Performance Suspension Question

[Slider128]

I have combed the site for information on the BMW Performance Suspension (PS) and I am almost sold on getting it for my 128i non-sport suspension. I wonder if you guys could comment on how you think the PS for 128i would help to solve the following complaints. 1) The left front feels higher than the right front. Both do not feel the same. 2) Understeer -- I have added weight to the front to improve tire grip which has reduced understeer, but the height difference is still an issue. 3) The right rear feels like it is too low -- and the car tends to lean to that side too often, especially on these Dallas, Texas crested roads. 4) The turn in, especially to the left is slow as if the rear of the car is dragging down performance. 5) The car tends to float and does not feel planted. What specific applications of PS and PS with M3 parts will improve these issues? Second question -- after installing PS and / or M3 parts, did anyone make further tuning efforts such as alignment, weight balancing, tire preassure tweaks, or different tires, etc., and how did you do it? I previously owned a '93 325i that someone had weight balanced and added rear spring stablizers. The car was really great, planted and on rails all the time. I could load the trunk with groceries and never felt any sagging at all. I want to add stabilzers to the right rear of the 128i, but after a few alignments, tire preasure tweaks and moving weight around, etc., I do not believe that any of this will solve the issues on my current 128i. I think it is the suspension, the front sway bar, the rear subframe bushings, springs and shocks and RFT tires that need changing. I really like the car in all other aspects. I think the engine and transmission work like gods together and I like the styling of this car. I do believe that our cars can perform in an outstanding way. I am willing to spend about 3K - 4K on this. Thanks in advance for your help.

[ianc]

The left front feels higher than the right front.

This seems to be an issue with your car. I would make some measurements and see the dealer about it if you can reproduce it and demonstrate it in a meaningful way, because this is definitely not normal...

If you get the PS, you cannot corner-balance the car like you would with a coilover setup since there is no means of adjustment. This could be a good or a bad thing, depending on how you look at it.

M3 parts will generally take some 'slosh' out of the suspension, tighten things up, and provide more precise control and better feedback. M3 front Wishbones are particularly recommended as they add camber to the front beyond what can be obtained with the stock pieces and this goes a long way to removing some of the factory understeer. Front sway bar will also help, as will subframe bushings, but the latter are lots of work\$$$, so should probably happen later in the process.

Floatiness and lack of 'plant' will definitely be helped most with the PS, coilovers or aftermarket spring\shock combinations.

Get that weird height difference sorted first!

ianc

[Slider128]

ianc -- Thanks for the info. Is the front sway bar the E93/M3? I noted the M3 front Wishbones in my front M3 list. And, I have read in other posts the M3 front control arms are recommended also. I know that the M3 rear sub frame bushings are expesive to install, but I feel that is why I am anoyed by the mushy right rear. I have also heard that some have installed the rear sway but decided to remove it later. I wonder why?

[ianc]

Front sway bars generally used are E92\E93. The E93 bar is a little thicker at 28 mm, and the E92 is 26.5 mm.

The reasons I've read for the removal of a stiffer rear bar is that since the car has no LSD, a stiffer bar will allow less body roll in corners and hence will tend to unload the inside rear more. This can allow wheelspin and trouble putting down power on corner exit. Unless you will track or autox the car, I wouldn't worry about it...

ianc

[tgxmike]

See Blue comments below

Originally Posted by Slider128

I have combed the site for information on the BMW Performance Suspension (PS) and I am almost sold on getting it for my 128i non-sport suspension. I wonder if you guys could comment on how you think the PS for 128i would help to solve the following complaints.

1) The left front feels higher than the right front. Both do not feel the same.

I do not have this issue, take measuements and see a dealer if it is real
2) Understeer -- I have added weight to the front to improve tire grip which has reduced understeer, but the height difference is still an issue.

Understeer is how these cars are designed. My solution was PS, new tires/wheels, and more pressure in the front than the rears (5psi difference)

3) The right rear feels like it is too low -- and the car tends to lean to that side too often, especially on these Dallas, Texas crested roads.

This sounds like the roads, but there is a slight difference in the L/R rear ride height w/ non-sport suspension. And is normal.

4) The turn in, especially to the left is slow as if the rear of the car is dragging down performance.

A number of things will cause/help this..... Tires, Camber, suspension roll, engine torque, etc, etc...

5) The car tends to float and does not feel planted. What specific applications of PS and PS with M3 parts will improve these issues?

I think just the PS to help everything settle out. I'm not sure you really need the exta M3 bits. The ROI (return on investment) is not so good in my opinion.

Second question -- after installing PS and / or M3 parts, did anyone make further tuning efforts such as alignment, weight balancing, tire preassure tweaks, or different tires, etc., and how did you do it?

I have a dedicated summer tire set. Sport edition 17x7.5et42 w/ 205/50 (42lb/corner) hankook V12 all around. running ~39psi front and 35psi rear

I previously owned a '93 325i that someone had weight balanced and added rear spring stablizers. The car was really great, planted and on rails all the time. I could load the trunk with groceries (groceries are very light....????) and never felt any sagging at all. I want to add stabilzers to the right rear of the 128i, but after a few alignments, tire preasure tweaks and moving weight around, etc., I do not believe that any of this will solve the issues on my current 128i. I think it is the suspension, the front sway bar, the rear subframe bushings, springs and shocks and RFT tires that need changing. I really like the car in all other aspects. I think the engine and transmission work like gods together and I like the styling of this car. I do believe that our cars can perform in an outstanding way. I am willing to spend about 3K - 4K (on a 4k budget, ~$2500 on the BMS PS, and another ~$1200 on wheels/tires. Thats really all you need for this car. I would do one at a time to see the incremental difference. start with wheels/tires) on this. Thanks in advance for your help.

[Slider128]

TGXMike -- Thanks for your responses. I really appreciate it.