Suspension Comparison: Double Wishbone vs. MacPherson Struts
A vehicle's suspension works with the steering system to lend the driver control over an automobile by, among other things, preventing excess body lean and absorbing bumps in the road. Rubber components, bushings, springs, shock absorbers, and more are linked together in different designs to make the most efficient suspension system possible. The two most common designs are MacPherson struts or double wishbone suspension. The two styles are not interchangeable, and the way they wear through parts differently.
Double Wishbone Suspension Basics
Of the two dominant suspension models in use today, double wishbone is older, but not by much. It predates the MacPherson strut design by a little more than a decade. Double wishbone designs got their name from the shape of their design, which relies on the shock absorbers and coil springs connecting both upper and lower control arms, with the lower arm connected to the steering knuckle and the upper arm attached to the frame of the vehicle.
Today, double wishbone suspension is more commonly found on vehicles that have a body/frame construction, while MacPherson struts are more commonly found on unibody designs. Some car owners interpret this to mean that double wishbone is used for trucks and vans whereas the alternative is for sedans and compact cars, but that would be an over-generalization. Vehicle design is too nuanced to make assumptions, which is why you need to check out your automotive maintenance manual if you’re wondering which kind of suspension you have.
The Basics of MacPherson Struts
While this strut design was named after the engineer who popularized it and refined it to its most recognizable form, the basic concept predates MacPherson’s work, as other designs using almost the same concept for a front-end suspension had been marketed prior to Ford’s first official MacPherson strut model.
The design is notably different from double wishbone suspensions, with the strut bolted to the hub carrier and directly connected to the body of the vehicle. In the MacPherson design, the strut is part of the steering geometry, providing the axis of inclination in that design. Typically, vehicles with MacPherson struts feature a coil spring above the shock absorber.
MacPherson struts benefit from a simpler design than double wishbone builds, and they also provide a smoother ride at highway speeds. Due to their construction, they are more common on unibody vehicles.
Comparing the Suspension Designs
The difference between MacPherson struts and double wishbone suspension is easy to understand from a construction standpoint, but you might be wondering why the two totally different designs have continued to coexist when many other automotive systems have found a dominant design model over time.
The fact is, there are pros and cons to each design. Understanding that requires a look at the drawbacks to each design, so you can see when it would be less advantageous in certain vehicles. Let’s look at the older suspension design first:
- Double wishbone’s complexity of design means more parts, and in turn, more parts that can fail
- It also has greater interdependence, meaning one part going bad can cause others to break before a fix is put in place
- It’s a much heavier suspension, adding more weight to the vehicle
By contrast, MacPherson struts avoid those issues, but have their own set of drawbacks:
- They are tall, so tall they often raise the profile of the vehicle and limit how low its ride height can be set
- This also moves up the vehicle’s center of gravity
- As they show wear, they often transmit more noise through the body of the car than double wishbone designs
- Their participation in the steering geometry can lead to trouble keeping solid contact with the road on all four wheels during cornering
- Torque steer is an issue at high speeds in FWD vehicles
Looking at the drawbacks and limitations of each design, it gets easier to see how the double wishbone suspension has held onto its corner of the market over the years. It might be more delicate, but it also allows for a lower center of gravity, better contact with the ground during cornering, and less torque steer, making it ideal for many smaller body performance cars, not just larger vehicles like trucks where the extra weight is less likely to be noticed. It’s also worth thinking about the increased weight of the double wishbone design as a neutral factor, because while it can hurt fuel efficiency it can help with traction when a vehicle is heavier, so it’s less a solid drawback and more a design feature that is sometimes desirable and sometimes not.
Even with the drawbacks the MacPherson design has, it’s still a solid performer and a much smoother ride at highway speeds. When the vehicle’s center of gravity won’t be artificially raised by the use of the architecture, it’s a good economy option for passenger vehicles that don’t necessarily need to worry about a lot of high-speed cornering.
Some newer MacPherson style designs further improve on its efficiency by separating the strut from the steering geometry to lower torque steer and avoid the issue relating to contact surfaces while cornering, and that does a lot to even up the performance between the two.
Maintaining Your Vehicle’s Suspension
MacPherson struts last a long time, and they’re less likely to have collateral damage happen to other parts when they wear, if they are replaced promptly. To make sure you’re staying on top of your strut performance, it is recommended that you check them every 50,000 miles to be sure they’re still working efficiently. If you notice that you’re getting worse performance, replace them before the issue becomes noticeable in day to day driving.
For double wishbone suspension designs, you are likely to notice problems holding alignment when a part wears significantly. It’s a good idea to inspect them regularly, but the change in vehicle alignment also serves as notice you should check them out right away, so you can determine which parts need to be replaced before putting in your order. You can find those parts easily using the VIN lookup on our site to make sure you only see the parts for your make and model.
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