Truth be told, I've been sitting on the suspension photos of our 2011 Hyundai Sonata GLS for some time. You know, things get busy around the office, a Leaf shows up, there's a hot story or three, and if you're not careful six months go flying by.
No more. I'm blowing the cobwebs off these ancient stills and trotting them out for all to see.
Why am I telling you this? I dunno. I guess I wanted to let you know why the Sonata's suspension bits and pieces look so sparkly and clean in the following pictures.
To the surprise of no one, the front end of the Sonata is propped up by MacPherson struts.
As with nearly all front-drive cars with transverse engines, the Sonata's steering (green) acts behind the front axle centerline.
A direct-acting stabilizer bar is used, so named because the drop link (yellow) attaches directly to the strut housing.
The Sonata's hollow lower control arm is made from a pair of welded steel stampings and its longer leg stretches forward. Three easily accessed bolts make ball joint replacement a simple task.
Here's another shot of the forward leg of that lower control arm. You can see how it's shaped to provide tire clearance at full steering lock.
We've stuck our head under the dashboard for this shot and we're looking straight up. The white arrow is pointing out the face of the brake pedal, and the green arrow is pointing off-screen toward the steering wheel.
Between them is the electronic power steering unit (yellow), a so-called column mounted unit because it's located under the dash in the steering column. Column-mounted EPS works in lighter cars, but not in a heavier vehicle like the Ford F-150, which uses rack-mounted EPS.
Why? The power steering unit of course adds muscle to your steering input. If you add that power-assist torque within the column, upstream of the steering rack & pinion gears, those gears have to be strong enough to handle the extra load.
That's OK in lighter applications, but something like a 4x4 truck needs much more steering assist, and a suitably-powerful column-mounted EPS unit might apply too much load to the pinion gear. Therefore, in heavier applications you won't see the EPS unit here; instead it will reside on the rack itself, downstream of the pinion gear.
As expected, the Sonata's front brakes consist of single-piston sliding calipers and ventilated rotors. But the calipers themselves are a little unique because the sliding half is made from two pieces that are bolted together. To the right of the split line, the hydraulic side that houses the piston is made of aluminum. To the left, the fingers that wrap around and clasp the opposite pad are made of cast iron.
The rear half of our Sonata sits on a multilink setup that's a bit more interesting.
A single trailing arm (black) locates the wheel in the fore-aft direction. Farther aft, the upper link (yellow) and lower link (white) define the camber angle as the wheel moves up and down. Finally, the stubbier toe-link (green) holds the wheel and tire at the desired toe setting throughout its travel.
Here's another look from the front, with the trailing arm's forward mounting bushing in the foreground.
We have a better view of the lower link (white) which is made of aluminum, carries the spring and has an eccentric inner mount for camber adjustment. Above it are the upper link (yellow) and the toe link (green), also with an eccentric adjustment for toe-in on its inside end.
Even though it's dark in color, the rear upright (yellow) is in fact made of aluminum. The shock absorber bolts directly to it, so its motion ratio is a straight 1-to-1. Meanwhile, the stabilizer bar sits far inboard at something like a 0.45-to-1 motion ratio and the spring, slightly further outboard, appears to be sitting at 0.65-to-1.
In other words, the apparent spring rate at the wheel, the wheel rate, will be about 65% softer than the spring rate itself. If the spring's stiffness was 200 lb/in (I have no idea - this is just an example), then the wheel rate, the one that really matters, would be 130 lb/in. Motion ratios closer to 1-to-1 allow softer (and lighter) springs to get the same job done, but packaging constraints don't often make that practical.
The stabilizer bar drop link has this big bar code sticker on it, making it a bit hard to follow the link from the bar end to the place where it bolts into the aluminum lower link.
The lower link connects to the upright via a pillow ball for higher lateral stiffness than one could get with a rubber bushing. It looks cockeyed because the suspension is at full droop. Things square up better when the suspension settles to ride height.
The toe link passes through a gap in the trailing arm to connect directly to the upright. Of course the toe link is still shorter than the other links so it can induce a stabilizing dose of roll understeer as the outside tire loads up in corners.
Just like the front, the rear sliding caliper uses a two-piece design, with aluminum on the inside and cast iron outside.
Our Sonata GLS rides on aluminum alloy wheels, 6.5 inches wide, 16 inches in diameter and with a 43 mm offset, as you can plainly see here. Wrapped in P205/65R16 Kumho Solus KH25 all-season rubber, the mounted assemblies weigh 44.5 pounds apiece.
The sportier Sonata 2.0T looks much the same underneath, but nearly-invisible things like spring rates and internal damper settings in the struts and shocks will differ according to its slightly different mission. Similarly, the EPS calibration under the dash is also set to generate a bit less assist so the steering doesn't feel quite so light as this. Much more visible are the tires, which can range up to 245/45R18.
Dan Edmunds, Director of Vehicle Testing
tjpark01 says:
05:58 PM, 02/ 3/11
Always the most interesting LT posts. This is what I wait to read. So much of the chassis is invisible. Thanks Dan.
kplacer says:
06:53 PM, 02/ 3/11
Wow, some very lightweight pieces in that suspension. I wonder how well it holds up to a series of Michigan potholes? Especially after a few years of road salt?
roadburner says:
07:22 PM, 02/ 3/11
It's very interesting to get a look at the most important components- and it is always a good read.
acbayard says:
07:24 PM, 02/ 3/11
@kplacer: The car is fairly light - and I seriously doubt South Koreans don't know how to factor in road salt, considering how South Koreans salt more liberally with bigger winter budgets than most US municipalities.
speedracer1407 says:
07:28 PM, 02/ 3/11
These suspension walkarounds are my absolute favorite part of IL. Good to see that Dan hasn't given up on them, as they seemed to have been dropped from his agenda lately.
Question for Dan:
Having geeked out on suspension designs for many years, I find the placement and size of the "upper" control link on the rear suspension pretty unusual. There are probably some perspective issues with the shot, but in the photo that shows both the uppers and lower links from the rear, the upper link appears virtually the same length and mounted with the same "droop" as the lower link. Most multilink designs, even simple 4-link ones like this, have a noticeably shorter upper link that is mounted quite a few degrees off-parallel to the lower link. With the Sonata's near-parallel upper and lower links, is there little or no dynamic camber dialed its rear suspension? Strut-type rear suspensions get away with limited dynamic camber, but every multilink rear suspension I've ever seen has links arranged for pretty substantial dynamic negative camber.
actualsize says:
08:37 PM, 02/ 3/11
Actually, I've done a few others recently -- but over on our Straightline blog, where I post walkarounds for short term cars we may only have for a week or so.
http://blogs.insideline.com/straightline/MoreCategories/suspension-walkarounds/
And I'm going to get very busy on these again, as a whole new crop of long-term cars is coming into the fleet.
litewerk says:
12:02 AM, 02/ 4/11
I, too, offer a sincere thank you, Dan. This is truly a most excellent, educational, and informative post with fantastic pictures and a great write-up/explanation. I really like it the most on those occasions when we get away from our opinions, likes/dislikes, etc.
fundango says:
05:47 AM, 02/ 4/11
Good stuff, thanks.
coxwill says:
08:17 AM, 02/ 4/11
Walk around of the Countryman please! I want to see changes MINI made for the AWD and higher weight.
actualsize says:
08:51 AM, 02/ 4/11
@speedracer1407:
Several points:
1) Any independent suspension will have a better camber curve than a strut. Struts go slightly positive as the lower control arm swings up and shortens, pulling the bottom of the tire in with it. Struts are found at the back of many FWD family cars, so we're ahead of the game here.
2) The upper arm is a little shorter than the lower one, so the tire's camber will go negative as it compresses. And remember *key point* these two arms are vertically quite close to one another, so a little goes a long way. You see dramatic differences in arm length where high-mount upper arms are employed, where the upper and lower elements are 12 to 18 inches apart.
3) This a FWD car, so the rear wheels aren't delivering any torque and the car isn't prone to power oversteer. Obvious amounts of dynamic (and static) rear camber are more critical in RWD applications. The fact that rear struts are ever considered at all on FWD cars but are never seen on RWD ones makes this point.
Mutlilink and double wishbone rear suspensions pay ride & handling dividends because they have more favorable dynamic camber and dynamic toe (aka bump steer) possibilities, but they are more expensive because of all of the extra parts. Still, It's no coincidence that the best-handling small FWD cars --Mini, Mazda3, Focus, etc.-- have multilink rear suspension.
bthayer23 says:
11:55 AM, 02/ 4/11
Any thoughts on that front steering knuckle? It looks like it's been designed to minimize torque steer. I'm not sure if the GLS has enough power to twist the wheel, but the 2.0T might.
2slow says:
02:32 PM, 02/23/11
I think the confusion surrounding the link lengths and camber gain comes from their descriptions. It appears as if the link described as the "toe link" is actually the link controlling the camber curve. The link described as the "upper link" is actually controling toe. The 10th picture shows that the short link is the highest link in the vehicle. The longer link behind WC is at about mid height when compared to the other longitudinal links. This would make it more of a "toe link"
dalexxx says:
03:19 PM, 12/11/11
@2slow, if that is true then it would appear that the car will experience roll over-steer, which you must know is very bad. Based on the fore-aft locations and the relative lengths of the links, the article appears to be right.