2010 Volkswagen GTI: Suspension Walkaround
June 30, 2010
More than a few of you have been getting impatient for this one. The wait is over. The suspension walkaround of our 2010 Volkswagen GTI long-term test car is finally here.
The going wasn't as smooth as I'd hoped. Volkswagen uses annoying, easy-to-lose lug nut caps that must be removed with an annoying, easy-to-lose wire removal tool, and a liberal coating of tire black at the last carwash may have ruined my pair of jeans. Oh, how I despise tire black.
Enough of my whining already. On with the show and tell.
Up front we see your basic MacPherson strut suspension and some red brake calipers.
But those red brake calipers ain't Brembos. They're single-piston sliding calipers like we see on a lot of other smaller cars. That's no bad thing, but these aren't racing bits. The rubber caps that conceal the two pins on which the sliding half slides are indicated by the yellow arrows.
The L-shaped lower control arm (orange) is stamped from a single sheet of steel, and a long slender stabilizer bar drop link (green) connects the stabilizer bar to a point high on the strut housing where it can stay clear of the tire while the strut steers left and right.
As expected, front-engine, front-wheel drive equals a steering linkage (orange) that acts behind the axle centerline.
But the trick aluminum front suspension subframe (green) is not something we often see. It's a bolted-together structure that holds the steering rack and the stabilizer bar, and it also carries the forward and aft pivot points for the lower control arms. The whole affair ultimately bolts directly to the unibody (yellow) with no rubber bushings in between to dull steering response.
Here's another look at the stamped steel lower arm and the way it mounts to the nifty aluminum subframe. DIY aficionados will appreciate the easily-serviced lower ball joints that bolt straight on. Autocrossers might consider taking a hacksaw to those overlong bolts(yellow) and save like 80 tons or something.
This under-car view (from the right side this time) shows some of the bolts that hold this subframe together. This is starting to look expensive. But it's also looking light and strong.
Peeking further underneath we see that the subframe has one more job to do. It carries a torque mount that controls the roll motion of the engine when you dump the clutch, make a shift or simply roll on and off the throttle in stop-and-go traffic.
That extra black bracket on the transmission end takes away the bending moment from the long through-bolt (yellow), putting it in double shear instead. The other end of the torque link, which is in direct tension when under load, connects to a large bushing housed neatly in the middle of the subframe.
Torque mounts are nothing new to front-drive cars, but this design is unique, and very effective.
Back to more mundane stuff. Here's the top end of the strut and the shock tower.
Before we head to the rear, here's another look at those spiffy red brakes.
The rear suspension wears another pair of red-painted single-piston sliding brake calipers, but these squeeze solid rotors instead of ventilated ones.
More importantly, the GTI's rear suspension uses a multilink setup with a blade-style (green) trailing arm. There are three lateral links in there, but here we can only see the main lower one (yellow) that also carries the spring.
Ah, that's better. The main trailing arm (blue) simultaneously locates the wheel in the fore-aft direction while it handles all of the torque loads from braking. The now-familiar curved upper link (yellow) hold the top of the wheel at the proper camber angle while the lower links (orange and green) handle most of the lateral loads.
And, as we've seen many times before, the forward of the two (green) is shorter, and it therefore swings in a tighter arc to create some dynamic toe-in on the loaded side as the body rolls.
I dreamt about a meteor shower last night, so forgive me for going a little arrow crazy. All of the colors (and their targets) are the same as the previous slide, with one exception: The white arrow indicates where the stabilizer bar link connects directly to the trailing arm.
Here's another view of the same thing. You can see how the mounting point is integrated into the connection between the trailing arm and the rear knuckle casting.
The coil spring sits about midway along the length of a main lower link that's so long it almost meets its mate from the other side in the middle. My eyeball estimate says the arm ratio is about 0.60:1 or so.
The rear shock absorber, however, bolts directly to the cast-iron rear knuckle for a direct-acting 1:1 motion ratio.
Like the front, the rear suspension subframe mount (orange) is direct-mounted to the body.
We haven't yet seen any bump stops because they reside at the top of those shock absorbers.
Finally, those 225/40R18 all-season tires and controversially-styled 18" wheels weigh 50.5 pounds when mounted.
Dan Edmunds, Director of Vehicle Testing @ 7,858 miles