I remember aftermarket polyurethane suspension bushings being almost universally available for road cars from 10+ years ago. But it seems like no one is making them for newer cars nowadays.
What gives? Did car manufacturers move away from big squishy suspension pivots? Did the aftermarket move on to better materials? Or did they just fall out of favor and is everyone just running on stock rubber bushings?
lack of a market for racing newer cars?
NVH. Plain and simple.
There are places that sell bushings by size rather than application. Energy Suspension comes to mind. You can go to their website and scroll thru all the different styles and sizes. Pieced together a set for the 2002 race car once upon a time and it was about half the cost of buying a "kit" from one of the BMW vendors that was essentially and maybe even exactly the same thing. The thing is, bushings don't know they are suppose to be more expensive when they go into a BMW or Porsche until someone slaps a BMW or Porsche sticker on them.
I have never felt that newer cars really need the bushing upgrades that the older one do. The chassis now are just so darn stiff that the suspension can be tuned to do its actual job without leaning on the bushings. Little bit of wiggle is not the complete end of the world even on a track in this case.
The older cars used to use the bushings as a part of the suspension and the NVH. Putting in poly was the only choice.
Poly wears out too fast too. And noises without regreaseing.
wearymicrobe said:I have never felt that newer cars really need the bushing upgrades that the older one do. The chassis now are just so darn stiff that the suspension can be tuned to do its actual job without leaning on the bushings. Little bit of wiggle is not the complete end of the world even on a track in this case.
The older cars used to use the bushings as a part of the suspension and the NVH. Putting in poly was the only choice.
This.
I dont know how much of a factor this is but i think the amount of engineering that goes into bushings has gone up tremendously. I would say it's probably now the norm for a bushing to be designed to be stiff in one axis and soft in another. It's probably harder to design aftermarket bushings that don't have unintended consequences these days, and there were already plenty of unintended consequences when basically all the bushings were solid and cylindrical.
Appleseed said:NVH. Plain and simple.
NVH?
Noise, Vibration, Harshness(?).
Not certain on the last one, but captures the intent.
Correct.
I always thought it was "harmonics."
Trackmouse said:Poly wears out too fast too. And noises without regreaseing.
I find that poly usually lasts much longer, although if it's used in an application where a bushing needs to deflect off of its axis (like multilink rear suspension) that will put a lot of stress on the poly bushings and might cause them to wear faster than rubber, since they don't like to flex so much.
I'm pretty sure, at least with most modern rear suspensions, if you put non-compliant bushings in there, nothing would move. At all.
In reply to Streetwiseguy :
Many suspensions need some compliance in the bushings. On a 4-link solid axle rear end, it's overconstrained if you have solid bushings on both ends of all five links.
In reply to mck1117 :
Which is exactly what I have and have done, the lack of rear suspension movement is crazy.
mck1117 said:In reply to Streetwiseguy :
Many suspensions need some compliance in the bushings. On a 4-link solid axle rear end, it's overconstrained if you have solid bushings on both ends of all five links.
Which brings up a question for myself that I've been wondering about; if one were to put poly bushings on just one end of their rear trailing arms which is the best location. The body end or the spindle end?
WildScotsRacing said:mck1117 said:In reply to Streetwiseguy :
Many suspensions need some compliance in the bushings. On a 4-link solid axle rear end, it's overconstrained if you have solid bushings on both ends of all five links.
Which brings up a question for myself that I've been wondering about; if one were to put poly bushings on just one end of their rear trailing arms which is the best location. The body end or the spindle end?
I know that using poly on the spindle end and rubber on the body end is a good way to get more stiffness without much increase in NVH.
IMO, with a 4 link, poly / rubber combo will probably still bind too much. I'd rather see either poly or rubber at one end and a flex joint at the other end. Or better yet, berkeley NVH and run flex joints at both ends.
rslifkin said:IMO, with a 4 link, poly / rubber combo will probably still bind too much. I'd rather see either poly or rubber at one end and a flex joint at the other end. Or better yet, berkeley NVH and run flex joints at both ends.
A triangulated 4-link should ideally have some kind of spherical bushing (like a flex joint) at all ends, because every link has to pivot freely on 2 axes or there will be bind. If cylindrical bushings (the worst kind for this type of suspension) must be used, they should be rubber to allow for maximum off-axis articulation. Land Rover uses a torus-and-hourglass bushing arrangement on their 4x4s to prevent bind:
In reply to GameboyRMH :
So essentially, for a Mactrut rear rear suspension with trailing arms, poly at either end is the worst possible thing you could put in it, and heim joints will perform more accurately than rubber bushings correct?
In reply to WildScotsRacing :
Yep at the cost of NVH and the need to replace the joints more often. But for racing, those are secondary concerns.
WildScotsRacing said:In reply to GameboyRMH :
So essentially, for a Mactrut rear rear suspension with trailing arms, poly at either end is the worst possible thing you could put in it, and heim joints will perform more accurately than rubber bushings correct?
Technically correct, but the difference between "ideal" and "worst possible" is much smaller with that kind of suspension because very little off-axis movement is needed. A triangulated 4-link needs so much off-axis movement that it's kind of wrong to say there's an "axis."
Stefan said:In reply to WildScotsRacing :
Yep at the cost of NVH and the need to replace the joints more often. But for racing, those are secondary concerns.
Well, in that case looks like I'll be spending some money with Pierce Motorsports before next season starts. They build a tubular aluminum rear trailing arm set with heim joints pre-installed for the Mazda BG chassis cars, or in my case my Escort, for only a couple hundred bucks.
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