Suspension Bushings Are Small Yet Important Pieces of Your Suspension System

Photography Credit: Kevin Adolf

Tires, springs, shock absorbers and anti-roll bars get a lot of attention, but what about those unassuming bushings–you know, the little blocks of rubber tasked with locating all those suspension components day in and day out? Perhaps it’s time to think about them. 

Just about every mass-produced car has been delivered with rubber bushings. Rubber does a fine job of locating suspension pieces without transmitting too much noise, vibration and harshness. However, there’s one small problem with these rubber bushings: They don’t last forever. Over time, rubber can crack, split and deteriorate. 

Plus, rubber isn’t the toughest material ever made. If you’re hurtling around the track, would you rather have your suspension parts located by tough, firm bushings or ones that are a bit squishy?

The aftermarket, as usual, has come to the rescue with replacement bushings formed from polyurethane, a stronger, moldable material.

When to Replace

“You should think about your bushings [as] a wear-and-tear part,” explains Michael Santa Cruz, director of marketing for urethane bushing maker Energy Suspension. If a handling issue, like poor control or accelerated tire wear, isn’t tied to the usual suspects–springs, tires, alignment and shock absorbers–then perhaps the bushings have sheared, worn out or simply given up the ghost. Basically, the suspension elements are moving in ways they aren’t supposed to because of a bad bushing. 

First, do a visual inspection. Are the bushings still there and in one piece? Then do a dynamic test. “I kick the tire backward–seriously,” says Ground Control’s Jay Morris. If the tire moves, then perhaps the bushings are no longer doing their job.

While bushing replacement is usually associated with older, higher-mileage cars, that’s no longer always the case. Michael Santa Cruz explains that today’s heavy, high-horsepower cars can quickly shred the stock rubber bushings. The new Dodge Challenger, he notes, is on that list. 

The technological aids found on a lot of these newer cars can help diagnose a bushings issue, too, he continues. Is the ABS or stability control kicking in sooner than expected? If so, perhaps a compromised bushing is allowing something to move outside its planned range. 

Photograph Courtesy Energy Suspension

Too Tough for Street?

“The current perception of urethane bushings–at least here in the United States–is that they are hard to install, equate to harsh ride, produce embarrassing squeaks, are a PITA to regrease/maintain, and that the resulting suspension performance and NVH are equal parts tradeoffs,” says Tom Phan of bushing maker Whiteline USA.

However, he notes, modern manufacturing techniques and design can cure those issues. Features like pin-holing, tapered contact faces, scallop voiding and pocket knurling can provide the desired performance without harsh degradation of NVH levels.

Energy Suspension’s Michael Santa Cruz adds a little perspective: “What’s harsh to you is soft to me and vice versa. It’s like when you lower your vehicle: It looks better, handles better but doesn’t ride better.”

The GRM staff’s experience? Generally polyurethane bushings create more NVH, but rarely is it objectionable. If you want a factory ride, yes, stick with rubber. If you’re redoing your suspension and want to sharpen the handling, then upgraded bushings will often deliver as promised.

Photograph Courtesy Energy Suspension

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Comments
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msterbeau
msterbeau New Reader
8/3/20 10:09 p.m.

Next step: Spherical bearings and rod ends.  :-)

wspohn
wspohn Dork
8/4/20 10:49 a.m.

The reason for staying with rubber is that the solid bushes (poly, Delrin etc.) rotate in the suspension components, need some sort of lubrication, and wear themselves as well as the suspension bits they run in.  The rubber don't move, they just flex (and of course eventually wear out that way)

The reason for not staying with the old style rubber bushes is that it seems that it is becoming more and more difficult to source decent rubber today. In the old British car world, much (most?) of the rubber bushes come from China or India and while one batch may be great the next may be crapola.  Owners are finding that they are changing them again after less than a year on the car when the OEM bushes would last years.

The market is strange - I would gladly pay 3 or 4 times as much for bushes that would last a long time or chrome bits that didn't need to be stripped and rechromed out of the box if they are to last any time at all, but the vendors tell me that people opt for the cheapest part (and then bitch when they get what the paid for).  (Hint to MG owners - never use anything but the MGB V8 'metalastic' bonded rubber/steel bushes - they still seem to last well).

Given that, I think that the solid bushes will gain a following, as they offer both bragging rights and reasonable longevity (haven't seen any complaints about the solid bush quality control, but maybe I haven't noticed).  Just remember that bushes like that don't make their wear noticeable until it is great enough that it may also require replacement of some suspension bits (I am assuming that no one ever checks anything under their car that doesn't make noise).

ProDarwin
ProDarwin UltimaDork
8/4/20 10:56 a.m.

I've never had poly suspension bushings create an objectionable amount of NVH.  But in my experience they wear out much quicker :(

 

Unfortunately, for many vehicles, replacing the rubber bushings is nearly impossible, or stupid expensive, or NLA.

Tyler H (Forum Supporter)
Tyler H (Forum Supporter) UberDork
8/5/20 1:45 p.m.

Polyurethane bushings are often misapplied.  It's not NVH, it's the fact that it takes a 20 ton press to get the OE bushing out, and then you can just push a greased up poly bushing in by hand?  There is a lot of slop there with poly bushings.  They float around on-center and then the take-up is abrupt because they're less compressible than rubber when corner loads build.  

If a suspension component moves through more than one plane in it's travels, don't put a polyurethane bushing in it.  They're not good in control arms and trailing arms.

Just because it's aftermarket and it's red doesn't mean it's an upgrade.  

MrFancypants
MrFancypants Reader
8/5/20 6:48 p.m.
Tyler H (Forum Supporter) said:

Polyurethane bushings are often misapplied.  It's not NVH, it's the fact that it takes a 20 ton press to get the OE bushing out, and then you can just push a greased up poly bushing in by hand?  There is a lot of slop there with poly bushings.  They float around on-center and then the take-up is abrupt because they're less compressible than rubber when corner loads build.  

If a suspension component moves through more than one plane in it's travels, don't put a polyurethane bushing in it.  They're not good in control arms and trailing arms.

Just because it's aftermarket and it's red doesn't mean it's an upgrade.  

If the replacement bushing isn't precisely the correct size doesn't that suggest a manufacturing or design issue? I'm fortunate enough that I was able to replace my stock, void filled control arm bushings with solid rubber bushings from a performance model from the same manufacturer. The new bushing was rubber encased in a metal sleeve and with some grease it went in so easily I could have pushed it in by hand (I used a hammer and a block of wood).

Regarding trailing arms....  I don't see why a poly bushing with a metal sleeve through the center and washers on the outside can't work. No twisting forces would be applied to the poly because of the sleeve.

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