Handling Part 2:
It is hard to place this subsection properly because while it is very important to your car’s handling characteristics, it is also semi-dependent on your choice of wheels and tires and your suspension mods. There are certain wheel and tire fitments that require pretty aggressive camber settings to even fit on the M3 but you probably should not be running those fitments if you as a driver are not ready for an aggressive alignment. Likewise there are certain settings you have little control of without some suspension mods. This is more to inform you of the importance of each aspect of a proper alignment so you will be able to judge what changes your car might need later on.
Caster is the angle between the steering axis (imaginary line between the center of the strut mount/upper ball joint and the lower ball joint) and the vertical axis of the wheel. Positive Caster (above, top left) angles the top of the strut backward or the bottom of the strut forward, giving the a car’s steering a self-centering characteristic. The principle is similar to how casters (above, top right) work on furniture, the pivot point is forward of the vertical axis of the wheel which will then naturally follow the direction of motion. This means that while driving straight ahead your wheels will naturally return to the straight ahead position. Naturally this makes the steering a little heavier because there is more force pushing it back to center. However, the benefit of positive caster on a track car is not related to steering effort or centering, although both are nice to have. The real benefit is that because your steering wheels are angled back at the top, you get more dynamic camber. Dynamic camber is the additional camber gained while turning. Because the struts are angled towards the rear of the car, as you are turning, the outside wheel will gain camber and the inside wheel will lose camber. Imagine the E46 pictured above was turning normally, the driver’s side front tire would be the inside tire and the passenger’s side front would be the outside tire. See how the inside tire has gained positive camber? That is due to an aggressive caster setting. Positive camber on the inside wheel works on the same principle of negative camber on the outside wheel, it compensates for the weight transfer and roll of the vehicle so your tires get the best contact patch possible (less important on the inside wheel due to weight transfer, but it doesn’t hurt).
Camber is the angle difference between the centerline of the wheel and true verticality. Negative camber is denoted by the bottom of the wheel sitting further out from the vehicle than the top of the wheel (when viewed from the front/rear of the vehicle). Positive is of course the opposite, top further out than bottom. The benefit of a reasonable amount of negative camber is an improved contact patch while turning. Better contact patch = more grip. More grip = happy you.
Camber adjustment is a careful balancing act between wanting maximum grip in turns and keeping enough of a contact patch in the straights for sufficient braking and acceleration. This can also change over time as you grow in confidence and start carrying more speed into corners. At that point you’d want to increase your front camber to account for the increased lateral load. Similarly in the rear you want a reasonable amount of camber so you remain planted but not so much that you lose grip when accelerating. And worse still, it also semi-depends on the track you’re at! The fewer turns at the track the less camber you’ll effectively use. You’ll kind of just have to get the feel for it. Easy way to tell if you have too much camber is if the inner edge of your tires is significantly more worn than the outside edge so if your tires look like they came off of your friend’s hellaflush show car you should probably consider easing up on the camber.
Toe refers to the angle at which the front or rear wheels are pointed in relation to the centerline of the vehicle. Positive Toe or “Toe In” is when the wheel is angled inward towards the vehicle. Negative Toe or “Toe Out” is the opposite, wheel angled away from the vehicle. This setting has, by far, the biggest effect on tire wear out of the three. You might be thinking “well why don’t we just point them all perfectly forward and have done with it?”. That is of course the most moderate approach and will give you very neutral handling but there are benefits to small changes in either direction if you are looking to tweak your car’s handling characteristics. Just keep in mind any amount of toe will affect your tire wear as you are essentially scrubbing the tire sideways slightly as you drive.
First let’s talk about front toe and how it affects handling. Front toe in will give the car more straight line stability because the wheels are pushing inward from both sides. It is common for road vehicles to have a bit of toe in for safety and predictability. Front toe out on the other hand will give the car a certain amount of agility to your steering, giving the car an immediacy in steering feel and low effort to initiate a turn.
However, once you are mid-corner each setting actually behaves completely differently. Because the car’s weight has shifted primarily to the outside front tire at this point on the turn, the toe settings have an inverse affect on handling. Toe in will have your outside tire pointing further into the corner which makes mid-corner steering more responsive and less prone to understeer. Similarly, toe out mid-corner will be more prone to understeer and less immediate steering. As such, it is not advisable to go to crazy with your front toe settings in either direction, a small amount of toe out on a tight course or a small amount of toe in on a wide track will do you fine, experiment a bit and see what you like.
In the rear of the car toe has similar effect that translates differently due to the inertia of the vehicle and the more static nature of the wheels’ direction. A bit of toe in at the rear will give your car a tendency to follow the front wheels more closely and give better stability under cornering and braking, but you’d also be more likely to induce push understeer when accelerating out of a turn. Toe out on the other hand would make your car pivot around its center and give it the tendency to oversteer in turns and under acceleration after a corner. Common practice on the M3 is to set your rear for a tiny bit of toe in and zero toe in the front, so give that a try and then tweak it to your liking.
-Side Mentions: Thrust Angle and Steer Ahead:
Thrust angle is the angle between the difference in left to right toe settings divided by 2 and the centerline of the vehicle itself. Ever see a truck on the freeway that looks like it’s driving crooked? It probably had a messed up thrust angle so it has a toe bias to one side. Steer ahead is the angle (measured from the centerline of the vehicle) at which your car will move when driving on a flat road with the steering wheel straight. These settings aren’t really subjective at all, just make sure they’re as close to zero as possible, ideally both zero if your frame/suspension is undamaged and your alignment shop is thorough.
-E46 M3 specific settings for spirited driving:
Caster: To taste. Roughly 7 degrees is a common setting (requires caster adjustable camber plates)
Camber: Front: -2 (conservative) up to -3.6 – Rear -1.8 (conservative) up to -2.5.
Toe: Front: 0 degrees – Rear: .08 – .15 degrees
Drive it stock first if you can. A large majority of M3s will already have had some suspension work done and that’s fine, but the best way to get an understanding of the car is to drive it as close to a factory setup as possible. If it has stock springs still throw on some new dampers (if the existing dampers are blown) and give it the beans. This will give you the best sense of how the car was designed, what the limits are of the factory suspension, and most importantly it will give you a baseline for the car’s handling characteristics. That way, you know if something you change later actually makes the car feel/perform better or worse. And above all else remember, you could have a $10,000 professionally tuned racing suspension, but if you don’t know to drive with it it’ll be worse for you than a cheaper and more forgiving setup.
As mentioned in the wheel subsection, front camber plates are absolutely necessary for fitment of a lot of the larger tire sizes. Also, as mentioned earlier on this page in the alignment subsection, negative camber is necessary for keeping a proper contact patch while cornering. Having the freedom to adjust your camber is an essential part of modifying your vehicle for the track and we recommend it to anyone.
We recommend a set of Vorshlag Camber Plates due to their versatility. These camber plates not only give you all the camber adjustment you’d ever need, they also adjust caster, and can be used with almost any suspension setup (must be specified at time of purchase).
As mentioned earlier on page 6, a strut brace is not all about looks, it serves an important purpose on the E46 M3. We recommend running some kind of strut brace whether it’s a simple one or a big race brace. The large mounting plates act as an additional strut tower reinforcement and pressure distribution system. As you might remember, the strut towers are a potential point of failure on this car so they can use all the help they can get. Furthermore a strut brace will benefit you on the track by reducing chassis flex allowing for more immediacy in steering response, so the benefits are two-fold.
Lowering springs are a thing of course, and if you want to track on them go ahead, but you’re going to be leaning everywhere with spring rates that low. If you’re going to get yourself a track suspension setup just save your money until you can get something relatively nice. Lowering springs will not help you much in track conditions due to their focus on ride quality.
Choosing a set of coilovers for the track is actually harder than it sounds. Do you want stiffer custom spring rates? Well BC BR Coilovers will offer you pretty high spring rates with their custom swift spring option, but their damping is not the best. KW V3 Coilovers will give you some pretty solid damping but their spring rates are generally lower and more geared towards comfort. You can buy KW springs separately in higher spring-rates but you can only go up maybe 1-2kg/mm before you stare over-stressing the dampers. If you want a combination of much higher spring-rates and high damper rates, you’ll want to look into one of our options below. Please note, the coilover kits listed below are very expensive and are in no way required for a track car, they are just the most suited for track use.
–True Coilover Rear
Before we get into some of the specific coilovers, we’re going to go over a term that needs some explaining. “Coilover kit” is the general term used to describe an aftermarket suspension that is purchased as a set and designed specifically to work as a unit and most commonly offer ride height adjustment. A bog standard “Coilover Kit” will come with a set of springs and matching dampers. Additional items may include: top mounts, sway bar end-links, wheel hubs, camber plates, etc. but this will vary by manufacturer and coilover model. This is what the term has evolved into currently. Originally the term was very literal, a coil spring encircling a shock absorber = coil over. This is why when we use the phrase “True Coilover” when we are discerning between a coilover kit that has a coil spring over a shock vs one that uses a factory configuration of a separate spring and shock.
While this distinction is hardly worth mentioning if you buy suspension just to lower your car, it is actually a very important topic when it comes to tracking. This is due to different types of springs having different behaviors. A “linear” or “constant pitch” spring is one that has a constant rate throughout its range of motion. In the case of a 100lbs/in spring (very soft for a car suspension but makes a good example spring), if it is compressed with 100 lbs of pressure it will contract by 1 inch. 100 more pounds of pressure = 1 additional inch. 1000 pounds = 10 inches and so on. This behavior is desirable because you get very predictable behavior from the suspension. A “progressive” or “variable pitch” spring on the other had is a spring that will progressively react differently depending on how much pressure is exerted on it. It may start out as 5 pounds = 1 inch and then work its way up to 10 or 15 pounds = 1 inch, so the way it responds is inconsistent depending on the frequency and amplitude of the surface you are driving on.
We’re getting to the point don’t worry. You see, when a rear suspension has a separate spring and shock, that means the spring is sandwiched between the chassis and the lower control arm and does not have a shock in the middle to support the spring. If you use a linear spring in this position (see image 1 left) you run the risk of the spring eventually warping with the arc of the suspension arm because more pressure will be exerted on the inner edge of the spring. With a Convex Barrel Spring (see image 1 right) we see a spring design that telescopes in on itself as it compresses giving it self centering properties, which is why we typically see this type of spring used in a separate spring and shock setup. However the downside of this design is that, because the outer coils are smaller diameter than the inner coils, the spring is inherently progressive and therefore not as desirable for aggressive cornering. Tapered/conical springs (see image 2) are, for the same reason, not as desirable on a track suspension because a tapered spring is essentially a convex barrel spring cut in half.
Another benefit of the coil over shock configuration is that by combining the spring and the shock you get 1-to-1 motion between the two. This means that the damper can be tuned more accurately for the spring without having to deal with more minute movements of the spring translating to large movements of the damper. And last but not least, this spring placement allows for use of lower spring rates to achieve a specific target wheel frequency due to the reduced motion ratio between the wheel and the spring. More pressure is exerted on a spring closer to the pivot point so a higher spring rate is required to counteract that pressure (think how a nutcracker works, it multiplies pressure at the handles into huge pressure at the pivot point). Essentially this allows for greater freedom in choosing spring rates. With a separate spring and shock setup an 8kg/mm spring in front calls for about a 12kg/mm spring in the rear. Once you start getting into the 10-12kg/mm range in the front you’re getting into pretty ridiculous rates in the back (15kg/mm+). With a true coilover rear you’ll be around a 10kg/mm spring with a 12kg/mm front, much more attainable.
However, it’s not all sunshine and rainbows, if you’re going to be running a true coilover in the back of your vehicle you need to be aware that it will put more stress on your rear shock mounts. As such we advise use of shock tower reinforcement plates at the very least, as well as weld-in reinforcement plates if you want to be as safe as possible. If you’re also going to be installing a roll-cage in your car you can have the strut towers welded to the cage for added strength.
–Twin-Tube vs Monotube
Whole articles have been written about Twin-Tube shocks vs Monotube shocks, it’s a very well documented subject so we’ll try so summarize the important points. Monotube is just better for several reasons, none of which are really debatable. With a twin-tube setup (above, left) you have an inner tube and an outer tube, with gas and oil mixing within the outer tube. This mixing of gas and oil can exacerbate a condition called aeration, which is essentially foaming of the oil inside the shock body. In a monotube shock (above, right) you have a piston separating the gas and oil, meaning you are less likely to experience aeration. The monotube design also allows for 1) a bigger piston, meaning more fine tuning of valving, 2) higher oil capacity, meaning better heat dissipation, and 3) separate gas reservoir provides a damping effect when the oil shifts rapidly under compression, meaning you’ll have and overall smoother compression stroke. There isn’t really a debate about it, but don’t just assume because a shock is monotube that it’s better than another. Monotube just provides a better base to build off of than a twin-tube, but you can still have an inferior monotube shock.
The KW Clubsport is KW’s more track oriented line of coilovers. They feature higher spring rates and adjustable damping for both rebound and compression. The valving in this kit will be a lot more aggressive than with their normal V1-V3 kits because it is built for tracking. This kit utilizes a twin-tube configuration, however KW’s setup combats some of the inherent drawbacks of the design. External reservoirs are mounted to each shock which allows for more fluid to be stored in the shock body, promoting better head dissipation and discouraging aeration. KW has furthermore proven that they can utilize the valve space given in a twin tube design to great effect with their V1-V3 coilovers so you can feel confident that they have done the same with their Clubsport Kit.
AST & Moton are world renowned in the world of motorsports. They offer the same technology used in their race winning suspension systems in their street and track focused systems. This kind of technology does not come cheap, but these are going to be some of the best coilovers you can get for your E46 M3. Every AST and Moton coilover is a monotube design so you don’t have to worry too much about aeration or overheating. Most come with remote reservoirs for even more oil capacity and heat dissipation, they are engineered to be used in the most extreme conditions so your average track day will be like child’s play.
The AST 5100 series is a great option if you’re really interested in the previously mentioned true coilover rear setup. The good: true coilover rear option, super high quality damper tuning, and free customization of spring rates. The less good: top mounts cost extra, and you only get rebound adjustability. Honestly however rebound adjustability is plenty to work with and you would in no way be disappointed having the AST 5100s on your car. AST also make the 5200 Series but it is priced so closely to the Moton 2-Ways that we would recommend just spending the extra on the Motons as their valving is superior.
Once you make the jump to Moton, your cheapest option is going to be their Moton 2-Way “Clubsport” coilovers. With this kit you get 15 levels of rebound and compression damping adjustment. The damping on Moton coilovers is hands down some of the best you’ll ever experience, but the cost of entry is understandably high. For example, springs are not included in the base price of this already expensive kit. This does give you the option of sourcing your own from your favorite spring company or using a set you already own which is a plus, most companies won’t give you a discount if you don’t want their springs. If you choose to buy them from Moton you of course have the option of choosing your own custom rates and your dampers will be tuned to match them. Oddly enough however, top mounts are included in the price so the not-including-springs thing balances out a bit.
The Moton 3-Ways add low-speed compression adjustment on top of the adjustments on the 2-ways, and the top model 4-Way kit adds low-speed rebound adjustment. This allows for ridiculous amounts of fine tuning to the suspension that is beyond most individuals. We recommend the 2-Way Clubsports as they are the most affordable and 2-Way adjustability is already plenty of freedom for customization. On every version of these coilovers you’ll get a choice between a factory configuration or paying a bit extra for a true coilover rear. We have of course given our opinions on the benefits of a true coilover but, given the drawbacks, a separate shock and spring will still work well for you in the case of a coilover kit as nice as Moton.
These are a bit tricky, they affect spring rate but also do not, depending on what your car is doing at the time. Sway bars go by several other names: anti-roll bar, roll bar, anti-sway bar, and stabilizer bar. From these names you may have been able to deduce a sway bar’s function, it reduces body roll. Reducing body roll can of course be achieved by increasing the rate on your coilover springs, but that doesn’t always produce your desired results. Too high of a spring rate can lead to skipping over road imperfections and overall instability in corners.
Sway bars compliment your suspension by adding additional spring rate to the suspension only while cornering. The twisting force of the bar applies force to the outside wheel at a progressive rate, so while cornering you can stay level without the use of spring rates that cannot cope with normal road irregularities. Generally you’ll want to pair softer springs with relatively aggressive sway bars. If you’ve custom ordered your suspension with higher spring rates (around 10kg/mm front, rear will vary depending on if you have true coilover rear) you will not need to worry as much about an aggressive sway bar. Some M3 owners will run a slightly higher spring rate in the rear, paired with a thin sway bar or no sway bar at all. This keeps your rear inner tire from lifting in the middle of a corner so you can keep on the throttle.
This is all down to personal preference, some people find they like a little more oversteer, some like a little more understeer, it varies. We recommend fitting your car with both a front and rear sway bar if your suspension has relatively soft spring-rates. If you already have higher spring rates our best advise would be to try getting a front sway bar first so you can test aggressive front + stock rear, and aggressive front + disconnected rear. Once you give both setups a try you can see if the behavior of the rear suspension is to your liking or if you want a little more oversteer, at which point you’d then replace the rear bar with a thicker version. H&R makes both a front and rear sway bar for the E46 M3, and both are adjustable via the end-link mounting holes. It would also be a good idea, while you’re testing suspension setups, to purchase a set of springs that are 1kg/mm stiffer than your current rates. Then you can swap around springs to test the balance of different setups.
- Engine Bay
Handling Part 2…(page 8) – Current