I know there must be more Toyota Lexus enthusiasts here so I would like to kick off this forum with a pretty difficult question that has been stumping me. Any of you that reads Lexus brochure boilerplate might know about this and want to chip in. Any suspension geeks might know something as well.

Lately I have been working for Falken as a suspension consultant, mostly helping to dial in Dai Yoshihara's Lexus IS350 drift car. The normal dynamic issues got straightened out in a couple of test sessions and the car got performing reasonably well except in a few weird ways that seriously hampered it. As you might not know, self steering and a strong self aligning torque is very important in a modern pro drift car as the high speeds and crisp presentation of a drift and crossovers are very important to get good scores. Thus many times the car will have to self steer as the driver has a hard time physically moving the steering wheel fast enough.

We had set up the suspension geometry for good self steering with 10 degrees static caster, 12 degrees of kingpin inclination angle. 6 inches of pneumatic trail and a Dave point 15mm off the center, good for feel with little side scrub. Should normally self steer like a mofo. Too bad it would not. This made the car very hard for Dai to drive like the top pro he is. What struck me as odd is that the front steering had very little Ackerman angle in the steering geometry. The steering knuckles were angled upward so the tie rods would travel in an downward arc.

This made for a very linear, shallow and slight gain in the Ackerman curve as well as increased bumpsteer (hint of sarcasm here) With little Ackerman, we had to add nearly 3/4" of toe out and the car side this odd side squirm with a lot of tire squeal under turn in/ drift initiation. So I tried a bunch of things and the last straw was to make some new knuckles to give more Ackerman by relocating the tie rods. This did the trick and transformed the car. It now self steers pretty well. We are now running a normal amount of toe out, 1/8".

My question is why did Toyota do this? I have noticed that Japanese suspension engineering often has gimmicks to solve geometric problems that often cause other worse problems. The NSX, 300ZX 350Z and RX8 has these issues. So I am wondering why, do any of you have one of these cars and have read road tests, brochures and other official boiler plate? I want to know the thinking behind this. It is a very deliberate design issue. I want to understand why this great, well-engineered car car has this.

How does slip angle tie in?

Not much once its in drift, pro drift cars actually understeer heavily off throttle