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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 07-17-2009, 01:10 PM   #1
SeanC
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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, -2 to -2.5 degrees is good.

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 09:29 AM.
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Old 07-17-2009, 01:26 PM   #2
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im always running my own camber, caster, and toe out settings, and have never really found a working solution. i run -1 in the back, -.75 in the front camber, stock toe (which i will change), and have found the stock caster settings to be adequate. i'll definitely give your style a try next time, but its difficult since i'm in a 4dr

do you have any recommendations for the longer wheelbase sedan?
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Old 07-17-2009, 01:27 PM   #3
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useful stuff, thanks!
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Old 07-17-2009, 01:31 PM   #4
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Quote:
Originally Posted by carbon323 View Post


im always running my own camber, caster, and toe out settings, and have never really found a working solution. i run -1 in the back, -.75 in the front camber, stock toe (which i will change), and have found the stock caster settings to be adequate. i'll definitely give your style a try next time, but its difficult since i'm in a 4dr

do you have any recommendations for the longer wheelbase sedan?
The wheelbase length is the same on an e46 coupe and a e46 sedan. Although my info is based on an e36 M3, similar conclusions and numbers apply to any BMW, because of the way the factory aligns these cars.

All in all, you want to get rid of the front toe-in for better turn-in, get a more aggressive front camber if you can, and get a "mild" camber and toe-in for the rear end.
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Old 07-17-2009, 01:32 PM   #5
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Anybody know what the best camber/caster plates are for a track/street driven 330?
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Old 07-17-2009, 01:35 PM   #6
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Originally Posted by SpeedDemon View Post
Anybody know what the best camber/caster plates are for a track/street driven 330?
What do you mean by "best"? Depends on how much camber you want to run on track. Vorshlag should cover you up to -4 degree camber IIRC.
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Old 07-17-2009, 01:41 PM   #7
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Quote:
Originally Posted by SpeedDemon View Post
Anybody know what the best camber/caster plates are for a track/street driven 330?
i use bavauto's street/race camber kit up front and simple correction arms which replace your control arms in the back. it gives you more than enough flexibility for a multi-purpose car. and you can dial in settings in the middle of the track when you need to
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Old 07-17-2009, 06:46 PM   #8
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Getting rid of staggered rims helps too.
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Old 07-17-2009, 07:25 PM   #9
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Wow, WhyTF did they set that much rear camber and toe? No wonder it handled like a big turd. You have found the secret to a nice, neutral set up for stability to ~100mph. It all centers around zero front toe, no more than -2.0 rear camber and shallow rear toe between .20 and .30.

Always have the car set for alignment like you drive it most of the time, ie; sitting in the seat 1/2-full tank of gas etc. and run spec from that. Otherwise ensure that the alignment shop uses a machine with ballast compensating software. Current line of Hunter and Beissbarth racks have this capability.
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Old 07-17-2009, 07:36 PM   #10
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Old 07-17-2009, 09:31 PM   #11
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Could someone please explain to me what "toe-in" means? I'm new to all this suspension stuff
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Old 07-17-2009, 09:59 PM   #12
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Could someone please explain to me what "toe-in" means? I'm new to all this suspension stuff
Sure! I'll try to put it as simple as possible for ya

There's 3 major components of handling tuning (known as alignment), which refer to the way your wheels/tires position in relation to each other, the suspension, and the car itself. You'll notice that suspension tuning tends to focus on handling vs stability, depending on the car and it's primary use.

1) Camber - This is the most obvious one. Camber, when you look from the front or the back of the car, is the slant of the wheels. Remember, as you turn, weight gets transferred. On a zero camber setting, the momentum of the chassis would cause the tire to roll onto its outer edge, thus reducing grip. Increasing camber increases the cars ability to track and it's stability at high speeds, at the expense of handling ability.

Negative Camber=



This car has negative camber. As a result, it will exhibit excellent turn in BECAUSE as the car rolls into a turn, the wheel will become more and more centered and parallel with the road, causing the most contact and as a result more grip. The downside of this, however, is that less of the tire is in contact with the road in straights reducing stability.

Positive Camber=



This car has positive camber. As you can probably guess, it will be much more stable at high speeds, because, like a motorcycle, it's track is reduced and the car has less tendency to roll. And for obvious reasons, it will unfortunately tend to wash out in the corners.

---------------------------

Toe In/Out is the amount in which your front or rear wheels point inward (toe in) or outward (toe out)



^This is a Toe-In setup. Most cars are set up like this from the factory. In general, increased front toe in provides greater straight-line stability at the cost of some sluggishness of turning response, as well as a little more drag as the wheels are now driving a bit sideways. Toe-out in the front wheels, will result in more responsive steering and quicker turn-in. However, front toe-out usually means a less stable car (i.e. more twitchy).

The rear wheels of a car should are usually adjusted with some degree of toe in. In general, like the front, the more rear toe-in, the more stable your car will be. Keep in mind, however, that increasing toe angle (front or rear) will result in decreased straight line speed.

---------------------------------------------------

Caster



The best way to think of caster is like a shopping cart; the center of mass of the wheel is in front of the linkage, not directly under it. Caster provides a degree of self-centering for the steering - the wheel casters around so as to trail behind the axis of steering. This makes a car easier to drive and improves its straight line stability. Excessive caster angle will make the steering heavier and less responsive, although, in off-road racing, large caster angles are used to improve camber gain in cornering.

------------------------------------------------------

If you are truly interested in tuning suspensions properly, become familiar with the terms understeer/oversteer, slip angle, weight transfer and roll center, spring and shock rates and their effects, and the concept of the circle of forces. If you have any questions feel free to PM me and ill try my best to explain the concepts to ya.


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Old 07-17-2009, 10:14 PM   #13
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That fully explains everything for me, thank you so much i had my car aligned a while back and I was too embarrassed to ask what the different terms meant. I only just found out what yaw was yesterday as well
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Old 07-17-2009, 10:24 PM   #14
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That fully explains everything for me, thank you so much i had my car aligned a while back and I was too embarrassed to ask what the different terms meant. I only just found out what yaw was yesterday as well
ya man dont ever be embarassed to ask. how do ya think we all learned?

if u have any other questions feel free to hit me up m8
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Old 07-17-2009, 10:26 PM   #15
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oh this is awesome! good info guys!
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Old 07-17-2009, 10:27 PM   #16
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wow, good thread and replies. i learned quite a bit.
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Old 07-17-2009, 10:44 PM   #17
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First interesting and smart thread in the General Forum in a while.

Link to bimmerworld for the shims does not work. Also I didn't know the trick with the shims worked on E46 as well.
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Old 07-17-2009, 11:12 PM   #18
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I looked and couldn't find any shims for the E46 on Bimmerworld as well.

I think that getting rid of staggered wheels is probably the biggest way to get rid of factory understeer. My 255/35-18 tires and 4x8.5" wheels are coming here by Tuesday It'll be nice to go back to a squared setup like I had on my last E46; I had 235/45-17 tires on the 7.5" wide wheels on my 328i.
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Old 07-17-2009, 11:29 PM   #19
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Good thread. I run the same 0 toe F too. About 1deg F and 1.5deg R camber. Don't worry about getting different wheels. Just tighten up the front end with sways or coilover/shocks. I have a very neutral setup. I can work understeer and oversteer throttle alone. Running 225's up front and 255's in the rear.
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Old 07-17-2009, 11:45 PM   #20
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I've never quite understood how caster on a car is adjusted and how it affects it. I guess I never really looked into it.

So anyway, so 000 on the front toe setting? My question is, from the bmw recomended stock how much will going to 000 on the toe will we feel.
I frequent 80mph sometimes 90+ but really I'm mostly at 70mph, would I notice a difference if I went to 000 on the front toe?
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