2009 Honda Fit Sport: Suspension Walkaround
March 09, 2009
Ever wonder what it looks like behind the wheels of your car? Never removed a tire in your life? Well, even if you have, there are subtle details you might overlook.
Here, then, are a few suspension photos of our 2009 Honda Fit Sport.
Honda Fits have a simple strut front suspension with a one-piece lower control arm. You can also see the rear-mounted steering rack that all transverse-engined front-wheel drive cars have. And you can see why this results in a forward-mounted brake caliper.
But let's change the angle a bit for a couple of other nuggets.
We can see that the caliper is a single piston sliding design. Changing Honda brake pads is as easy as it gets. You simply remove the lower slide bolt (just left of the lower bellows), rotate the main sliding half of the caliper up 180 degrees using the identical upper bolt as your pivot, push back the piston, slap in some new pads and put it back together. It takes five minutes tops if you have the wheels off, a few basic tools and some confidence. Really. The most likely way to screw it up is to over-torque the slender slide bolt when you put everything back together or forget to install the pad anti-rattle clips. New rotors add to the time and the degree of difficulty, but not by much.
And check out that long slender black stabilizer link. It attaches directly to the strut housing, which means the stabilizer bar (just visible at the bottom end) enjoys nearly 100% efficiency with respect to the motion of the tire: wheel goes up 2 inches, the stabilizer bar end moves up the same as it twists the bar.
While this design is becoming more common, a lot of cars still don't have this. Instead their stabilizer bar links mount to the lower control arm (LCA), usually about halfway between the ball joint and the arm pivot axis. This means that the stabilizer bar motion ratio is only 50 or 60%. When the wheel moves 2 inches, the stabilizer bar end moves only one inch or so. This inefficiency means the car with the LCA mount will need a bigger stabilizer bar to generate the same roll stiffness as one mounted like the Fit.
How much bigger? Well, the spring rate of a torsion bar is proportional to its diameter to the fourth power. Our Fit has a 22 mm front stabilizer bar. If it attached to the LCA with a 60% motion ratio, it would have to be 25 mm in diameter to generate the same approximate roll stiffness.
Here is our Fit Sport's rear suspension. It's a semi-independent twist beam, a simple design that leaves room for a deep well between the wheels--one of the reasons why the Fit can carry so much stuff. The Sport has a 17 mm rear stabilizer bar, but it's all but hidden from view. Non-Sport Fits don't have a rear stabilizer bar, but that's not really true.
That's because a twist beam is nothing more than a giant, car-wide stabilizer bar with wheels on the ends. It's one piece, but because it's so wide it twists, hence the semi-independent designation. Another way to look at it is as a too-wide motorcycle swingarm with one wheel facing out of each leg.
Since the whole thing behaves like a stabilizer bar, increasing the roll stiffness can be accomplished by adding material across the middle to make the beam torsionally stiffer. Here an additional 17 mm stabilizer bar has been welded-in where it can span across. You can see the round nub end of it in the center of the picture. The beam doesn't twist very much, so 17mm isn't as impressive as it sounds. A standard Fit without this kind of supplemental rear stabilizer bar will understeer a little more, but it doesn't feel dramatically different.
Dan Edmunds, Director of Vehicle Testing @ 3,718 miles.