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Rubber -v- Polyurethane... or hybrid? |
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GreggR
AMC Addicted Joined: Aug/21/2009 Location: Painesville, OH Status: Offline Points: 1267 |
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Posted: May/21/2015 at 8:48pm |
This got bandied-about quite a while back, but I couldn't locate the thread...
There were some good arguments made for a hybrid Poly-Rubber bushing set-up. I'm wondering if any one has done this as a handling/ride quality compromise. Where would you use Rubber? Where would you use Poly? Think a street car that would see some track-day action. Good handling while keeping most of your fillings in place... Gregg
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No matter where you go, there you are... Buckaroo Banzai.'75 Hornet Hatchback
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Online Points: 4473 |
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Type (w/o parentheses) in a google search box (theamcforum.com bushings rubber urethane) and you'll get the following: http://theamcforum.com/forum/urethane-or-rubber-bushings_topic57792_page1.html
I have an American and although I know others who are in love with urethane and use it everywhere they can on the car, I would not use it at the rear of the leaf springs. It makes the car feel like it's at a rodeo. However, your and other's experience may differ.
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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uncljohn
AMC Addicted Joined: Jan/03/2013 Location: Peoria AZ Status: Offline Points: 5394 |
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Polyurethane does not flex at all or very little anyway and most of the suspension parts on the era cars being restored by us are put together with rubber that absorbs impact such as from cracks in the road for example and certainly bigger and other types. Polyurethane will transmit those impacts through to the body of the car. Any movement of the suspension parts is cushioned by the rubber pieces much of them having been vulcanized to the bushing or what ever it is encased in again absorbing the stress and cushioning the impacts to the rest of the car. The polyurethane does none of that, if you put I together correctly it rotates, and if wrong will not rotate and the part it is in try's to flex instead causing stress or potentially can cause stress. That is why the suspension stiffens up and the ride becomes jarring and noisy. You could if you wanted to get rid of the polyurethane and machine aluminum pieces to go in and they will have just about the same effect.
AMC's front suspension depends on the cushioning affect of the rubber, 'specially the lower control arm. Now I am speaking of the 1970 and up ball joint cars. I have never owned something with a trunion and for a reason. But I suspect their lower control arm has the same flaws. Of the some 2 dozen or so I have rebuilt, the lower control arm is prone to damage at the pivot point in part because of the non linear twisting motion it goes through and the rubber bushing allows that to take place, and putting in a polyurethane piece forces the lower control arm to flex even more as it pivots. I won't use a Polyurethane piece unless there is nothing available and then there is no choice, polyurethane is machinable and parts can be made from it for a multitude of applications of which nothing else can be found. And I have done so over time. Tom J has probably experimented more with Polyurethane front suspension pieces on early trunion equipped AMC cars that any one I am aware of over the years. |
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70 390 5spd Donohue
74 Hornet In restoration 76 Hornet, 5.7L Mercury Marine Power 80 Fuel Injected I6 Spirit 74 232 I-6, 4bbl, 270HL Isky Cam |
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Fluffy73
AMC Addicted Joined: Nov/21/2007 Location: Castlegar, BC Status: Offline Points: 3059 |
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I like using Polyurethane on the sway bar bushings and end links. It tightens those up nicely, but doesn't effect the ride in any way. What it does do is impact the handling a bunch and helps the car stay as level as it possibly can.
Strut rod bushings should stay rubber as they need to be able to move and absorb torque and shock. I think we've had a few members here with broken strut rods and/or strut rod frame brackets from using Poly bushings there. I do like Polyurethane ball joint boots. They don't split/degrade as easily but is sometimes difficult to find them in straight black. Often times, these come in blue, red, green and that stands out too much to me if you're trying to go for stock-appearing. |
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I am genetically incapable of being Politically Correct.
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carnuck
AMC Addicted Joined: Mar/31/2010 Location: Seattle Status: Offline Points: 3942 |
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I have mixed the strut arm bushings with rubber in front and poly in the back. I should do that with my Eagle wagon too, but I'll be lucky to just get the parts swapped now.
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Got an Eagle?
http://forums.amceaglesden.com |
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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5807 |
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Seems like the rubber strut rod bushings might be out of production, Moog appears to have dropped all AMC stuff and I'm not sure if anybody else makes the strut rod bushes. The other rubber bushes are still available from other manufacturers.
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5458 |
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NAPA NCP274-9054 (Machine strut) |
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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White70JavelinSST
Supporter of TheAMCForum Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4866 |
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The WhiteJavelin has poly strut rod bushings, probably 7 or 8 thousand miles on them now, no troubles, but I don't hit every bump I can like I was driving a stolen car. It's not a daily driver either. I will say too, that when I raise the car into the air for service work, I put the jack under a block of wood near the lower ball joint to keep the suspension under as much compression as possible. Currently the car is on jack stands, for this work I removed the shocks and made droop limiters to keep the suspension compressed so the strut rods aren't damaged.
And the leaf springs have poly bushings also, the ride feels great. Also have sway bars with poly. So far so good. Your experience may differ. Attention to detail is important, even when driving. Armand |
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70 Javelin SST, second owner, purchased 1972
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Lucas660
AMC Addicted Joined: Apr/16/2012 Location: Vic, Australia Status: Offline Points: 1344 |
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Don't forget to use the special grease. I'm into poly.
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prostreetamx
AMC Addicted Joined: Jul/15/2007 Location: Las Vegas, NV Status: Offline Points: 1532 |
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I have poly everywhere in my front suspension and low sidewall 17" tires. This car got beaten up pretty hard on a recent trip to San Diego and bottomed out a lot. It rides much rougher on bad roads with the poly but rides like a dream on smooth roads with a very firm and predictable ride manners. This car has Shockwaves instead of coils in the front so my suspension travel is limited some compared to the coils. This car is my daily driver with over 40k miles on it over the last 4 years. I had been running a rubber bushed 4 link in the rear but the torque of the Hemi and some other factors led me to replace all the rubber bushed rod ends with stainless 5/8" rod ends. I ripped the mount off the axle and frame which caused some misalignment which contributed to the rubber ends premature failure but the summer heat in Las Vegas also kills the rubber pretty quick. I've have stock replacement strut rod bushings crack in less than 1 year. I switched to the 2 piece Ford style bushing on my other AMC's.
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Richard Payne
Las Vegas,NV 72 5.7 Hemi Javelin 77 Prostreet 401/727 AMX, [/URL] |
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