Here’s The Engineering Behind Why The Can-Am Maverick’s Suspension Looks So Insane

Hello fellow Autopians and welcome to another edition of “Ask an Engineer.” This time a question came to me via our very own David Tracy who was sent a photo of the new Can-Am Maverick R side-by-side off-roader with an arrow pointing to a very unusual front suspension and “WTF?” written next to it. I took a close look at it, and used by background as a suspension engineer to break down why the suspension looks as wild as it does.

Here’s the photo in question:

As it turns out, The Drive recently published a story on the new Maverick R in which they state that according to Can-Am, the new suspension provides “better load distribution, improved roll center height, and spot-on geometry” by “[minimizing] spindle length, scrub radius, and kingpin angle” which results in “effortless, predictable, point-and-shoot steering and reduced kickback in rough terrain.” Those sound some significant improvements, so let’s dig into this new suspension design to see if we can justify Can-Am’s claims.

[Editor’s Note: Huibert Mees led the design of the Tesla Model S’s suspension, and that of the 2005 Ford GT, so when I saw this suspension, I figured I’d reach out to him to get the real story on what’s going on. -DT]. 

Side-By-Sides Are Off-Road-Focused Toys

The term side-by-side refers to a type of off-road vehicle that is actually more a cross between a Jeep and a roll-cage with wheels. They machines are designed strictly for going off-road, although in some states you can drive them on-road as well though I wouldn’t recommend doing that very often. Side-by-sides have few of the usual safety systems that modern cars have other than seatbelts. I’ve driven these, and I felt very vulnerable. Still, sometimes it’s easier to drive between trails on-road than to pull it on and off the trailer every time.

Back in 2018, on a trip to Sedona AZ, my son and I decided to rent a two-person side-by-side for an afternoon and go drive the desert trails. It was insanely fun, and afterwards I did what any proper car guy would do: I bought a Polaris RZR-S900.

I had it for a couple years and had a great time with it. Unfortunately, where I live there are only a few trails to ride on, and after a while, doing the same trails over and over gets a bit boring, so I sold it. If I ever live in a place with more varied trails, I will definitely get another one. They really are awesome fun.

The major thing that makes side-by-sides so fun is the fact that they are amazingly capable off-road. I used to go down trails, without hesitation, that would require Jeep drivers to plan and survey and use spotters. I just bombed down them without thinking. I never got stuck.

One time, after I taught my daughter how to drive my new machine, she decided to go through the biggest mud pit I had ever seen. The whole thing was surrounded by other vehicles and people hoping someone else would be the first to go in. My daughter didn’t stop to think and drove straight in. At first, she was going too slow, and I had visions of getting stuck and wading through several feet of mud to get out. I yelled “power!!!” and she floored it. Four giant rooster tails flew off the tires and waves of mud flowed over the sills, filling the vehicle. But we made it through. Here is the aftermath with a very proud driver and her father:

Like I said, they are insanely capable and fun vehicles.

Long Arms

The key thing that makes side-by-sides so capable is the suspension: long control arms with lots of wheel travel, big knobby tires, and high ground clearance. Having lots of wheel travel helps keep tires in contact with the ground to maintain traction. The wheels are also placed right at the front and back of the vehicle, so the approach and departure angles are essentially vertical (90 degrees).

These angles are critical in off-roading because they determine how steep a hill or rock you can approach/depart.

Having owned one of these for several years, I was able to get a good look at how the suspensions were designed and what makes them tick. While I was impressed by the vehicle’s capabilities, I was never very impressed by the suspension design itself. In fact, when I was thinking about buying one, I did some research and I found that a lot of owners were replacing suspension bushings regularly. At first I thought this was strange but bear with me and you’ll understand why this was happening.

Big Tires, Small Wheels

The tires on these things are huge, but the wheels are actually quite small. RZR S900 tires are 27″ in diameter but sit on a 12″ wheel. This leaves very little room for the brakes and suspension links that have to fit inside the wheel.

The result is that the upper and lower control links are not very far apart vertically, which leads to a problem. When cornering, the side force generated by the tire at the contact patch is reacted by the upper and lower links. Let’s suppose we have a 100 lb. cornering force and let’s suppose the dimensions of the suspension are as follows:

Using a “sum-of-moments” strategy that engineers are taught in engineering school, we can calculate the forces in the upper and lower links required to resist this cornering force:

Notice how a 100 lb cornering force has translated into a 243lb force in the lower link and a 143 lb force in the upper link. Also notice that the directions of the upper and lower link forces are opposite. This is because the cornering force will put the lower link in compression and the upper link in tension. Of course, these forces travel down the links and go right into the bushings connecting the links to the frame. That’s a lot of force these bushings have to withstand which helps explain why so many owners had to replace them in their vehicles. That short span and those high forces meant they were wearing out too fast!

Another problem is that when resisting the forces coming down the links, the bushings connecting the links to the frame — bushings that are made of rubber — will deflect slightly and those deflections cause the camber angle of the wheel to change. Remember, camber angle is the vertical angle of the wheel when viewed from the front.

Let’s suppose the bushings deflect 0.1″ under these loads. That means the camber angle in our example vehicle will change by 1.6 degrees:

We could reduce these forces and the corresponding deflections by making the vertical distance between the links larger, but since the outer ball joints and the links all have to fit inside the wheel, the only way to do that would be to make the wheel bigger, which means making the tires bigger.

A Better Way

But what if there were a way of reducing these forces while still keeping the same wheels and tires? Let’s look at what Can Am did with the Maverick:

The company moved the upper link from inside the wheel to way above the top of the tire. Now, while this is the first time I’ve seen this design used in a side-by-side, it is actually very common in passenger cars and has been used for over 30 years. I believe the 1989 Ford Thunderbird was one of the first, if not the first, car to use such a tall spindle which placed the upper control arm above the tire instead of inside the wheel. Someone please correct me if they are aware of an earlier example of this type of suspension. [Editor’s Note: Yes, we have readers that nerdy. -DT]. 

Image via www.classiccars.com

Notice how the upper link and upper ball joint are way up above the tire while the lower link and ball joint are still down inside the wheel. This design is now quite common in cars with a double wishbone front suspension and the reason it is done in cars and one of the reasons I believe Can-Am did it in the Maverick is because of this:

If we apply the same 100 lb. cornering force as we did in our earlier example, our lower link force has dropped from 243 lbs down to 152 lbs and our upper link force has dropped from 143 lbs. down to 52 lbs. That’s a huge difference. Remember, these forces travel down the links and into the upper and lower bushings. What do you think will happen to the durability of those bushings if the forces are cut down like that? They will last a whole lot longer, that’s what. They will also deflect a lot less.

If we used the same bushings we did in our earlier example, the upper bushing, which now sees a load 1/3 as big as it was before, will only deflect 0.03″ while the lower will only deflect about 0.07″. They are also much farther apart so instead of the camber angle changing by 1.6 deg., it will now only change by 0.3 deg.:

A few degrees of camber change under cornering may not be a big deal for an off-road vehicle, but it can be critical in a road car, especially if it is a high-performance sedan. It can make the difference between good cornering or tearing up your tires.

However, let’s suppose that a road car still has acceptable cornering performance with 1.6 degrees of camber change. This means that with a tall suspension like this, the bushings can now be made a bit softer which would give a better ride, less road noise and an overall nicer experience for the occupants. Or we could split the difference and soften the bushings only a little bit to give better ride as well as better cornering.

There are similar benefits to be gained under braking since the upper and lower arms resist the forces of braking in the same way they do cornering, only this time viewed from the side of the vehicle instead of the front. Increasing the vertical distance between the upper and lower control links has the same effect of reducing the braking forces the links have to resist.

I don’t know if this is what Can-Am meant when they claimed the new design provides “better load distribution” but reducing the forces in the control links is most definitely an advantage of moving the upper arm above the tire.

Now let’s look at the specific design improvements Can-Am made in the new suspension — [minimizing] spindle length, scrub radius, and kingpin angle —  and then we’ll talk about how these changes may have resulted in the improvements they claim.

Roll Center Height

As we read earlier, Can-Am claims the new suspension design improves the suspension roll center height. The Drive article does not state if Can-Am raised or lowered the roll center height, but I believe they raised it. Let’s see how that works. Moving the upper arm above the tire allowed the company to play with the front view angles of the control arms which allowed them to design a much higher suspension roll center. The suspension roll center is the point around which the body rolls when you go through a turn. Kind of like how the hinges of a door form the axis it rotates around.

And the height of the roll center relative to the center of gravity of the body determines how much roll you will get. In a nutshell, the lower the roll center, the more body roll you will get and the more work the springs and suspension have to do to counteract that roll.

To learn about roll centers in more detail, check out:

and

Look at the control arms of the Can-Am Maverick X3, which has a suspension geometry very similar to my old Polaris RZR S900:

Notice how the upper and lower links are effectively parallel to each other. If we want to find the roll center of this suspension, we would extend the lines going through the upper and lower links until they intersect. Hang on, you say, parallel lines don’t intersect! That is true, so when we are faced with this situation, we draw the line from the tire contact patch parallel to the lines through the links, and where that line crosses the centerline of the vehicle is our roll center. Like this:

Now let’s look at the new Maverick R:

Notice how the upper and lower links are angled relative to each other. If we now do the same thing as we did before to find the roll center, we get:

It’s not obvious from this image, but the roll center here is much higher than in the Maverick X3. Let’s overlay them so you can see the difference:

There is a clear difference. The reason this is possible is because with a high mounted upper arm, you can decrease the vertical distance between the control link inner pivots while keeping the vertical distance between the outer pivots large. This simply isn’t possible with a suspension like the X3 has because the pivots are already so close together.

Of course, this is by no means a scientific analysis. I’m just drawing lines on photos, but you get the idea. For a proper analysis I would need to know the exact locations of each of the suspension attachment points and run them through a computer program. But I don’t need to go into that much detail to see that Can-Am has made a significant change to the roll center of their new suspension. And it’s all because they moved the upper arm out of the wheel and above the tire.

As I mentioned earlier, the lower the roll center, the more roll you will get in a turn. So, by raising the roll center as much as Can-Am did, you can expect a lot less body roll in the Maverick R. If you’ve watched the videos or read the article linked above, you know there are downsides to having a high roll center, namely jacking and track change during ride events (in other words, significant vehicle geometry changes depending upon if you’re in jounce or rebound), but while these negatives can become a big problem in road cars, I doubt they would present much of an issue on dirt where traction is limited anyway.

Scrub Radius, Spindle Length, and Kingpin Angle

[Ed Note: You can visualize scrub radius by watching the video above; notice how the tire isn’t just spinning about a vertical axis going through its center (like a coin would if you flicked it on a tabletop — this has a zero scrub radius), it’s making a “sweeping” motion, the nature of which can be described by the scrub radius. -DT]. 

Can-Am claims the new suspension improves the scrub radius, minimizes the spindle length, and reduces kingpin angle. I’m lumping all of these together because they are intricately related to each other. Scrub radius is the front view distance between the point where the kingpin (a line going through the centers of the upper and lower ball joints; think of this as the axis about which the tire rotates while the steering wheel is turning) intersects the ground and the center of the tire contact patch. Spindle length is the distance from the kingpin axis to the wheel center:

Let’s talk about each of these one by one.

Scrub Radius

Suspension engineers care about scrub radius because braking forces together with this distance cause a moment or torque around the kingpin axis which tries to steer the vehicle. (And you generally do not want the car to steer under braking).

The only thing stopping the suspension from actually steering left or right is the steering system itself, but this means the braking forces are pushing and pulling on the steering. As long as the braking forces are the same on the left and right front wheels (which they would be if you’re on dry pavement), these forces cancel each other out. But if the braking force on one side is greater than the other, like it might be if one wheel is on ice and the other on pavement, or one wheel loses traction for some other reason, the steering system will get pulled or pushed left or right and the only thing that resists this force are your hands holding the wheel. You would feel this as a pull on the steering wheel while braking.

Spindle Length

In a similar way, the spindle length works together with forces coming from impacts, like hitting a pothole or a rock on the trail, to cause a moment around the kingpin axis which also tries to steer the suspension.

The big difference is that potholes and rock strikes rarely happen on both sides of the car at the same time.  So, while under normal conditions, the braking forces coming from the left and right suspensions will balance each other out, this is never really the case for potholes. The result is the steering system gets a hard pull, or “kickback”, when you hit a pothole.

What Can-Am Did

Now that we know about scrub radius and spindle length, let’s take a look at what Can-Am did. This will also help answer the third thing they minimized: kingpin angle.

By moving the upper arm above the tire, Can-Am essentially did this:

By itself, moving the upper arm above the tire doesn’t change anything if the upper ball joint falls on the same kingpin axis as before. The scrub radius is still the same and the spindle length is still the same. But look closely at the photos of the Maverick.

It looks like that ball joint is really far out over the tire. So let’s move our upper ball joint farther out as well:

It looks like we made the spindle length smaller and the kingpin angle smaller. In fact, the kingpin angle reversed direction. But we made the scrub radius bigger. That’s not good.

Clearly, moving the upper ball joint outboard isn’t the only thing Can-Am did with the new suspension design. If we want a smaller spindle length AND we want a smaller scrub radius, we are going to have to move the lower ball joint outboard as well. Unfortunately, this gets into a new problem we haven’t discussed yet: brake package.

Brake Package

Up to now, we haven’t discussed the braking system because it hasn’t been important yet, but when we talk about moving the lower ball joint outboard, we need to look at the brakes. This is because the lower ball joint is almost always constrained by the brake rotor, which is in turn constrained by the caliper, which is then constrained by the wheel:

Here you can see the lower ball joint sitting very close to the brake rotor. If we want the ball joint to move outboard, we will need to move the rotor outboard, but it is held in place by the brake caliper and the caliper can’t move outboard because it is constrained by the wheel. All these things conspire to stop the lower ball joint from moving outboard like we want unless the end of that chain, the wheel, changes.

So let’s look at the wheel. The Maverick X3, which is the previous Can-Am model, has a 14″ wheel as the base wheel. The Maverick R, on the other hand, has a 15″ wheel as its base wheel. Would a bigger wheel allow for our brake rotor and lower ball joint to make outboard?

Yes, it can. Using a bigger wheel gets it away from the caliper and allows the caliper to move outboard. Once the caliper moves, the rotor moves with it and gives us the space to move the lower ball joint outboard as well. Notice that doing this reduced the scrub radius and the spindle length, just like Can-Am said they did.

Kingpin Angle

You can also see how moving the upper arm up above the tire and moving both ball joints outboard gave us the opportunity to reduce the kingpin angle. Reducing the kingpin angle will have the effect of reducing the effort it takes to steer the vehicle and give the “point and shoot” steering Can-Am claims.

I do have to point out one thing here, though. Using a bigger wheel and moving the brake rotor and lower ball joint outboard has absolutely nothing to do with moving the upper arm up above the tire. Put a 15″ wheel on the X3 and you could have moved the brakes and lower ball joint outboard just the same and get the same smaller scrub radius, spindle length, and reduced kingpin angle. It would NOT, however, give us the higher roll center. For that, we really need to get the upper link out of the wheel and up above the tire so that we can play with the vertical distance between the inner and outer pivot points.

All in all, a very cool suspension design with enormous benefits, which is why they have been in use in cars for over 30 years. It’s nice to see this concept finally being used in off-road vehicles as well. Plus, out in the open like it is, it looks insane!