Is this true about urethane bushing?

[romtrt]

I read it from vwvortex.com forum it came from a book Chassis/Engineering design.

URETHANE BUSHINGS

In recent years, several companies have offered urethane suspension bushings. These plastic bushings look great on the parts shelf. Unfortunately, the urethane used in the products we have evaluated is not a material well suited for suspension bushings.

Disadvantages
Depending on the application, suspension bushings must allow movement in different planes. The most common plan e of movement is simple rotation. Rubber bushings allow rotation by the internal shear of the rubber itself. This means there is no sliding motion between any of the members. The rubber flexes allow the inner and outer sleeves to rotate relative to each another. Since there is no sliding motion, there is no friction-caused wear and no need for lubrication. Because the rubber is molded to the inner and outer sleeves, there are no critical tolerances to maintain during manufacturing. This is one of the features that allows rubber bushings to be made inexpensively.

When a steel or urethane suspension bushing is used, the bushing material cannot deflect. There must be some sliding motion to permit rotation between the inner and the outer sleeve.

Many people who buy aftermarket urethane bushings believe that the urethane behaves like hard rubber, but most urethane suspension bushings are so hard that they have to be considered solid, because they offer little ability to absorb rotation shear within themselves. The only way a rigid suspension bushing can allow rotational movement is if one of the mating surfaces slides on the other. This sliding action demands close manufacturing tolerances and lubrication for satisfactory operation. The aftermarket urethane bushings we've tried did not meet these requirements.

Greasing the bushings before assembly works for a few weeks until th grease is forced out or washed away. Once the grease is gone, the urethane is again able to bind to the steel sleeves, and the driver hears squeaks and moans. Without lubrication the urethane can stick to the steel, and the suspension does not move smoothly.

Urethane bushings could be customized to provide better service by hand-fitting the bushings to obtain proper clearances and installing grease fitting for regular lubrication.

[Fishboy55]

If you're asking if you'll experience more vibration, especially at idle with Urethane bushings, the answer is yes. If you're asking if the vibration is so bad that it outweighs the advantage of never having to replace an engine mount again, the answer is no. I've had solid urethane bushings for several years on all four corners of my motor and the vibration is minimal and certainly something you get used to.

[peanotation]

I still don't have a single squeek from any four corners of my car, and saying that the grease gets forced out or washed away kind of sounds outdated. Specifcally, the grease that comes with Prothane brand urethane bushings is named "SuperGrease" for a reason, as it is waterproof and by far the "greasiest" grease i've ever used. If I get a glob or a tiny bit on any of my tools or my gloves, you have to use brake cleaner to get it off, otherwise it spreads FOREVER and will wind up all over the place like sand. Unfortunately, this is a huge pain when applying the grease, but well worth the effort.

The flexing that this article mentions, however, has always irked me a little bit. The galant was designed with rubber bushings in place, and the engineers accounted for these tolerances to allow for suspension movement. By placing borderline-rockhard bushings in their place, I always thought that maybe the suspension pieces as a unit were now out of spec to what the engineers had in mine. Maybe it was a good thing that trailing arm had laterall movement? Maybe it's necessary for the rear lower control arm to have some bob in it? What I know for sure is that the car is ultimately more predictable, consistent, and much better overall in handling.

Energy bushings, which require graphite (suspect of wearing or getting washed out IMO) are the bridge between the gap of OEM slop-dog rubber bushings and Prothane urethane john holmes hardness. They are moderately flexible, and would probably agree more with the author's opinion.

If you're asking if you'll experience more vibration, especially at idle with Urethane bushings, the answer is yes. If you're asking if the vibration is so bad that it outweighs the advantage of never having to replace an engine mount again, the answer is no. I've had solid urethane bushings for several years on all four corners of my motor and the vibration is minimal and certainly something you get used to.

Total agreement here. Stiffer bushings for the engine is only negative on the comfort level, but you learn to appreciate and enjoy the moderate vibration of the motor. For me, the sheer joy of driving a modified vehicle is having the direct response and consistency of performance. With the right suspension, transmission modifications, etc., the car becomes an extension of your mind, requiring no thinking as you try to account and respond to indifferences and different reactions from taking the same turn, at the same speed, in the same gear, through the same apex.

Romtrt I know you've always been nervous about the urethane bushings, as word of mouth in your area suggest they are a negative modification to the car to which only bad things will come. Maybe so for other cars, as all cars were not created equal by any means, but for the 7G specifically I do not know of any complaints, other than the installation process

If you are still worried about the effects, even after this thread and the 12+ pms we've exchanged on this subject, then don't do it! It's your car and you should be happy with it, don't feel pressured to think that you're missing out on something. Solid dampers with sway bars and strut braces will still build you a pretty sweet road machine, but just remember in the back of your mind that there's always that last 15% to make a truly elite-handling car.