David S. Wallens
David S. Wallens Editorial Director
8/3/20 2:55 p.m.

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.

Read the rest of the story

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) GRM+ Memberand 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.

MrFancypants
MrFancypants Reader
2/13/21 9:03 p.m.

I answered my question by installing the parts (poly bushings in trailing arms).  There's zero noise from the poly bushings because there's no actual friction between the bushing and anything else; the bushing exists to fill a void.  Just as with the stock rubber piece that was there, there's a metal insert within the bushing that the bolt goes through to secure the arm to the chassis; so it's metal to metal contact. 

Handling is improved more than I thought possible; conceptually I understood that toe deflection at the rear would impact how the car turns, but the most noticeable change is how much steering accuracy and response is improved.

I'd have been perfectly happy to use solid rubber instead, but as far as I can tell this isn't a thing that exists.

350z247
350z247 Reader
2/14/21 1:12 p.m.

In reply to MrFancypants :

Definitely agree on the steering improvements. I replaced every single bushing on my R53 Mini with poly bushings and any other wear point (ball joints, tie rods, endlinks, etc.), and the biggest difference I noticed was the steering. The rest of the handling and ride didn't really seem to change much, though.

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