"the shock bushings are 2/3 cheaper. I hope there's no real reason for that."

Shock bushings see only vertical load while rear sway bar bushings see a significant angular component-- one portion is compressed roughly the width of the flattened bar piece.Roughly 1/3 is exposed to the pressure so the bushing needs to be 3 times harder than one that sees a 360 degree load!

The rear 20 mm sway bar pushes on the end link with 160+ pounds per inch of deflection without washers to distribute the force it will smash right thru the average rubber bushing.So the durometer of the bushing is significant in the first 2" of body roll as the bushings get compressed. The sway bar may do nothing then work a lttle till the bushing is fully compreessd, then finally act as designed.

A simple 20 mm bar may [with solid urethane] provide 3 times as much resistance in the first 1" of roll [1/4" of bar movement]compared to a rubber bushing......38lbs vs 0-12 lbs ........even a quarter of a turn on the compression nut is meaningful.

Setting up bars to handle the varying load and yet not feel excessively stiff over unibumps [one wheel bumps] is difficult!

"The Shore hardness is measured with an apparatus known as a Durometer and consequently is also known as 'Durometer hardness'. The hardness value is determined by the penetration of the Durometer indenter foot into the sample. Because of the resilience of rubbers and plastics, the indentation reading my change over time - so the indentation time is sometimes reported along with the hardness number"http://www.matweb.com/reference/shore-h ... meter.html

The Active 20 mm bar and factory hardware is a great place to start as you can always make it softer by backing off the bushing nuts or harder in intial impact by using metal washers to build up the compressibility of the bushing [as the rod is threaded so the nut will not overcompress the bushings which will ultimately make them split!

The front 29 or 28 mm bar has only 2 end link bushings with significant play [again the thread limits] to avoid impact harshness in the typical 1" bump.The bar is as strong as the springs [limit of the normal ratio 50/50] but isolated by the bushing so it never moves the full 1" in a 4" wheel movement.

The TOTAL roll front stiffness [springs plus friction plus bar plus bushings] is not linear [166+166=332 #per inch].......it might be 200, 240, 290, 310 say 1040 not 1328 with new bushings adjusted just right maybe only 800 # with worn bushings and an 1/8" slop.......an extra 1.5" of body roll.

Modern strut designs use a softer bar connected directly to the strut so there are no bushings to create variability and changes with age/wear.....the Q is maintenance intensive to maintain as new performance!!!!!!!!!!!!!!!!!

The tire sidewall stiffnesss is a critical part and the bushings [slope of engagement curve] are tailored to a specific tire sidewall compression curve as is the camber gain angle in the suspension........usually the company sends the requirements to the tire manufacturer and they build a tire to fit then 2-3 brands are tested and the winner gets the contract.......obviously in Fords case the low cost was more important than specs but then again they may have met them new but not after a year [of stress] who knows.

The new BMW 745 has the most advanced sway bar control system. It is electronically coupled as to attack and release [which means it acts like a here to fore unavailable variable bar].

It engages with G force [0.2 G]and stops at 0.7 G so the driver can feel the rear end slipping. In Rain the roll correction force is muted to follow the traction of the tires.

It is complex by not like the old Q Active system.The racing rule of thumb is the bar and springs should be equal stiffness [at the max] but no extra shock stiffness should be added to compensate for the bar.Whereas the BMW has variable stiffness rear shocks which when coupled with a variable bar is ideal!

Those of us with a Q are stuck with selecting springs, shocks, and bars, we can live with and fine tuning the bushings to minimize attack point for the roads we drive on.A trip on a bad road can kill you or at least [wear the skin off your elbows] if your car is optimized [handling] for a smooth road.

Back to bushings they require at bit of thought about what you want and your local roads and how often how long you might ride on bad roads. Same with shocks as they all are stiffer in cold weather, same with tires as the compliance [stiffness varies with temperature].

The nice thing about bushings is with a couple of turns on a nut you can soften the whole setup in 10 minutes if you can contort yourself under the car. Believe me I have had my legs hanging out at a few rest areas!

Bushing preload: For those that want to try getting it perfect.

Getting a Q to handle the same turning left or right is a challange partially because the front [rear] springs are so soft [166 [122] pounds per inch].With a 170 # driver and nothing else [assume 85 pounds on the front and rear] and the driver left of the centerline [center of gravity ----- measure the fender opening height from ground all around loaded and unloaded]. If perfect the front should drop 0.25" and the rear 0.35".

The weight balance is not perfect! So the drivers side will drop more than the passenger side: something like 0.35"LF and 0.15"RF [0.45LR and 0.25RR] creating preload on the sway bars even as the bar attempts to return the body to the static unloaded condition.

The Eibach lowering springs are as soft or softer in the center 1" where they would be normally sitting still [even though lowered]! Then they stiffen in rate in the next 3" of compression.

Anyway back to the 0.2-0.3-0.4" difference left to right, the sway bar is attached at the midpoint of the lower traverse arm [so a 1 to 4 reduction].......you need a 0.05-0.1" metal washer on the LEFT front and rear sway bar end link to equalize the distance...... so that the bushings have the same compression load.

What happens if you don't: after years and year miles and miles the bar may actually bend [take a set] or worse the bar may not be perfectly flat as mounted especially after an accident.

On race cars or cars with adjustable coil overs one would set the left coils higher to level the car [assuming the static weight is the same left to right].

The rubber bushings take up the slack in passenger cars as they never know the weight distribution in the car.

:bowdown

Whew! Thanks, Dennis. That's a lot to chew on.

What I'm taking away from this right now is that until/unless Joe and company at Infiniti of Scottsdale can come up with durometer numbers for the shock bushings or an appropriate factory buletin, it sounds as though I shouldn't take them at their word that the shock bushings are okay for the sway-bar application.

I was afraid of that.

I was dubious as they sent two real bar bushings -- at least I have something to compare.

Thanks again!

The point was that if you box in the bushing ends that contacts the bar on the rear with a metal washer, the force gets distributed more around the circumference of the rubber in a more equal manner so the bushing will not split as soon.But the ozone will still change its properties.As you can see the 1/2" bushings allows 2x plus 2x [on the other side] or 2" less however much you compress them plus their resilence of constantly decreasing slack........for sure the first 2" of wheel movement is not linear as that would only compress the 4 bushings 1/2" or 25% so each might be 0.06".

I really hate the way they couple the rear sway bar to the lower arm way too much room for misadjustment. I am constantly tightening the nuts as the rubber changes every few months.

The use of urethane bushings takes away much of this slack.

What one could do is measure the force to lift a wheel....the problem is there 1032 [+-] static pounds on each rear tire....it should be 122 pounds more per inch plus what ever the bar is doing.,,,,kind of hard to find accurate to a pound 1600 pound scales