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Background: this is in reference to the previously mentioned 2004 Subaru Impreza WRX Wagon. This isn't a track car: it's only for fun street commutes and general Daddy duty.

The car has upwards of 115K miles now and I'm hearing what sounds like aged bushing clunks and creaks coming from the rear suspension, especially at fairly low speed largish bumps and dips. I recognize that the bushings are consumable parts so I'm planning to replace the ones that I can do with hand tools and task out the ones that I can't.

So, here's the question: which type of bushing will have a longer lifespan, stock replacements or urethane "upgrades"?

I am very aware of the NVH price that must be paid with a full set of urethane bushings but I'm willing to consider it if it means a longer time between replacements. At the same time, a full set of stock replacements will also feel much better than the frankly weary parts that I have in there now.

Additional information on which bushings can definitely be replaced with hand tools, which definitely can't and which are on the borderline would also be appreciated by both me and future readers.

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Probably very vehicle dependent. On my MR2, they last the same (about 8 years), with the OEM ones cracking and the poly having the holes grow bigger to the point of clunking. On my Eclipse, they all seem to last forever. –  Brian Knoblauch Sep 1 '11 at 15:31

2 Answers 2

up vote 4 down vote accepted

In my experience, Polyurethane bushes last longer than standard rubber ones, as the plastic doesn't perish in the same way that rubber does.

As you mention, there is a price to this, as they are generally harder than the equavalent OEM bushes, however many manufacturers offer a variety of stiffnesses, depending on the intended use - some of the softest ones aren't much harder than stock, wheras full race-spec ones will be. One caveat to be aware of is that the added stiffness of the Poly bushes will put additional strain on the other suspension components, which can lead to them failing through fatigue earlier than they otherwise would - In particular it is not recommended to use stiff bushes in some designs of trailing arm suspension for this reason.

As to which can be easily replaced by hand, a general rule of thumb is that any bushes that are pressed in to surrounding metal will need to be pressed out again, and thus will be difficult to do without a hydraulic press - though not normally impossible if you have a big vice, a 'suitable sized drift' and a big hammer! Any bush which is simple clamped in place by the component it is bushing should be fairly easy to replace.

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One option for bushings that aren't easily removed (I know this sounds a little crazy, but I've seen it specified several times) is to burn them out. You burn the rubber and then clean out the remaining. –  ManiacZX Aug 31 '11 at 18:31
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@ManiacZX, wow, I'd forgotten that people do that. The face I just made summarizes my opinion: uncontrolled combustion inside a critical suspension component sounds ... bad. –  Bob Cross Sep 1 '11 at 16:47
    
@Bob, agreed, it sounded pretty crazy to me when I read it in the steps on how to replace the bushings on my car. Even though there were photos showing the steps too. Then when a group of guys from the car club were doing someone's set of bushings, this was done. Really though, a little gasoline fire on a steel LCA, long enough to melt some rubber, probably not hurting the metal. Just make sure to have a fire extinguisher handy!!! –  ManiacZX Sep 2 '11 at 3:04

I have had this on various occasions on all my Subarus once they get old, and on my Forester STi at only 70k miles!

  • Polyurethane bushes on the much harder STi suspension last less time than rubber - it seems they are so hard the impact transferred to them is higher (have to replace every 25k or so - but this one is set up for track, despite being my commute vehicle)

  • Polyurethane bushes on the stock suspension last longer than rubber (never replaced a polyurethane one yet once they are in)

If your one is set up for normal usage, I would suggest polyurethane will last longer.

I don't have any quantitative guidance on which are harder or easier to remove though.

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