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Suspension & Braking
Have some questions about suspension or brake setups for your E46 BMW? Get all your answers here!

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Old 10-16-2010, 10:06 PM   #1
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How To Kill Understeer?

Thats my question. We all know that E46 understeers quite alot, so what things could be done to get rid of it. In other words what particular part would yield the best results.

I just came back from a full day track event, the car performed flawlessly but it oversteers pretty bad, obviously less then it did when it was stock but still not quite there yet.

So, lets discuss it.
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Old 10-16-2010, 10:16 PM   #2
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wider spacers in the front?...
just my 2 cents.
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Old 10-16-2010, 10:26 PM   #3
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More track time....
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Old 10-16-2010, 10:54 PM   #4
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Simple things to start with would be tire pressures, alignment and a square tire/wheel setup. You might be surprised what you can accomplish with these things alone. After that, you could consider adjustable sway bars. If you want the ultimate ability to dial it in, then you might consider good coilovers with the ability to adjust damping and experiment with spring rates.
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Old 10-17-2010, 02:58 PM   #5
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add more negative camber to the front. I've got AST adjustable top mounts installed.
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Old 10-17-2010, 03:00 PM   #6
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simple things to start with would be tire pressures, alignment and a square tire/wheel setup. You might be surprised what you can accomplish with these things alone. After that, you could consider adjustable sway bars. If you want the ultimate ability to dial it in, then you might consider good coilovers with the ability to adjust damping and experiment with spring rates.
+1
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Old 10-17-2010, 04:31 PM   #7
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i'm not trying to knock you, but technique does a lot too.

other than that, square setups ftw.
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Old 10-17-2010, 06:03 PM   #8
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Thanks all for the good ideas.

The season is over, so over the winter I want to save up for a few improvements. Square rims and compound tires are on the way, now I'll need to save up for a set of hotchkis sways. I dont want to go coilovers as of yet but I will consider camber plates.

Keep em coming guys.
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Old 10-18-2010, 02:36 AM   #9
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More camber and 255s at all 4 corners definitely reduced the understeer. I think a better coilover setup would help. My PSSs tend to roll quite a bit on the track.

I just went from max caster to min master on my vorshlag plates. Which increased my front neg camber from 2.5 to 3.3 degrees. This definitely helped with the understeer.

Understeer isn't the most terrible thing either...just sayin'
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Old 10-18-2010, 10:53 AM   #10
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If you want easy, just adjust tire pressure and add a thicker rear sway bar. Basically every aspect of the OEM suspension is biased to understeer. Radical alignments will only chew up your tires on the street.
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Old 10-18-2010, 10:55 AM   #11
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Once the square wheel/tire setup is done, as mentioned above your next best bet will be camber.

You can't go wrong with UUC for your camber adjustments!

Their front camber plates offer the following:

Front Camber/Caster Adjustment Range
Camber: -2.0 to +2.0
Caster: -.75 to +.75

Their Chromoly Adjustable Rear Control Arms offer and from adjustment range +1.0 to -3.0.

Click HERE for more information.


Please let us know if you have any questions! Feel free to shoot me a PM or email.

Best,
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Old 10-18-2010, 11:22 AM   #12
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Get rid of those ugly heavy wheels, get some square 255's, set of sways and coil's, and increase negative camber. Game.Set.Match.
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Old 10-18-2010, 06:09 PM   #13
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PARAMETER TO INCREASE OVERSTEER
Front Tire Pressure Higher
Rear Tire Pressure Lower
Front Tire Width Larger
Rear Tire Width Smaller
Front Camber More Negative
Rear Camber More Positive
Front Springs Softer
Rear Springs Stiffer
Front Sway Bar Softer
Rear Sway Bar Stiffer
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Old 10-18-2010, 06:42 PM   #14
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Thats my question. We all know that E46 understeers quite alot, so what things could be done to get rid of it. In other words what particular part would yield the best results.

I just came back from a full day track event, the car performed flawlessly but it oversteers pretty bad, obviously less then it did when it was stock but still not quite there yet.

So, lets discuss it.
My 330ci pushed really bad toward the end of sweepers when it was stock. It would turn in very well off braking but as soon as the load would begin to even out to neutral, the front would understeer horribly. I installed Hotchkiss sways and they helped tremendously. I would try the sways and see how you like it.
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Old 10-18-2010, 07:08 PM   #15
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My 330ci pushed really bad toward the end of sweepers when it was stock. It would turn in very well off braking but as soon as the load would begin to even out to neutral, the front would understeer horribly. I installed Hotchkiss sways and they helped tremendously. I would try the sways and see how you like it.
All street cars, unless ultra high performance are designed to understeer on purpose. Although oversteer is quicker than understeer, oversteer can be dangerous to someone that is driving beyond there ability. Its much easier to control a car in a skid than when it is spinning. Oversteer gets you wrapped around a tree. Understeer gets you in a head on accident with the tree.
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Old 10-18-2010, 07:41 PM   #16
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Good good ideas !

Do you guys think its better to go 255/40/17 all around or 245/45/17 (get more sidewall on there) also should I make them flush with the rim, meaning on a 9" rims or I can overlap a bit and put them on an 8" rims?

There wont be any price difference with these as I get a deal on them, so its a matter of which is better.

Amy thoughts are appreciated.
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Old 10-18-2010, 07:51 PM   #17
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I think you are at the crossroads where you need to decide if you want looks or speed? 1st off, the very 1st thing you should do to get rid of under-steer is to get rid of your staggered setup. I don't think going 255 all around is a good idea because it dramatically increases rolling resistance and softens up the feel of the car. You want the tires to be a tad bit stretched over the rims for maximum stability. In fact I think 235 all around are just about ideal for this car with proper rims. If changing out the rims is not an option then your next bet is stiffer rear sway bar. Front camber can help, bit it's going to come at a cost of less comfortable freeway drive, the car is going to want to shoot side to side every time you go over an imperfection.

p.s. what tire pressures are you running?
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Old 10-18-2010, 08:51 PM   #18
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I think you are at the crossroads where you need to decide if you want looks or speed? 1st off, the very 1st thing you should do to get rid of under-steer is to get rid of your staggered setup. I don't think going 255 all around is a good idea because it dramatically increases rolling resistance and softens up the feel of the car. You want the tires to be a tad bit stretched over the rims for maximum stability. In fact I think 235 all around are just about ideal for this car with proper rims. If changing out the rims is not an option then your next bet is stiffer rear sway bar. Front camber can help, bit it's going to come at a cost of less comfortable freeway drive, the car is going to want to shoot side to side every time you go over an imperfection.

p.s. what tire pressures are you running?
Actually I'm not a the crossroads, I only did a few very little aesthetic mods for my car, I'm way more into performance then looks.
Rims you see in my sig are for show only. I bought this car when the season was coming to an end and first focused on suspension. Didnt want to buy track rims/tires this season as I wouldn't be able to use them much, I only took this car out 3 times for fun racing. By the time next season comes up, I'll be all set. Sways are already on my list.

I already have quite a bit of tramline, its not bad at all but its there.

Right now I'm at 35psi rear(235 tire on a 9") and 32psi front(235 tire on 8")
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Old 10-18-2010, 09:44 PM   #19
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I don't think going 255 all around is a good idea because it dramatically increases rolling resistance and softens up the feel of the car. In fact I think 235 all around are just about ideal for this car with proper rims.
That really all depends on the suspension setup (spring rates and damper settings). Suspension is all about balance. More tire means more grip which can in turn lead to more body roll (ie, soften up the feel). From a performance perspective though, I'm not sure that I agree that a 235 square setup is optimal for these heavy pigs but it certainly wouldn't overwhelm a stock-ish suspension. I'm running 255/35s on 18x9s all around but I'm also running significantly higher than stock spring rates with some really good dampers.
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Old 10-18-2010, 09:46 PM   #20
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Good good ideas !

Do you guys think its better to go 255/40/17 all around or 245/45/17 (get more sidewall on there) also should I make them flush with the rim, meaning on a 9" rims or I can overlap a bit and put them on an 8" rims?

There wont be any price difference with these as I get a deal on them, so its a matter of which is better.

Amy thoughts are appreciated.
I have 255/40R17s on 17x9 APEX ARC8s. The tires a flush with the wheels. I think 245/45R17 would be too big? Maybe 245/40R17?

Going from 225fr/245rr to 255 square reduced understeer quite a bit! I keep tire pressure the same front and rear.

BTW, you can get 255/40R17 Nitto NT05s from discounttire.com for $128 ea...not sure if that is better than the pricing you are getting now.
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