1985 Porsche 911: Suspension Walkaround
You're not just seeing things. Our 1985 Porsche 911 really does look all awkward and dangly when perched on our Rotary 2-post lift.
We'll soon see why. Those tires are about to come off so we can see what a *26-year-old Porsche 911 suspension looks like up close.
This classic 911 suspension only lasted four additional model years after our car was built. Things finally started to change when the 964-based 911 came out in 1990.
*49 years if you hark back to its debut in 1963.
We're used to seeing struts defining the upper suspension mount and steering pivot in modern Porsche 911s, and we're seeing the same thing here. Thing is, the familiar coil-over spring seems to be AWOL.
No spring down here, either...not that we can see, anyway. Ah, but a torsion bar is hidden inside the lower arm's main tube along that thin white line. This type of torsion bar arrangement is called a parallel bar layout because the bars run parallel to the direction of travel.
The invisible t-bar is mated to the visible outer tube via a hidden splined joint at the forward end (yellow). Here the torsion bar rotates in lock-step with the lower control arm as the wheel moves up and down.
But our concealed torsion bar can only become a spring if its opposite end is held fast so it cannot rotate.
That happens here, inside an aluminum block (yellow) that is bolted to the unibody. This block defines the pivot point and cradles the rear bushing for the lower control arm, but it's also the stopper for the torsion bar.
The torsion bar's end is capped with a fitting that contains an adjustment screw, and the point at which this screw makes contact with the inner face of the block is the point where this end of the torsion spring is prevented from rotating. Because it is threaded, ride height adjustments are easily made by twirling this bolt.
In true 911 fashion the steering rack sits behind the front axle centerline -- probably for packaging reasons. A steel turnbuckle (green) serves as the steering tie rod. Loosen the jam nuts and rotate the center portion with all those vise grip marks to grow or shrink it the desired amount, then re-tighten the jam nuts. More elegant designs provide hex flats on this tube so you don't have to use vise grips. I'm more than surprised that I'm not seeing that here.
Meanwhile, the link-less stabilizer bar plugs directly into a bushing (orange) on the lower control arm.
The design of the strut -- particularly the lower ball joint -- is perhaps the oddest bit so far. This old Porsche (coming to PBS this fall) does not use the sort of front knuckle arrangement we're used to seeing, the kind where the strut bolts to a separate cast iron or aluminum hub carrier at a point somewhere north of the axle centerline. Here the strut runs all the way down and is more-or-less permanently mated to the steering arm (yellow) and an old-school spindle. The lower ball joint (green) bolts directly to the bottom of this assembly, so there's no doubt about the geometry of the steering axis.
Yeah, we could use some new tie-rod ends; the boots are shot but they're not dried out and making noise yet.
You've heard of monoblock calipers, right? These are not them. Yes, you're looking at four-piston fixed calipers, but they're made up of four main parts, held together with eight bolts and hydraulically connected by a crossover pipe.
At first glance the rear of our Porsche also seems to lack any visible means of support. There's no strut, nothing you point at and call a multilink.
A trailing arm (yellow) locates the axle in the fore-aft direction and resists accel and brake torque. We've seen something similar in Ford's control-blade multilink setup.
But this arm is also the torsion arm for the rear spring. The free end of a two-foot long (give or take) torsion bar connects to this blade at its pivot point (white.) The fixed end resides near the center of the car in close proximity to one coming from the opposite side. This layout sometimes goes by the name "cross bar" because the torsion bars run perpendicular to the direction of travel.
Even though this component looks similar, this is nothing like Ford's control blade multilink rear suspension. That's because there's only one additional link (if you can call it that), not three.
That "link" is a massive hub carrier that bolts to the torsion arm to make them both into a rigid semi-trailing arm, where "semi" stands for the resulting angled pivot axis. With no distinct upper and lower links, the camber changes radically as the suspension hinges on this single axis. What little control there is depends on the utter rigidity of this aluminum casting. And so we get the dune buggy posture seen in photo number one when the car is raised off the ground.
Likewise the rear bump steer characteristics are only defined in a rudimentary sense. The angled pivot axis is good in that it causes the outboard rear tire to toe in as it loads up in a corner for a small dose of roll understeer. That said, any compressive deflection of the inner pivot bushing -- such as you might get when lifting off the throttle or braking into a corner -- is likely to generate rear toe out. Skilled drivers can use this to their advantage, but the unskilled might find themselves facing the wrong direction. That the engine is located in the trunk only adds to the amusement.
Generally, this sort of behavior is why they always used to teach braking in a straight line. The more sophisticated rear suspensions we have today have arguably led to a newfound emphasis on trail braking at performance driving schools because it's harder to get many new cars to rotate on command.
Unlike the 911's front torsion bars, the rear ones lack any provision for height adjustment. It's something of a trick to get the ride height and weight distribution right because you can't be off by a single tooth left to right.
Aftermarket companies like Elephant have come to the rescue with devices like this that ease the pain. It's still best to have the left and right bars on the same tooth, but this added adjustment makes it easy to square up and weight-balance the rear suspension at any reasonable height you choose.
You may have noticed the rear stabilizer bar peeking out from the shadows in many of the previous shots. Here we can see that a stubby link connects it to the cast aluminum semi-trailing arm, not the blade-like torsion arm.
The rear shocks also mount to the massive semi-trailing arm. Their close proximity to the exhaust system is a temporary condition that ceases to be an issue when the car is on the ground.
The rear brake calipers are pretty much the same as the fronts: four-piston fixed calipers bolted together from four main parts. And it looks like Porsche has been using electronic pad wear sensors for some time, too.
In a curious twist of mass management (or a wild coincidence) all four of our 1985 Porsche 911's tire and wheel assemblies weigh 39.8 pounds apiece. The front tire size is 205/55R16 and the rears are 245/45R16. Both have the same rolling diameter but the wider rear tires and wheels are not heavier.
Dan Edmunds, Director of Vehicle Testing