What Are the Pros and Cons of Polyurethane Bushings?

Polyurethane bushings can improve a car’s handling, but they also stiffen the ride.

byHank O'Hop| PUBLISHED Aug 8, 2022 8:00 AM
What Are the Pros and Cons of Polyurethane Bushings?
Hank O'Hop
Share

The bushings between your car's suspension components are critical to both ride quality and responsiveness. Stock bushings are meant to balance compliance and performance. Once they get old and cracked, you lose both. Upgrading to polyurethane bushings can be a simple way to improve a car's responsiveness, but you need to understand what you're sacrificing before you commit to installing them.

The car world is full of people telling you what to do, what to think, and what to like. Manufacturers will say their hot rides are the pinnacles of performance and will assert that you won’t ever need to worry about upgrading those fine machines. Then you start reading car parts ads that make you feel that the car’s a pile of junk that can’t get out of its way unless you install whatever it is they’re selling. Obviously, someone’s blowing smoke. The remedy is to do your research, know your stuff, and resist influence.

Thanks to the unlimited information available to us today, it’s become less likely that people are tricked by marketing tactics, but that’s not always the case. It can be hard to get straight answers on something you don’t know much about if you just read through the brochure.

Take polyurethane bushings, for example. Companies claim they’ll seamlessly and unquestionably improve the handling and performance of your car, but is that really the case? Not exactly.

Like any other mod you make to your car, there are tradeoffs. Although polyurethane bushings work wonders in some areas, they are detrimental to others. That means you need to do your homework before you make this modification, and The Drive wants to help. In this article, we’re here to help you decide whether polyurethane bushings belong on your vehicle.

A polyurethane bushing before assembly. Take note of the independent center section. Hank O'Hop

What Are Polyurethane Bushings?

Bushings come in all shapes and sizes and play different roles in different systems. In the case of your suspension and driveline, bushings are used at every mounting location to reduce vibrations and friction. They can be found on your shock absorbers, control arms, sway bars, and virtually any other suspension component on your vehicle.

From the factory, cars use rubber bushings. Rubber does many things well, but it has some major weak points, especially when it comes to performance. Polyurethane is a material used in the place of rubber because it’s stiffer and more resilient to the elements and forces bushings are subject to.

The result is a bushing that’s better equipped to deal with high-stress environments typical of intense driving. It doesn’t flex nearly as much, nor will it break down due to the normal cycling of components. That’s why you find that many performance builds lean on polyurethane in place of rubber. Still, it’s no universally superior product, and you need to understand the pros and cons before you smack it on every mechanical connection that’ll accept it.

What Are the Pros of Polyurethane Bushings?

For this specific topic, performance is the name of the game, so we’ll start by talking about how polyurethane boosts performance when used in place of rubber.

Polyurethane has a higher durometer rating than rubber, which means it’s a lot harder, and it won’t deform as much as rubber. The increased stability of this material does a better job of keeping everything in proper alignment. When used on suspension components, that translates to less flex and body roll, allowing you to maintain stability in the corners and put more power on the ground.

We assembled this bushing dry for demonstration purposes. Keep in mind that you’ll want to use plenty of grease before assembly if you intend to install the bushings on your car. Hank O'Hop

Short-term stress isn’t the only factor, though. Throughout the years of countless driving cycles, the elements and numerous solvents under the hood and on the road will eat away at the rubber. Polyurethane’s resilience to UV rays, road salt, oils, and so on keeps it functional for years to come.

Polyurethane bushings are also much easier to install. Polyurethane and rubber bushings with pass-throughs for bolts feature a metal center section. Rubber bushings as such are considered a fixed unit, and the rubber is molded right to the center section. That means you need to press the entire assembly in place. Polyurethane bushings allow the center section to float. Because of this, the bushing comes in multiple pieces, allowing you to assemble it in place with relative ease.

Keep in mind that some polyurethane bushings do come preassembled and will need to be press fit. Hank O'Hop

What Are the Cons of Polyurethane Bushings?

As great as polyurethane bushings are, they are far from perfect. As we said, there’s a tradeoff involved. The number one thing to turn many off to this type of bushing is its impact on comfort. Less deflection means you’re absorbing the energy the bushings aren’t.

You also might have heard that polyurethane bushings create a lot of noise, which is true in some instances. Remember how we said that poly bushings have a center section that is independent of the bushings? Well, that allows things to move around. If those parts aren’t well lubed, you will hear a squeaking noise. Thankfully, all you need to do is apply some grease during installation and when the bushings start to squeak.

While a quick application of grease doesn’t seem like a big deal, it serves as a reminder that polyurethane bushings are something that you do need to keep up with. Even if the bushings come impregnated with a lubricant that reduces squeaking, you can still expect to grease your bushings from time to time. That isn’t the case with rubber.

A rubber bushing pre-installed on a control arm. Notice that there’s no grease fitting. In this case, even if there is a polyurethane bushing in place, applying grease requires disassembly. Hank O'Hop

Cost is the final point to address. We’re not saying that polyurethane bushings are an expensive upgrade, but you’re shelling out cash nonetheless. Unless your bushings are shot anyway, you’re spending money that you don’t technically need to.

Are Polyurethane Bushings Worth It?

Whether or not polyurethane bushings belong on your car depends on your preferences and how you use the vehicle. However, it’s worth knowing that changing the bushings alone isn’t guaranteed to have a profound effect on your car’s performance.

As with anything, it all comes down to how bad the original configuration is and how the aftermarket solution corrects the matter. In other words, polyurethane bushings will have a more pronounced impact on some applications than others.

If you want nothing more than the best performance possible, installing polyurethane bushings is worth the trouble. No matter the case, they will tighten things up and offer improvements in many areas. Don’t forget that a little bit can go a long way when we’re talking about performance. Also, if you’re taking the time to update other components like your control arms, springs, and shocks, not changing the bushings will prevent you from getting the most out of those performance upgrades.

In the case that you’re ok with taking a small hit to performance if it keeps your spine intact, then stick with the rubber. Even if polyurethane will make a difference, you have to remember that automakers aren’t going to dish out something sloppy and uncontrollable. They’re still plenty good enough to get down the road safely, but know that it’ll be a loose thread eating at the back of your mind when you start throwing other mods at it.

Hank O'Hop

FAQs About Polyurethane Bushings

Based on experience and commonly asked questions on popular search engines, these are

Q. How do you grease polyurethane bushings?

A. You should grease polyurethane bushings during assembly by applying it directly to the bushings. Thankfully, polyurethane bushings are also usually paired with grease fittings preventing the need to tear everything apart. As a rule of thumb, you should grease the bushings every five years or whenever they start squeaking.

Q. What is the best grease for polyurethane bushings?

A. Polyurethane bushings should be greased with silicone-based or lithium-based grease. Even though polyurethane is resistant to oil and other solvents, you never want to use petroleum-based grease when servicing these bushings.

Q. How long do bushings last?

A. Theoretically, rubber bushings should last for about 15 years, and polyurethane bushings can last the vehicle’s lifetime. However, the environments bushings are subjected to and the quality of their construction are major contributing factors. Ultimately, you will want to inspect the bushings between each season to determine if you can continue to use them.

Q. Is it dangerous to drive with bad bushings?

A. Yes, it can be dangerous to drive on bad bushings. As the bushings break down, steering and handling performance will deteriorate, reducing control of the vehicle. Also, let’s not forget that friction will increase, which can damage the parts they’re linked to.

Q. How do I know when my bushings are bad?

A. Severe rattling clunks and vibrations are all signs that the bushings are bad. If you’re unsure if the bushings are the culprit, simply take a look. Any cracks or other obvious signs of damage tell you it’s time for a replacement.

Learn More in this Helpful Video From Flyin' Miata

This clip from Flyin' Miata further demonstrates the differences between rubber and polyurethane bushings.

Read More From The Garage