E90Post
 


TireRack
 
BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Lighter wheels affect on suspension?



Reply
 
Thread Tools Search this Thread
      05-05-2009, 07:21 PM   #1
fnckr
Second Lieutenant
fnckr's Avatar
2
Rep
243
Posts

 
Drives: 2006 330i 6mt
Join Date: Feb 2009
Location: Parsippany, NJ

iTrader: (0)

Lighter wheels affect on suspension?

I know and understand all of the common answers like the car handles better, accelerates and brakes quicker, etc. I also know that less mass means the suspension can move up and down quicker because it now overcomes less intertia.

So, my question, and speaking in terms of the stock sport suspension on my 2006 330i, or really, in general, all suspension components remaining equal what affect do lighter wheels have on suspension behavior?

Put differently, will the ride be bouncy (under-damped) because lighter wheels require more damping since the spring is now free to over-power the stock damping as it no longer is burdened by the extra inertia of heavy wheels?

In my mind that seems likely and must be counteracted with stiffer damping, but I'm sure I'm missing something because everyone raves about their new tires or wheel/tire combos instead of RFTs.
Appreciate 0
      05-05-2009, 10:48 PM   #2
SV Concepts III
Lieutenant General
262
Rep
17,021
Posts

 
Drives: BMW Duh
Join Date: Apr 2005
Location: Santa Clara

iTrader: (13)

Send a message via AIM to SV Concepts III
Lighter wheels, if built properly (meaning they are not weak) should not have an effect on ride quality. Your car will be more nimble and have better acceleration because of the decrease in unsprung weight.
Appreciate 0
      05-06-2009, 04:07 PM   #3
fnckr
Second Lieutenant
fnckr's Avatar
2
Rep
243
Posts

 
Drives: 2006 330i 6mt
Join Date: Feb 2009
Location: Parsippany, NJ

iTrader: (0)

So lighter wheels wouldn't allow the spring to overpower the damping?
Appreciate 0
      05-07-2009, 05:00 AM   #4
GeekinE90
Private
GeekinE90's Avatar
Malaysia
0
Rep
60
Posts

 
Drives: E90 325i
Join Date: Nov 2007
Location: Kuala Lumpur, Malaysia

iTrader: (0)

For me, it changed the acoustic characteristics. After going from stock wheels to forged 18's the brakes tend to give out a higher pitch squeal when cold compared to a duller grunt when cold. After putting in the bigger/heavier discs, and calipers, it changed back to the original duller sound. Also road noise seems to have gone down and car seems slightly more comfy. However, its also feels more lazy and less nimble. Sigh.
__________________
| E90 325i Sparkling Graphite | VOLK Progressiv ME Forged 18's | Pilot Sport 2 F225/40 R255/35 | KW V2 Coilovers | M Tech Body Kit | M Tech CF Splitters | M Tech Boot Spoiler | BMW Performance Intake | BMW Performance Brake System | ACS Style Roof Spoiler | Blacklines | Chrome Tail Pipes | Vkool | M mobility Kit|
Appreciate 0
      05-07-2009, 08:46 AM   #5
Orb
Lieutenant Colonel
No_Country
37
Rep
1,747
Posts

 
Drives: 335
Join Date: Jun 2006
Location: Canada

iTrader: (1)

Quote:
Originally Posted by fnckr View Post
I know and understand all of the common answers like the car handles better, accelerates and brakes quicker, etc. I also know that less mass means the suspension can move up and down quicker because it now overcomes less intertia.

So, my question, and speaking in terms of the stock sport suspension on my 2006 330i, or really, in general, all suspension components remaining equal what affect do lighter wheels have on suspension behavior?

Put differently, will the ride be bouncy (under-damped) because lighter wheels require more damping since the spring is now free to over-power the stock damping as it no longer is burdened by the extra inertia of heavy wheels?

In my mind that seems likely and must be counteracted with stiffer damping, but I'm sure I'm missing something because everyone raves about their new tires or wheel/tire combos instead of RFTs.

Your suspension frequency will increase slightly which means better suspension response. Your dampening is a function of the suspension frequency so you have the right idea and it may require a small increase in dampening stiffness.

Orb
Appreciate 0
      05-07-2009, 07:02 PM   #6
fnckr
Second Lieutenant
fnckr's Avatar
2
Rep
243
Posts

 
Drives: 2006 330i 6mt
Join Date: Feb 2009
Location: Parsippany, NJ

iTrader: (0)

Quote:
Originally Posted by Orb View Post
Your suspension frequency will increase slightly which means better suspension response. Your dampening is a function of the suspension frequency so you have the right idea and it may require a small increase in dampening stiffness.

Orb
Just the person I was waiting for! I figured as much. Obviously it can't be that bad since many people have eliminated RFTs and moved to lighter wheels while keeping stock suspension and they still love the handling of their cars.

I have no interest in lowering the car from stock sport height, but just like on my motorcycle, I notice and like the adjustment ability of compression and damping. I figure a set of KW V3s are just what I would need as a spirited street driver; and perhaps some future occasional track usage. Would a rear sway be beneficial in any way?

BTW, when I say "spirited" I mean I'll drive for a few hours over nearly 250-300 miles of the same upstate NY and NJ roads I used to ride my motorcycle on, trying to recreate the experience. Obviously that is dialed down a little bit from a track pace.
Appreciate 0
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 05:27 PM.




e90post
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