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[C2] polygraphite, polyurethane sway bar bushings

 
Old 02-05-2019, 09:59 PM
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68hemi
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Default polygraphite, polyurethane sway bar bushings

It has been suggested that we should change the front sway bar bushings for improved handling. My question is should we use polygraphite or polyurethane?
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Old 02-06-2019, 09:12 AM
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DansYellow66
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I've used poly sway bar bushings on my cars since the late 70s and found no issues with them. They seem to slightly tighten up responsiveness of the sway bar but don't expect miracles. Having said that I still have the rubber bushings in the frame mounts of my 66 and poly on the spring links. The bigger big block sway bar and the size of the stock bushing retainer make using poly bushings a difficult fit. I would use the black polygraphite given a choice.
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Old 02-06-2019, 09:29 AM
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GUSTO14
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Changing to polygraphite, polyurethane sway bar bushings will have the same effect as increasing the size of the sway bar, without actually changing to a larger bar. Rubber bushings compress and distort so they delay/retard the standard bars reaction to inputs. Because poly bushings are stiffer, they respond to inputs almost immediately, just as increasing the diameter of the bar might.

By selectively replacing the rubber bushings with poly you can actually 'tune' the bars effect on the handling of the car. A good way to help you decide just how much bar you really want or need. Use rubber for the street and poly for autocross...

Good luck... GUSTO
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Old 02-06-2019, 11:16 AM
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colo63sw
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Search other threads on this subject. Some have had nothing but problems with poly bushings, they become brittle and crumble to dust.
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Old 02-06-2019, 11:23 AM
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I had poly bushings in my Malibu, I liked them. I put a Adco bar on the front of the vette with the supplied bushings. They squeak like crazy! They have to be lubed 2 or 3 times each summer of driving.
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Last edited by DSR; 02-07-2019 at 10:09 AM.
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Old 02-06-2019, 11:40 AM
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SWCDuke
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I don't know the difference between polyurethane and polygraphite. but "hard" front bar bushings will crisp up steering response and reduce the tendency of C2 small blocks to snap into oversteer at the limit. Since there is relative movement between the bar end and bushing they won't last as long as rubber, where all the strain is in the rubber itself, so they should be checked frequently for tightness and replaced when worn excessively.

RETAIN THE OE-TYPE RUBBER PILLOW BLOCK BUSHINGS. There is no technical reason to change them. In fact, it's a bad idea because they will wear because of relative motion between the bar and bushings and transfer more harshness to the frame. OE quality rubber pillow block bushings should last indefinitely because all the strain is in the rubber.

Duke
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Old 02-06-2019, 01:54 PM
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GTOguy
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The poly sway bar bushings I installed in my '65 GTO squeak like crazy, but have held up for years. I lube them with graphite spray every oil change. Never again.
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Old 02-06-2019, 02:25 PM
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Originally Posted by GTOguy View Post
The poly sway bar bushings I installed in my '65 GTO squeak like crazy, but have held up for years. I lube them with graphite spray every oil change. Never again.
It is my understanding that the polygraphite bushing have the graphite impregnated in them to fix this.
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Old 02-06-2019, 07:23 PM
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DansYellow66
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Originally Posted by 68hemi View Post


It is my understanding that the polygraphite bushing have the graphite impregnated in them to fix this.
That's may understanding too - but I think they still should be lubed up real good. I've never had any issues with squeaking poly bushings but I was probably lucky in my younger days and just can't hear them now a days.
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Old 02-06-2019, 07:37 PM
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rtruman
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They were highly recommended in 1996 .
My 63 had a lot of problems after I installed them' Went back to rubber
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Old 02-10-2019, 07:46 PM
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Originally Posted by rtruman View Post
They were highly recommended in 1996 .
My 63 had a lot of problems after I installed them' Went back to rubber
G them

I have had them on other old classic. I used the supplied grease but later had squeaks as well.

I am only interested in using them for the front sway bar as suggested by other for improved handling.
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Old 02-10-2019, 08:27 PM
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DansYellow66
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I believe at least the poly end link bushings are a no-brainer decision - what's to go wrong and firmer than rubber. I've run them on a number of cars since the 70s and never had one an end link bushing fall apart. But, you also the option of going to a little bigger front sway bar. If it's a small block car a big block sway bar is a pretty simple upgrade and shouldn't have any down side.
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Old 02-11-2019, 03:41 PM
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The base small block front bar was increased from 3/4" to 13/16" ca. mid-seventies. The base big block bar is 7/8", Z-06/F-40/41 is 15/16" and FE7 beginning in '75 is 1 1/8". Remember that an anti-roll bar's contribution to roll stiffness varies with the FOURTH power of bar diameter, so even a 1/16" increase in front bar diameter should noticeably increase understeer, but that's not necessarily a good thing. What you want is mid understeer on turn-in and near dead neutral at the limit of adhesion, and that's what hard front bar link bushings should help achieve.

The problem with SB C2s is that as roll increases, the front bar link bushings compress, which effectively transfers roll stiffness to the rear. This is why they can snap into oversteer at the limit. The problem is exacerbated by the lack of anti-squat in the rear suspension, so when you lift, the rear suspension uncompresses, and the outside rear wheel toes toward out direction and camber moves in the positive direction.

My Cosworth Vega had the same problem and urethane link bushings in the front was the solution. It's now dead neutral at the limit. I first installed OE hard bushings from a 70's Trans-Am, but they eventually disintegrated. I found aftermarket examples that appeared to fit the bar "cups" better and they have held up. So it pays to shop around and find a hard bushing that fits the cups well.

Also, I believe the AIM says to tighten the nut until it bottoms out on the thread in order to compress the OE rubber bushings. Don't do this with hard bushings or they will be overstressed since they have virtually no compliance compared to rubber. Just tighten to snug... say no more than 10 lb-ft and check frequently.

They really make certain cars much safer by preventing that viscious transition to oversteer at the limit of adhesion, especially on trailing throttle, like base suspension C2 small blocks and Cosworth Vegas. It allows you to push to the edge of the envelope with a lot more confidence that the car won't snap spin if you make a mistake, the road goes off camber, has a Cf reduction, or the turn is decreasing radius. Lifting should rapidly scrub off speed to get back into mild understeer without the rear stepping out. That kind of dynamic response can save you from a crash.

Duke

Last edited by SWCDuke; 02-11-2019 at 04:02 PM.
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Old 02-12-2019, 12:32 AM
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Default SuperPro Advanced Polyurethane Bushings

Has anyone had any experience with the new synthetic bushings by SuperPro? Someone on the C4 Forum happened to mention them as being much more compliant than normal polyurethane bushings but more durable than rubber. I also see that Summit has been carrying them for a variety of applications. (At Summit you'll need to search using Super Pro vs. SuperPro)

There's an excellent video her describing their functionality.SuperPro Bushings - The Best Suspension Bushings For Your Car (Advanced Polyurethane Bushings)

GUSTO

Last edited by GUSTO14; 02-12-2019 at 12:34 AM.
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