RUBBER BUSHINGS VS PU BUSHINGS
Rubber suspension parts or PU suspension parts? Which should you use?
Both Rubber and PU parts have their pros, and both have their cons.
In car suspension parts world, the majority of decisions comes down to these two materials and the inevitable question: which one is better for your car?
We will try to explain the pros and cons of both materials below.
Specifically we’ll look at the differences between rubber and PU in such areas as:
Before we explain difference between both materials, we want you to know that Noise, Vibration and Harshness (NVH) are relative to the driver.
Ride Quality
Smooth and Quiet ride vs a Bit more NVH
Rubber is a softer material than PU, so it dampens a lot of the road noise and vibrations from entering the cab of the car. In other words, it softens the blows from the road.
PU on the other hand is made to be a firmer bushing than rubber. This means more noise and vibration will be possibly transferred to the cab as the suspension travels. Some may feel the ride is pretty harsh, while others welcome the enhanced feel of the road.
Therefore, you have to choose between more tactile feel of the road (PU bushings) and a little bit quieter ride (Rubber bushings).
Lifespan
Repeat offender vs Longevity
What parts are you replacing when renewing your car's suspension system? In most cases that parts will be rubber OEM bushing. So it’s pretty safe to assume that replacing a worn rubber bushing with the bushing made from the same material will put you right back in this same spot one day. Entropy will eventually run its course again and the bushing will be worn out soon.
Rubber is soft, so it takes huge damage from heat, road chemicals, oil, UV rays. That means rubber bushing are already going to take a beating, and that is before you put the weight of the vehicle and the stresses of the suspension on them.
During suspension usage, the bushings stretch and compress to comply with the suspension movement, so in case of rubber bushings, rubber begins to wear and distort, leading your suspension to work less efficiently due to the failing part. Loose suspension parts, constant misalignment, and annoying noises are very common symptoms of a failed rubber bushings. When you use rubber bushings to replace failed rubber, don’t be surprised to find yourself in a similar situation several years down the road. Rubber bushing is like a tire, in that eventually the bushing will wear out and need to be replaced necessarily. Some would rather keep the soft bushing and its characteristics even if they have to replace it again in the future.
Others, however, want a part to last the lifetime of their vehicle. That’s where PU wins. PU is a firmer material and suits better to be used as bushing in car suspension. PU is resistant to heat, road chemicals, other oils and UV rays. PU is weather proof and also wear resistant at the same time. Rubber is damaged easily by repeated flexing and stretching while PU doesn't have that problem, so PU bushings doesn't warp or distort in the way rubber does.
Therefore, you have to choose between parts that last the whole lifetime of your car (PU bushings) and parts that have to be replaced every few years (Rubber bushings).
Feel of road
Standard Feel vs Enhanced Feel
Rubber bushings come stock with brand new cars. Car manufacturers use rubber bushings for suspension for decades. We don’t know the actual reason for that, but some people suppose that this was because car manufacturers thought rubber is the “best”, other people suppose that rubber is just “cheaper” to use for suspension bushings. Using a rubber bushing as a replacement will give you the same feel your vehicle had before the rubber failed.
PU bushings will give the driver an enhanced feel of the road and controllability of whole car. Many drivers desire to feel every bit of the road to maximize their ability to drive. With the PU bushings installed, the car becomes an extension of the driver himself, and could be controlled far better and easily than rubber bushings would allow.
Therefore, you have to choose between enhanced feel of the road (PU bushings) and standard feel of the road (Rubber bushings).
Performance
Standard Steering and Handling vs Enhanced Steering and Handling
Using a softer material such as rubber for a suspension bushing means foregoing a lot of performance benefits in order to achieve a smoother ride. The effect of this is a smoother ride in the car. However, this can lead to a lot of excess suspension movement and a slower response time in your handling. This is usually acceptable when you’re going slowly in a straight line. However, what if you drive fast and want to turn quickly?
PU bushings are much firmer than rubber ones, so it doesn’t flex or deflect as much as rubber. By reducing the excess suspension movement, PU makes the suspension more efficient and more responsive to the driver. PU bushing usually deliver the best balance between NVH and performance.
PU is better choice not just for race car drivers, but also driving enthusiasts who want more performance and handling from their own car. For many drivers who like to drive their car aggressively and don’t mind the added NVH, PU bushings bring the performance boost.
Therefore, you have to choose between enhanced steering and handling (PU bushings) and standard steering and handling (Rubber bushings).
Squeaking
No opportunity for squeaking vs Opportunity for squeaking
In rubber bushings rubber is chemically bonded with the outer shell. So from the moment you install the rubber bushing, you don’t have to worry about squeaking. Squeaking occurs when the bushing rubs against metal. Because the rubber is affixed to the metal and can’t move in relation to the metal, there isn’t an opportunity for squeaking. That’s why there is no need for re-greasing rubber bushings after installation.
PU is a different story. Many people believe that PU bushings will surely squeak. This is not true. PU bushings can squeak, only if you don’t use grease. PU bushings usually do not have a chemical bond with the housing they’re installed into, but rather a mechanical bond. A mechanical bond occurs when the larger PU bushing is installed into the slightly smaller hole. The pressure between the bushing and the metal keeps the bushing centered. Due to this mechanical bond, there is an opportunity to squeak for PU bushing. If the bushing rotates and rubs the outer metal shell as the suspension works, squeaking can occur. This is where the grease is necessary. If you grease PU bushing during the installation and install the PU bushing properly there will not be any squeaks. All you need to prevent your PU bushings from squeaking is just to re-grease it every 4-5 years.
As a conclusion, PU bushings can squeak when installed improperly or without greasing them during installation, but if you install it properly in accordance with provided installation manual and re-grease it every 4-5 years, there will not be any squeaks.
VERDICT / FINAL THOUGHTS
Summarizing the facts above, we can conclude that every driver need to make decision which bushings to use - PU ones or rubber ones, by himself, in consideration of his own driving style and driving habits.
If you drive slowly, don't need enhanced feel of road and enhanced performance, can't deal with a little bit increased NVH, but ready to renew your suspension bushings every 1-2 years - you will probably don't need PU, just choose rubber bushings and go with it.
If you drive aggressively, want to feel every bit of road, prefer enhanced steering and handling of your car, want your suspension parts to be used as long as your car is operable, but in the same time you deal with a little bit increased NVH and ready to re-grease your PU suspension parts every 5 years - PU is the only and right choice for you.