2009 Mazda 6 i Grand Touring: Suspension Walkaround
November 24, 2009
After looking back through the archives, I realized that our 2009 Mazda 6 had not yet undergone the suspension walkaround treatment. This aggression will not stand, man. You deserve a peek.
Each long-term test of course ends as it began: the car is taken to the test track to see how it fares when driven at the limit.
The Mazda 6 recently underwent its wrap-up testing, and by chance we had a 2010 Ford Transit Connect delivery van at the track on the same day for unrelated purposes. Comparisons were unavoidable after the Transit beat the Mazda 6 in the slalom (61.9 to 60.9 mph) and tied it on the skidpad (0.79 g).
Some of that difference is down to the absence of electronic stability control (ESC) on the Transit we tested, whereas our Mazda 6 has an ESC system that can't be completely disengaged. And the system fires-off somewhat easily because our 4-cylinder Mazda 6 rides on rather pedestrian Michelin Energy MXV4 S8 tires.
Despite those limit-test numbers, the Mazda 6 performs admirably in day-to-day driving due to a well thought-out suspension.
The Mazda 6 uses double wishbone front suspension with a high-mount upper arm. Consistent with the low-end price-point of a family car, all of the main parts are made of steel or iron.
Here's another view of the high-mount upper control arm (yellow) and the coil-over spring and shock assembly (blue). Remember not to call it a strut because the coil-over here does not perform any wheel-location duties. That is to say, if it were absent, the upper and lower arms would totally control the caster and camber of the wheel throughout its range of motion.
A familiar L-shaped lower arm is used, and the Mazda 6 uses the same sort of cantilevered rear bushing we saw on the Mazdaspeed 3 and Focus, albiet this one rests in an aluminum housing.
The 6's transverse engine and front-drive layout make it necessary for the steering rack (green) to be mounted behind the front axle centerline.
The lower end of the shock absorber bolts to a fork (yellow) that splits around the front drive axle on its way to the lower control arm.
The front stabilizer bar (green) attaches to the fork via a short link (yellow). While this may look like a direct-acting design, it isn't because the fork mounts to the lower control arm some distance inboard of the lower ball joint.
Here's a close-up of the lower ball joint (yellow) and the attachment point for the coil-over's mounting fork (green).
Mazda NVH engineers (Noise, Vibration and Harshness) decided they needed to add a mass damper to the upper arm to quell a particular harmonic they didn't think you'd like. Every suspension design represents a complex mechanical structure, and no two are alike where harmonic resonances are concerned. We've seen mass dampers pop up in all sorts of places on various cars in these walkarounds.
Front braking duties are carried-out by one-piece ventilated front rotors and single-piston sliding calipers.
Changing pads involves nothing more than removing the lower slide bolt (black) and pivoting the caliper up on its mate. Rotor changes require the entire caliper and caliper frame to come off, and that means removing the two yellow bolts.
If you find yourself going after those hose bolts, stop. You're doing it wrong.
Moving on to the rear, we see a larger version of the control blade rear suspension we saw in the Mazdaspeed 3 and Ford Focus.
Like those other cars, the control blade (blue) is a thin trailing arm that locates the wheel in the longitudinal direction and stabilizes the hub against torque inputs. The upper link (green) and the primary lower link (black) define the camber angle and camber curve, while the tiny toe link (yellow) works with the primary lower link (black) to control toe-in.
The primary lower link (white) may look like a control arm because it's so big and fat and has a lot attached to it. But it's got only one bushing at either end, so it's a link.
Like the Mazdaspeed 3, there are two bump stops in play. The primary urethane one is somewaht soft and is designed to engage gradually, giving some of the benefits you'd get with a progressive-rate spring. The harder rubber one is more of an ultimate travel limiter--the true role of a bump stop. But it doesn't engage abruptly and slam home because of the presence of its urethane counterpart.
As we've seen before, the forward toe-link (green) is much shorter that the longer, rear-placed primary lower link (yellow), and that means the rear wheel will toe in as the wheel compresses and the toe-link swings through its tighter arc.
Over toward the right, the stabilizer bar is tucked away, nearly out of sight. The connecting link is nearly invisible in this view.
Even up close it's hard to see how the stabilizer link drops through an opening in the lower control link.
Left to right: the inner pivot bushing, the stabilizer bar link, coil spring and urethane bump stop, hard rubber bump stop landing, outer pivot bushing.
Inside the circle you'll see where the toe link can be adjusted to set static toe in during a wheel alignment. One half of the threaded section has left-hand threads and the other half has right-hand threads. Loosen the jam nuts on either end and the center section can be easily twirled to adjust the length of the link without removing it.
Lower down, we can see that the rear shock absorber mounts directly to the rear knuckle for a 1:1 motion ratio and maximum efficiency.
Here's a close-up of the knuckle (yellow) and the three bolts (blue) that attach it to the control blade (green).
Rear braking comes from this FoMoCo single-piston sliding caliper and a non-vented rear rotor.
The aforementioned Michelin Energy MXV4 S8 all-season tires, size 215/55R17, are mounted on 17" x 7" aluminum alloy rims. Together they weight 47 lbs.
Dan Edmunds, Director of Vehicle Testing