Author Topic: Polyurethane Bushings  (Read 358 times)

kingwil

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Polyurethane Bushings
« on: September 10, 2018, 03:37:01 PM »
No doubt this topic has been talked about over the many years that this Forum has been active.  However, I haven't seen anything recently and technology has improved over time. 

I have a 1979 TA with an Original WS6 Handling Package with the 4-wheel disc brakes and 15X8 Aluminum Snowflake Wheels.  When I say original, the car has the original OEM Rubber Bushings on it, that are now 39 years old.  Car and handling is tight, however, seeing as the car will be 40 years old next Spring in 2019, I was thinking of putting on Polyurethane Bushings on the front and rear suspension.

Before we get into the discussion and suggestions on new bushings for the WS6 suspension, my 1979 TA has gone through an evolution over the years and although it looks original from a distance, it has had many modifications, which may influence suggestions on this forum:

Car from Factory:  79 TA with T-Tops, A/C, WS6 Handling Package with 4-wheel disc brakes, Power Steering, power windows, power door locks, 2.73 posi rear end, 403/TH350, 70-series tires on 15X8" snowflake wheels

Current Configuration:

9.6:1 compression 403 with a race-prepped TH700R4 overdrive Tranny (rated for 700HP) with 4.10 8.5" 10-bolt posi rear end,
Headers, 2.5" Pypes Exhaust with X-Pipe flowing to stock chrome exhaust tips.  This car runs 12.87 @ 101 mph at the track.

Herb Adams VSE Solid Body Mount / Lowering Kit - lowers front end approximately 1" - helps prevent front sub-frame sag
Herb Adams VSE Front Structure Kit - support bars that run from the A-Arms to the Firewall to help prevent front subframe sag
Competition Engineering Bolt-In Sub-Frame Connectors to create a full-frame car - these were welded in after bolting up
P255/60R15 Tires on Front and P275/60R15 Tires on the back.
Hooker 4-Point Rally Bar for added support in the car

This car handles great and has had one alignment done in it's 39 year old life.  Therefore, it has cracked and bulging OEM rubber bushings on the front and back of the suspension.  Since the car will be 40 years old, I noted in the Ames Performance Firebird Trans Am Catalog that I picked up at the Pontiac Tri-Power Nationals in August at Norwalk Raceway Park in Northern Ohio, that there are many options available for rebuilding the suspension from using OEM parts to aftermarket polyurethane parts.  Here are my thoughts on upgrading the suspension and need some feedback based on your experience with suspension upgrades:

Front Suspension:

Moog Upper and Lower Ball Joints
Moog Inner and Outer Tie-Rod Ends
Energy Suspension Polyurethane Upper and Lower Control Arm Kit (8 pieces for the front end)
Energy Suspension Polyurethane Bushings/Frame Brackets and Polyurethane End Links for the Front 1 1/4" Sway Bar
KYB Gas Performance Front Shocks

Rear Suspension: 

Energy Suspension Polyurethane Leaf Spring Cushion Kit
Energy Suspension Polyurethane Leaf Spring Bushing Kit for front eye bushings and rear shackle bushings
Energy Suspension Polyurethane Bushings/Bracket Kit for 1" Rear Sway Bar
KYB Gas Performance Rear Shocks

I want to retain the factory 1 1/4" solid front sway bar and solid 1" rear sway bar that came with the car.  Although I have replaced the front coil springs and rear 4-leaf, leaf springs in the back, I am planning on keeping the springs as well.  Considering that I have solid body mounts, front structure kit, sub-frame connectors, and so on, am I on the right track with the polyurethane bushings for the front and rear suspension?  At this time, I am not looking to replace the engine and tranny mounts with polyurethane.

I remember the polyurethane bushings coming out in the early 90's (maybe before that?) and since we are approaching 2020, there has been significant improvements in the polyurethane bushings in the last 25-30 years.

Please provide the pros and cons for EOM Rubber Bushings vs. the Polyurethane Bushings and if you have Energy Suspension Polyurethane Bushings or another brand of Polyurethane Bushing on your car and if it improved handling. 

Thank you in advance for your feedback.
 
79 Nocturne Blue 403 Firebird TA
72 Viking Blue 455 Cutlass Convertible

79T/Aman

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Re: Polyurethane Bushings
« Reply #1 on: September 10, 2018, 05:20:00 PM »
I have gone over poly bushings in the past, and nothing has changed when it comes to polyurethane, as for technological improvements there has been some made, Delrin bushings.

I would install tall upper ball joints instead of stock (raised roll center, geometrically increases the effectiveness of the sway bar and coil springs)
KYB shocks my be a little on the harsh side, Bilstein HD may be a better choice.
Poly bushings in the front sway bar to make it more effective.
Rear sway bar should be 3/4" if it is a stock WS6 bar...maybe you have a HA 1" rear bar?
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Grand73Am

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Re: Polyurethane Bushings
« Reply #2 on: September 10, 2018, 07:03:41 PM »
I wouldn't use urethane bushings for the front control arms. They can't twist, so they wallow out. And there's the squeaking problem when the grease goes away. Not worth it.
I'd use Moog rubber bushings. They twist, as control arm bushings are designed to work. The originals have lasted nearly 40 years, so you can expect long life from new ones too.
Urethane is okay for non-twisting situations. But better grease up those sway bar to frame bushings good with the sticky poly grease, or they'll be squeaking.
Urethane isn't needed for the front leaf spring eye.
Steve F.

79T/Aman

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Re: Polyurethane Bushings
« Reply #3 on: September 10, 2018, 07:43:19 PM »
forgot to mention about the poly and leaf springs as Steve said NO poly in the front leaf spring eye and don't use poly leaf pads either they don't grip the leaf spring and cause the rear end to shift, this is why we don't use them.
Poly front eye bushings will cause binding and spring rate creep resulting in snap over steer, especially with that big rear bar.
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kingwil

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Re: Polyurethane Bushings
« Reply #4 on: September 12, 2018, 02:59:10 PM »
The plan is to use plenty of lubricant on the polyurethane bushings, since these bushings need to be able to rotate within the sleeve, and not twist and stretch (and deteriorate over time) like a rubber bushing would.  So, let's assume that the "squeaking myth" is addressed for Poly.  Based on the commentary, it sounds like Polyurethane Bushings gets "2 thumbs up" for the Front Sway Bar and End Links, and also for the Rear Sway Bar.  The sway bars and associated brackets/bushings do not have direct contact with the road and would not transfer NVH (noise, vibration, and harshness) from the Road to the Cab like Polyurethane Front Control Arm Bushings and Polyurethane Rear Leaf Spring Front Eye Bushings and Rear Shackle Bushings would.

Let's address the Front Eye Polyurethane Bushing for the Rear Leaf Springs on a late 70's TA.  79T/Aman and Grand73am, what year car and model did you put Polyurethane Bushings in the Front Eye and have disasterous results to formulate the opinion that Poly should not be used for the Front Eye? What brand of polyurethane bushing did you use and how long ago did you put in the poly bushings and have less than adequate results?  Can you elaborate in detail on this binding issue in the Front Eye?     

Next Question.  Typical Rubber Bushings have a Durometer Rating of 50A and Polyurethane Bushings typically have a durometer Rating in the 65A to 85A range depending on the manufacturer and location (front control arms, sway bars, rear leafs, etc,...) the Poly Bushing is used on the car.  Can you tell me what brand you used for Poly and what durometer rating the bushings had? 
   

79 Nocturne Blue 403 Firebird TA
72 Viking Blue 455 Cutlass Convertible

Re: Polyurethane Bushings
« Reply #4 on: September 12, 2018, 02:59:10 PM »

Grand73Am

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Re: Polyurethane Bushings
« Reply #5 on: September 12, 2018, 07:13:13 PM »
I would say the "rubber deteriorating over time" assumption is the myth. While it's technically true that it will eventually deteriorate, it will be a long time before it does. In my car restoration hobby and business, spanning 40 years, I really have only seen bad rubber bushings in 50's and early 60's cars. From the late 60's and up, they're usually replaced only because it's something you do when rebuilding the front suspension, so everything will be new. For example, I have a 75 with 170K miles on it, and the original rubber bushings are still good. I'm going to rebuild the front suspension next year, but not because of the bushings. It will be because the lower ball joints will have worn out, not the bushings. The bushings in these cars are pretty stout. While it's apart, I may as well install new Moog bushings, although it probably still doesn't need them. I have a 73, that I rebuilt the front suspension 20 years ago with new Moog bushings, and it's still good today. And these are regularly driven cars, not cars that don't get out much. So, the idea that rubber deteriorates quickly is a false assumption.

On the other hand, I have tried urethane control arm bushings in the past, wanting to believe the claims about durability. But after only a year of light use, I noticed them becoming loose, and I eventually took it apart to see what was happening, and the bushings had wallowed out. So, they didn't last very long. That's when I realized that urethane was not a suitable material for that purpose, and I'll never use it for that again. 79T/Aman has probably seen much more of that than I have, considering the nature of his business. So, I only use Moog oem type replacement bushings since then, since I know what kind of longevity I can expect from them from my personal experience. If I wanted to upgrade from rubber, I'd get the Delrin bushings that 79T/Aman mentioned, since urethane is not an upgrade.

As for the leaf spring front eye bushing, the leaf springs I've bought in the past come with a rubber eye bushing installed. I've never seen a rubber front eye bushing wear out, so I've never seen the need to replace it with urethane. It is in a position where some degree of flexibility helps, something urethane isn't good at.

For the other purposes that urethane is good for, Energy Suspension was good quality.
Steve F.

Jeremy

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Re: Polyurethane Bushings
« Reply #6 on: September 12, 2018, 07:27:14 PM »
Tried poly bushings and didn't keep them for long.  I had them in the leaf springs, control arm pads, and a arms.  Replaced them all.

I feel that handling has gotten better going back to the rubber.

My car is braced very similar to yours.  Solid subframe bushings, subframe connectors that are welded in.  Front structure kit.  Steel rocker extensions welded in.

If you don't want rubber, I'd go Delrin or greasable steel.

Not a fan of poly.  I found that it was non linear in its performance.  Seemed to bind and squeak as well.

Jeremy

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Re: Polyurethane Bushings
« Reply #7 on: September 12, 2018, 07:27:48 PM »
As for shocks, I'm a fan of the ridetech single adjustables.

NOT A TA

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Re: Polyurethane Bushings
« Reply #8 on: September 12, 2018, 08:44:04 PM »
Worn front spring eye bushing. I've seen quite a few.

John Paige
Lab-14.com

428Bird

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Re: Polyurethane Bushings
« Reply #9 on: September 13, 2018, 05:35:36 AM »
forgot to mention about the poly and leaf springs as Steve said NO poly in the front leaf spring eye and don't use poly leaf pads either they don't grip the leaf spring and cause the rear end to shift, this is why we don't use them.
Poly front eye bushings will cause binding and spring rate creep resulting in snap over steer, especially with that big rear bar.

Absolutely. Nothing quite as scary as having your car start rear steering like a forklift under hard acceleration. I was making a left turn and started rolling on the throttle midway through the turn. The rear axle shifted and spit out the bottom pad on the drivers side, causing the rear to shift in such a way that sent me to the right (remember, I was turning left).

Never-ever-ever again. I pulled what was left of the pads and replaced with rubber.

Britt
1975 Trans Am turned into a mix-year 73'ish Formula. 4" Stroked 400, Edelbrock Heads, Comp Cams XR-288-HR, Harland Sharpe 1.5's, Peformer intake with 800 Q-Jet. Hooker Super comps through 2.5" exhaust and Ultraflows. Super T-10 with 3.73's

79T/Aman

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Re: Polyurethane Bushings
« Reply #10 on: September 13, 2018, 02:03:53 PM »
forgot to mention about the poly and leaf springs as Steve said NO poly in the front leaf spring eye and don't use poly leaf pads either they don't grip the leaf spring and cause the rear end to shift, this is why we don't use them.
Poly front eye bushings will cause binding and spring rate creep resulting in snap over steer, especially with that big rear bar.

Absolutely. Nothing quite as scary as having your car start rear steering like a forklift under hard acceleration. I was making a left turn and started rolling on the throttle midway through the turn. The rear axle shifted and spit out the bottom pad on the drivers side, causing the rear to shift in such a way that sent me to the right (remember, I was turning left).

This is more common that most know about, I had a local customer that kept shifting the rear end on his car at the strip, simple fix was to put the rubber pads back in.

Never-ever-ever again. I pulled what was left of the pads and replaced with rubber.

Britt
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79T/Aman

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Re: Polyurethane Bushings
« Reply #11 on: September 13, 2018, 02:13:13 PM »
quote  "Let's address the Front Eye Polyurethane Bushing for the Rear Leaf Springs on a late 70's TA.  79T/Aman and Grand73am, what year car and model did you put Polyurethane Bushings in the Front Eye and have disasterous results to formulate the opinion that Poly should not be used for the Front Eye? What brand of polyurethane bushing did you use and how long ago did you put in the poly bushings and have less than adequate results?  Can you elaborate in detail on this binding issue in the Front Eye?"

The year and model  of car is not the significant factor here, it is what the front bushing has to be able to do while in service.
The front leaf eye has to articulate putting a solid type bushing in it's place reduces the ability to articulate and causes rate creep, the leaf spring binds and the rate goes up causing an oversteer situation.
If a more solid front bushing is needed a spherical bearing is the best approach but a stiffer leaf spring is needed to make up for the rate lost from the rubber bushing twist.
Rear up in the VSE book where Herb talks about A-arm bushing material, I would not follow VSE practice to the T now a days though because of the vast improvements made in modern tires VS when Herb wrote the book, but the bushing material portion of the book is stile 100% valid .
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Re: Polyurethane Bushings
« Reply #11 on: September 13, 2018, 02:13:13 PM »
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