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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 07-17-2009, 10:59 AM
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SeanC SeanC is offline
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How to get rid of the factory understeer on a stock car ;)

Lessons learned from a bad alignment... Read on (long, but I think informative).

So we all know that we're safer with what BMW chose for us, but hate that understeer. Here's what you can do about it without running a square setup, getting sway bars, or changing the suspension altogether. A little story first

I recently got new tires and have been driving on them for nearly 2 weeks without an alignment and finally found the time to get it done yesterday. Off to the shop and they came up with a "sport" alignment specs for my car. Computer also told us that no weights are necessary for the alignment...

An hour later the car is off the rack, I look at the rear tires and wow, looks great with -2.7 degree negative camber on each side and has a total toe-in of about 0.53 degrees.. Front cambers are at about -1.3 degree and there is a total front toe-in of about 0.28...

I was told that I would need a more negative camber up front, but I don't have adjustable camber plates, so that's all they can do, fine, and I'm out for a drive...

And it drives like a frigging FWD car! WTF?

Here's the catch:

Much less negative front camber than the rear, too much front toe-in makes the car understeer like crazy. Turn-in has decreased a lot and I find myself putting extra effort to make the car turn. Certainly not what I wanted.

So I start digging up the forums, and came with the following info. BMW aligns the car in such a way that it has some front toe-in for directional stability (and more tire wear!), and the front camber is not enough for a nice turn in (lets the front tires lose traction easily at a fast curve so you remember to slow down and do not die)... And in my case this imbalance is even more pronounced, since the rears sit at a -2.7 degree camber (when I sat in the driver's seat this camber went up to a whopping -3.5 on each side , which is why you should sit in the car while getting an alignment).

Here's what I did and what you can do to correct your stock specs:

0. Never get an alignment with no weights in the car. You can have the weights that the factory recommends on each seat, but better yet, sit behind the wheel with a full tank of gas.

1. Zero that front toe-in, these cars are not highway cruisers but twisty killers, so you can trade some of that directional stability for MUCH better turn in, less understeer, and better tire-wear.

2. Never run too much negative camber with that much toe-in in rear, you'll need new rear tires in NO TIME.

So, here's what I recommend on a street driven car:

Front:

Camber: Can't do much about the camber on a stock car, might as well keep it stock and take care of the toe only. If possible, run an aggressive camber up front, about -2 to -2.5 is an acceptable range.

Toe-in: 0 total toe-in. As close to 0.00 as possible per side.

Don't worry about the tire-wear with that much negative camber, which happens when too much negative camber is combined with too much toe-in (this will drag the tire on the inner side, whereas running an aggressive negative camber with no toe-in will simply cause it to "roll" on the inner side. Dragging the tire will cause it to wear quickly, rolling the tire won't).

Rear:

Camber: -2 degree negative camber with YOU SITTING BEHIND THE WHEEL.

Toe-in: 0.20 total toe-in (0.10 per side). Never toe-out on the rear wheels.

If you're not allowed to be there while getting an alignment, have them set the rear camber to -1.5 and total toe-in to 0.30.

I hope this helps somebody out there. It is extremely important to get a proper alignment, and you can have much better handling than what the factory decided for you and improve your tire wear while doing so.
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Last edited by SeanC; 07-18-2009 at 07:28 AM.
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  #2  
Old 07-17-2009, 02:41 PM
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KrisL KrisL is offline
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I recommend a bit of front toe OUT.
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Old 07-17-2009, 02:47 PM
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Excellent opinion and information.
Thank you Sean.
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Old 07-17-2009, 02:47 PM
akhbhaat akhbhaat is offline
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Good stuff.
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Old 07-17-2009, 03:06 PM
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Quote:
Originally Posted by KrisL View Post
I recommend a bit of front toe OUT.
Yeah, I think I have 1/16 out up front, 3/16 in out back. 0 up front will make the car a little twitchy in a straight line on the street... at least on the E46. Racers probably run 0.

-2.0 camber in the rear is the max I was told to run and that's what I have. -3.0 up front = killer (hard) cornering ability at speed.
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Old 07-17-2009, 03:33 PM
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Quote:
Originally Posted by jvr826 View Post
yeah, i think i have 1/16 out up front, 3/16 in out back. 0 up front will make the car a little twitchy in a straight line on the street... At least on the e46. Racers probably run 0.

-2.0 camber in the rear is the max i was told to run and that's what i have. -3.0 up front = killer (hard) cornering ability at speed.
+1!
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Old 07-17-2009, 05:07 PM
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SeanC SeanC is offline
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Quote:
Originally Posted by KrisL View Post
I recommend a bit of front toe OUT.
I would, too, but I think it's a little bit unnecessary for the street. My commute is mostly highway, so I want to keep the directional stability a little bit while maximizing tire wear. If that doesn't make sense, please see my reply to Jeff below.

Quote:
Originally Posted by jvr826 View Post
Yeah, I think I have 1/16 out up front, 3/16 in out back. 0 up front will make the car a little twitchy in a straight line on the street... at least on the E46. Racers probably run 0.

-2.0 camber in the rear is the max I was told to run and that's what I have. -3.0 up front = killer (hard) cornering ability at speed.
I think any toe-out up front would be more responsive but less stable than a zero toe. So I would assume that racers run a negative (toe-out) toe than 0 up front, which is certainly what you and Kris are running
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