2011 Lexus IS-F: Suspension Walkaround
When it first came out, the Lexus IS-F could be summarized by the classic phrase "close, but no cigar," especially in the suspension and steering departments.
This 2011 Lexus IS-F (and the 2012, as well) incorporates numerous tweaks meant improve the handling and steering while making the ride less brittle. It worked well enough that the boys in the office pronounced the reworked IS-F cigar-worthy after driving this one around a few days and testing it at the track.
Much of what Lexus did consists of invisible suspension recalibration, but it's worth a look anyway.
And you've probably figured out by now that these are homemade photos taken before we installed our new Rotary 2-post lift.
Like all Lexus IS of the current generation, the ISF rides on double-wishbone front suspension.
The upper wishbone (yellow) is made of stamped steel, while the lower one (green) is more of an L-shaped arm that's been welded up from several smaller pieces of steel.
Compared to the 2010 IS-F, the 2011 coil-over front springs are softer by 5 percent while the damping levels generated by the shocks are between 10 to 20 percent stiffer depending on what shock piston speed you're talking about.
The L extends towards the rear in the IS. The fore-aft component of larger impacts is turned through 90 degrees in this sort of layout, with a large-volume bushing is waiting at the far end to absorb them as in-out twitches.
We can also see hints of the aluminum front subframe that cradles the engine and carries the lower elements of the suspension.
From here it's a little easier to see the aluminum front subframe and how it is mounted to the body above.
Interestingly, the IS-F employs an aluminum knuckle (green) with a separate steering arm/ball joint carrier (yellow) bolted to the bottom.
This design makes it easy for Lexus (or some enterprising aftermarket company) to make meaningful tweaks to the front-acting steering geometry by producing a substitute piece with altered dimensions. In fact it is likely that such a change was made for 2011, but none of my Lexus contacts can confirm it.
We can't see the electric power steering head unit, but I have been able to confirm that its assist curves were altered for 2011 to produce more natural feel and feedback.
The 2011 IS-F uses the same front stabilizer bar as last year, and the arm of the electronic height sensor (yellow) piggybacks off it to measure body height for comparison with the other three corners in the ECU. This placement works because both of these move together in lock step with the lower control arm via a shot stabilizer bar link (green.)
On the right, the necked-down end of the shock absorber (black) suggests that these are twin-tube shocks, made by Tokico, as it turns out.
The wheel bearing and hub assembly contains the required wheel speed sensor, and the whole mess is held to the knuckle (aka 'hub carrier') with four bolts that make for easy service.
This close-up shows how the upper arm is made from light gauge steel that's been folded to give it extra strength. The high-mount arm placement keeps the loads low in the arm and the upper ball joint.
Six-piston Brembo fixed calipers and 14.2-inch ventilated and cross-drilled cast iron rotors handle the stopping chores. Cooling air comes their way through ducting built into the front bumper and grille.
These calipers feature an "open window" design with an easily removed bridge bolt for quick pad access.
Out back it's a multilink suspension with five distinct links and a coil-over shock,
A pair of upper links are splayed apart to approximate an upper arm while a forward link controls the toe angle.
Many of the rubber bushings contained within the end links we see here (and later down below) have been re-tuned for 2011 to make them stiffer laterally for precise wheel control but softer torsionally so the members move freely and don't bind so much to reduce harshness.
The inner end of the toe link features an eccentric cam for toe adjustment.
Like the top, two lower links work together to behave like a one-piece a-arm. The outer end of the rearmost lateral link (green) pivots on a spherical joint (pillow ball in JDM terms) for high lateral rigidity when cornering and almost zero torsional friction.
That main lateral link is beefed up like that because it carries the load of the spring and shock at a motion ratio of about 0.7-to-1 and the stabilizer bar at 0.5-to-1 or thereabouts.
2011 and later cars also benefit from a much needed increase in rear negative camber, which increases from negative 0.75 degrees to negative 1.5 degrees. Whether this was done by making the top links shorter or the bottom links longer is unclear. Because of cost it is unlikely that Lexus retooled or re-machined the aluminum knuckle at their outer ends or altered the subframe ears to which they attach at their inner ends.
The rear suspension height sensors (green) attach to the main lateral link using the same bolt that holds the stabilizer bar's drop link in place.
Unlike the front, the rear coil-over shocks are made up of monotube dampers, and the spring rate is unchanged from 2010.
Smallish-looking 2-piston fixed Brembo calipers put the squeeze on the rear rotors,
The rotors they grab are 13.6-inch ventilated and cross-drilled units. But the hat-section of the rotor (and a cable on the other side) indicates the use of hidden drum brakes for parking.
Finally, a Torsen mechanical diff resides in this housing. Before, a brake-based torque vectoring pseudo-LSD was employed, but there's usually a delay associated with that kind of system. No to mention that asking a computer to dab the inside brake when you're hard on the gas seems a bit counter-productive.
That system is still in place, but with a Torsen mechanical diff things go much more seamlessly as it operates more subtly in the background.
And all of it rides around on Bridgestone Potenza RE 050A summer performance tires. The fronts are 225/40R19 tires and 8-inch wide wheels that together weigh 49.5 pounds mounted and ready to roll. The rears likewise are 255/35R19 tires and 9-inch wheels that weigh 54.5 pounds.
These changes don't sound like much, but never underestimate the value of good tuning, particularly bushing tuning and shock valving. And that extra rear negative camber is nothing to sneeze at, either.
For me, these changes transform the Lexus IS-F from a boy-racer car with an aftermarket vibe that made it feel less than polished to a factory-tuned car that comes across like everything fits together and works as intended. I enjoy driving this car much more than its predecessor.