Learn Me: Polyurethane bushings

Went to get an alignment done on my work beater, 1991 Infiniti G20.  Alignment shop tells me my control arm bushings are bad, he can get me new control arms for 130 each.  I check Rock Auto and they are 169 for the pair including shipping.  I vaguely remember Energy Suspension selling polyurethane bushings for the same year Nissan Sentra SE-R, while the control arms are slightly different from the G20, the bushings should interchange.  I can get a set of bushings from Jegs for 38 plus shipping.  Will the poly ride terrible and shake my fillings loose? I'm already running 240/40/17 with a 2 inch drop spring (may go down to a 15 inch fitment in the future), will polyurethane bushings make the ride unbearable?

Unbearable is relative to the individual. Poly will absolutely harsh up your ride quality/NVH. It will also absolutely do remarkable things to quicken your steering/suspension responsiveness. I love the Poly in my Escort. I would not tolerate it in SWMBO's car (our nice, comfortable car.)

Poly requires race car levels of maintenance and frequent lubrication. Rubber bushings depend on rubber deflection in order to move, and they'll do that until they rip apart. Poly bushings act more like a bearing between the poly and the steel insert, and need grease to keep moving. That's where the extra NVH comes from - you get freer movement but every little ripple gets pushed through. Then, if the grease goes away, they seize up and your suspension loses the ability to follow the road. BTDT.

I would go rubber on anything that has a license plate.

How often would you have to re-grease the poly bushings on a car that's, say, driven only on weekends and 2x track-days a month during summer?

Also, do you have to take the bushings off to properly grease them?

Based solely on my own personal experience with my 2002, poly bushings haven't really needed much attention and still seem to be working fine. It's a very simple suspension design, and I have to wonder if that plays into the equation.

I put poly bushings in all around the Miata suspension that became my Exocet suspension.  Never again.  Noisy from day 1 despite liberal greasing during assembly, now binding as it ages.  Will be going back to rubber bushings this winter.

I've use poly, OEM rubber, HD rubber, and all metal bushings and for a street car, even a low mileage street car I'd go rubber.

Poly works in some applications but not others. All metal bushings are great for quick responce and precise handling but suck for NVH. They are track only items.

NVH effects depend on the car too.  Honestly, I hardly noticed an NVH difference in the Jeep when I switched from shocks with big, squishy rubber bushings to ones with spherical bearings at the mounts. 

Whether they need grease and how much they'll increase NVH depends on the suspension/bushing design. On my Corolla which has all poly bushings on the front, the only clearly noticeable difference from rubber is in longevity...as in, poly lasts much longer. There's probably more noise but it's not that easy to tell over the solid engine mounts, spherical bearing camber plates, and various coilover noises.

SivaSuryaKshatriya said:

How often would you have to re-grease the poly bushings on a car that's, say, driven only on weekends and 2x track-days a month during summer?

Also, do you have to take the bushings off to properly grease them?

I've had a set start to misbehave on me after no more than a few hundred miles, and had a set last for years without problems. Same kind of car (guess what it was? C'mon, guess) It's hard to come up with a solid number from those data points.

They do need to be disassembled to properly grease them. Some people will install zerks, but I'm not convinced they put the grease where it needs to be.

Factory rubber will last for a decade or two in most applications. There are some M5 bushings that come apart quickly under braking loads, but the solution there is to use the bushings from the heavier X5 instead of poly.

I rebuilt the front end on my daily driver over 15 years ago with all poly bushings. I don't do squat to them, they are quiet, and the ride is not harsh.  It probably is time to go back in and see how they're doing, but I have nothing negative to say about poly. If I remember correctly I purchased the entire front end kit from Just Suspension. 

I've run full poly in my last three daily drivers.

The first one (B13 Sentra), I disassembled every year and re-greased everything.  This got old quick. I had installed zerks, but no grease ever got in there like disassembling did. Poly felt like 10psi too much air in the tires, autocross mistakes were amplified with poly.

The second (D21 Hardbody) I didn't re-grease at all, and it was fine. I did not really notice much difference in ride or handling.

The third ('77 C10) I haven't re-greased yet, but probably should. It feels less sloppy than a 40 year old truck should.

All of these squeak nasty below freezing.

The fourth (V8 Firefly, not a daily) I don't remember greasing when I assembled the suspension, and it squeaks like a mofo all the time.

I will likely do poly on all my beasts, but "ride quality" and "what you can put up with" are all very subjective things.

Just keep in mind that bad ride quality is the same thing as "having trouble absorbing road irregularities". Which is bad from a keeping your tires attached to the ground sort of view.

http://energysuspension.com/energy-tech/frequently-asked-questions.html

use the black bushings from what I have read, they have graphite in some applications to cut down on the squeaks typically associated with poly bushings

I have used energy suspension bushings in the past and they didn't hold up. Here's a buddy who doesn't like poly either.

https://www.youtube.com/watch?v=QwlofW23Jyk

ALL of my poly have been black.

I've used the ES goop.

I've used Synthetic Grease.

I've used Moly Slip grease.

I've used Never-Sieze.

I've mixed my own concoctions o f those.

They still squeak, especially below freezing.

I had polys in my last tercel with absolutely no issues.  My current has none...as I plan to make my own control arms with Delrin/ball style joints.

I have whiteline polys in my Yaris...the front I like...but the rear is a goofy design that ive seen alot in modern cars where the bushing is mounted the other direction and relys on a sideways deflection.  Anyways they've been on for about 5 years and maybe 100k with no real issues.

Id like to redesign those too.  But that will probably never happen.

I always wanted to groove a few spirals in a poly bushing in conjunction with a zerk. The spirals would hopefully do a decent job of spreading the grease around. 

Appleseed said:

I always wanted to groove a few spirals in a poly bushing in conjunction with a zerk. The spirals would hopefully do a decent job of spreading the grease around. 

Some of the newest models have a quilted or knurled texture where grease needs to go to help retain the grease.

Mine only got a little when they first went in, they've been fine for almost 2 years now. At this point, rubber LCA bushings would be in "cocktail weenie down a banquet hall" condition.

I've got polys in my Miata, and while I haven't had issues with them squeeking, I'm looking for something better.  My issue with them is that when first installed they're wonderfully smooth, enough so that an A-arm in the chassis by itself will gently pivot to point straight down purely under its own weight.  Once they've been in the car for a few weeks/months though, they squeeze enough of the grease out that you get stiction.  Stiction is bad because it's contributing to the spring rate but in an inconsistent fashion.  If it goes long enough without relubing, the car becomes prone to sudden oversteer.  Quilted surfaces, zerk fittings, they help prolong the life of the grease, but they really don't replace the need to periodically pull it all apart and redo everything.

One thing people have been pursing on miataturbo.net is a replacing the steel sleeves with 2-piece oilite ones.  The idea is that now you have oilite-on-oilite movement, which is self-lubricating, instead of steel-on-poly which is not.

Poly bushings bind up in applications where the bushing needs to move in more than one axis.

red_stapler said:

Poly bushings bind up in applications where the bushing needs to move in more than one axis.

Delrin bushings do that.  Polys usually have enough give in them to allow it, at least with the geometry and bushing size on the Miata.

codrus said:

red_stapler said:

Poly bushings bind up in applications where the bushing needs to move in more than one axis.

Delrin bushings do that.  Polys usually have enough give in them to allow it, at least with the geometry and bushing size on the Miata.

Yeah they'll allow some, but often not enough. If you have an arm that has to move significantly on more than one axis, I'd either leave it with rubber, or put poly on the outboard side and rubber on the inboard side (gives some extra stiffness with little to no increase in NVH and only increased bind on one end), or if you're ready for lots of NVH and maintenance effort, switch it to some kind of spherical bearing.

Ok, to add another point of discussion. Or threadjack.  What about straight urethane bushings? I was told they are harder than OEM rubber but softer than polyurethane. When i rebuilt the front of my Opel GT, they had poly listed for track/high performance and urethane for street and better than rubber. So I installed the urethane. Been a few years now but not a lot of miles. Still seem tight but have picked up a shimmy that I think is either wheel bearings or warped rotor as it does it more on mild braking. Seems to be noticeable after I upsized wheels from 13" to 14" and wider, 5" to 6.5". Did brakes at the same time, replacing rotors. Shimmy gets less with more time driving. Which tells me I really should drive it more. No mention of plain urethane here, only rubber, polyurethane and delrin.

This is one of those things that starts to make a street car in to a race car. My Porsche has either poly or delrin bushings (I forget at the moment) and they need replacement about every two years.  The lower a arms were the worst. They take a pounding and brake apart.  The steering and handling goes sideways really fast. Potholes were the major issue.