This time it's the 2011 Acura TSX Sport Wagon's turn for the suspension walkaround treatment, the first one shot in my new driveway.
As we go along, take a moment to refer back to the 2010 Honda Accord Crosstour walkaround. Apart from the TSX's obvious lack of AWD, there are many similarities in the overall suspension layout and the basic look of the various bits and pieces. Some of the parts may in fact be shared, but it's quite likely that many are not.
That's because the TSX Sport Wagon is smaller and more svelte than a Crosstour. Our TSX Wagon is 2.3 inches narrower, 7.8 inches shorter (less tall) and 7.4 inches shorter (less long). Its front and rear track widths are 2.7 inches narrower and it rides on a wheelbase that's 3.6 inches shorter. Our Sport Wagon weighs some 282 pounds less, too.
Let's take a look.
Just like the Crosstour, the TSX benefits from double wishbone front suspension. The upper wishbone (white) is a high-mount A-arm, while a forward-facing L-shaped arm (green) does the business down below. A coil-over spring and shock assembly (orange) keeps it all suspended at the proper height.
Sometimes this type of coil-over is mis-identified as a strut, but that's utterly incorrect. A strut is a specific type of beefy shock absorber that also locates and secures the upper working end of the suspension, doing away entirely with the need for an upper arm. Here, with an A-arm doing the location management, this shock absorber is just a shock absorber, a non-locating suspension member that literally puts a damper on things lest they get out of hand. The fact that it carries the spring, too, is not the defining characteristic that would make it a strut.
The TSX uses a forward facing L-shaped lower wishbone/control arm. Lateral loads are taken up by a fairly rigid rear pivot bushing at the crook of the "L".
A softer forward bushing absorbs the fore-aft component of things like pothole strikes, which come into the control arm at the ball joint (black). That force amounts to a torque that pivots around the harder rear bushing, sending the energy to the forward bushing as a momentary lateral deflection.
The upper arm can be made of thinner material on account of the leverage afforded by its high-mount position. As is customary, its pivot axis inclines up in the direction of the front of the car to enhance anti-dive characteristics under braking.
Like nearly all front-drive cars with transverse-mounted engines, our TSX settles for steering that comes in behind the axle centerline. The engine and transaxle occupy the space ahead, resulting in a strip of available space between the engine and the firewall.
We're peering down into that space from the engine compartment, and what we see is a rack-and-pinion unit with electric power assist working directly on the rack itself. This is preferred from a driver's perspective, as the shafts and u-joints of the steering column itself retain a bit of unmasked mechanical feel.
This is also a better way to go for durability because the assist is downstream of the rack and pinion mesh point. Column-mounted EPS acts upstream, resulting in high loads on the gear teeth as the full brunt of the power assist feeds through the pinion teeth.
Lightweight cars can get away with column EPS because the assist loads aren't terribly high; something like a Ford F-150 has far higher steering loads and must use rack-mounted EPS.
The coil-over shock absorber employs a fork (yellow) that splits the load path in two and diverts it around either side of the drive axle, terminating at a bolted joint at the lower control arm. The connection itself sits inward from the lower ball joint, which results in a motion ratio for the spring and shock that's something less than 1-to-1 from the tire's perspective. Looks to me like it's 0.7-to-1 or thereabouts.
The TSX's stabilizer bar link connects to the lower arm (yellow) at a point even further inboard than the spring and shock. An apparent motion ratio of 0.45-to-1 results, which means the stabilizer bar itself (green) is thicker and heavier than it would otherwise need to be for the same roll stiffness if it had a motion ratio closer to 1-to-1.
Engineers know this stuff very well, but packaging considerations oftentimes run the show.
Press on the TSX's brake pedal and you'll be squeezing one-piece ventilated cast-iron brake rotors with single-piston sliding brake calipers.
In case you're new to the walkaround, here's the skinny on sliding (aka floating) brake calipers. Basically, the hydraulic piston rides inside a caliper body that slides on two pins. Little bellows keep the sliding surface clean and retain the grease within.
When you press on the brakes the piston is hydraulically pushed out (yellow) against the inner brake pad, which promptly contacts the inner face of the rotor. At this point it can go no farther, so the floating nature of the caliper and the principle of "every action has an equal and opposite reaction" conspires to send the caliper body itself in the opposite direction (black) instead.
But the caliper body has fingers that wrap behind the outer brake pad, and before long these pull the outer pad up against the outer face of the rotor. In case you lost count this is the point at which both pads are gripping the rotor, the point at which braking begins
All of this happens very quickly because the clearances involved are tiny; the two-step nature of the process is not readily apparent in most cases. The lion's share of the sliding happens gradually over time as the pads wear down and the at-rest position of the caliper shifts inward.
The TSX's rear end rides on a multilink setup. An upper A-arm locates the top while two lower links (black and green) locate the bottom. A short toe link (white) keeps the wheel pointed in the right direction.
This view from below shows how the two lower links (yellow and green) approximate a lower control arm. Also, the shortness of the toe link (white) relative to the rear lower link (green) is there to create a stabilizing dose of roll understeer. When compressed together the toe link's tighter arc pulls the front of the wheel inwards, a trait that is especially useful when the outer tire's suspension loads in a corner.
The rear stabilizer bar (green) comes in from behind to meet up with its short drop link.
Another view of the same stuff, but here the aluminum knuckle is more visible.
We haven't been able to clearly see the attachment points for the coil-over shock (yellow) and the stabilizer link (green) and this view is only slightly better. The important thing to note is that both connect directly to the aluminum knuckle, which means they move in lock-step with the tire at a 1-to-1 motion ratio.
Also, the toe link (black) sports an eccentric cam on its inner end for easy toe-in adjustments.
The coil over mounts high in the fender, which means it needs a pretty big shock tower to live in. This isn't a bad plan for a sedan, but it takes a bite out of cargo space in a wagon. It's no wonder the Acura TSX and Honda Crosstour suffer a bit in the cargo department.
Solid cast-iron rotors and a single-piston sliding caliper handle the stopping chores at the back end.
The rear brakes are of course hydraulic, but the parking brake function is energized by a cable and lever (yellow) that actuates the piston mechanically.
Hey, look -- I found my scale. The TSX wagon rides on 225/50R17 Michelin tires that come mounted on 17-by-7.5-inch aluminum alloy wheels. Together they weigh 46 pounds -- about average for OE hardware in this size.
The term "Sport" in the name raises expectations in the minds of some enthusiasts. The 2011 Acura TSX Sport Wagon is not something you'd want to autocross, but its suspension works from a design and concept standpoint. As is, it's a comfortable and well-mannered wagon that is fun and entertaining to drive in the civilian sense. A set of stickier tires and perhaps some mild aftermarket tuning bits would likely make it come alive.
Dan Edmunds, Director of Vehicle Testing
eclogite says:
04:50 AM, 08/24/11
Interesting and informative as always. Thanks Dan! I really like your techincal blog posts.
vvk says:
06:48 AM, 08/24/11
Thanks, Dan!
So, where did the money go? I don't see anything here a $10k econobox wouldn't have. No aluminum, no trick bushings...
actualsize says:
08:05 AM, 08/24/11
The very fact that it has double-wishbone front suspension and multilink rear suspension puts this a couple of classes above a typical el-cheapo econobox, a class of cars that almost always rides on a combination of front struts and a twist beam rear axle. Other money has been spent on interior trim and equipment that's also a few notches better than the low end.
titancrew says:
08:10 AM, 08/24/11
@vvk,
Really? How many $10k econobox have double wishbone front suspension? or even an independent rear suspension? Only a few 25k mid-sized sedans have double wishbone front suspension (Accord, Mazda6, Fusion). Even the 30k Regal don't have it.
blueguydotcom says:
08:20 AM, 08/24/11
Drove a TSX last weekend. Hadn't driven the new model yet. Not bad. I had just piloted a Regal Turbo with substantially more HP and I'd take the TSX over it in a heartbeat. The suspension, drive, etc wasn't exactly sporty but it was engaging enough. And boy is that 2.4 a smooth engine. Night and day from the crappy 2.5 in my Mazda.
juan_mx says:
08:21 AM, 08/24/11
Thank you Dan!
As you say, it looks very similar to the Crosstour, but it is missing the dual piston calipers in the front, and the rear brakes are also different, in the Crosstour they have a parking brake drum, and in the TSX the parking brake cable moves the piston (is it cheaper?).
I agree to some degree (not in the $10k) with vvk, it does not look very expensive looking from the bottom, I wonder if the regular Accord has the same bits underneath.
And....sorry to insist again....Any chance to do the 2011 Jetta TDI?
fordson1 says:
09:31 AM, 08/24/11
Agree on the double wishbone front - nice setup.
The multilink rear is a bit more common - you can find an aguably better one than this in a ten-year-old Focus.
The brakes...looks like the typical Honda underwhelming brake setup. $35k is getting kinda high for vented fronts, solid rears, with single-piston floating calipers at both ends.
My GTI has the same caliper setup, but bigger rotors front and rear...and it's about 450 lbs. lighter.
church123 says:
11:46 AM, 08/24/11
Fordson1,
I think if you look at the historical performance of Honda's FWD chassis rear multilink setups, it is hard to find better. This suspension geometry has been so successful in so many competition venues it's got a lot of accumulated credibility.
On the brake front, you can buy a $70k BMW with floating calipers front and rear these days. I agree that Hondas have often underperformed braking wise, but it isn't the basic hardware configuration. As long as your caliper is stiff enough, even a single piston setup is fine. And on a FWD car, so little braking is handled by the rear (about 20% or so - because of the front biased weight distribution and additional weight transfer under braking), solid rear rotors aren't really a big deal.
No, the problem with Hondas is that the company tends to spec really crappy brake pads, and they often accompany very pedestrian tires. Since your max braking is limited by tire grip, you're already behind the 8-ball. And then when you throw in inferior pads (designed to wear long and dust little with no noise vs the German approach of a little dust and noise is worth being able to stop from 120 mph), you don't get much rotor torque to begin with, and they overheat fast.
If you do put good tires and pads on a setup like this, it will perform just fine. For example, when Honda first released the S2000, they spec'd sticky tires and relatively (for them) aggressive brake pads. This resulted in 60-0 distances of under 110 ft in most tests and no fade - all using single piston sliding setups with vented front and solid rear. But as the model aged and they dialed back the edginess, they switched to longer wearing, more wooden feeling pads and less sticky tires. Braking got worse and complaints of fade under heavy use began to surface. Conversely, cars like the Civic, with average or worse braking performance from the factory, suddenly have race worthy brakes with just a pad and fluid change.
Just one more example, IMO, of where the marketing and accounting folks are ruining Honda and Acura vehicles.
audisport says:
12:39 PM, 08/24/11
@actualsize- So the extra money was spent on fake metal trim??
actualsize says:
01:28 PM, 08/24/11
@church123, @ fordson1: It's not the single-piston sliding caliper that is at issue -- those can be found on lots of cars that stop well and don't fade after repeated heavy use. I do agree that Honda brakes tend to be undersized, tend to fade and stink, tend to have so-so panic stopping distances compared with other cars we test under the exact same circumstances. I think their rotors are small and lack the thermal mass found elsewhere. Low rolling resistance tires play a role, too. Their cars pass the mandated FMVSS minimum performance tests, no doubt, but oftentimes they are nowhere near best in class -- or even average. Aside from our objective testing, it is my personal experience that this has been the status quo for years. My 1989 Civic Si had crummy brakes, as did the 88 CRX I had before that.
fordson1 says:
01:55 PM, 08/24/11
church123 - thanks for the edification, and I agree with much of what you said - did not mean to diss the car's multilink rear so much as to agree with a previous poster that it's not really a premium item nowadays, and your reference to its racing heritage (installed in way-sub-$35k cars, by the way) is noted.
Yes, you can buy a $70k BMW with floating calipers front and rear these days, and they are roundly criticized for that. Caliper stiffness is key, but I think as you get into larger cars, with larger calipers and larger pad area, the tendency of the pads to twist against the rotor face becomes more of an issue. Caliper stiffness will help that to a degree, but multi-piston designs help to present the pad face to the rotor in a more controlled fashion - you know all that.
You are dead right on the crappy Honda pads and especially the crappy tires. I think there is some law that says Honda has to use one size or another of Michelin MXM4s or Goodyear RS-As.
Rotor torque will of course be helped out with better pads, and I'm all for that, but on a 3600+ lb. wagon I would like to see something larger than an 11.8" rotor. I have that large a front rotor on my '03 SVT Focus. The Focus weighs almost a thousand pounds less than this TSX. Wheel size becomes a limiting factor, and the TSX has 17" wheels, but VW for example fits 12.3" rotors inside 17" wheels.
Your example of the better pads on early S2000s is illuminating, and as you say points up how Honda is being penny-wise...however another thing working in favor of the simple brakes on those cars was the fact that they were around 2800 lbs., were rear-drive cars with a low CG, more neutral front/rear distribution and thus didn't suffer a lot of dive and resultant weight transfer onto the fronts.
All said and done, yeah, they are probably OK with sliding-caliper design on this car, but along with the better pads and tires they could use a larger rotor, at least in front.
landel1 says:
03:11 PM, 08/24/11
@ vvk, What you cant tell just by looking at it is that Acura has incorporated their active damper system into the suspension. This means that there is an electromagnetic fluid inside the shock absorber that varies in resistance depending on the charge of the magnets in the shock absorber. This means the car can handle well while still providing a smooth ride. Thats where the extra money went. And I'm not completely sure about the trim on the interior, but i do know that acura used real metal on the TL and on the last generation TSX so i would think they used real metal on the current one as well.
Thanks Dan i always love the suspension walk arounds
juan_mx says:
03:30 PM, 08/24/11
The European version of this wagon, the top of the line version of the Honda Accord Tourer, comes with 12.6" vented rotors in the front and 12" solid rotors in the rear (with the same engine).
church123 says:
08:32 PM, 08/24/11
Yes, I think we're in general agreement Fordson1. As another poster pointed out, Honda(Acura) does have a larger brake package available on this basic chassis. Here in the US though, we only get it on the TL chassis (which manages to fit 12.6" rotors front and 13.2" rear on 17" wheels. Seeing as how the rotor cost difference has to be about $25-$30 total, it seems silly to _not_ do this. Yes, your unsprung mass will go up a couple lbs, and this might drop your EPA rating a couple tenths of a mpg, but is braking where you want to compromise?
But, I can live with that if they just give us the right pads/tires. Having raced old Hondas in the past, I've been amazed that even the crappy sub-10" rotors and flexy single piston calipers on some 20 year old Hondas will go an entire 25 hour race with 1 or sometimes 2 pad changes. It just tells me that Honda is being lazy or cheap not specing something even a little better.
stovt001 says:
07:00 AM, 08/25/11
Great walkaround as always. I learn so much from these. Thanks!
msmlexis says:
10:52 AM, 08/29/11
I have an 06 TSX 6 speed and really want the new one. Is the suspension basically the same as this car.