Both the M3 and the SLK have standard driver and passenger frontal airbags, front side-impact airbags, head airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control and electronic stability systems to prevent skidding.
The M3’s corrosion warranty is 8 years and unlimited miles longer than the SLK’s (12/unlimited vs. 4/50,000).
BMW pays for scheduled maintenance on the M3 for 4 years and 50,000 miles. BMW will pay for oil changes, tire rotation, lubrication and any other scheduled maintenance. Mercedes doesn’t pay scheduled maintenance for the SLK.
There are over 12 percent more BMW dealers than there are Mercedes dealers, which makes it easier to get service under the M3’s warranty.
The M3’s 4.0 DOHC V8 produces 186 more horsepower (414 vs. 228) and 74 lbs.-ft. more torque (295 vs. 221) than the SLK300’s standard 3.0 DOHC V6. The M3’s 4.0 DOHC V8 produces 114 more horsepower (414 vs. 300) and 30 lbs.-ft. more torque (295 vs. 265) than the SLK350’s standard 3.5 DOHC V6.
For better stopping power the M3’s brake rotors are larger than those on the SLK:
M3 |
SLK300 |
SLK350 |
|
Front Rotors |
14.2 inches |
11.8 inches |
13 inches |
Rear Rotors |
13.8 inches |
10.9 inches |
11.4 inches |
The M3’s standard front and rear disc brakes are vented to help dissipate heat for shorter stops with less fading. The rear discs on the SLK350 are solid, not vented.
The M3 stops much shorter than the SLK:
M3 |
SLK |
||
80 to 0 MPH |
195 feet |
202 feet |
Road & Track |
70 to 0 MPH |
153 feet |
175 feet |
Car and Driver |
60 to 0 MPH |
105 feet |
112 feet |
Motor Trend |
For better traction, the M3 has larger standard tires than the SLK (F:235/35R19 & R:265/35R19 vs. F:225/45R17 & R:245/40R17). The M3’s tires are larger than the largest tires available on the SLK (F:245/40R18 & R:265/40R18 vs. F:225/45R17 & R:245/40R17).
The M3’s standard tires provide better handling because they have a lower 40 series profile (height to width ratio) that provides a stiffer sidewall than the SLK’s standard 45 series front tires. The M3’s optional tires have a lower 35 series profile than the SLK’s optional 40 series front tires.
For better ride, handling and brake cooling the M3 has standard 18-inch wheels. Smaller 17-inch wheels are standard on the SLK. The M3’s optional 19-inch wheels are larger than the 18-inch wheels optional on the SLK.
The M3 offers an optional driver-adjustable suspension system. It allows the driver to choose between an extra-supple ride, reducing fatigue on long trips, or a sport setting, which allows maximum control for tricky roads. The SLK’s suspension doesn’t offer adjustable shock absorbers.
For a smoother ride and more stable handling, the M3’s wheelbase is 13 inches longer than on the SLK (108.7 inches vs. 95.7 inches).
The M3 Sedan has standard seating for 5 passengers; the SLK can only carry 2. The M3 Coupe has standard seating for 4.
The M3 Convertible has 35.4 cubic feet more passenger volume than the SLK (84.2 vs. 48.8).
The M3 Convertible has a larger trunk with its top down than the SLK with its top down (7.4 vs. 6.5 cubic feet). The M3 Convertible has a much larger trunk with its top up than the SLK with its top up (12.4 vs. 9.8 cubic feet).
The M3’s standard easy entry system glides the driver’s seat back, making it easier for the driver to get in and out. An easy entry system costs extra on the SLK.
The M3’s standard power windows have a locking feature to keep children in the rear seat from operating them. Mercedes does not offer a locking feature on the SLK’s power windows.
The M3’s rain-sensitive wipers adjust their speed and turn on and off automatically based on the amount of rainfall on the windshield. This allows the driver to concentrate on driving without constantly adjusting the wipers. The SLK’s standard manually variable intermittent wipers have to be constantly adjusted.
While driving with high-beams on, sensitive light sensors available for the M3 detect other vehicles which could be blinded and automatically switch to low-beams. The SLK doesn’t offer automatic dimming high-beams.
The SLK’s optional cornering lamps activate a lamp on the front corner when the turn signal is activated. The M3’s standard adaptive cornering lights turn the actual headlight unit up to several degrees, depending on steering wheel angle and vehicle speed. This lights a significant distance into corners at any speed.
A power rear sun shade is optional in the M3 Sedan/Coupe to help block heat and glare for the rear passengers. The SLK doesn’t offer a rear sun shade.
The M3’s standard power mirror controls are mounted on the armrest for easy access. The SLK’s power mirror controls are on the center console where they can’t be seen without the driver completely removing his eyes from the road.
The M3 will cost the buyer less in the long run because of its superior resale value. Kiplinger’s estimates that the M3 will retain a greater percentage of its original price after two and four years than the SLK.
M3 |
SLK |
|
Four Year |
42% to 44% |
31% to 32% |
Two Year |
60% to 62% |
45% to 46% |
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