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
carguy622 says:
10:23 AM, 11/24/09
That's too funny, a Transit Connect beats a Mazda6 around the slalom. What's next a Buick with a stick?
On a more serious note...non-defeatable stability control, on a Mazda?
vvk says:
10:52 AM, 11/24/09
Even delivery vans from Europe beat what we presume to be a "sporty" sedan.
Dan, as always, thanks for a great article. I have a question: what can you tell us about the unusual parking brake arrangement? Typically we see a small drum in the back that serves as a parking brake. Looks like Mazda6 has a different setup. Last time I saw this was on the old SAAB 900 from the 80s.
adamb1 says:
11:02 AM, 11/24/09
215/55r17's are really quite narrow and tall for a car of this size. I'd bet the V6 model does much better with its 235/45/18's.
94_gsr_cpe says:
11:18 AM, 11/24/09
Good to see that there are no real surprises with the suspension. If it ain't broke don't fix it. Now all im waiting for are some adjustable coilovers so i don't cringe when I see a Transit.
nomercy346 says:
11:19 AM, 11/24/09
"Even delivery vans from Europe beat what we presume to be a "sporty" sedan."
Acceleration wise full size trucks beat what Europeans presume to be a "sporty" car. lol
jstandefer says:
11:34 AM, 11/24/09
Dan, another great suspension walkaround! How familiar are you with the history of Ford's Control Blade rear suspension? Mazda has a history of passive geometry-changing rear suspensions such as the Twin Trapezoidal Link (TTL) used in the 323s, 626s, MX-6s, Probes, later Escorts, MX-3s, Proteges; Dynamic Tracking Suspension System (DTSS) used in the second generation RX-7; and E-link suspension used in the 929. (Of course, there is also Mazda's adventure in active 4-wheel steering, but that's another story.) Do you think the Control Blade is an evolution of Mazda's previous designs, or a whole separate development on Ford's part?
yellowbal says:
11:36 AM, 11/24/09
It looks like more manufacturers are using the rear disc brakes for the parking braking instead of a drum hub. Is that good or bad?
chavis10 says:
11:48 AM, 11/24/09
One of the few regular cars that still features a control arm front suspension. Would be nice to see some aluminum in there but I guess that's too much to ask.
adantium says:
02:11 PM, 11/24/09
Hi,
"This aggression will not stand, man. You deserve a peek."
I think you were thinking of the word Transgression. But I won't hold it against you since it was such a lovely walk through.
87bonnev says:
02:23 PM, 11/24/09
Full Disclosure: I am as GM chassis engineer.
Nice post, Dan. As a suspension engineer I love these. I am glad you recognize that every suspension is a compromise, and that there is no one "right" way to do anything.
Two small comments:
1. Most chassis engineers typically refer to a suspension part as a "link" if it reacts load in tension sndmpression only, hence a "two-force member". The Mazda rear suspension spring arm could be can be classified as such since it supports both tension & compression down its length as well as the bending forces due to the spring. But then many call it a spring link...
2.@ jstandefer: Trailing blade-type suspensions have been used by many manufacturers. GM uses it on 2004-present Malibu, as well as 2010 Lacrosse, Regal & Insignia FWD versions. Honda uses a similar set-up on the Pilot and Odyssey (sp?). The most difficult part of designing this suspension is getting the blade to be just flexible enough to not inhibit motion, but still be strong enough to resist the road loads.
ocramida says:
03:02 PM, 11/24/09
87bonnev, so it sounds like chassis engineers should be pretty well-versed in metallurgy/materials science to do their job well. This sort of stuff fascinates me BTW. If I didn't have such crappy grade school math/algebra teachers (they didn't do a very good job translating complex ideas into real-world applications) I would have defintely become a engineer.
94_gsr_cpe says:
03:15 PM, 11/24/09
87bonnev, know of anyone who needs BSEE's in the automotive engineering biz?
f1mom says:
03:15 PM, 11/24/09
adantium:
If you have not seen The Big Lebowski, you need to.
Now.
We'll wait.
jstandefer says:
03:17 PM, 11/24/09
@87bonnev: Thanks for the clarification! After further reading about Control Blade, I think I originally misunderstood its purpose. It is a clever design that is vertically compact (more interior/cargo space) with a few other advantages. I had the impression it attempted passive rear-wheel steering such as the Mazda suspensions I mentioned.
chunky_azian says:
05:48 PM, 11/24/09
@ocramida
I don't think that designing suspension needs a heavy dosage of material science. The metallurgist job is to cook up new materials that can do what can't be done in the past. You just need to know what the materials you have on hand can and cannot do and pick the right one for the job.
Based on my machinery design class, a suspension engineer needs a solid understanding of geometry and trigonometry (where things are), kinematics (how things move, calculus is useful here) and dynamics (what make things move). You need to know vibration and finite element analysis, which tells you how things(Ford's control blade) flex.
87bonnev says:
04:26 AM, 11/25/09
Full disclosure: I am a GM chassis engineer.
Thanks to all for the interest in my profession.
@ocramida & chunky_azian:
Knowledge of metallurgy helps, since suspensions use so many different materials. chavis10 is right; generally less expensive cars have less aluminum and more steel/cast iron, since aluminum is more expensive. But aluminum is also less strong & stiff compared to steel, so the parts are larger in volume to make up for that. In general chunky_azian has it right as to what training one needs to be a suspension engineer. (My particular specialty is FEA and dynamics/kinematics.)
@jstandefer:
All suspensions (front & rear) are designed to steer slightly under cornering forces without adding steering wheel angle, as Dan mentions in his post above. Fronts are generally designed to toe out (front of wheel outboard) as tghe wheel moves up toward the body; rears the opposite, hence the shorter toe link compared to the spring link/arm. This leads to understeer at the limit of tire adhesion. Dan generally calls these features out in his walkarounds.
@94_gsr_cpe:
Wish I could help; jobs are still very tight across the auto industry. Try joining LinkedIn.com as a start, and join some of the interest groups. Many jobs are posted there.
adamb1 says:
06:28 AM, 11/25/09
"@94_gsr_cpe:
Wish I could help; jobs are still very tight across the auto industry. Try joining LinkedIn.com as a start, and join some of the interest groups. Many jobs are posted there."
Currently have opening for BSEE capable of designing electricals and programming automated assembly and test equipment. Send resume to jobs@automationtool.com.
audisport says:
12:22 PM, 11/25/09
Still cracks me up that the "Japanese" Mazda6 is assembled by Ford and the UAW in Michigan, yet the the Ford Fusion is assembled in Mexico. I love pointing that out to all of the foreign car bashers around Metro Detroit.
prndlol says:
06:15 PM, 11/25/09
87bonnev, i'm guessing your username refers to the 1987 Bonneville. Did you work on that car? I remember going to the 1987 Toronto Auto Show as a preteen and thinking the new model was a great-looking car inside and out. Qualities it lost during the '92 and '96 redos...
626gt says:
07:23 PM, 11/25/09
What happened to the Mazda - on it's initial test you recorded a .84 skidpad & a 63.2 slalom? That seems like a large change to .79 & 60.9?
626gt says:
07:29 PM, 11/25/09
What happened to the Mazda - on it's initial test you recorded a .84 skidpad & a 63.2 slalom? That seems like a large change to .79 & 60.9?
tommyz23 says:
07:25 PM, 01/16/10
You can disable the DSC on the car by holding down the DSC button for 5 seconds. The skid indicator light will come on. DSC is now disabled until you restart the car.