
Tesla Model S Suspension Walkaround - dmmalam
http://www.edmunds.com/car-reviews/track-tests/2012-tesla-model-s-signature-performance-suspension-walkaround.html
======
becauseracecar
Car suspension tuning is a very subtle and difficult black art. It's all about
what's happening dynamically in response to transient inputs (go around a
corner, hit a bump, etc.).

I believe Lotus does a lot of engineering consulting helping other
manufacturers dial in suspensions. I wouldn't be surprised if Tesla had them
consult.

Even some of the big car companies have trouble dialing in suspension on their
own (I'm looking at you underdamped Japanese cars). European brands tend to be
really good at this, and can take the same raw materials that everyone else is
working with and create superior setups. Porsche somehow manages to start with
the 911 where they stick the engine way out behind the rear axle (high polar
moment of inertia, poor front/rear weight distribution) and make it handle
beautifully. VW cars also tend to have great suspension tuning. Being able to
keep the weight low to the ground in the Tesla contributes to a low center of
gravity and I imagine must really help enormously.

Also the body under-tray is beautiful, like something you'd expect to see on a
purpose built race car, probably helps a lot with the aerodynamics. I imagine
more and more cars will get similar under-trays to improve aerodynamics and
fuel efficiency.

It's interesting there is strong anti-dive geometry built into the car,
probably to avoid problems with throttle lift oversteer caused by
inexperienced drivers. I wonder if the current Model S handling leaves
anything to be desired when driven to it's absolute limits and how the car
would handle with some of the anti-dive geometry removed. Removing this
geometry is a common mod on some cars.

~~~
josephlord
"Porsche somehow manages to start with the 911 where they stick the engine way
out behind the rear axle (high polar moment of inertia, poor front/rear weight
distribution) and make it handle beautifully."

Actually there are some benefits to the arrangement. The high polar moment of
inertia actually should make any spin slower to start and easier to catch than
a mid engine arrangement. Under hard braking the weight shifts forwards so the
weight distribution changes to more balanced than with other arrangements.
Under power the weight is over the rear wheels for power out of the corner.

A 911 behaves differently to other cars but I'm not sure the arrangement is
actually worse in most dynamic scenarios. Understeer into the corners is the
main dynamic weakness when pushed really hard and can be compensated for by
trail braking into the corners. I guess you can get into trouble if you go
into a corner too fast, panic brake and lose the rear end but if you are used
to the set up you can make use of it.

[I've only driven a 1980's 911 so maybe I'm over extrapolating to all rear
engined cars and I've never tried a mid engined car. This book is really good
at explaining how do get the most out of different weight distributions and
has some fun stories (I've got the first edition but it probably isn't much
different): [http://www.amazon.co.uk/Porsche-High-performance-Driving-
Han...](http://www.amazon.co.uk/Porsche-High-performance-Driving-Handbook-
Elford/dp/0760327548)]

~~~
beachstartup
i've owned an NA2 NSX and a 997 911 GT3 and the NSX was much easier to lose
control in. it felt unstable in general.

911 grips harder as you turn harder, very strange to get used to but once you
'get it' it feels great. obviously there is a limit but you are not going to
hit it on the street in a car like a 911.

i haven't driven any modern mid-engine cars like the R8 or boxster though, i'm
sure it's vastly improved from the NSX, which was basically designed in the
80s, so no fault to it. it was a great car. can't wait to see the new one.

right now i drive a performance sedan but my next car will be a "regular" 911,
probably a 991 S.

as for the tesla... eh. doesn't give me that "gotta have it" feeling. i still
want gasoline and a clutch. call me old fashioned.

i would be interested to know the % of current tesla owners that have ever
owned "real" sports cars, not just "sporty" cars. it doesn't strike me as the
same crowd.

~~~
dbrian
Definitely not the same crowd. It's still a 4 door sedan. They're competing
against the Panamera not the GT3.

~~~
beachstartup
also, my current car is an E63 AMG PP, that's the crowd i was comparing, i.e.
me.

------
dmmalam
For comparison the McLaren MP4-12C [1] has probably the most trick setup you'd
see this side of a early 90s Williams F1 car [2][3]. Notice on the 12C how the
rebound/compression dampers from each corner are cross connected instead of a
roll bar, and the z spring at the back to resist high downforce.

Considering the Williams F1 active system was developed for the 1992 season,
I'm kinda disappointed that no fully active system has ever hit a production
car. The best we've seen is active damping on several cars. Bose had a pretty
cool prototype [4], but never hit prod. The neat thing about electromagnetic
damper/springs is that they can regen for a EV.

If your unfamiliar with car mechanics, then this is a good serious of short
video tutorials [5].

[1] [http://www.edmunds.com/car-reviews/track-
tests/2012-mclaren-...](http://www.edmunds.com/car-reviews/track-
tests/2012-mclaren-mp4-12c-suspension-walkaround.html)

[2] <http://vimeo.com/22195303>

[3]
[http://scarbsf1.com/williams_active/WilliamsF1_ACTIVE_SUSPEN...](http://scarbsf1.com/williams_active/WilliamsF1_ACTIVE_SUSPENSION_SYSTEMS.htm)

[4]
[http://www.bose.com/controller?url=/automotive/bose_suspensi...](http://www.bose.com/controller?url=/automotive/bose_suspension/index.jsp)

[5] <http://www.youtube.com/playlist?list=PLE067A7397E1AF108>

~~~
ricardobeat
Ah, I remember seeing the Bose videos and wondering when it would hit the
market. I'm also waiting for those airless spoked tires!

Mercedes and BMW have their own active suspension systems that are standard in
the high-end models, not sure if they look as magic as Bose's.

~~~
dmmalam
Pretty much all systems marketed as 'active' aren't really 'fully active'.
Remember from mechanics/Differential Eqns, a suspension system is basically a
damped harmonic oscillator. The two main constants are the springing and
damping. The majority of cars just have electronically variable dampers. ie
the same oem parts from bilstein/dephi/bosch with some silly marketing acronym
on like Porsche PASM, MagneRide etc.

Some have variable strength roll bars, but roll bars are really just a 'hack'
anyway. Very few have used a variable springing system (Merc ABC). An air
suspension can change springing and ride height, but's it's slow.

In addition to low latency damping/springing adjustments/ride height, a fully
active system in able to apply force into the suspension so the attitude of
each corner is under complete software control, milli by milli. You can have a
perfectly smooth ride, but no roll. All current non-active designs are a
compromise between sporty and confort (high vs low springing/damping
constants, and movements in attitude due to
accelerating/braking/downforce/cornering/road surface.

The main problem with fully active is that it uses quite a bit of power and is
very complex. Here's some more info
[http://www.autozine.org/technical_school/suspension/tech_sus...](http://www.autozine.org/technical_school/suspension/tech_suspension3.htm)

------
heironimus
Everybody thinks this is cool, but nobody (myself included) knows enough about
car suspensions to comment!

~~~
untog
I think it's a symptom of "Tesla = auto upvote on HN" syndrome. If this had
been "Ford Focus S Suspension Walkaround" (or "Porche 911", for that matter) I
doubt we'd be seeing it on the front page.

~~~
enraged_camel
If all of your comments are this impressive, I guess I'm going to have to go
with "untog = auto downvote" from now on.

~~~
chollida1
I'm not sure your comment was all that appropriate.

I think untog's comment is spot on. There are lots of stories that seem to get
upvoted for reasons other than their own merit.

Pointing that out in this case is probably appropriate.

~~~
damon_c
He should have used a "==" though...

Edit: Oh wait sorry no... I suck!

------
S_A_P
When I look at this, I cannot how complicated it must be to build a world
class automobile. Its all the more impressive that this is the first ground
up(vs the roadster being an electric Lotus) car from a start up. Impressive
indeed!

~~~
thoughtsimple
More or less what I was thinking while reading the article. How do you even
staff up for something like this? I guess a lot of recruiting in Detroit or
something.

~~~
krschultz
"Huibert Mees is the Chassis Systems Technical Fellow responsible for the
design and engineering of the Model S chassis systems. He joined Tesla from
Ford Motor Company, where he was responsible for all the chassis systems and
vehicle structure of the Ford GT supercar. Huibert has been working in the
automotive industry for over 20 years, and was responsible for the rear
suspension design of the Lincoln LS and Jaguar S-type as well as numerous
advanced chassis design concepts at Ford."

Both SpaceX and Tesla are largely built on skimming the superstars out of the
entrenched players. There are plenty of people that are _really really_ good
at their jobs at Boeing, Lockheed, Ford, General Dynamicsm, etc. They are
generally underpaid, undervalued, and given little freedom relative to their
skillset. But they stick around in those companies because that's where you
have to be in order to work on really cool stuff like the Ford GT 40 or a
space rocket.

Tesla and SpaceX offer the same cool stuff to work on, without the crappy low-
value coworkers that never get fired, legacy systems holding you back, and the
opportunity to do things as you believe they should be done.

This is part of why the old companies will have a hard time noncompeting. Not
only are SpaceX and Tesla disrupting their business, but Elon Musk is stealing
from their top tier talent pool that could defend against disruption.

~~~
tocomment
How specifically did he recruit them? Did he just show up at the factory one
day? (I'm really interested in the detailed logistical steps of how one starts
a brand new car company)

~~~
revelation
If you want to take Tesla as an example for how to start a brand new car
company:

1) Spend 6 years at an insanely high burn rate with zero revenue for research
and development to create a marketable car

2) Have enough brand loyalty to delay delivery to your high-earning clientele
multiple times

3) Hustle Daimler into investing to do payroll at the height of the financial
crisis, with Daimler themselves having no money

4) Hustle the DOE into funding your fully electric sedan while having only a
taped together basic model to show for it, with your competition (Toyota)
being granted billions just to refit a factory

~~~
nijk
5) design and build and deliver a car.

------
nwhitehead
Reading about suspensions reminds me of the inerter (J-damper) [1] used in F1
racing. It was discovered by analogy with electrical circuits; it was the
missing mechanical part corresponding to a capacitor.

[1] <http://en.wikipedia.org/wiki/Inerter_(mechanical_networks)>

------
alimoeeny
So HN Tesla owners, how happy are you with the car itself, not considering the
ideas behind electric cars and what not, just with the car and driving
experience and charging, worrying about running out of juice ...?

~~~
tlb
It's fantastic. Best thing I've ever driven, regardless of environmental
impact. It's silent and odorless, responds instantly and precisely, and it
seats 5 adults + 2 kids comfortably.

A niche benefit: I live in the mountains and it handles going down much better
than gas cars, where you have to downshift and use engine braking to avoid
burning the brakes. It uses 12 miles of range going up, and gains 4 back going
down so the average is close to a flat road of the same distance.

~~~
laacz
5 adults + 2 kids comfortably? In a car with max 5 seatbelts?

~~~
nathanm412
It has connection points to fit rear facing child seats in the rear storage
compartment.
[http://www.teslamotorsclub.com/attachment.php?attachmentid=7...](http://www.teslamotorsclub.com/attachment.php?attachmentid=7839&stc=1&d=1342467308)

~~~
BHSPitMonkey
1\. Attach seats

2\. Don't get rear-ended

~~~
chiph
It's almost certainly safer than the late 1960's station wagon we had when I
was a child, with the backwards-facing seats in the cargo area. The rear
crumple zone on it was everything behind the axle.

<http://www.youtube.com/watch?v=siT-SIfOnQw>

------
stephengillie
Those batteries sure take up a lot of space. I wonder what their physical
volume is -- compared to a 15 gallon gasoline tank.

The slide-out brake pads are a neat idea, but I'm wondering why, as the
caliper still has to be removed during a brake change to pull off the rotor.

Those aluminum pieces can't be cheap. Neither can the 4-piston brake calipers.
Nor the armored underbelly. It's definitely performance-oriented.

~~~
peterwwillis
About 26,472 cubic inches. Fifteen gallons is 3,465 cubic inches. (Taking the
wheels off, if the car were rectangular its dimensions would result in around
696,581 cubic inches of volume, so the battery pack takes up about 3.8% of
that)

Rotors don't have to be changed as frequently as pads. It's probably a lot
easier this way vs dismantling the whole thing.

~~~
stephengillie
Thanks for that info! So the batteries take up about 9 times as much space as
a gas tank?

If you do not replace the rotor when you replace the pads, a machine shop has
to grind the rotor, so its surface will be flat to work effectively with the
new pads. If you don't, the pads won't make full contact with the rotor, and
maintaining the brakes would make them operate _worse_ until they wore in.

~~~
cincinnatus
Brakes in electric cars receive vastly less wear than conventional vehicles,
feels like literally an order of magnitude. They really only come into play at
all during final stopping and emergency braking. The separate parking brake
design on the Tesla is an interesting related detail.

~~~
stephengillie
Interesting -- so braking system consumables should last ~4 times as long as
on a fossil-fueled car?

~~~
cincinnatus
In my experience so far (Prius, 110000 miles) it is more like 5x. And the
Prius brakes are tiny things, especailly compared to the huge brakes on the
German cars I've owned in the past. The Tesla S is comparable to them in
weight and handling, and the brake system looks comparable too. From the
testing and reviews we know it has excellent stopping distance, so it looks to
me like the best of both worlds. I wouldn't be surprised if it gets 10x the
lifetime out of brake pads, depending on driving conditions of course.

------
Moto7451
They have a Model S sans bodywork (just the lower frame, drivetrain, and
suspension) at the Tesla Store here at the 3rd Street Promenade in Santa
Monica. If you get a chance to stop in a Tesla Store, it's definitely worth it
to see the intricacies of the suspension.

------
DEinspanjer
Pretty pictures, but I just like how I can push the buttons on my screen and
make the car go up and down. ;)

Actually, when I first read this doc a couple of weeks back, it showed me the
reason for something I had noticed. If I have my foot on the brake while
changing the suspension level, I've noticed that when I let off the brakes,
the wheels shift a bit. Turns out that for the front tires, it doesn't lift
and lower straight up and down. There is a bit of horizontal motion as well.

------
GotAnyMegadeth
First thought was "Tesla have finally built an electric AT-ST!"

~~~
toomuchtodo
Whoa. Whoa. Whoa. Mars first, _then_ the electric AT-ST.

~~~
omegant
You really need a AT-ST for mars exploration.

------
jleader
"21x8.5 inches +40mm" on the wheels. Gotta love the auto industry's ambivalent
relationship with the metric system! Too bad they didn't try a little harder,
they probably could have expressed one of the dimensions in micro-furlongs.

------
tocomment
Why is the regenerative braking limited to .25g? Even if they can't charge the
battery faster than that, couldn't they dissipate the extra power some other
way?

~~~
dmmalam
Some electric trains actually do this, they dump the energy as heat in a bank
of resistors. The motor on a tesla is on the rear axel, but most braking power
is dissipated from the front axel due to the weight transfer. The question is
if you also had a front axel motor (like the Model X), how much regen could
you do. I remember reading somewhere that induction motors don't regen that
well at low RPMs, hence you need to supplement with friction brakes. Anyone
with a better understanding care to comment; would it be possible to build a
car with no friction brakes, just 100% regen? I suppose you could always apply
a counter torque to the motor.

~~~
jstanley
"would it be possible to build a car with no friction brakes, just 100%
regen?"

No. The force provided by regenerative braking is proportional to your speed.
Without friction, it would be impossible to reach 0 speed.

~~~
dmmalam
So the regen force would still exist (?), just it would be really small, and
so taking a long time to fully stop. Would it be possible to apply a reverse
torque to the electric motor to decelerate faster. For example, I'm thinking
about a hypothetical race car that could have no traditional hydraulic braking
system to save weight, a large amount unsprung.

------
NDizzle
I'll never look at my Galant VR4's suspension the same again. I knew it was
old and bad, but this really drives that point home.

------
cake
Pretty amazing yet totally normal not to see any exhaust system that I'm used
to see on every car ;-)

------
deadfall
Has anyone wrecked one of them yet? I bet trying to get it fixed would be
ridiculous.

~~~
pyre
How much would Google self-driving car equipment reduce the time between
charges? I imagine that such a system would mean fewer accidents.

