2009 Suzuki SX4 AWD: Suspension Walkaround
September 16, 2009
Our long-term 2009 Suzuki SX4 didn't get the suspension walkaround treatment the last time it was car of the week, but it wasn't my fault. Someone stole my car. There was an earthquake. A terrible flood. LOCUSTS!
But everything is all better now. The Suzuki is up on jack stands and it's not too terribly hot outside. Let's take a peek inside those wheel wells.
The SX4's front suspension is pretty standard compact car stuff: A MacPherson strut (white) and a rear-facing L-shaped control arm (yellow).
Of course the L-shaped lower control arm has a single ball joint. The dual-pivot setups we've seen lately need a pair of separate links to go with them.
As with most strut set-ups, a pair of large bolts clamps the the strut firmly to the knuckle. There isn't any camber adjustment here, but loosening these bolts can yield small changes because of the clearances within. (Don't forget to re-torque them properly)
Many carmakers that use this type of connection also sell necked-down bolts that increase these clearances to allow for additional camber adjustment in the event of "crash damage". Don't know if Suzuki has these in their parts catalog, but I would not be surprised.
Any camber adjustment performed by loosening this connection will throw the front toe-in out of whack, so the toe needs to be reset after any camber adjustment is made, no matter how small.
The stabilzer bar is connected directly to the strut via a long, slender link (yellow). And if you think this rear-mounted steering rack looks a bit higher than usual, you're right.
The steering rack (green) sits up high for one simple reason: the power take-off (white) that sends power to the rear wheels has dibs on the space. The stabilizer bar (yellow) may look like it makes a dead end at the bushing, but it's an illusion; in reality it dips down under the PTO housing.
Meanwhile, the front subframe uses a solid mount (orange) that stands clear of it all to make room for the overslung steering rack and underslung stabilizer bar.
Here we can see the PTO housing (white) and propshaft emerging from beneath the steering rack (yellow).
The SX4's front brakes consist of single-piston sliding calipers and ventilated rotors.
Sliding calipers like these are absolutely the easiest type of brakes to work on. Simply remove the retaining bolt on the lower slider...
...like this, and...
...gently pivot the sliding half of the caliper up on the upper bolt, which you don't even have to loosen.
At this point the pads practically fall out by themsleves.
Of course this is a simulation. These pads are not thin enough to need changing.
If this were a real pad change, I'd go through additional details about shims, anti-squeal compounds and how to retract the pistons, just like I did on the Nissan 370Z fixed-caliper pad change. For now, know that this job is a fairly simple DIY that requires no exotic tools.
In back, the SX4 uses the same sort of one-piece semi-independent twist beam axle that we saw on the Honda Fit and Insight. It basically amounts to a huge, car-spanning stabilizer bar with wheels on the ends. What's confusing the view here is our AWD SX4's rear differential
This type of axle isn't a great choice for off-road vehicles because opposite-phase wheel articluation -- the amount one wheel can go up compared to the amount the opposite one can hang down -- is somewhat limited. And you can't really change it because a twist beam can only twist so much. We've all seen what happens when you bend a paper clip too far back and forth for too long.
But the SX4 isn't a full-blown off-road vehicle, it's a car-based SUV with all-wheel drive. A "soft-roader" intended for use in snow and on maintained fire roads. And for those purposes the twist-beam design works just fine.
Like all such designs, the SX4's twist beam mounts to the chassis in just two places, one per side. The bushings are angled (yellow) to help them better cope with the combined need to deal with longitudinal road inputs and lateral cornerng forces.
The torsional stiffness of the cross-car part of the twist beam (the twisty bit) is brought up to the engineers' desired specifications by means of a permanently welded-in stabilizer bar (white) that runs inside.
You've heard be go on about motion ratios before. With a twist beam, we don't look at the lateral lower control arm to determine these ratios -- we look at the longitudinal "swingarm" portion of the beam instead.
This fact gives the twist beam a very unique difference: the shock absorber's motion ratio relative to the wheel can be greater than 1:1 because the shock can be mounted further away from the pivot than the axle. Here it looks like 1.2:1 or thereabouts.
The shocks (white) are the only things keeping the springs secure in their lower seat (yellow). Remove both shocks while the back is off the ground and the axle can easily be pulled down far enough to remove the springs. Moral: If you jack up the rear to change shocks, change them one at a time.
The rear differential of the AWD SX4 hangs beneath the unibody, mounted separatly from the suspension. In fact the twist beam itself (white) has a gentle arc that's shaped to keep it above and out of the way of the diff.
The diff itself is mounted in 4 places (yellow). The rear mount is broad so that it can more easily deal with the torque reaction that comes when power is applied from the propshaft (aka driveshaft).
The forward part of the housing contains the coupling that distributes power to the rear wheels in i-AWD or AWD-lock mode, and various wires (black) run inside to control the mechanism.
Of course this means that the propshaft that runs down the center of the car from the engine turns all of the time, even when the selector switch is in 2WD (front-wheel drive) mode.
Here we can see that the SX4 uses single-piston sliding rear brake calipers and solid rear rotors.
A word about that rust on the hub: Our SX4 had the most buildup of any of the 17 or so cars I've given the walkaround treatment, by far. I had to use force to get the wheels off after I removed the lug nuts, and I had to use emery paper to remove the rust so I could get them back on and properly torqued. And just like the others in this series, this is a California car.
The parking brake is cable-operated, so changing the rear pads will require the removal of both slider bolts; the stiff cable prevents the caliper from being hinged up when just one is removed.
Our SX4 came with Bridgestone Turanza EL400 (02) tires, size P205/60R16. The rims are 16 x 6 inches.
The offset of any wheel can usually be determined be looking at the inside of one of the wheel spokes and reading a sequence of numbers. Suzuki removes all doubt by spelling it out clearly.
Dan Edmunds, Director of Vehicle Testintg @ 13,854 miles