ATTN: Don't buy REAR Stoptech SS Lines!!

[CF-Shane]

I had a 93 S10 where, I shit you not, the ABS consisted of a speed sensor and valve (rear wheels only) that would quite literally shut off your rear brakes when they locked up. You'd be amazed at what manufacturers can get away with when it comes to naming parts in a sales brochure. Take the Yaris for example: I see a solid beam rear axle with coil springs, and Toyota's marketing department sees a "tortion beam rear suspension". Yeah, ok. When I hear that I think of tortion bar suspensions that are typically found in older Chrysler cars and modern 4x4 trucks, not a plain beam and springs suspension. It all comes down to properly applied naming or not, they'll call it what it needs to be called to sell vehicles.

[xed]

Originally Posted by CF-Shane

... they'll call it what it needs to be called to sell vehicles.

Salesman: Here is one of my favorite features on the Yaris. This is the new actuated rotating bidirectional beverage retention device. We call it ARBBRD for short.

Buyer: You mean the nifty cup holder?

Saleman: errr, yeah the nifty cup holder.

[WolfWings]

Originally Posted by CF-Shane

Take the Yaris for example: I see a solid beam rear axle with coil springs, and Toyota's marketing department sees a "tortion beam rear suspension".

There's a difference. The Yaris' "solid beam rear" actually appears to be under torsional load from what I saw, looking at it after I had my TRD rear sway bar installed. The fact that the 'solid beam' is a near-duplicate of the rear sway bar but attaches to mounts more-or-less one-bolt-higher than the sway-bar shows it actually is a torsion beam, not a true 'dead axle' design. The fact that there is no mount for a track rod/panhard rod (Suspension SP-62) shows that (at a minimum) the rear suspension is a twist-axle rear, which means that, yes, the rear beam is designed to be under torsional forces like a torsion-bar setup.

The only difference between a 'twist axle' rear and a 'true' torsion-beam rear is if the rear axle is two parallel (at rest) rods cross-linked or one single rod. The two parallel rods gain a minor design-engineering-simplicity advantage at a moderate complexity disadvantage. The single-beam is, in effect, two half-length torsion bars linked at the mid-point by comparison, and more math and proper design can let it perform almost well as the two-rod setup AFAIK, though it doesn't add as much chassic-rigidity as the two-bar setup. This is (I believe) why a rear sway bar is so noticable on the Yaris.

[CF-Shane]

Originally Posted by WolfWings

There's a difference. The Yaris' "solid beam rear" actually appears to be under torsional load from what I saw, looking at it after I had my TRD rear sway bar installed. The fact that the 'solid beam' is a near-duplicate of the rear sway bar but attaches to mounts more-or-less one-bolt-higher than the sway-bar shows it actually is a torsion beam, not a true 'dead axle' design. The fact that there is no mount for a track rod/panhard rod (Suspension SP-62) shows that (at a minimum) the rear suspension is a twist-axle rear, which means that, yes, the rear beam is designed to be under torsional forces like a torsion-bar setup.

The only difference between a 'twist axle' rear and a 'true' torsion-beam rear is if the rear axle is two parallel (at rest) rods cross-linked or one single rod. The two parallel rods gain a minor design-engineering-simplicity advantage at a moderate complexity disadvantage. The single-beam is, in effect, two half-length torsion bars linked at the mid-point by comparison, and more math and proper design can let it perform almost well as the two-rod setup AFAIK, though it doesn't add as much chassic-rigidity as the two-bar setup. This is (I believe) why a rear sway bar is so noticable on the Yaris.

Thank you for the explanation, you learn something every day and I stand corrected. I have found surprisingly little about the Yaris' rear suspension except for advertising jargon and was calling it as I saw it. Another thing I found surprisingly little information about was the availability of rear sway bars. So they make a huge difference on the car I take it?

[WolfWings]

Originally Posted by CF-Shane

So they make a huge difference on the car I take it?

Changed the car from being squirreley and 'squiggley' when in extended turning (sweepers or doing figure-eights around a pair of orange cones in a parking lot) to taking a quick 'set' under load and being very easy to control with throttle-adjustments and responsive to turning. Exactly what you'd expect from an unstiffened chassis suddenly getting properly stiffened, much more than just a rear sway bar would normally grant on a FWD car.

Without the sway bar the car felt like it was near-constantly under torque steer (the fuel cut-off deceleration causing it even under engine braking at highway speeds) but once I had the sway bar put on what I thought was torque steer turned out to just be how loose the rear chassis was magnifying things to very noticable levels.

Hell, without the bar I felt unsafe doing my figure-eight practices to get used to how the car handled. I couldn't get myself to break 25mph. Once I put it on I had to stop when my passenger/friend started complaining about the alternating side-to-side G-forces I was pulling off doing 35-40mph figure-eights for ten seconds non-stop. Car feels much more chuckable, very much like my 89' Corolla FX used to feel, or my 86' Civic Hatchback felt.