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Why do people love poly bushings so much?

If you’re cruising through online forums on car upgrades, the topic of poly bushings will invariably show up.  Poly bushings are something that many people feel very strongly about, but why?  These are just small chunks of rubber down under the car, how much of a difference could they make?  The answer is, well, it depends on your perception.  Where one person may find Polyurethane bushings completely unnecessary, their fellow drivers might deem them completely required.  It all comes down to the age old comfort/performance balance.  So if you’ve come across this blog wondering about why people love poly bushings so much, there are two reasons:

Poly Bushings Last Longer

Although this might not be the case with all polyurethane, as described in this article, well engineered poly bushings will last a lifetime.  Powerflex, one of the world’s top designers and producers of these products offer a lifetime warranty for this reason.  Powerflex bushings have a number of key features that are responsible for their longevity in particular, including a self lubricating  polyurethane material, as well as specially designed grease retention grooves in any areas that contact bushing races and housings.

Polyurethane bushings, due to the molecular structure, have a higher propensity to tearing.  That’s why you must always grease them before installing or you may run into long term issues with the bushing tearing.  Powerflex however, has a proprietary compound that provides a self lubricating property, which means that even after years of use, they won’t tear like other brands.  The likelyhood of a bushing tearing also depends on the action placed on it.  Bushings that see regular twisting motions are more likely to suffer from issues, like control arm bushings.  If you use Powerflex in these positions, you mitigate the risk of any of the commonly associated issues, and you can happily keep them there for the lifetime of the vehicle.

Poly Bushings Handle Better

Powerflex Black steering rack bushings help immensely with steering precision, control, and feel.

In addition to the longevity benefits of polyurethane, specifically Powerflex with their lifetime warranty, handling is a prime focus for anyone looking to upgrade to poly.  To get a car to handle its best, it has to have a very dialed in alignment.  This differs from car to car (and platform to platform), but generally as an example, a front wheel drive car will require around 2-4 degrees of negative camber on the front, and .5-1 degree of toe out to encourage sharp turn in response.  On the back you’d want either zero, or a very slight toe in to help with straight line stability, and a small amount of negative camber under 1 degree if possible.  A soft front sway bar will help with mechanical grip as the body rolls, and a stiff rear sway bar will help the car rotate through corners.

These are all general basic setup numbers, which will differ slightly depending on application and situation, generally in increments of half degrees.  Now, as you can tell these are all very small amounts, but they will make a big difference.  That’s where a stiff polyurethane bushing will come in.

If you are going to maintain a very precise dialed-in suspension setup, you have to try to eliminate flex anywhere you can.  For cars that regularly see a race track, that means seam welding chassis components that are spot welded from the factory, adding reinforcement in the form of strut braces and roll cages, and swapping all the suspension bushings for polyurethane. Sometimes in racing applications, bushings are replaced with solid plastic, or removed all together in favor of metal joints.  Afterall, bushing deflection will kill your setup.

The Harshness Compromise: Street vs Race

Now, I will assume the majority of the people reading this article aren’t interested in shaving a half second off their average lap times at Laguna Seca.  I’d hazard to guess that you’re here because you are wondering if it would really be worth it to put poly bushings in your street car, and are worried about the reduction in ride quality.  If this is the case, you shouldn’t worry, as long as you are installing poly bushings specifically designed for the street.  As described in this article, all poly is not created equal.  Any manufacturer can design a polyurethane mold to be as soft as jello or as stiff as a hard hat.

Poly Bushings Hardness

Powerflex Street (Purple)

Powerflex Poly Bushings Purple StreetPowerflex Street bushings come in around 80 on the Shore-A hardness scale.  These are stiffer than normal rubber in most circumstances, but not by much.  With Powerflex Purple street bushings, you will notice a more refined and direct handling car, without noticing a substantial amount of harshness.  This is because your street car is still absorbing NVH in the shocks, struts, springs, tires, chassis flex, and existing rubber bushings.  The added bonus is that many poly bushings are much easier to install, so you can make this upgrade without having to press new conventional bushings in.

If you are planning on getting the most bang for the buck, focus on the subframe bushings and control arm bushings, as bushing deflection in these areas are the most likely to negatively impact your alignment.  The video below shows what bad sub frame bushings can look like, as well as new OEM control arm bushings.  There is a considerable amount of movement.

Powerflex Race (Black)

Powerflex Trailing Arm BushingsPowerflex Black racing bushings are meant to be, well, for racing applications.  If you are tracking your car and want to eliminate as much alignment-destroying bushing deflection as possible, then you are looking to replace as many of your suspension and subframe bushings as possible with Powerflex Black.  Coming in around 95 on the Shore-A Durometer scale, these are much stiffer than the street bushings, more resembling the stiffness of a shopping cart wheel.  When paired with some chassis stiffening, low profile tires, and sport/race oriented suspension, you will definitely feel the difference in NVH.  However, it won’t matter because without all that pesky bushing deflection your tires will be glued to the tarmac. Let it be known that some bushings are only available in Black, such as in BMW rear trailing arms, due to the extreme nature of the position and minimal NVH impact.

So, if your bushings are getting old, dry rotted, and soggy, you know a change has to happen soon.  If you are on the fence about getting polyurethane bushings for your street car because you’re afraid of your ride becoming overly harsh, don’t.  The average sporty street car will only benefit from a Powerflex Purple makeover.  We carry a wide variety of Powerflex bushings for your street or race car, and if you are looking for something we don’t have on the website, drop us a line.  It’s also worth noting that there is a rebate currently going on.  Save 10% on Powerflex bushing sets when you buy 3 or more, not bad huh?

eEuroparts.com Poly Bushing Rebate

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