eBMWParts
Results 1 to 4 of 4

Thread: What would happen if you narrowed a rear subframe and left everything else the same?

  1. #1
    Join Date
    May 2008
    Location
    New England
    Posts
    996
    My Cars
    E36 M, E32 740i/6, 997 S

    What would happen if you narrowed a rear subframe and left everything else the same?

    Let's say that theoretically you wanted to take a rear subframe and remove 2 inches from the width. All of the control arms remain the same and you shorten the half shafts by one inch on either side. What happens to the geometry? Would it be ruined? Improved? Let's assume this is a multi link setup like on an E39 or an E90.

  2. #2
    Join Date
    Aug 2013
    Location
    Seattle, WA
    Posts
    1,433
    My Cars
    1999 BMW M3 Coupe
    Disregarding any structural implications or things like where the spring hats are and a number of other things, for the suspension it should function the same except the track would obviously be 2 inches narrower and the wheels an inch further inboard on each side. The suspension would articulate the same since the arms are all the same length, but narrowing the rear track isn't usually a good thing for performance. Usually people try to do the opposite and go as wide as they can.
    1999 M3/2/5 - Titanium Silver - Track/Weekend Toy


  3. #3
    Join Date
    May 2008
    Location
    New England
    Posts
    996
    My Cars
    E36 M, E32 740i/6, 997 S
    Awesome. I know that the ackerman geometry gets messed up if you shorten or lengthen the wheelbase but I didn't know if something similar would happen if you narrowed the rear track via the subframe width. Looking at diagrams it appears the roll center would raise slightly and the instant centers would move outward from the wheels a small amount. I'm not sure what effect that would have on handling though.

  4. #4
    Join Date
    Apr 2005
    Location
    ATL
    Posts
    164
    My Cars
    '91 325i
    You are correct on roll center/ ic. Mostly just the weight transfer will be affected I think, the reaction from each wheel loses its moment arm to act against vehicle roll.
    Harrison Motorsports
    Motion Control Suspension
    Daytona M3

Similar Threads

  1. quick coilover question. Narrower diameter rear springs?
    By budget76 in forum Suspension Tech and Handling sponsored by eBMWParts.com
    Replies: 2
    Last Post: 12-30-2010, 02:38 AM
  2. Those with rear subframe problems read this...
    By dc516 in forum 1991 - 1999 (E36)
    Replies: 23
    Last Post: 05-11-2007, 03:14 AM
  3. Reinforcing rear subframe
    By TYE in forum 1991 - 1999 (E36)
    Replies: 12
    Last Post: 02-10-2002, 03:15 PM
  4. Replies: 0
    Last Post: 11-17-2001, 04:31 PM
  5. Question about rear subframe failure
    By Jeff P in forum 1992 - 1999 M3 (E36)
    Replies: 4
    Last Post: 04-11-2001, 02:26 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •