The Bird needs some TLC. One of those items are the subframe bushings. What do you guys like and why? Rubber? Poly? solid?

I will be putting some kind of subframe connectors in eventually. So, whatever will compliment with the connectors would be appreciated.

Many more questions to follow!

Dave

I'll give you the same answers as last time. Reread my post on page 2 and 3. Follow as prescribed.

/forums/ubbthrea...true#Post106330

Subframe connectors usually require solid bushings.

or at least poly...

Robert

I've had subframe connectors on cars with stock bushings and they work good too. It just depends on how solid you want it.

Depending on the style of subframe connector, using rubber mounts can be a really bad idea.

My car has welded subframe connectors, with the connectors tied to the car's floor. But they left rubber body mounts. Time to change them. How?

I understand the issue of flex at the body/ subframe and tying the front and rear together. But isn't that what we are trying to do?

In other words, with a solid frame, typically, rubber was used from the factory. If the connectors are not welded to the floor pan, should I still stick with solid or poly mounts?

I just want to stiffen up things a bit. Vert with a bit more power than stock.

Dave

Polygraphite would be my choice....

That will be a fun task... Not!

Typically, the connectors aren't cut and welded into the floor pans like that. And most will replace the bushings at the same time as the connectors are added so changing them out again isn't an issue. I have one vert that doesn't need them and the other has Global West.

With a solid frame from the factory (which I am assuming you mean a full-frame), the whole frame is isolated from the body structure with mounts. With subframes and connectors, you are either bolting or welding to the rear, which has no isolation, and then connecting to the front with the bushings of your choice. Not the same as the full-frame setup.

Note on modern cars the entire subframe is integrated in the body without isolators. This is more like the solid bushings with subframe connectors.

Poly will last much longer than rubber, but it won't last forever. Just do solid and never look back. There is no reason not to.

P.S. One guy on another forum used polygraphite and complained of squeeking noise after installing connectors.

Here is some more reading:
http://forums.performanceyears.com/forums/showthread.php?t=548969&highlight=bushings

Note, be careful as some people on the thread switched confused the original intent which was body bushings as opposed to control arm bushings. If you see Del-A-Lum or Delrin they are talking about control arms.

Quote: P.S. One guy on another forum used polygraphite and complained of squeeking noise after installing connectors.

Probably used plain poly. The graphite stops the squeaking... I've had connectors with polygraphite mounts and no 'sounds'. Some problems could be attributed to not tightening your mounts enough.

Got it. Now I can see why the solid mounts would be of benefit. Even if the subframe mounts aren't fully welded, it appears to make more sense after crawling under the car.

Dave

If you use solid mounts you will lose all the vibration insulating factor that the mounts were designed for. If you use polygraphite you will get all of the advantages of the solid mounts and retain some on the insulating factor the mounts were meant to give.
Subframe connectors are designed to give your subframe a stabilizing factor. The rear wheels can push directly on the frame when connected, instead of the sheet metal floor being part of the 'push'. The polygraphite mounts will not take away any of the 'push' factor. They will retain some of the insulating purpose even if you have connectors. All cars have insulating mounts for ride comfort. I would really think about it before I eliminated them, that's what you do with a solid mount, you are eliminating the mounts your 1st gen was designed to have....

Make it two votes for polygraphite.

- Jake

As the rear frame rails are solidly welded to the rear of the body assembly, the leaf spring bushings are the component that absorb the forces of road vibration and drivetrain action. The subframe connectors do very little, if anything, to affect the rear suspension. What they do is help prevent the body from twisting, or in the case of convertibles, sagging as well.

I disagree. The differential pushes on the leaf springs. The springs push on the front spring perch. The front perch fastens directly to the connector. The other end of the connector pushes on the subframe. This 'bridges the gap' between spring and frame. The engine rattles the subframe. The subframe mounts isolate the vibration to some extent. This is basic car body design. If you elimanate the bushings with solid metal you change the basic design. IMO Solid bushings are for all out race cars only... You will never get the ride that an 'isolator' will give you with solid metal bushings...

Both ends of the rear leaf springs are insulated from the body by rubber and steel (or poly and steel) bushings. At no point does the direct movement of the differential transfer to the frame without passing through a bushing.

The front spring perches provide a method to tuck the spring eyes out of the way while giving access to the front eye bolt. There is no steel-to-steel connection between the leaf springs and the rear subframe. Also, the rear axle is further isolated with rubber pads on the spring perches.

Car technology has changed dramatically over the years. Full frame vehicles, including newer trucks, use isolated body mounts. New true unibody cars use energy absorbing mounts on the engine and transaxle only, there is no separate frame and the suspension directly bolts to body components. Our cars were transitional, neither full frame nor true unibody, and therefore have the worst of both worlds. The front insulators do serve a purpose up front, but when adding subframe connectors, particularly welded connectors, the function of the front insulators is modified.

To me, a properly bolted in connector is the same as weld in connectors. Welded or bolted, the body is still completely insulated/isolated from engine vibration(not to be confused with road disturbances) with body mounts. If you go solid there is no insulation/isolation. I see no purpose at all to get rid of the isolation.. unless you are just running at the track...or you like vibration.

The suspension itself...the leaf and coil springs, and the shocks...are the primary absorbers for the vibration that transfers from the road.

On the front end, the bushings mount the stub frame to the body shell. Unlike a true unibody, all the front end sheet metal is hung off the front of the firewall and supported by the stub frame. The stub frame has four bolts connecting it to the body shell, and two bolts to support the front end sheet metal. The front mounts help cushion the radiatior by suspending the core support on rubber cushions, but the rear four don't contribute all that much to ride comfort.

The engine and transmission are mounted with rubber or poly insulators as well in production cars. This serves the purpose of absorbing minor vibration. A well balanced drivetrain should not produce excessive vibration. Body mounts don't absorb much of this type of vibration.

Look at any of the new, high performance cars. The Challenger, the Mustang, the Camaro. All of these are unibody cars, and all have the suspension directly bolted to body components, and one of the first steps in further enhancing these vehicles is to further stiffen the chassis by adding subframe connectors. With the suspension directly connected to the body, where does the vibration go? It is simply dissipated across the chassis.

I had solid mounts on my 79 TA and you can feel the difference. It feels just like you have something up against the body that shouldn't be.... you get more vibration from the engine. The body mounts do serve a purpose quite well. That is, if you haven't eliminated them with solid mounts..... It's really easy to picture what they do. And what they can't do if they are solid. The bottom line is; Expect some extra vibration with solid body mounts.

I've talked to (and my personal experience) is quite the opposite with solid mounts. Plus, when things like mounts are designed they are designed to absorb vibrations of a particular amplitude and frequency. Once you change the material from rubber to poly you affect the frequency range for the damping. So it doesn't work the same as saying "well it's softer therefore you get a little more damping."

If you have a problem with solid mounts either you need to get better engine mounts (if it's engine related) or better shocks (if it's road input related). Those are the things that should be doing the damping, not your subframe.

The type of polygraphite that was formulated to make subframe mounts was designed to absorb the same vibrations that the original rubber was. The only difference is less 'flex'. It's the 'perfect mount'. Just as solid as solid mounts but with the dampening capibility.... My 79 TA that had the solid mounts, and extra vibration due to them, was a frame off restore with attention paid to detail. The only mistake made was the solid mounts. The new owner agreed and has already switched them back to polygraphite style 'dampening' mount with great results. The odd vibration is now gone.

I'd love to see the data that shows these mounts of different material absorb the sample frequency range amplitude levels.

As for switching between the two, there are plenty of studies where some participants that received the placebo pills (sugar pills) instead of the real medicine somehow still noted an improvement.

If you look at the link I posted earlier there are plenty of people running solids (on 2nd Gens even) without this affect.

Common sense tells you the polygraphite will absorb vibration better than solid metal... If you choose to ignore the common sense of it then look at the manufacturer material related specs and see that the material is much more 'insolating' than solid metal. The manufacturers all state it clearly.... If you have a scientific mind you can do a little digging and find the difference between solid polyurethane and solid metal. There's a very big difference in properties.... Why do you think that polygraphite is used in all the other suspension upgrades? Why not just use washers instead of bushings? Make yourself a solid metal car? The answer is that polygraphite does the job much better than solid metal.

Common sense tells you the polygraphite will absorb vibration better than solid metal... If you choose to ignore the common sense of it then look at the manufacturer material related specs and see that the material is much more 'insolating' than solid metal. The manufacturers all state it clearly.... If you have a scientific mind you can do a little digging and find the difference between solid polyurethane and solid metal. Very big [/quote]

And what you are failing to understand is damping characteristics related to frequency range. Just because something is squishy or squishier does not mean it will damping in the same frequency range. This applies to vibration as well as well as noise and hydraulics. Some frequencies are not felt by the driver. Sometimes the solution is not to necessarily dampen all vibrations, noise, or hydraulics, but rather to move them outside of the range where the driver or system is affected by it. Ergo squisher is not always better.

Common sense would have us believe two coins (one twice the weight of the other) would not reach the ground when dropped at the same height. But wind resistance aside, we learned in grade school that gravity ultimately determines the acceleration of the coins and therefore they would land at the same time.

I understand frequencies and dampening due to my training in the field. A little 'post high school' physics is all it takes. Or about ten minutes of reading will do also. And neither is as good as having tried out just about every combination at the track and on the street. It's not complicated and it's easy to understand that polygraphite works better than solid metal for these bushings.... It was a big and great thing when they came out with plain poly for it. Now you have the graphite added to take away the squeak. It's a good thing. Been there and done that. The solid bushings are just for racing/racers. They are great for that. For your Sunday cruiser, keep your polygraphite in the mix.

If you understood it, you wouldn't be treating a Dynamics problem as if it were a Statics one. Nothing mean intended, just stating the facts

Problem? There's no problem at all..Dynamics or Statics. Just good solutions.... Solid metal mounts for racing applications and polygraphite for street applications (with occasional track use).

See, now you're just trying to get the last word in, well it didn't work. So hah!