You never got to see the Lambda-platform underpinnings of the 2008 Buick Enclave we used to have in the fleet because, at that point, I hadn't yet begun my suspension walkaround series.
No problem. Our 2010 Chevrolet Traverse gives us another chance because it also rides on the same Lambda platform, as do the GMC Acadia and discontinued Saturn Outlook. And prototype examples of a yet-to-be-released Cadillac Lambda SUV are almost certainly running around behind the fences of GM's various proving grounds.
All of this means the Lambda platform is still very relevant. Let's have a look.
The Lambda platform is a front-drive architecture with a transverse-mounted engine and transmission. So it's no surprise that our 2010 Chevy Traverse rides on MacPherson strut front suspension.
Like almost every front-drive chassis out there, the Traverse's rack and pinion steering (green) does its work from behind the front axle centerline. Further out, the front wheel bearing rides within an aluminum front knuckle (yellow).
Here's another view of the same components.
The front stabilizer bar connects directly to the strut housing via this slender link. It connects to a point high up on the strut so there's no interference as the strut sweeps left and right during steering maneuvers.
Those two bulges in the brake caliper (green) make it easy to tell these are 2-piston sliding (aka floating) brake calipers. And check out how taut the brake hose is when the suspension is at full droop and full left lock. That's an admittedly uncommon circumstance, but it still looks like they've used no more material than is absolutely necessary.
Here you can clearly see that the lower control arm is made of two pieces of stamped steel that are welded together.
Here's another look at the dual-piston brake calipers and their ventilated rotors.
Multilink suspension is used in the rear. Here we see an upper link (yellow), a toe link (green), and a lower arm (orange). But this doesn't look like enough links to keep the wheel pointed properly. What's missing?
Before we find out, have a quick glance at the rear brake hose which, like the front, is no longer than it needs to be.
And here's your missing link. The lower aluminum arm (orange) that looked like an A-arm in the last picture is really an H-arm. But the stray leg of the H in the foreground does not connect to the knuckle. No, it connects to a slender vertical link (white) that connects to the knuckle at the top.
GM calls this a "linked H-arm", and since that seems descriptive enough, we'll roll with it.
Here's what's going on: The background leg of the H connects to the knuckle at a single point, like an A-arm would. So far so good. Since the free end is not connected to the knuckle, the toe-link (green) can apply torque to the knuckle to add dynamic toe-in without binding any of the bushings. The vertical link that's connected to the free end of the H absorbs the torque reaction cause by braking and, in AWD models, acceleration.
This angle shows this last point a bit more clearly.
The rear leg of the H-arm (white) connects directly to the knuckle. The front leg of the H (green) connects to the vertical link, and this allows the shorter toe link (yellow) to pull the front part of the knuckle inwards as the body rolls for a stabilizing dose of toe-in without causing any binding the neighboring bushings; the top of the link simply shifts left and right slightly to absorb this motion. But the link's vertical rigidity absolutely keeps the knuckle from rotating during accel and braking.
Meanwhile, the upper arm (yellow) is far enough above the tire's contact patch that it doesn't have to exert much effort to hold the top of the knuckle at the proper camber angle. That's why it can have this curious shape cut from a flat piece of steel.
This overhead view shows how the upper camber link and the vertical link share a common pivot axis and mounting bolt.
The aluminum H-arm carries the coil spring and bump stop about 60% of the way out from its inner pivot point. The shock absorber mounting bolt, just visible in the background, connects to the other leg of the H at more or less the same 0.60:1 motion ratio.
Don't worry too much about the bent appearance of the spring. This straightens out somewhat when the car is sitting on the ground and the suspension is compressed to the neutral position. Things get pretty parallel when the suspension compresses further with additional load.
Single-piston sliding brake calipers and ventilated rotors take care of rear braking.
Our Traverse is a 2WD model, so of course its rear hubs don't have any drive axles poking through the center.
Our Chevy Traverse rides on these optional P255/55R20 tires. Sure they look "better" than the 18s, but the ride is nowhere near as smooth and compliant as our departed long-term Buick Enclave, which rode on 18" rims and higher-section tires. OK, some of that has to do with the Buick ride tuning philosophy, but we can't ignore the fact that these tires have less sidewall and they weigh a full 71 pounds when mounted on their heavier "dub" rims. Maybe we should re-insert the letter "m" into that nickname.
Dan Edmunds, Director of Vehicle Testing

drhorrible says:
05:16 AM, 07/ 7/10
The 1st picture looked like what you would see if you parked overnight in metro Chicago except the tires wouldn't be there and the jack stands would be cinder blocks.
vvk says:
06:19 AM, 07/ 7/10
Nice. That rear multilink is why these wagons ride and handle OK despite their size and bulk. I recently drove an old Mercedes W201 (190) that was the first car with this kind of IRS and both ride and handling were absolutely fantastic. W201 came out in 1982.
bodyblue says:
07:04 AM, 07/ 7/10
20" wheels are stupid enough, really stupid on a family car......18 is quite big enough for anything not going for the gangsta look. AND they weigh 71 freaking pounds! 20" inch wheels and a, what, 140 MPH speedo in a family hauler that will never go past 80, 99.9% of the time? Car makers play to the lowest common denominator ...not just GM also.
cello_one says:
07:50 AM, 07/ 7/10
Question: how does the H arm and spring/shock arrangement on the Traverse compare to the Flex, with its in board shocks?
I agree on the 20", even on a LARGE wagon like the Traverse, 18s look like they feel the wheel wells just fine.
breadwagon says:
08:42 AM, 07/ 7/10
wow, I'm surprised by the amount of aluminum that is used (front knuckle and rear H-arm). I was expecting 100% bulky heavy steel like the front lower control arm. It's actually quite impressive. Kudos to the lambda platform!
hybris says:
10:21 AM, 07/ 7/10
Those are some wide tires especially for a crossover.
dgcamero says:
02:52 PM, 07/ 7/10
I thought the ride on the FWD Traverse with 18's I had as a rental was nausea inducing (couple of friends agreed). The rental AWD Acadia I had with 19's rode just right though. I wonder if the ride would be just right on a Traverse with 19's?
bimmerjay says:
07:29 PM, 07/ 7/10
The 20" wheels are particularly stupid because they're an inexpensive cast wheel - hence the massive weight. It's the only way to have gigantic dubs like this on a family SUV. And it comes at the cost of ride quality and fuel economy. Proper lightweight forged 20" wheels would cost thousands more and the moms and dads buying these things would balk at that price.
stovt001 says:
10:38 PM, 07/ 7/10
Sure it is rebadged half to death, but the Lambda platform is a homerun for GM. This is excellent stuff, especially the use of aluminum.
@drhorrible: thieves in Chicago are thoughtful enough to leave it on blocks? That's nice. Around here, they'll drop it to the ground when they're done.
87bonnev says:
06:11 AM, 07/ 8/10
DISCLOSURE: I am a GM suspension engineer who worked on this vehicle.
Nice write up, Dan. Only one minor correction; all the steel links in the rear suspension are forgings, including the camber link. (It would be very hard to cut or stamp a piece that thick.)
I tend to agree with all the comments on bigger wheels/shorter sidewall tires not riding as well. But people like the look, so we make them. (I personally think the 18" wheels ride and look just fine.)
narg says:
12:55 PM, 07/12/10
87bonnev,
I LOVE my Traverse. Thanks so much for the great engineering.
I have to comment on the 20" wheels though. Yes, they look great. But I'm over 40 and ride is more important to me now than looks. I wanted an LTZ model, but did NOT want the 20" wheels. I think it's great GM offers them, but to force them on buyers is bad. Especially the older buyers who will most likely be able to afford the LTZ who would prefer ride over looks. GM really messed up on this one. I ended up with an LT2, and still miss the features that the LTZ would have provided.
87bonnev says:
09:45 AM, 07/13/10
DISCLOSURE: I am a GM suspension engineer who worked on this vehicle.
Thanks for the kind words, narg.
I tend to agree with you re: ride versus looks. Another example is the Lacrosse CXL vs CXS. The CXS is the more "luxurious" version and comes with the 19" wheels and tires, while the CXL has 18" wheels and tires. I happen to think the 18"s look fine, but do agree that the 19"s look "better". But in pothole-plenty SE Michigan, those 19"s not only ride worse, but are much more likely to be damaged too. (I know several BMW owners who have had multiple sets trashed on our lousy roads. Admittedly, not much of an issue in SoCal.)
One might think it would be easy to just swap out the 20" wheels on a Traverse for a set of 18"s. However, we do customize ride tuning to match the tire, so an LTZ with 18"s may end up riding worse than with the 20"s. (Keeping in mind that ride quality is VERY subjective.) But wheel/tire packages vs. trim level quickly descends into marketing, where most of us engineers fear to tread. Maybe your local Chevy dealer would be game to letting you try this out?
I will forward your request (18" tires & suspension tuning available with LTZ package) on to Chavy marekting, since based on these threads there does seem to be a demand for it. But I am sure somebody from Chevy is checking these posts anyway; contrary to what many of the posters here seem to believe, we do take these kinds of tests seriously.
09trvslt1 says:
07:16 PM, 08/12/10
I added 20 to my Traverse and can't say I notice the change. What I would like to see is trim levels disappear and all options a la carte. Solid color interiors should be available on the LTZ you pay extra so you should get a real interior option. I'd love to see the brick color added to Traverse and brushed aluminum to the dash...oh what the hell just put the acadia's dash in the Traverse (come to think of it I might do that). Power hatch should be standard. Factory DVD added to the accesories catolog.