# Front sway bar frame bushings purpose?



## GtoFM (Mar 23, 2018)

Project: ‘64 GTO - Daily driver (when finished), stock engine, front disc conversion is complete and front end has been rebuilt with rubber bushings, except sway bar bushings have not been installed, 15/16”. Trying to keep it as stock as possible.

I know exact replacement bushings are very hard to find and those offered by Ames (Moog), NAPA, AC Delco, etc. seem way to tall. They must be compressed over 1/2”! Ames suggested using a jack but the front end lifts off the ground before bushing compresses.

The C2 Corvette, ‘63-‘67, offers a similar 15/16” bushing with the top ridge, however it is 1/4” shorter than the examples above, clamp to frame.

Are the bushings meant to just secure the bar to the frame or do they play a part to reduce roll? I’ve read countless threads and only able to find a partial answer. An alignment service tech wrote in 2010 ~ “…the sway bar should twist with about 20 ft lbs of force”.

As I understand it, the sway bar must spring to compensate for roll during cornering. Does the bar move within the bushing or is the rubber designed to flex enough? Polyurethane bushings are lubed so I’m guessing the bar rolls within, eliminating bushing twist. Will the after market rubber bushings compressed too tightly hinder the torsion effect of the bar from one side to the other? If the Vette bushings tighten up enough to secure the bar, will they be loose for torsion response? 

Again, no autocross, drags or parking lot drifting planned. I am just curious and want a good street ride.


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## GTOTIGR (May 3, 2020)

Hi GtoFM.

Are your brackets that hold the sway bar bushing original / OEM? I used stock rubber replacements with original (replated) brackets on my 65 with no issue. I believe I used a light grease to lube the inside of the bushing where the sway bar sits to eliminate squeaking.

The sway bar will move inside the bushing both vertically (since it’s attached to the A-arm, via the end-links), and horizontally/ side-to-side due to the force when turning. I’d imagine that if you kept the sway bar attached by the end-links and did not install the sway bar bushings and brackets that attach to the frame that you have a lot of clanging and banging while driving. Not to mention a poor handling vehicle. Just the car movement on the road surface would result in rattling.

They definitely play a part in preventing roll.

If your not OCD about originality you can buy new brackets with bushings in a kit that should work fine.


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## GtoFM (Mar 23, 2018)

I do have original brackets but the replacement bushings seem too tall. Did you use rubber or poly and do you remember the brand and where your bushings came from? How far did they protrude from the top of the bracket?
Originality is not a necessity.


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## LATECH (Jul 18, 2018)

Saw them off


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## PontiacJim (Dec 29, 2012)

GtoFM said:


> I do have original brackets but the replacement bushings seem too tall. Did you use rubber or poly and do you remember the brand and where your bushings came from? How far did they protrude from the top of the bracket?
> Originality is not a necessity.


I believe you will also need the matching brackets for the poly bushings. I went with a larger front sway bar on my '68 so I needed the new brackets because the holes were larger and the bushing physically taller. Double check the inside diameter of the poly bushing to make sure you were sent the correct ones.

And, as *LATECH* suggested, you could saw/grind some of the flat base off to fit as long as it doesn't get too thin.


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## GTOTIGR (May 3, 2020)

GtoFM said:


> I do have original brackets but the replacement bushings seem too tall. Did you use rubber or poly and do you remember the brand and where your bushings came from? How far did they protrude from the top of the bracket?
> Originality is not a necessity.


I used OEM rubber replacements with original brackets. It’s been a while so I’ll have to check my receipts. 

Do your brackets look like this?


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## Sick467 (Oct 29, 2019)

My polyurethane front sway bar bushings (on a [email protected] build of mine) wore out prematurely after about 5,000 miles, but I had a leftover set from a Cheby project. They were the right inner diameter, but were too tall. I took the flat side that seats on the frame to a belt sander to get the height correct making sure that I did not get tehem so hot that they melted, just dusted the material off. They have been working fine now for 10,000 more miles. I left the final height so that the bracket had about an 1/8" gap on both ears before tightening down. Too much height means that the bushing gets compressed too much and will stress the bushing causing splitting and ultimate failure. Too little height and the sway bar will have room to shift up and down/fore and aft causing clunking and a lack of performance. 1/10th to 1/8th inch of gap between the bracket and the frame seat at finger nut tight would be were I put it, then tighten it down. That's for poly bushings. Rubber bushings might like a 1/16th to 1/8th more since they are usually less dense and more squishy.

Typically, poly bushings (being more rigid) rely on the slip between the bushing and the bar hence some grease to avoid squeaking. Whereas rubber bushings (being more flexible) will actually flex/twist with the movement of the bar. Greasing rubber bushings is not typically needed as slippage between the bushing and bar is not happening nor required.

I think my original poly bushings may have failed due to too much lube. I lubed the inner hole AND the outer surfaces thinking that would help eliminate the feared squeaking. Lubing the outer surfaces may have allowed it to shift in the bracket rather than stay seated at the frame and bracket. Eventually the bushings squished out and cracked some. I only lubed the hole on the next go around and all is good with no squeaks. I use synthetic grease for these types of bushings since petroleum lubes can advance deterioration by softening the bushing.



GtoFM said:


> I know exact replacement bushings are very hard to find and those offered by Ames (Moog), NAPA, AC Delco, etc. seem way to tall. They must be compressed over 1/2”! Ames suggested using a jack but the front end lifts off the ground before bushing compresses....


1/2" sure sounds to be excessive, even for rubber. I would never use a jack and the weight of the car to compress sway bar bushings.



GtoFM said:


> ...The C2 Corvette, ‘63-‘67, offers a similar 15/16” bushing with the top ridge, however it is 1/4” shorter than the examples above, clamp to frame....


Are these rubber? These sound much more promising than those that need a 1/2" of compression even for rubber. I would still consider sanding them down since a 1/4" of compression seems a bit much. I would install them as supplied and watch the bushing as the bracket is tightened down. They should budge out some, but not so much that they distort and look akward. Meaning that the ridges that run along the bracket loose contact with the bracket. If they budge out away from the bracket...you have too much compression and budge and need to lose some hieght.



GtoFM said:


> ...Are the bushings meant to just secure the bar to the frame or do they play a part to reduce roll? I’ve read countless threads and only able to find a partial answer. An alignment service tech wrote in 2010 ~ “…the sway bar should twist with about 20 ft lbs of force”...


Yes, the bushings are to secure the bar to the frame AND play a small part in reducing roll. Their main function is to secure the bar. Rubber bushings will not aid in reducing roll as much as the more stiff poly bushings, but the difference is not too noticeable. Rubber will give more and allow for a smother transition yielding a softer ride while the polys give less and react in resisting roll quicker. So, poly reduce roll a bit more than rubber. This yield more performance handling. The difference between the two types is not important to most folks who just cruise and are not looking to get that fraction of a second out of there lap time.



GtoFM said:


> ...As I understand it, the sway bar must spring to compensate for roll during cornering. Does the bar move within the bushing or is the rubber designed to flex enough? Polyurethane bushings are lubed so I’m guessing the bar rolls within, eliminating bushing twist. Will the after market rubber bushings compressed too tightly hinder the torsion effect of the bar from one side to the other? If the Vette bushings tighten up enough to secure the bar, will they be loose for torsion response?...


I touched on the difference between poly and rubber above with respect to how they slip, or not, with the bar. Too much compression on either type of bushing causes premature bushing failure not so much how they function (up to the point of failure, that is).


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## GtoFM (Mar 23, 2018)

GTOTIGR said:


> I used OEM rubber replacements with original brackets. It’s been a while so I’ll have to check my receipts.
> 
> Do your brackets look like this?
> View attachment 157225
> ...


My brackets don't have the tabs to retain the bushing. I'll post pics later. Thanks


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## GtoFM (Mar 23, 2018)

Sick467, thanks for all the advice, especially the measurements!


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## GTOJUNIOR (Aug 7, 2011)

'64-'65
Sadly no one makes an exact replacement bushing.


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## GtoFM (Mar 23, 2018)

The pic shows my original bracket and the bushings offered from 2 sources. Cutting to fit is an option but as you can see, equal amounts must be removed from top and bottom to keep the bar centered. It can’t be seen but the bottom (rounded side) of the bushings are flat so the bulge must be shaped Into the rubber. Also the bore is barely 3/4” so there’s another gap to take up.
I am ordering the Vette bushings to compare. Will update after test fit.


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## GTOTIGR (May 3, 2020)

Hi GtoFM.

I’ve used P-S-T on my 68 with great success. OEM quality, fit and function. 






PST | Sway Bar Kits | Solid Front Sway Bar | Solid Rear Sway Bar


Hollow front sway bar, hollow rear sway bar, performance sway bar, pro touring sway bar, name it we have it since 1984.




p-s-t.com





The brackets and bushings look factory, those Delco and Moog you’ve pictured do not.






Suspension - Suspension Components


Suspension - Suspension Components




p-s-t.com


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## GtoFM (Mar 23, 2018)

GTOJUNIOR said:


> '64-'65
> Sadly no one makes an exact replacement bushing.
> View attachment 157236


GTOJUNIOR,
If the SU-1148 15/16" bushing on the right is handy, what are the dimensions? (HxWxD) How does it set in that bracket? Vettes use a spacer between the frame and mounting bracket that may give the needed compression.


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## GTOJUNIOR (Aug 7, 2011)

Sorry not available to provide that detail.


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