I had the summer tires on the Civic, which were slightly taller than the OEM stockers, the speedo was near bang on.

My smart had the best of the bunch. Depending if I had the summer, winter or intermediate tires installed, the speedo was either bang on, or +/- 1-2% on that car.
MightyMouseTech is offline  
0
Reply With Quote
      07-05-2013, 06:02 PM   #18
JimD
Colonel
 
JimD's Avatar
 
Drives: 128i convertible
Join Date: Apr 2009
Location: Lexington, SC

Posts: 2,531
iTrader: (0)

My bummer is the only vehicle I've driven with such an inaccurate speedometer. I've been driving 40 years. GPSs are very accurate if your speed is steady. I have the digital speed option without correction. It reads the same as the GPS. I look at it or the GPS.
JimD is offline  
0
Reply With Quote
      07-05-2013, 06:28 PM   #19
doublevanosrc
Loves Runflats.
 
doublevanosrc's Avatar
 
Drives: 2013 VW GTi
Join Date: Jul 2009
Location: Austin. Tx

Posts: 1,851
iTrader: (1)

Garage List
2011 BMW  [0.00]
2011 BMW  [0.00]
BMW have always had inaccurate speedos dating all the way back to the E36 and E39.
__________________
2011 135i M Sport
Gone and missed
doublevanosrc is offline   United_States
0
Reply With Quote
      07-05-2013, 07:00 PM   #20
Dackelone
Moderator
 
Dackelone's Avatar
 
Drives: 135i Silber mit/Rot 6MT N54
Join Date: Feb 2010
Location: Bayern, Germany

Posts: 15,128
iTrader: (1)

^^Actually the speedo in my e39 is more accurate than in my 135i (e82).

By German law the speedo have to report a faster speed then TRUE vehicle speed. Normally they give us a 3% to 5% fudge factor. Meaning when you are driving 100 kph you true speed might only be 95 kph(to 97 kph).


You can have your kombi(speedo cluster) coded to rear TRUE vehicle speed IF you like. I had the M3 digital speedo coded to my cluster... and for that you can either have it read TURE vehicle speed or the 3-5% buffered value. I chose to have it read true vehicle speed.


OP - are you running OE tire sizes(brands) and wheels? Larger tires can also change your speedo calibration.
Dackelone is offline   Germany
0
Reply With Quote
      07-05-2013, 09:46 PM   #21
pj.rodriguez
Major
 
pj.rodriguez's Avatar
 
Drives: Alpine White 128i Cabrio
Join Date: Jun 2013
Location: Toronto, Ontario, Canada

Posts: 1,027
iTrader: (6)

Garage List
Quote:
Originally Posted by rking117 View Post
Mine can be as far off as 50% depending on how much wheel spin is involved. LOL
bahaha. Indeed it can be 50% off!

And thanks for all the input. I knew there must have been a regulation somewhere written in any country about over estimating speed, because yeah, it would be kind of sketchy if you were seeing 100kmh but driving 120.

Good to know that there actually is 5%. Saves from speeding tickets! haha
pj.rodriguez is offline   Canada
0
Reply With Quote
      07-05-2013, 09:49 PM   #22
pj.rodriguez
Major
 
pj.rodriguez's Avatar
 
Drives: Alpine White 128i Cabrio
Join Date: Jun 2013
Location: Toronto, Ontario, Canada

Posts: 1,027
iTrader: (6)

Garage List
Quote:
Originally Posted by Dackelone View Post
^^Actually the speedo in my e39 is more accurate than in my 135i (e82).


OP - are you running OE tire sizes(brands) and wheels? Larger tires can also change your speedo calibration.
OE tire sizes and OEM rims. style 263 (i think. The multiple-spoke sport package rims)
pj.rodriguez is offline   Canada
0
Reply With Quote
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 -5. The time now is 07:12 AM.




1addicts
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST