F30POST
F30POST
2012-2015 BMW 3-Series and 4-Series Forum
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > Wheels and Tires -- Sponsored by The Tire Rack > Tire Size & Speed calculations
European Auto Source
Post Reply
 
Thread Tools Search this Thread
      04-01-2016, 04:08 PM   #1
LUV335
Private
United_States
8
Rep
53
Posts

Drives: 2012 F30 335i MPPK
Join Date: Jan 2014
Location: Houston

iTrader: (0)

Tire Size & Speed calculations

I am curious to learn how tire size, if at all, affects speed,distance, traction, stability control etc. calculations.

If I have 18s and go to 20s how does the computer calculate the correct speed? How would the car know that with bigger wheels every revolution covers a little more distance? There is ~11.1% more distance covered per revolution just based on going from a rim size of 18 to 20.
Appreciate 0
      04-01-2016, 04:24 PM   #2
.BMW.
Brigadier General
.BMW.'s Avatar
Sweden
359
Rep
3,054
Posts

Drives: BMW F11
Join Date: Jun 2013
Location: Sweden

iTrader: (0)

With larger wheels the tire profile is reduced, which means that the overall tire diameter is kept almost the same.

The tire profile is reduced by 5% for every inch in wheel diameter increase.

For example for 225 tires:
225/45-18, tire diameter 25.9"
225/40-19, tire diameter 26.1"
225/35-20, tire diameter 26.2"
Appreciate 0
      04-02-2016, 01:09 PM   #3
baozi
Registered
0
Rep
4
Posts

Drives: E93 M3
Join Date: Jan 2013
Location: Brooklyn NY

iTrader: (0)

questions on tire.

i have 435i x drive coupe, i buy a m3 19s rim. what sizes of tire should i get. Thanks.
Appreciate 0
      04-03-2016, 09:31 PM   #4
LUV335
Private
United_States
8
Rep
53
Posts

Drives: 2012 F30 335i MPPK
Join Date: Jan 2014
Location: Houston

iTrader: (0)

Quote:
Originally Posted by .BMW.
With larger wheels the tire profile is reduced, which means that the overall tire diameter is kept almost the same.

The tire profile is reduced by 5% for every inch in wheel diameter increase.

For example for 225 tires:
225/45-18, tire diameter 25.9"
225/40-19, tire diameter 26.1"
225/35-20, tire diameter 26.2"
Thanks. So I guess one has to be careful in choosing the tire and rim size to keep the overall diameter the same? If overall diameter is different it will effect the speed and distance calculations?
Appreciate 0
      04-03-2016, 10:36 PM   #5
oln08
Private
13
Rep
68
Posts

Drives: '08 BMW 335i
Join Date: Aug 2009
Location: California

iTrader: (1)

Quote:
Originally Posted by LUV335
I am curious to learn how tire size, if at all, affects speed,distance, traction, stability control etc. calculations.

If I have 18s and go to 20s how does the computer calculate the correct speed? How would the car know that with bigger wheels every revolution covers a little more distance? There is ~11.1% more distance covered per revolution just based on going from a rim size of 18 to 20.
Check this out. Much easier than doing your own calculations.

https://www.rimsntires.com/specspro.jsp
Appreciate 0
      04-07-2016, 03:07 PM   #6
E30toF30
Lieutenant
Canada
48
Rep
581
Posts

Drives: 2015 F30 335xi M Perf. Edition
Join Date: Mar 2015
Location: Vancouver

iTrader: (0)

Quote:
Originally Posted by LUV335 View Post
Thanks. So I guess one has to be careful in choosing the tire and rim size to keep the overall diameter the same? If overall diameter is different it will effect the speed and distance calculations?
The tire/wheel shop should be able to easily help you find the right combination of wheel and tires so that you maintain as close to stock spec as possible (or do it yourself with that online calculator in the link above).
Anything within 3% of the original overall diameter is considered acceptable and and somewhat within spec.
Appreciate 0
      04-08-2016, 09:57 AM   #7
Keith@tirerack.com
Moderator
48
Rep
104
Posts

Drives: 2001 BMW 330i & 1991 BMW 318i
Join Date: Feb 2016
Location: South Bend, IN

iTrader: (0)

Quote:
Originally Posted by LUV335 View Post
Thanks. So I guess one has to be careful in choosing the tire and rim size to keep the overall diameter the same? If overall diameter is different it will effect the speed and distance calculations?
Yes, the overall diameter is what is most important. When you make the wheel larger, you will make the tire lower profile. As long you keep the overall diameter close, your vehicle will not notice the difference.

Keep in mind, lower profile tires will ride stiffer and you will have to steer clear of potholes as the lower profile tires do not provide as much protection.
__________________
Keith. Tire and Wheel Forum Moderator. Tire Rack Sales Rep Keith@Tirerack.com
http://www.tirerack.com/a.jsp?a=AH8&url=index.jsp

Please refer to 'Keith/BimmerPost' as your previous contact when you order online to help support this forum.
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 -4. The time now is 11:36 PM.




f30post
f30post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2016, 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