Matt Harwood

Should I replace my body mount bushings?

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I'm making my winter To Do list for the Limited and was thinking about the rubber body mount bushings. My car rides pretty well, but big bumps still really upset the car and crash through the structure. My '41 Cadillac 60S didn't feel like that and I have a '41 Roadmaster convertible sedan that actually feels better too--just a quiet THUMPTHUMP, not a KABANG! It's a giant limousine, it should really have better isolation, right? The shocks are all rebuilt, I have the tires aired down to about 30 PSI to help with the impact harshness, but I still cringe when I'm approaching big bumps. I was under the car recently and saw that all the body mount bushings were pretty well shot--the body has never been off the frame. They're crushed down and brittle.

 

So do you think putting new ones in would make any difference in the way it crashes over big bumps? They're readily available and I can probably remove the bolts, raise the body slightly, and slide new ones in there without too much difficulty.


Worth it or not? What say you?

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Matt,

Depends on how many bushings there are and how hard to get to.

Seems like a big job if that is all you are doing.

But if they are available, why not.

At least you will sleep better knowing you did it.

Got pictures of what they look like now ?

 

Another thing to check is the 4 rubber bumpers in the suspension.

My fronts were missing when I got the Buick, and the "A" arms were bottoming out on the frame.

Made your KABANG sound...............

 

Mike in Colorado

Edited by FLYER15015 (see edit history)
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Matt, 

    The body mount bushing in my 1925 Buick were original and rock hard black rubber.  They are only 1/4" thick, but they are 70 durameter rubber when new and they have reinforced webbing in them.  Some of the reason for using them is that the frame does twist and it is not rigid. They should not be overly difficult to change.  You may have some other issues, but those body mounts are well past their time to provide any shock control.    Hugh

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As the body mounts get old they may shrink or compress as well as harden.  The hardtop 40 Buicks that I've dissected have rubber on both sides of the frame at the connection points, the point being there is plenty of opportunity for the body to frame bolts to become slightly loose, but not because the fasteners have loosened.  I say rubber but the material looks like conveyor belt material and appears as a fiber reinforced rubber.  If shrinkage has occurred, then the body mounts may not be as tight as they once were.  You may see some improvement if they are tightened after inspecting to be sure they are indeed loose. You may see more improvement by replacing the rubber mounts.  I'd also note that the rubber in each mount may not be equal in thickness as some may have been adjusted or shimmed in the factory to accommodate variances in the frame or body.  Whether you tighten or replace the rubber mounts, be cautious of your body alignment.

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The shimming of the body mounts has a lot to do with how the doors close. Changing things that are OK may open up a real can of worms.

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I did some looking in the manual and the car has 11 body mounting points per side. Ken is right, it appears that there's a bushing above and below, probably to keep the bolt from transmitting noise into the cabin. Then I looked at Steele Rubber's prices for said little biscuits--$14 each. So I need 44 of them at $14 each. That's like $650 worth of little rubber biscuits. Hmm, I'll have to see if there's either an alternative or maybe just replace the ones between the frame and the body. I understand that body alignment depends on them, but I can manage that. 

 

We had a long drive today, maybe 220 miles, and the car performed perfectly. It just crashes a little harder. I think I'll give it a try if I can find some suitable bushings that aren't so expensive.

 

Thanks!

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I cut mine out of one of these.  You can get used ones for free from any heavy truck repair or body shop. They are similar in thickness and composition to what was on my car.

 

 

8D515F0D-DBAB-416B-8479-76359F1F96A0.jpeg

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Here's the page from the shop manual showing the mounts and how they're configured:

 

1201780742_n_021942BuickShopManual-Body-012-012.thumb.jpg.d99fb06775d85c7621c05aacb333dcd8.jpg

 

This is the bushing that Steele offers for $14.60, which is 5/8 thick and two inches square:

 

019299c353349274d4613ded2e65.jpg

 

CARS sells these round ones that are 1/2" thick for $6.75 each:

 

s-l300.jpg 

 

I also just saw that Bob's sells this as an assembly for $15.50 (I believe they have the picture upside-down--my guess is that the square bushing goes between the frame and the body):

 

BM-518.jpg

 

Hmmmm...

 

 

Edited by Matt Harwood (see edit history)

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Matt, 

    Making your own pads will be the least expensive option.  You can buy a punch set or get the right size off Ebay and you can punch them out in a vise with wood on the back side.  It looks like most of the replacement bumpers do not have the reinforcing webbing, and I would suggest that the reinforcing webbing is important for longevity of the rubber in service.  I originally made a set for my car using just rubber, and I noticed that the rubber would tear, so I purchased the reinforced rubber which prevents the rubber from tearing.  I did not use the non reinforced rubber pads.  Look for 70A buna rubber nylon reinforced.  Mud flaps and conveyor belts are probably reinforced.        Hugh

 

1844037443_2016-03-0319_44_13.thumb.jpg.5539df77d58a5dc535d4dca52f9ae418.jpg

164085652_2016-03-0319_25_42.thumb.jpg.18da1c66db612c74a8e4451332b2c155.jpg

 

Edited by Hubert_25-25 (see edit history)
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Excellent advice, guys! That's exactly what I'll do. McMaster-Carr seems to have fabric-reinforced neoprene sheets that are 1/2-inch thick that's a fraction of the cost of the reproduction pieces. That's where I'll start.


Thank you!

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As an interesting side note and for future posterity on topic searches for this thread, the convertible in 1940 only has rubber mounts between the body and the frame, nothing under the frame.  I suspect this arrangement was for improved rigidity in the convertible bodies.  It is likely that convertibles of other years have this same arrangement of rubber between frame and body only, with no rubber under the frame.  

Edited by kgreen
typo (see edit history)

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3 hours ago, kgreen said:

As an interesting side note and for future posterity on topic searches for this thread, the convertible in 1940 only has rubber mounts between the body and the frame, nothing under the frame.  I suspect this arrangement was for improved rigidity in the convertible bodies.  It is likely that convertibles of other years have this same arrangement of rubber between frame and body only, with no rubber under the frame.  

I found some information in relation to shimming body mounts in convertibles which may be useful to you:

"Convertible models are to be shimmed using hard shims except for #6 and #7 center body bolts which use the closed car soft body shims. When shimming, the top should be loosened and when lowering the top , care should be taken to see that the top pilots of the windshield with no excessive strain."

 

My 40 super has 22 mounting locations. Between the body and frame was a square piece of rubber that was about half an inch thick and soft. Under the frame was a thicker and harder round rubber I think acted like an insulation washer against the bolt. A friend gave me a sheet of rubber built for absorbing vibrations in machinery mounts. I will use that for the square pieces between body and frame. On other forums I've seen the word "hockey pucks" used in relation to body mounts. I'm not sure if they actually used hockey pucks as a substitute or just called them that because they are similar size and shape. I haven't found anything suitable for the round ones yet and I'm not prepared to pay the price for Cars/Bob's body mounts.

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