Cars like the 2011 Nissan Leaf, Toyota Prius and Honda Insight are all about their unique fancy-pants drivetrains, but they're supposed to be affordable, too. Experience tells us this combination produces few surprises in the suspension department.
Still, the Leaf was the landslide winner in our recent suspension walkaround poll. You asked for it, you got it. Here's the all-new 2011 Nissan Leaf in a compromising position in my driveway.
To the surprise of no one, the Leaf's front end is propped up by MacPherson struts.
The lower control arm (yellow) is of the one-piece stamped steel variety, and it pivots on two simple bushings.
The Leaf's electric-assist power steering (white) operates from behind, just as it would in any other front-drive machine with a transverse engine -- or in this case a transverse electric motor.
A long slender link (yellow) connects the stabilizer bar directly to the strut housing for a 1:1 motion ratio that extracts the maximum efficiency from the stabilizer bar.
In keeping with the mission and price point of this car, the knuckle is made of cast iron. Remember, all of the cost resides in the batteries and electric drivetrain.
The stabilizer bar (yellow) is mounted behind the steering rack, so it must bend and turn along a tortured path to arrive where the drop link can meet it.
Check out how small the locating bushings are for the L-shaped lower control arm. We can't see it, but the front one in the crook of the L is bound to be much firmer because it handles most of the lateral cornering loads. Because it's so small, it might just be a pillow ball in this case.
The rear one will be softer so it can absorb any fore-aft impacts seen at the wheel. Imagine whacking the ball joint in the foreground left-to-right with a hammer. The harder forward bush stays put and acts as a pivot, sending your hammer blow into the picture toward the center of the car at the rear bush. That's how the fore-aft component of a pothole strike gets absorbed.
Of course the up-down portion of the pothole strike gets handled by...
...the spring and damper, of course. Yes, it rained the day before I shot these pictures. Dirt everywhere.
The most surprising element of the Nissan Leaf's suspension has got to be these brakes. As you can see they are two-piston calipers. I'd have thought a car of this size and weight would have no trouble with single-piston calipers. We almost never see dual-piston sliders until we get to something the size and weight of a Ford Flex.
And that's before you factor in the serious amounts of regenerative braking afforded by the electric motor. These babies are going to be very lightly used much of the time.
Still, the brakes have to be certified without the help of regenerative braking, and the Leaf does weigh almost 3,400 pounds. Its small wheels mean small rotors, which means little leverage for the brake calipers. It may well add up. Nissan wouldn't go to the extra expense unless it was warranted.
This is a symmetrical brake casting used on both sides of the car. If you look carefully you'll see that the bleed fitting at the top has been screwed into the letter R, leaving the letter L opposite untouched to signify this as a left front brake. On the other side the L is pierced and the R is intact. The big blue inked R means something else entirely.
The slender lines indicate the pins on which the caliper slides as the brakes are pressed.
Out back, the Leaf is suspended by a simple twist beam axle.
A twist beam is one large piece that's welded together from several smaller parts. Because of this it's not a fully independent type of suspension, but we can call it semi-independent because the central beam that spans the car is designed to twist so the wheels do experience at least some independence. In reality a twist beam axle is a giant stabilizer bar with wheels on the floppy ends.
Technically, we can't call this part the stabilizer bar because the whole twist beam is a stabilizer bar, but this welded-in supplemental stabilizer bar serves no other purpose than to increase the roll stiffness of the entire twisty beam to a point where the engineers are happy.
Because the spring platform and the other welded-on bits act like huge gussets, the twist beam doesn't twist much until you venture inboard of all this stuff to where the beam is just a beam.
This bushing and its opposite number on the other side are the only places where the twist beam is located in 3D space and attached to the car. These pivot bushings, therefore, are very important.
In the interest of harshness -- the fore-aft component of impacts -- you want them soft. But if they're soft they will deflect in corners and create the dreaded roll toe-out, otherwise known as roll oversteer. Bad news.
The compromise solution everyone has adopted is this angled orientation of the bushings.
Ventilated rear rotors and single-piston sliding calipers slow things down in the rear, but the Leaf's parking brake is a cable operated drum that's hidden inside the rotor's "hat" section.
Bridgestone Ecopia low rolling-resistance tires are the standard fitment. They weigh 41.5 pounds mounted and ready to go on their cast-aluminum wheels.
We saw nothing of the Leaf's electric drive system or its batteries this time because it's all hidden by these aerodynamic belly pans. Maybe next time I'll dig out some wrenches and take a peak. I'll need a more traditional 2-post garage lift to do that justice, I think.
Dan Edmunds, Director of Vehicle Testing @ 1,403 miles
elgac says:
11:12 AM, 03/29/11
What a waste of a suspension walkaround.
actualsize says:
11:19 AM, 03/29/11
Don't fret none. I'll do all of the long-term cars eventually.
carguy622 says:
11:43 AM, 03/29/11
Actually Dan, I don't think it was a waste. Thanks for your time and hard work. I appreciate all of the suspension / engineering posts.
bodyblue says:
11:43 AM, 03/29/11
Thanks, Dan...nice as always!
tjpark01 says:
12:04 PM, 03/29/11
Boo-ring! BMW 5 series would have been much better seeing that they have ditched the struts for the new 5, for a multi-link front. Or the Equus, as you have done one for the Genesis V6, it would be nice to see the difference in the two cars built on the same platform. Who ever voted for the Leaf, what the heck did you think you were gonna see?
ufoninja says:
12:20 PM, 03/29/11
Good job Dan as always. Even though a twist beam suspension is not fancy, its nice to see how they work. Nothing wrong with looking at basic stuff from time to time.
elgac says:
12:34 PM, 03/29/11
That was not meant to be a knock against Dan.
He does a great job and was just giving what the masses want, but you can tell he could have given you this walkaround while the Leaf was parked across town.
mfennell says:
12:35 PM, 03/29/11
"Technically, we can't call this part the stabilizer bar because the whole twist beam is a stabilizer bar, but this welded-in supplemental stabilizer bar serves no other purpose than to increase the roll stiffness of the entire twisty beam to a point where the engineers are happy."
I'm having trouble visualizing how it contributes meaningfully to roll stiffness. It's a long little tube loaded (mostly) in bending rather than torsion. Its effect must be awfully subtle compared to the thick-appearing, heavily gusseted channel section connecting the two control arms. Maybe loading it in tension serves some purpose? Otherwise why not just spec a thicker beam or slightly stiffer springs and save weight/money?
In contrast to others, I find seeing the choices made in cheap cars at least as interesting as the expensive ones.
panerai250 says:
01:06 PM, 03/29/11
Those must be "leaf" springs. ;D
throwback says:
01:07 PM, 03/29/11
I wonder how much the range would increase if it had more aluminum in the suspension.
subytrojan says:
01:08 PM, 03/29/11
Great job as always, Dan!
A big reason why I voted for the Leaf is because I wanted to see how easily (or not) Dan could make it to his house given the Leaf's range.
thegrocer says:
01:20 PM, 03/29/11
Damn, that was boring...it looks just like the Mk IV bits under my New Beetles...the only even mild surprise was the dual piston front brakes.
greenpony says:
02:06 PM, 03/29/11
What's that yellow car?
vigilante_dr says:
02:12 PM, 03/29/11
Why don' t you test that Mono Tracer. I read about it being available through 21st Century Motoring for the low price of 65,000 dollars.
bankerdanny says:
03:33 PM, 03/29/11
See, I found the vented rear disk's to be as big a surprise as the 2-piston front calipers. My MkIV Jette 1.8T uses solid disks, I'm pretty sure my V8 equiped '96 Taurus SHO didn't use vented rear disks, and I know my E28 335i BMW didn't. Granted the latter 2 cars are much older than the Leaf, but both were larger performance sedans.
cjsg35 says:
04:11 PM, 03/29/11
WTB Juke walk around pretty please =)
acbayard says:
05:33 PM, 03/29/11
So basically it uses the Nissan Versa's existing suspension layout - with better brakes.
uncanny_man says:
07:58 PM, 03/29/11
You know, these kinda posts are quickly becoming my favorite part of insideline. Thanks Dan.
thegrocer says:
08:51 AM, 03/30/11
Brakes are definitely the only surprise here...must have had to spec something that will stop it unassisted in a strictly hydraulic pressure only scenario.
blueprint1 says:
09:40 AM, 03/30/11
To show how greenies don't know zilch about cars, you can read their comments in blogs to the effect that electric cars won't cost a thing to maintain. Electric cars are heavy, and thus require beefier brakes that will be more expensive to maintain. Ditto for suspension parts and bushings, supporting the weight of a midsize car.
Oil and filter changes are just about the only economy.
Dan, it would be interesting to post on the required Leaf service as per the owner's manual.
mfennell says:
11:37 AM, 03/30/11
The brakes are compensated by the regen capabilities the electric motor provides. I understand brakes on the Prius last forever and it has relatively weak regen. I don't see why the suspension components are such a problem as long as they're sized for the job. My 4000lb Jaguar seems no more unkind to them than my 2600lb E30 BMW.
I think EVs will prove to be pretty cheap to operate although modern cars are so maintenance free it may be in the noise, at least in the mid term. An electric drivetrain IS far more simple than a typical (and sometimes glorious) ICE. In the longterm, there's just far less stuff to wear out.
Replacing the battery is the gorilla in the room. It's hard to say how it will all work out.
The only scheduled maintenance related to the electric drivetrain on a Volt is changing the battery and power electronics cooling fluids @ 150k miles.
langjie says:
01:54 PM, 03/30/11
wow, 205 tires? I'm surprised they don't use prius-like 185's
cz_75 says:
11:52 PM, 04/ 7/11
How about a John Deere lawn tractor next? A vehicle that actually does something with its suspension would be of interest, but an appliance on wheels not so much.
nissanmasttech says:
03:26 AM, 04/ 8/11
Nothing new here, all these parts are right off the shelf. I expected to see more aluminum.
bodyshopboy says:
03:27 AM, 04/ 8/11
Nice walk around. Bit of a let down since there were no exotic electric drive train parts evident. I'd love to see it with the belly pans off. Might be just as few surprises, but who knows?
rick8365 says:
10:11 AM, 04/ 8/11
"I'll need a more traditional 2-post garage lift to do that justice, I think."
Are you listening, Mrs. Edmunds?!? :-)
dorikin_86 says:
12:32 PM, 04/ 8/11
Thanks Dan!
As much as I enjoy reading about the MP4-12 and SLS - this is quite interesting to read too.
Engineering a paper pin is harder than a 747 because of the price point - You can learn a lot from something 'economical'....if you can call the LEAF that...
pei_asdf says:
10:26 PM, 04/ 8/11
Great walkaround. I am not familiar with car's mechanical parts beside what they are for so it is great for me to read your suspension walkarounds. I have learned a lot from those articles. I didn't even know twist beam existed until this article. Thank you.
juan_mx says:
07:12 AM, 04/ 9/11
Looking at that lower control arm makes me realize how mechanical design has changed over the years. The Leaf's arm is a single piece of stamped steel and the ball joints are an integral part of it, no bolts.
20 years ago a VW Golf (2000lb) had a lower arm made of several stamped parts welded together and the lower ball joint was attached with three bolts.
cah11705 says:
02:56 PM, 04/ 9/11
Suspension walk around's are always interesting, but this got me thinking. Was there ever a walk around of the Z06?
omairkhanzada says:
11:34 PM, 04/ 9/11
Should've done a LF-A walk around!
tdiluv says:
04:51 AM, 04/10/11
Nice walk around article, can you do the Aventador some time?
morrisg2 says:
11:46 PM, 04/10/11
@greenpony: the yellow car looks to be a mid-50s Ford wagon of some sort, based on my memory of the tail lights. Yeah, I'm ancient.
I'm really surprised at the two bushings locating the front lower control arm! That just seems to be a little too cheap for me. Or else it really works well and is a sign of things to come, like all the new cars using twist beam rear suspensions. I was really a fan of the Datsun 510 when it came out with IRS in a low cost sedan. Uh, sorry, ancient again...
gasfreeleaf says:
07:55 AM, 04/13/11
Dan, I learned a lot from your professional observations. Thanks for your work and expertise.