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

Post Reply
Thread Tools Search this Thread
      03-31-2012, 03:45 AM   #1
Second Lieutenant

Drives: n/a
Join Date: Jun 2011
Location: East Bay, California

Posts: 286
iTrader: (1)

Question: Speedometer difference

I know that speedometer is generally off by about 4%, but after changing to AD08's (285/30/18) from the stock PS2 (265/45/18), the difference increased by a whole lot. Cruising on the highway, the difference is roughly 7mph. I was fine before when I had a 2 mph difference, but 7 is sort of too much. I'm always caught off guard now when I notice my speedo at 87-90MPH and then remember I'm going 80-82 MPH. Any way to fix this? And does this effect my odometer reading by much?
2011 e92 JzB 6MT
Akrapovic Evolution, ESS Tune, UUC SSK w/ DSSR, Stoptech SS brake lines, Eibach springs, OEM gloss black kidney grills, keyhole delete, LUX H8 3.0, full front clear bra, 20% tint, Macht Schenll Stud Conversion, Apex ARC-8 18x9.5/10 w/ 265/35 & 285/30 AD08's
Appreciate 0
      03-31-2012, 03:44 PM   #2
BMW Fanatic

Drives: slow
Join Date: Jul 2009
Location: Calgary

Posts: 3,314
iTrader: (11)

When I had the stock rims/tires on I averaged about 6% off of the speedometer compared to a GPS unit, in fact I tested this across several GPS units, TomTom, iPhone 4S Google Maps and one which I forget the name of. I doubt there is any way to correct this error unfortunately.

With regards to your odometer that is a very good question. Why don't you set cruise to 40mph and reset the reading, then use a timer to see if the miles add up in a period of say 3 minutes. If it is at 2 miles then obviously the odometer goes according to the speedometer and not real world speeds.
Appreciate 0
      03-31-2012, 04:19 PM   #3

calintexas's Avatar
Drives: 2010 E90 M3
Join Date: Nov 2009
Location: North Texas

Posts: 1,416
iTrader: (1)

Tire Rack has spec tables for all the tires they sell where you can find tire revs per mile so that you can find out what the impact of different tire sizes will be before you leap. My experience is that, unlike the speedometer, the odometer is fairly accurate with the standard tires (your results may vary). You can determine the error you now have by using a GPS to compare its distance traveled information with your odometer over say a 10 mile run.
Appreciate 0
      03-31-2012, 06:42 PM   #4
HP Man
First Lieutenant

Drives: Batmobile
Join Date: Aug 2009
Location: Everywhere

Posts: 312
iTrader: (4)

I asked the same question a couple years ago and nobody had a solution. Your best bet is to go up to a 295/30 as the diameter is very close to stock.
Appreciate 0
Post Reply


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 03:46 AM.

Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.,,,,,,,,, logo and trademark are properties of BIMMERPOST