By Seven minutes and fifty seconds. That’s how fast the BMW E46 M3 CSL lapped the Nurburgring in 2003. The CSL was the ultimate in design and performance for the E46 M3 Coupe, and one of the fastest things to ever roll out of BMW’s factories in East Germany short of their race cars. More recently, Richard Göransson posted a lap time in an E46 M3 CSL of just over seven minutes and twenty two seconds. The big difference there is that Göransson’s car had the advantage of several years worth of aftermarket performance engineering. Göransson’s CSL had a supercharger, full race exhaust, massive brakes, and (most importantly) upgraded suspension components. The E46 M3 suspension was a very good platform when it left the factory, but you can make it even better by taking advantage of its aftermarket potential!
Wait, you man it’s not already perfect?
Your suspension system has a few major jobs. Firstly, it needs to maximize the amount of contact that your wheel makes with the ground. Your tires can’t do their thing if they’re cambered at some ridiculous angle. Secondly, suspension needs to provide stability. Say you’re cruising on the freeway at 65 miles an hour, or speeding down the back straight at 150. If you hit a bump you want to feel it, but not get bumped off the road out of control! Last, it needs to ensure your comfort. Because if we didn’t want to ride in style, we would still be going everywhere in covered wagons.
Springs
Springs absorb the energy created when your vehicle hits a bump. When you’re driving along the highway or crawling over rocks, the springs in your suspension compress to let the wheels move up into the body without creating body roll or upsetting the balance of the car. Upgraded springs use different tensile strength loads and length to change the way your vehicle rides. Shorter springs let your vehicle sit lower, which increases stability while cornering. Longer springs lift your vehicle up, allowing for more suspension travel and ground clearance. Higher loaded springs will stiffen the ride quality and make your vehicle more responsive, while looser springs will soften bumps better and make things more comfortable at the cost of some body roll.
All the usual suspects have spring offerings for the E46 M3. If you’re looking for basic lowering, it’s hard to go wrong with H&R’s Sport lowering springs or Eibach’s Pro Kit springs. The H&Rs drop the car about 1.5-1.8” on average, and are designed to maintain the same OEM spring rates while improving response and lowering ride height. The Eibach springs only lower the car by 0.6-0.9”, but focus on tight handling and the utmost in performance at the expense of some comfort. If you’re going to be lowering a decade-old vehicle on springs, it’s probably a good idea to think about shocks as well. Your stock dampers are designed to operate within a certain range, and lowering springs tend to take them outside that range.
Shocks
Springs are great at absorbing energy, but bad at dispersing it. Shock absorbers, also called dampers, absorb energy from bumps and convert it to heat. When a shock absorber is compressed, a piston moves down into a tube full of hydraulic fluid, softening the blow from compression and then responding with like rebound (thanks to the magic of vacuums). Shocks determine the amount of travel– how far up and down your wheel can go on the suspension– as well as how the suspension responds to both compression and rebound. Tighter valved shocks will be slower to compress, leading to a firmer ride and flatter cornering; loosely valved shocks will compress faster, making things smoother but a little more wallowy. Upgraded suspension usually offers more travel and different valving, which changes the way your vehicle handles over bumps and uneven surfaces. High end shock absorbers sometimes have remote reservoirs for hydraulic fluid, or trade fluid-filled shocks for gas ones. Both of these systems can end up saving you unsprung weight.
Your E46 M3 came stock with shocks from Germany, and Bilstein is right there to keep things in the family. Bilstein’s B6 struts are direct upgrades for your stock suspension. The B6 monotube shocks are valved specifically for use with the M3, ideally with stock springs. If you want to go lower, Koni yellow struts are adjustable and designed for high performance applications.
If you’re looking to upgrade everything at once, a suspension kit or coilover kit can provide matched springs and dampers in one package. Koni pairs their Yellow struts with Eibach pro-kit springs, and Bilstein provides their own full setup with the B12 suspension kit. Buying a full kit will help to avoid incompatibilities, but you may still be able to find better value buying each part separately.
Sway Bars and End Links
Sway bars (aka anti-sway bars, anti-roll bars) work as a lateral brace between the left and right side of a car. The front and rear swaybars attach with links to the wheel hubs, and use torsional stiffness to keep the vehicle as close to level over its axles as possible. This allows the outside wheels to force the body and the inside wheels back down towards the ground. Aftermarket sway bars are usually both thicker and lighter than the OEM parts. End links connect your sway bars to the wheel hubs, and are often included with aftermarket sway bars. They can be mounted at different lengths and different points on the end of the sway bar, changing the torsional stiffness of the bar. This allows you to tune yet another aspect of your car’s ride.
The E46’s stock sway bars are 26mm in the front and 21.5mm in the back. That front one is pretty solid on turn-in, but BMW’s tendency towards ride comfort and luxury is visible in how much the body is still allowed to sway. Because of this, the factory sway bar setup tends to cause understeer and wallowing in corners. To correct this understeer, Hotchkis’s sway bars bump up the thickness of both the front and rear. Hotchkis’s front sway bar is over 30mm, and the rear sway bar is over 25mm. These thicker bars, combined with adjustable end links, result in adjustable stiffness from +11% to +49% in the front and +79% to +105% in the rear. This makes the car much more neutral around corners, and allows for more fun with the throttle pedal (I.E. sick drifts). Whiteline makes similar heavy duty front sway bars and end links, and have quieter bushings but a softer ride.
If you’re looking for BMW parts, check out the Motoroso Marketplace! There are tons of high-quality springs, dampers, and chassis reinforcement parts for M3s or any other vehicles you need to set up for the road, track, or dirt. If you’re looking for some help putting things together or need some inspiration, take a look at the Motoroso YouTube channel. There, we’re upgrading tons of install guides, must-have-mod lists, and build showcases to help you figure out exactly what you want to do with your vehicle.
