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Discussion Starter · #1 · (Edited)
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 :D

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... :confused:

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 :rofl:, 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 :thumbsup:
 

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Discussion Starter · #3 ·
:thumbsup:

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 :confused:

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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Discussion Starter · #5 ·
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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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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That fully explains everything for me, thank you so much :lmao: 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 :facepalm:
 

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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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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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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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Snap. Now that's dropping knowledge. I've got to check this closer when I get home. Can't read the tiny stuff in the pics from the phone.

I think I get it tho, caster on a car is what us motorcyclist refer to as rake a trail. And when its too little on a motorcyle, it encourages nimble and quick handling, but also what we call a "tankslapper" where the handle bar basically acts like a shopping cart wheel, cycling back and forth like crazy, uncontrollably as you go down the road. We alter ours by raising or lowereg the back or front relative to each other, or to do it without shifting the weight distribution greatly, you adjust its angle, but most bikes don't have this, from the factory, typically only race bikes do all that.

I think in the car world, its mostly drifters that mess with the caster, as it can help them in transitions, etc....

This thread FTW!!!! :D
 

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Nah, caster is only partly about stability, mostly about cornering traction.

Caster has the affect of tilting the front wheels in the direction you turn only when you turn the steering wheels. It helps like camber, but has the benefit of keeping the wheels standing up straight when the steering wheels is pointed straight. Because of caster only helping camber when the wheel is turned, you don't lose braking traction when braking in a straight line(large amounts of camber decrease straight line traction). The downside is that since you are tilting the front wheels to the left or to the right, you are tilting the tires up on their edges, and essentially lifting the front of the car when you do so.

This is why car's like the E30 M3 DTM race cars had around 15 degrees of caster, and needed power steering since it was so hard to turn the wheels even while moving. But the car was excellent at cornering and braking. Similarly, the non-M cars have around 5 degrees of caster which is better for street driving, the M3 has 7 degrees of caster since this improves cornering grip.
 
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