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The Z4’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The MX-5 Miata doesn’t offer pre-crash pretensioners.
The Z4 has standard Post-Crash Braking, which automatically apply the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The MX-5 Miata doesn’t offer a post collision braking system: in the event of a collision that triggers the airbags, more collisions are possible without the protection of airbags that may have already deployed.
The Z4’s driver alert monitor detects an inattentive driver then sounds a warning and suggests a break. According to the NHTSA, drivers who fall asleep cause about 100,000 crashes and 1500 deaths a year. The MX-5 Miata doesn’t offer a driver alert monitor.
Both the Z4 and the MX-5 Miata have standard driver and passenger frontal airbags, front side-impact airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras, available lane departure warning systems, blind spot warning systems, rear parking sensors and rear cross-path warning.
The BMW Z4 weighs 794 to 1118 pounds more than the Mazda MX-5 Miata. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts. Crosswinds also affect lighter cars more.
The Z4 comes with a full 4-year/50,000-mile basic warranty, which covers the entire car and includes 24-hour roadside assistance. The MX-5 Miata’s 3-year/36,000-mile basic warranty expires 1 year and 14,000 miles sooner.
The Z4’s corrosion warranty is 7 years longer than the MX-5 Miata’s (12 vs. 5 years).
BMW pays for scheduled maintenance on the Z4 for 3 years and 36,000 miles. BMW will pay for oil changes, lubrication and any other required maintenance. Mazda doesn’t pay scheduled maintenance for the MX-5 Miata.
The battery on the Z4 is in the trunk, which protects it from hot underhood temperatures that can degrade battery life. By keeping the Z4’s battery 20 to 30 degrees cooler, its life is increased by years. The MX-5 Miata’s battery is in the hot engine compartment.
J.D. Power and Associates’ 2019 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that BMW vehicles are more reliable than Mazda vehicles. J.D. Power ranks BMW 7th in reliability, above the industry average. With 37 more problems per 100 vehicles, Mazda is ranked 21st.
The Z4 sDrive30i’s standard 2.0 turbo 4-cyl. produces 74 more horsepower (255 vs. 181) and 144 lbs.-ft. more torque (295 vs. 151) than the MX-5 Miata’s 2.0 DOHC 4-cyl. The Z4 M40i’s standard 3.0 turbo 6-cyl. produces 201 more horsepower (382 vs. 181) and 217 lbs.-ft. more torque (368 vs. 151) than the MX-5 Miata’s 2.0 DOHC 4-cyl.
Regenerative brakes improve the Z4’s fuel efficiency by converting inertia back into energy instead of wasting it. The MX-5 Miata doesn’t offer a regenerative braking system.
The Z4 has 1.8 gallons more fuel capacity than the MX-5 Miata (13.7 vs. 11.9 gallons), for longer range between fill-ups.
The BMW Z4 comes standard with an automatic transmission, for driver comfort, especially in the city. Automatic costs extra on the MX-5 Miata.
An eight-speed automatic is standard on the BMW Z4, for better acceleration and lower engine speed on the highway. Only a six-speed automatic is available for the MX-5 Miata.
For better stopping power the Z4’s brake rotors are larger than those on the MX-5 Miata:
The Z4’s standard front and rear disc brakes are vented to help dissipate heat for shorter stops with less fading. The rear discs on the MX-5 Miata are solid, not vented.
The Z4 stops much shorter than the MX-5 Miata:
70 to 0 MPH
Car and Driver
For better traction, the Z4 has larger standard tires than the MX-5 Miata (F:225/45R18 & R:255/40R18 vs. 195/50R16). The Z4’s optional tires are larger than the largest tires available on the MX-5 Miata (F:255/35R19 & R:275/35R19 vs. 205/45R17).
The Z4’s standard 225/45R18 front and 255/40R18 rear tires provide better handling because they have a lower 45 series front and 40 series rear profile (height to width ratio) that provides a stiffer sidewall than the MX-5 Miata Sport’s standard 50 series tires. The Z4’s optional tires have a lower 35 series profile than the MX-5 Miata Club/Grand Touring’s 45 series tires.
For better ride, handling and brake cooling the Z4 has standard 18-inch wheels. Smaller 16-inch wheels are standard on the MX-5 Miata Sport. The Z4’s optional 19-inch wheels are larger than the 17-inch wheels on the MX-5 Miata Club/Grand Touring.
The BMW Z4’s wheels have 5 lugs for longer wheel bearing life, less chance of rotor warping and greater strength. The Mazda MX-5 Miata only has 4 wheel lugs per wheel.
The Z4 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 MX-5 Miata’s suspension doesn’t offer adjustable shock absorbers.
The Z4 has vehicle speed sensitive variable-assist power steering, for low-effort parking, better control at highway speeds and during hard cornering, and a better feel of the road. The MX-5 Miata doesn’t offer variable-assist power steering.
For a smoother ride and more stable handling, the Z4’s wheelbase is 6.3 inches longer than on the MX-5 Miata (97.2 inches vs. 90.9 inches).
For better handling and stability, the average track (width between the wheels) on the Z4 is 4.4 inches wider in the front and 3.8 inches wider in the rear than the track on the MX-5 Miata.
The Z4 sDrive30i handles at 1.00 G’s, while the MX-5 Miata pulls only .88 G’s of cornering force in a Car and Driver skidpad test.
The Z4 has a much larger trunk than the MX-5 Miata (9.9 vs. 4.6 cubic feet).
A low lift-over trunk design makes loading and unloading the Z4 easier. The Z4’s trunk lift-over height is 28.5 inches, while the MX-5 Miata’s liftover is 32 inches.
With its convertible body style, valet key and remote trunk release lockout, the Z4 offers cargo security. The MX-5 Miata’s non-lockable remote release defeats cargo security.
The Z4 uses gas struts to support the hood for easier service access. The MX-5 Miata uses a prop rod to support its heavy hood. It takes two hands to open the hood and set the prop rod, the prop rod gets in the way during maintenance and service, and the prop rod could be knocked out, causing the heavy hood to fall on the person maintaining or servicing the car.
The Z4 offers a remote vehicle starting system, so the vehicle can be started from inside the driver's house. This allows the driver to comfortably warm up the engine before going out to the vehicle. The climate system will also automatically heat or cool the interior. The MX-5 Miata doesn’t offer a remote starting system.
When two different drivers share the Z4, the memory system makes it convenient for both. Each setting activates different, customized memories for the driver and front passenger’s seat positions, outside mirror angle, climate settings and radio stations. The MX-5 Miata doesn’t offer a memory system.
The Z4 offers an optional heads-up display that projects speed and other key instrumentation readouts in front of the driver’s line of sight, allowing drivers to view information without diverting their eyes from the road. The MX-5 Miata doesn’t offer a heads-up display.
The Z4’s front power windows open or close with one touch of the switches, making it more convenient at drive-up windows and toll booths, or when talking with someone outside of the car. The MX-5 Miata’s power windows’ switches have to be held the entire time to close them fully.
If the windows are left open on the Z4 the driver can close them all from a distance using the remote. On a hot day the driver can also lower the windows the same way. The driver of the MX-5 Miata can only operate the windows from inside the vehicle, with the ignition on.
In case of a sudden change of weather, the Z4 offers an optional remote convertible top that can be raised from a distance to protect the interior of the vehicle from damage. The MX-5 Miata doesn’t offer a remote top, so the driver will have to run to the car, get in, turn the ignition on (with available power top) and raise the top to prevent the interior from being damaged.
The Z4’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 MX-5 Miata Sport/Club’s standard manually variable intermittent wipers have to be constantly adjusted.
The Z4 has a standard automatic headlight on/off feature. When the ignition is on, the headlights automatically turn on at dusk and off after dawn. The MX-5 Miata has an automatic headlight on/off feature standard only on the Grand Touring.
The Z4’s sun-visors swivel front-to-side to block glare from the side windows. The MX-5 Miata’s visors are fixed into the windshield header.
The Z4’s standard outside mirrors include heating elements to clear off the mirrors for better visibility. Mazda only offers heated mirrors on the MX-5 Miata Grand Touring.
When the Z4 is put in reverse, the passenger rearview mirror tilts from its original position. This gives the driver a better view of the curb during parallel parking maneuvers. Shifting out of reverse puts the mirror into its original position. The MX-5 Miata’s mirror doesn’t automatically adjust for backing.
On extremely cold winter days, the Z4’s optional heated steering wheel provides comfort, allowing the driver to steer safely and comfortably before the car heater warms up. The MX-5 Miata doesn’t offer a heated steering wheel.
The Z4’s standard dual zone air conditioning allows the driver and front passenger to choose two completely different temperatures so people with different temperature preferences won’t have to compromise. This makes both the driver and front passenger as comfortable as possible. The MX-5 Miata doesn’t offer dual zone air conditioning.
A built-in pollen filter removes pollen, exhaust fumes and other pollutants from the Z4’s passenger compartment. This helps prevent lung and/or sinus irritation, which can trigger allergies or asthma. The MX-5 Miata doesn’t offer a filtration system.
To keep a safe, consistent following distance, the Z4 offers an optional Adaptive Cruise Control, which alters the speed of the vehicle without driver intervention. This allows the driver to use cruise control more safely without constantly having to disengage it when approaching slower traffic. The MX-5 Miata doesn’t offer an adaptive cruise control.
The Z4’s optional Parking Assistant can parallel park by itself, with the driver only controlling speed with the brake pedal. The MX-5 Miata doesn’t offer an automated parking system.
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