In terms of keeping tires on the road, not all suspensions are created equal. In one corner, we’ve got the tried-and-true MacPherson strut, the Toyota Corolla of suspension systems. In the other, the sophisticated double wishbone setup, the choice of performance junkies worldwide.
But how does a MacPherson strut setup compare to a double wishbone suspension? Time to see why some engineers swear by one and others won’t touch anything but the other.
MacPherson Strut Suspension
MacPhersonstrut is effectively combines the functions of a damper and a spring into a single compact unit, simplifying the design and reducing the overall weight of the suspension system.
Its main component is the strut assembly, which includes a damper and a coil spring, with the damper controlling the motion of the spring to reduce oscillations and hopefully provide a smooth ride.
The strut assembly is attached to the car’s chassis via a strut mount. This mount allows the strut to pivot as the wheels turn, contributing to the vehicle’s steering. The bottom of the strut assembly is connected to the lower control arm, which is attached to the vehicle’s chassis or subframe. The lower control arm helps to control the vertical movement of the wheel.
The wheel carrier (or upright or steering knuckle) connects the strut assembly to the wheel hub and allows the wheel to pivot for steering. It also houses the wheel bearings and provides attachment points for the brake components.
How does a MacPherson strut work?
The main job of the coil spring is to support the vehicle’s weight and maintain its ride height. When the vehicle encounters a bump or pothole, the wheel moves upward, compressing the coil spring further.
The damper within the strut assembly dampens this motion, preventing the spring from oscillating uncontrollably and ensuring the wheel returns to its normal position smoothly.
The MacPherson strut helps to maintain proper wheel alignment by controlling the vertical movement of the wheel. The lower control arm and the strut assembly work together to keep the wheel in the correct position relative to the vehicle’s chassis.
The strut mount at the top of the strut assembly allows the entire strut to pivot when the steering wheel is turned. This pivoting motion is transferred to the wheel carrier, which turns the wheel in the desired direction.
Simplicity
MacPherson struts have fewer parts compared to past suspensions, so they are smaller, thus making them easier to package in smaller vehicles.
This construction made significantly more room in the engine compartment, which was a good thing for smaller vehicles and especially beneficial for vehicles using width-wise (transverse) engine layouts.
Cost-effectiveness
Because the struts are simple and have fewer parts, MacPherson struts can be manufactured for much less money, which also makes them easier to maintain relative to more complex suspension systems.
Lightness
Fewer parts mean a lighter suspension system, which results in better fuel economy and handling.
Worked With Unibody Cars
MacPherson struts capitalized on a newer development in automotive engineering: the unibody vehicle. The construction allows for the necessary strong top mount and the vertical space for the strut.
Crash Performance
The packaging of MacPherson struts within the front crash structure of vehicles results in far more easily engineered vehicles that can pass the more rigorous small overlap crash testing. In short, MacPherson struts have translated into safer vehicles for everyone.
Double Wishbone Suspension
As always, there’s an innovation in town that will flip the old tech on its head. Introducing the double wishbone suspension.
Overall, this type of suspension offers superior handling and performance compared to simpler designs like MacPherson struts. But as always, let’s dig in a bit more.
A double wishbone suspension consists of two wishbone-shaped control arms (upper and lower) connecting the wheel hub to the vehicle’s chassis.
Each arm has two mounting points on the chassis and one on the wheel hub, forming an A-shape (hence also called A-arms). The shock absorber and spring are typically mounted between the lower wishbone and the chassis.
But why develop an entirely new suspension system?
Get that Camber
As the suspension compresses when turning it creates negative camber which allows more of the tire to come into contact with the road surface.
You’ve seen the Tokyo Drift style car meets where all the cars are slammed to the ground and tilted? That’s camber… and a ton of negative camber.
Better Handling
More camber means a better direct translation of your steering inputs into cornering.
Less Torque Steer
For front wheel drive vehicles, a double wishbone suspension designed to minimize torque steer is better than a McPherson strut suspension. See the 2004 Mazdaspeed 3, because of its MAC strut suspension, you almost had to wrestle the steering wheel in hard launches because it always was “squirrely”.
Great Design Flexibility
Engineers have a much greater ability to specifically design double wishbone suspension to a desired camber, caster, and roll center by simply adjusting the double wishbone geometry. Brilliant design.
Space Usage
While requiring more horizontal versatility than a McPherson strut suspension, it requires less vertical space, allowing for a lower ride height without sacrificing suspension travel. If you want to slam your car, get a much lower in a double wishbone suspension.
Design and Construction
MacPherson
MacPherson struts are relatively simple and compact. An entire shock absorber and spring system is made into one unit. Generally, MacPherson struts are inexpensive to produce and occupy less lateral space, making them the predominant strut in small cars and cars with transverse engines.
On the downside, MacPherson struts do not give you the best camber control during suspension travel compared to some of the other designs.
Double Wishbone
The double wishbone suspension system is a little more involved, and thus more expensive to produce. Objectively, it looks a lot more sophisticated with curved upper and lower control arms, “wishbones”.
They are more complex because they need to provide some suspension geometry maintenance at varied suspension angles based on the task the car is intended to fulfill. It could be a race car, a drift car, a luxury car traveling over large distances at high speeds, it could be anything.
Performance and Handling
MacPherson
The MacPherson system is uncomplicated, compact and very affordable. It is going to be more than adequate for the vast majority of uses we encounter in vehicles – we’re talking about 99.9% of uses. Just keep in mind… Tuk tuks are a thing and they seem to get you wherever certain parts of town you want to go.
The well-used MacPherson system allows for decent steering angles and application, however, it may lead to slightly bigger body roll and perhaps not as much precision as the more high-end version of suspension.
Double Wishbone
The double wishbone suspension has stated benefits over the MacPherson system with more sophisticated suspension control, suspension camber control, better cornering, and improved body roll.
But… it is very expensive to build the double wishbone system, so you will only find it in higher performance and/or luxury vehicles.
Ride Quality
MacPherson
The MacPherson strut suspension is the sweatpants of the car world; it’s basic, effective, and inexpensive.
For everyday driving, it offers a pleasant ride, absorbing bumps nicely. Plus, it’s compact, which allows for longer legroom. If you’re really tall, this one is for you.
Double Wishbone
On the other side is the double wishbone suspension, which is a suit. It’s pricey and complicated, but it works like magic. Good handling has the tires glued to the pavement like sucker fish, which is great for cornering.
On the downside, it might not have the comforts of your daily work commute.
Cost
MacPherson
At this point in the article, we’ve pretty much beaten this question to death! Macpherson struts are simpler to manufacture and therefore not as costly. All for all 4 strut replacements may run you $1,000 – but you’ll be back on the road.
Double Wishbone
Conversely, a double wishbone suspension will probably be 2 or 3 times the amount.
And while most car fans and enthusiasts will say “You truly get what you pay for” and “you can absolutely feel the difference”, the truth will be known when the checkbook comes out!
Maintenance and Durability
MacPherson
Overall, MacPherson struts have an easier overall maintenance and duration in everyday use. This is due to the fact that they have less moving parts, which leads to less ability to wear or break down over time.
On top of that, when something does break down it’s easy and cheaper to just replace the individual separate parts rather than the whole complete system.
Double Wishbone
Double wishbone suspensions have far superior performance than MacPherson strut systems, but tend to have a little bit more maintenance. In terms of number of parts, double wishbone systems have more moving parts, therefore, more potential for components to wear out or break down, which could lead to more inspections and presuming higher repair business.
The only downside is that double wishbone systems are a MUST for performance vehicles. Performance vehicles are dealing with much larger forces, and forces in different directions and performance vehicles need the more expensive suspension components to handle those changes.
Once you buy into the performance vehicle world, you’ll be paying for that thrill for some time to come, and it is worth it.
Applications
MacPherson
Used extensively in compact and mid-sized automobiles, front-wheel drive automobiles, economy vehicles, as well as some SUVs and crossovers.
Double Wishbone
Commonly used in sports cars, luxury vehicles, racing vehicles, and off-road vehicles. Specialized vehicles require specialized equipment, most often depending on how the vehicle handles over terrain.
And whether it’s your Bentley or trophy truck, you will want more travel in your suspension, possibly with external reservoirs or air bags, which take up more space.
Comparison Chart
| Characteristic | MacPherson | Double Wishbone |
|---|---|---|
| Initial Cost | X | |
| Maintenance Cost | X | |
| Durability | X | |
| Space Efficiency (Horiz) | X | |
| Space Efficiency (Vert) | X | |
| Performance Handling | X | |
| Camber Control | X | |
| Daily Driving Comfort | X | |
| Design Simplicity | X | |
| Cornering Ability | X | |
| Tuning Flexibility | X | |
| Tire Contact In Corners | X | |
| Weight | X | |
| Parts Replacement Simplicity |
Advantages and Disadvantages
Double Wishbone Suspension Pros
1) Better Handling.
Double wishbone suspension provides excellent handling and stability, particularly during cornering. Its design allows for dynamic camber changes mid-corner that maximize tire contact with the road. This results in improved traction and superior control, especially on uneven or challenging terrains.
Many double wishbone designs allow the rear outside wheel to toe in under compression. This helps the car turn into the corner more quickly. This results in a vehicle that feels more agile and responsive.
2) Adjustable Geometry.
Double wishbone suspensions typically offer far more alignment adjustability, giving more options for camber, caster, and toe settings. This adjustability allows fine-tuning of the suspension geometry to suit specific driving preferences or performance requirements.
Finer control over the car’s alignment is particularly advantageous for car enthusiasts who autocross or take their car to the track.
Double Wishbone Suspension Cons
1) Complexity and Cost.
Double wishbone suspensions are more complex and intricate in design compared to MacPherson struts. They require additional components, such as upper control arms, upper ball joints, and additional bushings, which can increase development time and manufacturing costs.
The complexity of the system can also make repairs and replacements more time-consuming and expensive.
2) Increased Weight.
The additional components of double wishbone suspensions can contribute to increased weight, leading to higher unsprung mass. This additional weight can have a slight impact on fuel efficiency and overall vehicle performance.
However, advancements in lightweight materials and engineering techniques have minimized this drawback in modern designs.
MacPherson Strut Suspension Pros
1) Simple and Cost-Effective.
MacPherson strut suspensions are simpler in design, with fewer components compared to double wishbone systems. Their compact design makes them easier to install and maintain, leading to reduced manufacturing costs. This simplicity also translates into faster and more affordable repairs or replacements.
2) Space Efficient.
MacPherson struts are space-efficient, occupying less room within the vehicle’s engine compartment. This allows for more efficient packaging, leaving more space for other components or passenger accommodations. It is particularly beneficial in vehicles with limited engine bay space.
3) Good Balance of Comfort and Handling.
MacPherson struts provide a balanced combination of ride comfort and handling. Their design offers adequate shock absorption and stability, resulting in a smooth and controlled ride quality.
While MacPherson strut suspension systems may not match the handling performance of double wishbone suspensions, they strike a good balance for everyday driving, economy cars, and even some light-duty trucks.
MacPherson Strut Suspension Cons
1) Limited Adjustability.
Unlike double wishbone suspensions, MacPherson struts have limited adjustability options. This lack of adjustability may limit fine-tuning of suspension characteristics to suit specific driving preferences or performance requirements. Enthusiasts seeking a highly customized suspension setup may find this restrictive.
However, there are often aftermarket solutions for enthusiasts who own vehicles with MacPherson strut suspension. Camber plates and aftermarket control arms offer additional camber adjustments, for instance. Some aftermarket suspension components may also offer additional caster settings.
2) Increased Body Roll.
MacPherson struts have a tendency to induce more body roll during cornering compared to double wishbone suspensions. The interconnected nature of the system means that changes in one wheel affect the other, potentially reducing overall handling precision and responsiveness.
However, this drawback can be mitigated with proper suspension tuning and the addition of anti-roll bars. Anti-roll bars are also known as sway bars or stabilizer bars.