|
|
|
06-19-2016, 11:49 PM | #1 |
Private
25
Rep 81
Posts |
How do I correct my understeer?
I have a 128i that was awfully spongy after 70k miles on the non-sport suspension, so I upgraded to stiffer springs that dropped each end about 1 in. and koni orange shocks. The car corners much flatter and has a much higher overall G limit, but it also has significantly greater degree of understeer.
Any suggestions on how to remove this tendency to understeer and return to the more neutral handling of the stock setup? |
06-20-2016, 01:50 AM | #2 |
European Editor
10539
Rep 22,992
Posts |
Koni Orange shocks ? Did you mean Yellows ?
Sway bars are what you need. The non M-suspension 128i's did not have a rear sway bar. That's why BMW included them in the Performance suspension for the 128's. After sway bars.. you could go to a square tire/wheel setup. But sway bars is where you should start.
__________________
|
Appreciate
0
|
06-20-2016, 04:32 PM | #4 |
Private
25
Rep 81
Posts |
Yes, the Koni orange shocks are essentially a less stiff, non adjustable version of the Koni sport shocks (yellows).
To which end of the car would you suggest adding a sway bar? Physics would seem to dictate that by adding a front sway bar you flatten the front in corners and increase the grip of the inside front tire, but I have heard conflicting opinions on this. Increasing/decreasing the camber of the rear isn't my first choices as this is my daily driver and I don't want to be going through tires that much quicker. |
Appreciate
0
|
06-20-2016, 05:10 PM | #5 | |
European Editor
10539
Rep 22,992
Posts |
Quote:
Read this article on what TC Kline did... The ultimate handing machine: 128i ? http://www.1addicts.com/forums/showthread.php?t=575027 and this one is really just for reference on 128i's in general. 128i: Simple Fun, Great Price! ...in Bimmer Magazine... http://www.1addicts.com/forums/showthread.php?t=734600
__________________
|
|
Appreciate
0
|
06-21-2016, 01:24 PM | #7 |
First Lieutenant
52
Rep 374
Posts |
Does anyone know what makes the car understeer to begin with? Is it just the stock alignment settings (I believe the rear wheels have more negative camber than the fronts stock) and the staggered wheels?
__________________
New Car: 2019 Porsche 718 Cayman GTS | Stock for now Old Car: 2013 BMW 128i | 6MT | BMW Performance Grills | CDV Delete | SSK | Performance Exhaust | M3 RSFB | TCKR DA |
Appreciate
0
|
06-21-2016, 01:51 PM | #8 | |
First Lieutenant
50
Rep 379
Posts |
Quote:
__________________
Living the 1-life since 2013.
|
|
Appreciate
0
|
06-21-2016, 02:21 PM | #9 |
European Editor
10539
Rep 22,992
Posts |
You forgot tire age & brand/design and or miss matched tires.
__________________
|
Appreciate
0
|
06-21-2016, 11:29 PM | #10 |
Colonel
232
Rep 2,643
Posts |
Understeer is partly due to staggered tire sizes, but most of it is to do with the inadequacy of the MacPherson strut front suspension. The big problem is there is not enough negative camber on the front. The static front camber is close to zero. Other cars may gain negative camber as they roll in cornering, but there isn't much of this characteristic on the 135i front suspension. BMW have done a respectable job with the multi-link rear suspension on the 1 series, but it would have been really nice if they had a good double wishbone setup on the front to compliment it.
|
Appreciate
1
|
06-23-2016, 12:48 PM | #12 |
Second Lieutenant
39
Rep 257
Posts |
BMW designs their cars to have slight understeer for safety reason. They figure most people can control a little understeer. Better then the other option of having oversteer which most people cannot control. BTW when I changed over suspension from stock on my 135i, my first track day I had a lot of understeer. I changed 3 things. Stiffened up the suspension, got a bigger swaybar, the one one the M3. I put a bit of Toe out on my front tires, be careful with that. Changed things entirely, car is neutral with just a bit of oversteer when I want it. I also have other M3 swapped over on my car.
|
Appreciate
0
|
06-27-2016, 01:07 PM | #13 |
First Lieutenant
130
Rep 351
Posts |
Curing understeer mid-corner - stab the clutch and apply full throttle. This should eliminate all understeer and put the car into an oversteer condition. Problem solved.
Maybe this isn't the best way on a second thought...
__________________
Ohlins Road & Track Coilovers / Apex ARC 8's 245/255-35 MPSS / Wagner Downpipes / Wagner EVOII Intercooler / ER Charge Pipe / Forge DV / PowerFlex RSFB / PowerFlex Differential Bushings / MFactory 3.46 Torsion LSD / MHD Flasher
|
Appreciate
1
|
06-27-2016, 06:55 PM | #14 | |
Private
25
Rep 81
Posts |
Quote:
|
|
Appreciate
0
|
06-28-2016, 09:36 AM | #15 |
Second Lieutenant
39
Rep 257
Posts |
|
Appreciate
0
|
06-28-2016, 09:40 AM | #16 |
Major General
4338
Rep 6,196
Posts |
Staggerd tires are fine, but the front tires are not nearly wide enough.
Wider front tires, more front camber, and a stiffer front bar to limit roll. Will be much better. |
Appreciate
1
|
06-28-2016, 10:08 AM | #17 | |
Major
189
Rep 1,026
Posts |
Quote:
|
|
Appreciate
1
|
Post Reply |
Bookmarks |
|
|