Ford Bronco Sport Suspension Deep Dive 2021
It happened on the trail, in the parking lots and at home in my own driveway. “Is this the new Bronco?” They asked, pointing to the word “BRONCO” in large print on the radiator grille. “I thought it would be bigger. My confused inquisitors were right, the new Bronco IS bigger. What they were looking at was actually the 2021 Ford Bronco Sport, and more specifically, the most off-road version available, the Badlands.
As I would explain, unlike the body-on-chassis with removable roof and doors comparable to a Jeep Wrangler and Toyota 4Runner (and which I took a deep speculative dive months ago), the Bronco Sport is a compact crossover that’s a harsher offshoot of the Ford Escape. It uses a unibody design with a transverse engine driving the front wheels. But the Bronco Sport differs from the Escape in that it comes standard with all-wheel drive, rides on a slightly shorter wheelbase, has much chunkier front and rear overhangs, and has more headroom. ground.
And that makes the Bronco Sport interesting in itself. What’s wrong with a compact crossover with a bit of Bronco style and attitude? When I got back from my trail run, I removed the wheels to take a look below. Forgive the mud I missed at the car wash shift.
Because it’s a compact crossover, it’s no surprise that the Bronco Sport rides on a strut front suspension. But the spring rates, shock absorber calibration and other suspension components are optimized to suit its more rugged personality.
Before going too far, I thought about backing up and showing you something that I noticed when removing the front tire. The Badlands comes standard with 225 / 65R17 rubber, which is 28.5 inches in outside diameter.
The ability to fit larger off-road tires to strut suspensions is often hampered by a limited space between the tire and the spring perch of the strut. But here there is a lot of room, both above and behind the tire. I can’t speak to any other clearance issues that might prevent the fitting of bigger tires, but strut interference doesn’t seem to be an issue.
From here we can see that the lower control arm (yellow arrow) is aluminum. The stub axle (green) is made of steel.
The lower suspension arm uses an inverted L-shape which, among other things, makes it easier to produce a vehicle with a shorter front overhang. Here, the front bush (yellow) is aligned near the ball joint, which means that this will be the main load path for lateral forces when cornering. The rear ring (green) is larger and oriented horizontally, which makes it well suited to absorb longitudinal impacts applied to the wheel in the form of inward pulses.
A closer look at the lower control arm rear bushing shows details in its molded rubber form that are calibrated to absorb inward impulses.
My Badlands had a full aluminum skid plate attached under the front subframe. It’s more substantial than I’m used to seeing on vehicles in this class, although I blame myself for not removing it to see how well it protects various fluffy elements, such as the tank. lower radiator.
The front stabilizer link (yellow) is attached directly to the strut housing. This makes it a direct acting mount that gives the stabilizer bar a 1: 1 motion ratio.
The stabilizer bar itself wraps around the steering rack to pivot the bushings (yellow) which are tucked inside the rear bushings of the lower control arm.
With the steering rack and steering arm (yellow) passing behind the drive axle, the brake caliper should occupy the unoccupied space opposite to the front. This one is a single piston floating caliper, and it mounts to a fairly large ventilated front rotor with a decent amount of heat capacity.
Moving backwards, you can see a prominent swingarm (yellow), a vertically mounted long shock absorber (green), and at least one side link (red).
It looks like what Ford called a multi-link blade-control suspension, named after the thin (yellow) cross-section of the main swingarm. From there we can also distinguish three links: an isolated upper link (green) which is very easy to see, and two lower links a little less visible (red) which we will see better later.
Here it is evident that the swingarm and the rear knuckle (yellow) are joined together in a large steel weld. This means that the swingarm is 100% responsible for the front-to-rear position of the wheel and for controlling acceleration and braking torque. This massive attack ring (green) is also designed to dampen the rear component of impacts such as pothole impacts. Taken together, these swingarm features mean that the side links only have to worry about side loads. This makes the tuning engineer’s job a lot easier when it comes to optimizing their bushings, and that’s why I’m always happy when I see this variety of multi-link suspensions.
Here we can see the pair of lower links that we only had a glimpse of before. Clearly the front, called the tip link (yellow), is much shorter than the main rear cross link (green). The irony here is that the rear link has an inner eccentric (red) to adjust the static toe-in. So why is the front really the toe link?
You have to imagine what happens when the suspension moves, especially when the outer tire compresses in a long corner. The shorter toe link will oscillate in a much tighter arc than the longer rear link, and this will tend to pull the front edge of the tire inward and increase the rear toe-in for an extra dose of stability in the downs. long turns. The point is, something has to give in for this to happen.
That “something” is a bit of lateral flexion in the swingarm. Part of this is from the sideways crushing of the large bushing we saw at its front end, but additional gain comes from the lack of a 90 degree stiffening crease (yellow) and the reduced cross section. caused by the obvious hole (green) that we can see here right in front of the welded structure.
But there is something else of interest here, and that is the stabilizer bar mounting point (red). The link mounts directly to the swingarm, but that doesn’t give this mount a 1: 1 swing ratio.
This is because the swingarm itself oscillates in an arc centered on its front bushing, and the stabilizer link mounting point is slightly forward of the hub location, which can be inferred from the position of the hub. boot of the drive axle. The offset is not as large as the mystical marks seem to indicate. It’s still pretty effective at 0.90 or 95-to-1 or so, but it’s not 1-to-1.
This image shows that the main cross lower arm does a lot of heavy lifting. The shock (yellow) and spring (green) mounts directly to it, but I also like the simplicity of its aluminum design. This part also appears to be reversible, which means the left and right examples are probably the same part.
This simple design also makes viewing motion reports a snap. The spring appears to be about 55% of the inner pivot output, and the damper appears to be about 83%.
But that’s not entirely correct in this case, as the outer bolt doesn’t move 1 to 1 with the rear wheel. It is part of the swingarm structure, so it will move about 10% MORE than the tire because it is mounted behind the axle of the axle. Go back over some photos to see what I mean. If the outer pivot of the rear side connecting rod has a motion ratio of 1.1 or so, we need to increase the motion ratios of the spring and damper mounting points along its length accordingly.
Assuming my eyeball estimate of 1.1 to 1 at the outer end is correct, 0.55 to 1 becomes 0.61 to 1 for spring; 0.83 to 1 becomes 0.92 to 1 for the damper.
Bronco Sports rear brakes consist of a solid rear disc and a single-piston sliding caliper with an integrated electric parking brake actuator (yellow).
It has nothing to do with the suspension, but while I was here I thought I would share how the muffler body and exhaust tips are neatly packaged so they don’t get inside. the drag zone of the departure angle. Fairly tidy.
The Badlands, as I mentioned earlier, run on 225 / 65R17 tires which are 28.5 inches in diameter. These are Pirelli tires with a fairly docile pattern that works well in terms of ride comfort and quietness of the tread, but I wouldn’t want anything against anyone who chose to donate some of that in favor of an all-round tire. – more aggressive terrain. Right now, this suit weighs a respectable 52 pounds. Expect this to increase significantly if you go for a bigger or more aggressive tire.
All of the above adds up to a competent off-road crossover SUV, especially because the dimensions of the Bronco Sport are well optimized for off-road use. The Badlands in particular has a lot more to offer in terms of its larger 2.0-liter turbocharged four-cylinder engine and more capable AWD system with locking center and rear clutch differentials. Of course, it’s not the full body-on-chassis Bronco that’s designed to sit between a Toyota 4Runner and a Jeep Wrangler Unlimited, but I think there are a lot of buyers out there who don’t need it. . Ford certainly thinks so.