135i understeer--

[Ganicki]

Whats the best solution to keep the 135i from understeering--H&R Springs and strut brace are the only suspension mods at this point -- thanks G

[Roland135i]

I put on a strut brace.

Also 4 x 12mm spacers on front and back. This helped a bit, and gives the 135i a bit more firm grip and stance.

[Ganicki]

Am putting on 12 mm spacers also. That should help a little. What about a larger sway bar?

[DietTab]

fat sticky tires and big negative camber is the biggest change you can make. everything else helps, but the swaybar taxes your tires even more heavily.

[Ganicki]

Guess I'll just have to invest in some camber plates. Thanks.

[Ginger_Extract]

Fat tires and better suspension geometry. I have 255 square, and it's not nearly enough. If this car could run 18x10 square with some 285s like the 350/370Z guys, it would be much better off.

[fe1rx]

Originally Posted by Ganicki

Whats the best solution to keep the 135i from understeering--H&R Springs and strut brace are the only suspension mods at this point -- thanks G

This horse has been flogged to death.

Rear subframe bushings are #1, but I am guessing that you don't really want to hear that.

[fcman]

Originally Posted by fe1rx

This horse has been flogged to death.

Rear subframe bushings are #1, but I am guessing that you don't really want to hear that.

Your user name looks really familiar

[DietTab]

Originally Posted by fe1rx

This horse has been flogged to death.

Rear subframe bushings are #1, but I am guessing that you don't really want to hear that.

Rear subframe bushing will do absolutely 0 to help understeer, especially at the limit.

[fe1rx]

Originally Posted by DietTab

Rear subframe bushing will do absolutely 0 to help understeer, especially at the limit.

The car suffers from compliance steer aka passive rear steer because of the soft rear subframe bushings, so you are not only wrong, you are completely wrong. The effect is most pronounced at the limit, hence M3 rear subframe bushings (or equivalent) are most effective at the limit. Not that established internet wisdom means anything, but this was well established long ago by actual experience with the mod, should you care to search.

Not quite sure why I took the OP's bait, given that his first (or second) mod was a strut brace (aka useless). Faint hope he might appreciate actual information I guess.

And DietTab, sticky tires give you grip, but they don't give you balance. Negative camber saves your tires when cornering hard (and uses them up, when not) but doesn't change the balance all that much.

Sorry to say, but the best mod is the least glamourous one.

[DietTab]

Originally Posted by fe1rx

The car suffers from compliance steer aka passive rear steer because of the soft rear subframe bushings, so you are not only wrong, you are completely wrong. The effect is most pronounced at the limit, hence M3 rear subframe bushings (or equivalent) are most effective at the limit. Not that established internet wisdom means anything, but this was well established long ago by actual experience with the mod, should you care to search.

Not quite sure why I took the OP's bait, given that his first (or second) mod was a strut brace (aka useless). Faint hope he might appreciate actual information I guess.

And DietTab, sticky tires give you grip, but they don't give you balance. Negative camber saves your tires when cornering hard (and uses them up, when not) but doesn't change the balance all that much.

Sorry to say, but the best mod is the least glamourous one.

You are sorely mistaken. compliance steer? Way to make up imaginary things that don't exist. FWIW i have bushings on my car. They don't do a thing for understeer.

[John_01]

The rear subframe bushing mod is needed anyway. I found that adding M3 SFB upgrade by itself had a net effect of promoting understeer, but its a lot better than the nervousness and unpredictable effect of the stock subframe bushings. I'd go so far to recommend you don't use too much front camber with stock subframe bushings, as its not a nice feeling at the limit. Frankly, the stock rear subframe bushings are a total disaster and really don't belong on a BMW. The 1 series has a short wheelbase, so you will get pretty decent turn-in just by adding some front camber.

[Ganicki]

Wow-- Thanks guys, who's right and who's wrong? Someone help me out here. Thanks

[Kgolf31]

Here is a list in order of what you'll need.

Rear Subframe Bushings
Camber
Wider Wheels/Tires
Caster
Alignment for Toe Adjustments
Front Swaybar
Rear Swaybar


and honestly the list goes on.

There is a 100 ways to skin a cat, helping reduce understeer can be done multiple ways with multiple methods. Do for what works best with you and your budget.

[ilikebmxbikes]

Originally Posted by Ganicki

Wow-- Thanks guys, who's right and who's wrong? Someone help me out here. Thanks

I would largely go with Kgolf's recommendation. No single modification or few modifications will simply cure the understeer on the 135i. It needs a handful of revisions. And after you cure your understeer problem, you will want an LSD.

Originally Posted by Kgolf31

Here is a list in order of what you'll need.

Rear Subframe Bushings
Camber
Wider Wheels/Tires
Caster
Alignment for Toe Adjustments
Front Swaybar
Rear Swaybar


and honestly the list goes on.

There is a 100 ways to skin a cat, helping reduce understeer can be done multiple ways with multiple methods. Do for what works best with you and your budget.

[Ganicki]

Thanks. Will keep trying things until I find what works. Will talk to some of the track guys this weekend

[MightyMouseTech]

First thing to do is increase the front camber. That is a cheap and easy mod. M3 arms and some camber plates.

[02rsxpilot]

Originally Posted by Ganicki

Wow-- Thanks guys, who's right and who's wrong? Someone help me out here. Thanks

Fe1rx has the most comprehensive suspension write-up I've ever seen on a forum here on 1addicts. Ilikebmxbikes has what must be the most modified 135i in the history of the 1er. Kgolf is a consistent contributor to the autocross/track section of this thread and regularly posts results to back up his modifications. Each guy's work speaks for itself on here.

Other than that, this forum is loaded with folks that swear this car has horrible suspension and understeer and is virtually undriveable at the limit and yada yada yada and you need to spend thousands of dollars to make it road worthy. And not one of them could come within 10 seconds of Randy Probst time in a bone stock '09 135i with run flat tires at Laguna Seca (1:46), which tells you all you need to know about what the most important modification is.

At the end of the day, if you really think you need to fix understeer, you can do two things: increase front grip, or decrease rear grip. Make sure that for any modification you do, you understand how those two components will change as a result, because a lot of people on here will give you bad advice that might help mask bad driving habits but will actually decrease your overall grip, making you slower and a worse driver.

[Ganicki]

OK first things first--Kgolf--what would be the first thing to do to help me out--then 2nd, 3rd, etc-- knowing that I can't do everything at once--Thanks

[dcaron9999]

Im assuming that you will be lapping/autocrossing your car ...

Most meaningful and cost effective solution for me was to first do Front M3 Control Arms and Camber plates for about $1000 in parts and 2.5 hours of labor.

Second was to go with a square 255/35R18 Extreme Performance tire setup.

[fe1rx]

Originally Posted by Ganicki

OK first things first--Kgolf--what would be the first thing to do to help me out--then 2nd, 3rd, etc-- knowing that I can't do everything at once--Thanks

Clearly we need to step back even further:

1) brake in a straight line
2) release the brake as you turn in
3) turn in smoothly
4) maintain a balanced throttle to the apex
5) don't add throttle until you start unwinding the steering
6) add throttle smoothly
7) if you are overcome by the urge to spend money on your car, modify your car per Kgolf's list, starting at the top pausing to check the results whenever you run out of money

Sorry to have taken your bait. I knew you really didn't want to hear the answer.

[Ganicki]

[QUOTE=fe1rx;16717894]Clearly we need to step back even further:

1) brake in a straight line
2) release the brake as you turn in
3) turn in smoothly
4) maintain a balanced throttle to the apex
5) don't add throttle until you start unwinding the steering
6) add throttle smoothly
7) if you are overcome by the urge to spend money on your car, modify your car per Kgolf's list, starting at the top pausing to check the results whenever you run out of money

Sorry to have taken your bait. I knew you really didn't want to hear the answer.[/QUOTE

No. That's exactly what I wanted to hear. Just like golf. Get the basics down good and strong practice practice practice. Then when I feel that equipment will help the cause, I can try some things. Thanks