Poly vs. rubber inner wishbone bushings

[Sportsdoc]

I'm putting my rebuilt front suspension back together and am wondering if I should use the poly bushings as opposed to the rubber ones. This will not be a race car but I plan to drive it a decent amount. And I really don't ever want to take that suspension down again anytime soon!

What do you guys recommend?

 

[tosoutherncars]

I'm going poly - to me, it's not a joint that should be absorbing motion. That's what springs and shocks are for. Also, poly lasts much longer.

Others will cite comfort, and suggest rubber. I don't think there's a 'right' answer here, just a balancing of personal preferences.

 

[jlaird]

Rubber lasts decads.

 

[racingenglishcars]

On the one hand one could say that the rubber absorbs motion.
On the other hand one could say that it's going to in any case rotate around the bushing.
If it rotates and flexes, it doesn't wear as much as if it rotates with relative motion between adjacent parts.

 

[Luke_Healey]

I don't know if I had defective parts or what, but the poly bushings I put in a Volvo I used to have turned to liquid goo after two years. It's not applicable here, since I've never seen any on a spridget, but my car squeaked quite annoyingly all over the front and rear when I had them. I carried a can of silicone spray with me to keep it quiet.

Cornering didn't improve much, but the ride certainly got bumpier /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[racingenglishcars]

It is applicable here!

A guy came into the garage in Arlington Va. one time with a Pantera. He was complaining about squeeking in the suspension. I drove the car about 3 meters before it started squeeking so much I couldn't hear myself think. He had poly bushings installed about a week earlier, and that car has a LOT of suspension bushings. The bushings were apparently lubricated when installed, and it took about a week before the squeeking started. I didn't do any further work on the car. I guess he went back to where he had the bushings installed and had them changed to rubber. Costly mistake!

 

[spritenut]

I had all poly in one Sprite, never again!
I do run poly sway bar bushings but that's about it.

 

[dklawson]

Just this weekend I finished replacing the failed poly bushings on the Mini. They were only about 4 years old. I installed a new set of poly ones from a different vendor based on a friend's recommendation. Like Luke_Healey above, the poly ones I just removed had turned to goo. IF the ones I just put in fail in 3 or 4 years (and this time I'll be watching closer) I'm going to machine my own out of Delrin and see how much rougher or noisier they are in my car. The Mini is pretty rough and loud anyway so I might never notice the difference.

 

[aeronca65t]

I had poly in my street Spridget for years. Bought at Moss. No problems and no noise. Not really "too rough" either.

I've seen the rubber bushing "mush over" and the steel sleeves will rust. At that point, the rubber bushings are a mess to take out. The polys have held up well, don't have a steel sleeve (that can rust) and come out easily, even after years of use.

I guess your getting a mixed response on this question. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[dklawson]

I think the real issue with poly is who manufactured the parts and what material they're using. I have worked with cast urethanes at work. There are temperature curing materials and two-component (mix together like epoxy) compounds. My experience is that the two behave differently over time. The uncured materials are very subject to contamination by moisture and have short shelf lives. If the company producing the bushings has a "big name" and reputation to worry about you're probably OK with urethane. If you're buying un-branded poly parts from the usual sources, I think it's the luck of the draw and so far I've been unlucky.

 

[tosoutherncars]

You'll never guess which way I'm going...

Full kit (front & rear) $129USD shipped. That's;

1 set upper trunnion outer
2 set lower wishbone inner
2 set leaf spring rear eye/shackle
1 set leaf spring pad
1 set fron roll bar, 9/16"

26 pieces total. Ordered through a Rover dealer in the US that carries Polybush. Looking forward to fitting them, I will report back with results.

 

[Sportsdoc]

Definitely getting differences of opinion, but that's why I asked the question.

I think I'm going to keep the rubber bushings that came with my a-arm rebuild and spend my money on other parts. My list of parts needed/wanted continues to grow!

 

[dklawson]

I think you're just seeing different comments based on each of our personal experiences. I suspect if you could buy the kit that Duncan showed above... you'd be just fine.

 

[tosoutherncars]

Just as a reference for any who would like it:

https://www.polybush.co.uk has a list of all of their kits (most Austin Healey, MG, and Triumph among others.)

I ordered my kit from Atlantic British, who mainly sell Rover parts here in North America, and can special order any of the Polybush kits. https://www.roverparts.com They were excellent to deal with, I was very happy with the whole experience.

RE: squeaking... the website is explicit in stating that this should not be the case. Who knows...

 

[racingenglishcars]

I seem to have followed the polybush link and ordered a Frogeye set. I have been convinced by you guys that it's the way to go. I will just hold on to them for when I put the car back together and give a report then.

 

[Dave Russell]

The differences are that the original rubber bushings have a steel inner sleeve that is bonded to the rubber. The design is such that the outer rubber is firmly pressed into it's housing. The steel inner sleeve ends are firmly clamped into it's parts. There is no intentional rotating motion between outer rubber & it's housing or between the sleeve & it's clamped parts. The rubber only twists.

The installation instructions say to only tighten the sleeve end clamping parts with the suspension in it's ride height position. This prevents twisting the rubber beyond it's design limits as the suspension moves.

The poly bushings do not twist, but rely on relative rotation between the parts. Since there is no provision for regular lubrication of these now rotating parts which were originally intended to not rotate, there may be some squeeks if the bushings are not regularly greased.

Some poly bushings are claimed to be made of a material that doesn't require lubrication. Even so, they are likely to wear faster than properly installed original design rubber bushings.

Maybe ok for a race car, not so good on the street. The actual performance gain with poly bushings is little unless the car needs the ultimate for racing.
D

 

[PeterC]

Dave.... someone got it right. Thanks. Yes, they do work differently. Ask the folks with cracked aframes.

Peter C.

 

[tosoutherncars]

Dave.... someone got it right. Thanks. Yes, they do work differently. Ask the folks with cracked aframes.

Peter C.

I can't go along with that... yes, the A-arms are prone to cracking, but due to poor maintenance and/or weak points in the design. My '78 had a crack in its d/s A-arm when I bought it, and it had never been anywhere near a poly bushing. This is a very common fault in cars that have used rubber bushings throughout their service life.

 

[racingenglishcars]

Quite true about the relative motion between parts. I have also condsidered this before purchasing the bushing set. I will rely on the claim of self lubrication.

Also, since I have been a mechanic for more than 20 years and had to remove about a thousand positioning bolts rusted to the inner sleeves, that DON'T come out. I won't do that on MY car again. No way.

 

[PeterC]

Dave.... someone got it right. Thanks. Yes, they do work differently. Ask the folks with cracked aframes.

Peter C.

I can't go along with that... yes, the A-arms are prone to cracking, but due to poor maintenance and/or weak points in the design. My '78 had a crack in its d/s A-arm when I bought it, and it had never been anywhere near a poly bushing. This is a very common fault in cars that have used rubber bushings throughout their service life.

I've seen many cracked a-frames, and you're right, even un-maintained rubber bush ones. More problematic are the upper trunion bushings, I feel. That's when we see the loose shock arms. Of the non-rubber metalistic bushings I prefer the Super Pro from superpro.com.au NFI Peter