Hi all, hopefully somebody can answer this. After reading a lot of posts, everybody says how this and that helped the handling and I gathered sway bars help and improve the handling overall, at least on smooth surfaces. But when I'm taking high speed turns that aren't so smooth, the rear end is hopping around and it gets a little unsettled. How can I improve the handling so the rear end stays planted? Are sway bars the answer or springs or full coilovers? Appreciate any feedback.

 

Better dampning. Don't see stiffer springs or stiffer sway's as a answer, I'm thinking Tokico D-specs, not coilovers. Use sway's to get the at the limit behavior to your liking, but not to fix what you've got going on now.

Your car is a 04 coupe from what I could research, so you don't have the stiffer rear springs of the 05/06 sport suspension.

Honestly, you may be talking about road condition's that only very mild spirng rates or dampning settings can deal with. Meaning that you could end up dialing into a slower less playfull setup where road condition's aren't so poor.

 

Study Tireracks suspension tests: note that upgrades on BMW add only 1-2% for springs and 1-2% for sway bars AT BEST. AND THINGS ARE NOT CUMLATIVE..........2+2 doesn't = 4 maybe 3.3.

Tires are 90-95% of what's possible. The softest fastest wearing!

A mediocre stock car with the finest tires will easily outhandle a car with every aftermarket suspension goody AVAILABLE running on less than optimum tires.

As a side though examine BMW variable rear sway bar: it engages with wipers and measures rain rate to soften rear bar to protect the driver.
Driver adjustable [on the fly] shocks to compensate for bad road [non smooth track].

Adjustable springs [while in motion] other than variable rate vs length are a tough design. What about adding an auxillary air bag type helper spring whose pressure could be changed while driving.

 

Have you noticed some car magazines are now report a SPECIFIC number for understeer in excess degrees of front wheels angle as the speed goes up on slalom. Something like 1.25 degrees for an excellant car and 1.7 degrees for a mediocre one............that multiples by the ratio of rack vs steering wheel:

Something like 15 degrees of steering yields 1 degree of tire [every model different], so they are resolving the steering wheel angle to something like 1 degree or 0.066 degree of tire angle.

Not sure car owners can precisely describe understeer in 7 degrees of steering wheel position.

My car understeers WELL HOW MUCH please be specific in degrees of EXCESS steering vs ideal track at what speed and angle.

Frustrating for engineers to see comments without precise data.
If you know the precise amount of understeer, IT IS easy to calculate the required changes to correct...........to fix 10% understeer you only need to stiffen rear 10% [plus weigh ratio and correction for chassis twist rigidity] to neutralize under the exact same conditions.

Many vehicles are way over modified as to bone jaring stiffness!

http://www.auto-ware.com/setup/undr_mid.htm

http://www.rqriley.com/suspensn.htm

http://www.eng.auburn.edu/~dmbevly/mech4420/hw4.pdf

http://www.eng.auburn.edu/~dmbevly/mech4420/

 

http://www-nrd.nhtsa.dot.gov/vrtc/ca...2006010559.pdf

Homework that shows that if wet performance is important 4/32" is much safer than 2/32" current replacement standard.

Change tires when 60% worn rather than 80% worn. Especially with rear sway bars near neutral.