BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Wheels + Tires Sponsored by The Tire Rack
  TireRack

KEEP M3POST ALIVE BY DOING YOUR TIRERACK SHOPPING FROM THIS BANNER LINK!
Post Reply
 
Thread Tools Search this Thread
      11-14-2012, 11:40 PM   #1
Superfly_M3
Captain
18
Rep
964
Posts

 
Drives: 2011 M3
Join Date: Sep 2011
Location: Toronto

iTrader: (0)

Major Speedo Error

Hello,

Today I thought that I was going a little slower than was indicated and decided to check with GPS. Mind you its only an iPhone app, but it can't be off that much. I checked and my jaw dropped. Going indicated 80km/h GPS showed 73km/h. Going 140km/h GPS showed 129km/h. Thats 9%!!!

I just switched to 235/40/18 winter tires on OEM winter package rims - they have at least 60% thread left. My summers are 245/35/19F and 264/30/19R.

The diameter for the tires are:
235/40/18 - 25.40"
245/35/19 - 25.75"
265/35/19 - 26.30"

What could be wrong? Can it be fixed at the dealership through programing?
Where do our cars pick up the speedometer reading front or rear tires?

Thanks in advance.

Last edited by Superfly_M3; 11-15-2012 at 01:05 AM.
Appreciate 0
      11-14-2012, 11:57 PM   #2
smmmurf
Colonel
32
Rep
2,113
Posts

 
Drives: 2009 M3 Sedan 6MT
Join Date: Feb 2008
Location: Pleasanton, CA

iTrader: (7)

you should be running 265/35R19 not 265/30R19 in the rear

i used gps to verify my speedometer. it's about 2% error for me on stock 18's (75 indicated is 73)

speedometer is picked up off rear but the car gets wheel speed data from fronts and rears

if you do a burnout they know you are going 0-5mph even though your rears are going 30mph... that is how they have tried to get out of warranty claims in the past
__________________
M3 Sedan - AW/Black - 6MT - no moonroof - no folding seats - RAC RG63 - clear bra by Omega Werks
Appreciate 0
      11-15-2012, 01:02 AM   #3
Superfly_M3
Captain
18
Rep
964
Posts

 
Drives: 2011 M3
Join Date: Sep 2011
Location: Toronto

iTrader: (0)

right ... whatever stock size is, its a typo.
Appreciate 0
      11-15-2012, 01:36 PM   #4
ben@tirerack
M3Post Supporting Vendor
18
Rep
886
Posts

 
Drives: 740i
Join Date: Mar 2008
Location: South Bend, IN

iTrader: (0)

This is not completely shocking when you factor in that BMW speedo is usually reading a few percent high. Stack the ~3% error on the speedo with 3.5% error due to tire size variation and maybe a couple percent error in the GPS and you're right there.
__________________
_______________________________________________



To credit the forum, click through one of the banners in my signature and the top of the page, or call me direct at 877.522.8473 ext 660. Email:ben@tirerack.com
Appreciate 0
      11-15-2012, 02:33 PM   #5
M3PO
Colonel
M3PO's Avatar
34
Rep
2,777
Posts

 
Drives: '08 IB E92
Join Date: Sep 2011
Location: OC

iTrader: (7)

The M3 guys at the Airstrip attack this past weekend were noticing a significant difference between the speedo and their Vboxs. I have been driving past one of those police speed things that warns you to slow down and at 60 mph indicated, the display on the police thing shows 54. I am running 255/35/19 and 275/35/19.
__________________
2008 IB E92 M3| BBS | KW | Arkym | Platte Forme A.G. | Active Autowerke | K&N | Fabspeed | Dinan | Evolve-R
Appreciate 0
      11-15-2012, 02:34 PM   #6
m3an
Banned
m3an's Avatar
19
Rep
1,611
Posts

 
Drives: M3
Join Date: Oct 2010
Location: South Florida

iTrader: (2)

Quote:
Originally Posted by ben@tirerack View Post
This is not completely shocking when you factor in that BMW speedo is usually reading a few percent high. Stack the ~3% error on the speedo with 3.5% error due to tire size variation and maybe a couple percent error in the GPS and you're right there.

+1; I don;t think thats unreasonable at all
Appreciate 0
      11-15-2012, 03:12 PM   #7
Superfly_M3
Captain
18
Rep
964
Posts

 
Drives: 2011 M3
Join Date: Sep 2011
Location: Toronto

iTrader: (0)

This is insane. Can this be corrected at the dealer or through a tune?
Appreciate 0
      11-15-2012, 04:32 PM   #8
MSteve5036
Lieutenant
5
Rep
487
Posts

 
Drives: 2008 M3 / 96 328is
Join Date: Dec 2011
Location: blue dot

iTrader: (1)

I just thought thats how bimmers were. Most I or my friends have owned read high

Not trying to thread jack but anyone hit their limiter and at what speed?
Appreciate 0
      11-15-2012, 04:45 PM   #9
Z K
Colonel
Z K's Avatar
United_States
26
Rep
2,174
Posts

 
Drives: E90 M3, MK6 GLI
Join Date: Jul 2011
Location: San Francisco

iTrader: (3)

You have 235/40/18 all around!? That is way smaller in diameter than the front or rear stock size of the car. You get less ground clearance, higher rpms for the same speed, and just plain looks weird. The speed sensor is attached to the transmission which reads rear wheel speed. You should be running 245/40R18 or 235/45R18 all around if you want something closer to stock sizing.
Appreciate 0
      11-15-2012, 05:40 PM   #10
ben@tirerack
M3Post Supporting Vendor
18
Rep
886
Posts

 
Drives: 740i
Join Date: Mar 2008
Location: South Bend, IN

iTrader: (0)

Quote:
Originally Posted by Z K View Post
You have 235/40/18 all around!? That is way smaller in diameter than the front or rear stock size of the car. You get less ground clearance, higher rpms for the same speed, and just plain looks weird. The speed sensor is attached to the transmission which reads rear wheel speed. You should be running 245/40R18 or 235/45R18 all around if you want something closer to stock sizing.
235/40R18 all around is shorter, but it is the size that BMW supplies with their winter package, so it's certainly not an unreasonable choice.
__________________
_______________________________________________



To credit the forum, click through one of the banners in my signature and the top of the page, or call me direct at 877.522.8473 ext 660. Email:ben@tirerack.com
Appreciate 0
      11-17-2012, 02:58 AM   #11
Superfly_M3
Captain
18
Rep
964
Posts

 
Drives: 2011 M3
Join Date: Sep 2011
Location: Toronto

iTrader: (0)

Quote:
Originally Posted by MSteve5036 View Post
I just thought thats how bimmers were. Most I or my friends have owned read high

Not trying to thread jack but anyone hit their limiter and at what speed?
I don't get what you are trying to say.
What does speed and limiter has to do with this thread? ... not that you are trying to jack it or something like that.
Appreciate 0
      11-17-2012, 09:04 AM   #12
M3SQRD
Colonel
M3SQRD's Avatar
United_States
24
Rep
2,480
Posts

 
Drives: E92 M3s,R56 CooperS,F22 228iX
Join Date: Jun 2009
Location: EC

iTrader: (2)

Every BMW I've owned has had an error between 5-8% and the error is worse at higher speeds (e.g., on the track; also, it appears the speedo "calibration" curve is non-linear). Below 70 mph my errors have all been < 5%.
Appreciate 0
      11-19-2012, 08:57 AM   #13
MSteve5036
Lieutenant
5
Rep
487
Posts

 
Drives: 2008 M3 / 96 328is
Join Date: Dec 2011
Location: blue dot

iTrader: (1)

Quote:
Originally Posted by Superfly_M3 View Post
I don't get what you are trying to say.
What does speed and limiter has to do with this thread? ... not that you are trying to jack it or something like that.
Well its limited to 155...so when you get to the limiter does your car say 155 or something else?
Appreciate 0
      11-19-2012, 09:31 AM   #14
MrD1198
Enlisted Member
Germany
0
Rep
42
Posts

 
Drives: 2013 E92 M3/2009 Ducati 1198
Join Date: Aug 2011
Location: Germany

iTrader: (0)

I hit the limiter at 269 km/h on the digital read out which is about 167 mph. This is in a stock ZCP.
Appreciate 0
      11-19-2012, 03:15 PM   #15
Sleeper519
Captain
Sleeper519's Avatar
United_States
20
Rep
770
Posts

 
Drives: 08 E92 M3 DCT
Join Date: Nov 2009
Location: Atlanta, GA

iTrader: (0)

Mine has a 5% speedo error with stock wheels and tires. so, 2 mph at 40, 4 at 80, etc. I documented this by one of those radar "Your speed is ___" signs near my house. Now, my track tires are 18s, so that introduces another 2% error for a total of 7%, so when my speedo says 153 at Road Atlanta my gps tells me its really only 143.
__________________

2008 M3 Coupe / DCT // StopTech BBK 380/355 / Pagid RS29 / Motul / Apex Arc-8 / BFG R1S / Ground Control / MS filter / Performance spoiler / BPM tune // Road Atlanta 1:39.80 / VIR Full 2:10.87 / Barber 1:42.20
Appreciate 0
      12-08-2012, 12:10 PM   #16
MSteve5036
Lieutenant
5
Rep
487
Posts

 
Drives: 2008 M3 / 96 328is
Join Date: Dec 2011
Location: blue dot

iTrader: (1)

Quote:
Originally Posted by MrD1198 View Post
I hit the limiter at 269 km/h on the digital read out which is about 167 mph. This is in a stock ZCP.
I was also around there with stock 19s. I got to 168...wooo! im faster! lol
Appreciate 0
      12-08-2012, 06:50 PM   #17
Franken///M
A70
Franken///M's Avatar
Germany
2
Rep
258
Posts

 
Drives: '11 E92 M3 6MT
Join Date: Mar 2011
Location: Germany/Midwest

iTrader: (0)

I hit an indicated 169-170 in Germany. The car does read high compared to a GPS.
Appreciate 0
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 08:42 AM.




m3post
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