FuzzyLog1c

iTrader: (4)

I believe that Revshift's criticism was pointed at the entire family of polypropylene glycol prepolymers. Based on some informal reading at Dow, Wiley and Bayer, I'm not seeing anything that would even remotely suggest that this material would make a durable, long-lasting automotive bushing material. It just looks like bathroom/flooring caulk. To me, it just doesn't make sense to use something that was never designed to withstand mechanical stresses in application where harsh mechanical shock and vibration occurs constantly.

Bowtie70SS

iTrader: (10)

Yeah I read that and they were saying 2 part urethane is bad? If you look at the spec sheet it said something like 168hours till full strength. How is the other stuff cured? Moisture?

FuzzyLog1c

iTrader: (4)

That's an excellent question. I don't know the answer, and I can't find it yet. Presently, all I can say is that one advantage that a bushing fabricated in a factory or lab may have is that it is probably subjected to vacuum as it cures to remove air bubbles--both large and small.

Bowtie70SS

iTrader: (10)

Yeah that is true, they do sell vacuum tables for making signs but the cost would never be worth it. If you were going make round bushings then you could buy round stock and turn them down in a lathe/machine them. I guess I get carried away trying to do and fabricate stuff myself. I have to make things a lot of times and get into the fabricator/builder mindset like hey I can do that. Its hard to know when to say when sometimes.

Fuzzy_Wuzzy

iTrader: (8)

As long as the new material does not damage the stock rubber, even if it fails it will just revert to the stock bushings. If you want a weekend project that may or may not work give it a go. For the price i think the revshift bushings are a better bet. But I don't think your idea is all that bad. The trick will be finding the best material for the job.

GulfM3

iTrader: (14)

If you're looking for something to fabricate, make a couple sets of aluminum subframe bushings. I'd love to try a set, my bmr bushings squeak and groan.

Fuzzy_Wuzzy

iTrader: (8)

The beauty if your method works is that you don't have to remove the stock bushings, which is the PITA step

Revshift

Everything Fuzzylog1c said in this thread is accurate, so far. There are many different specifications to consider. The 2-part urethane sealant is not adequate. This is why those black aftermarket cts-v motor mounts are starting to crumble apart. There is a thread on here with pictures of what I am referring to.

No two polyurethanes are the same. Our polyurethane (the good stuff) consists of 4 to 6 different chemicals mixed together in very specific ratios. It is extremely involving and there is a lot to it. Vacuum chambers, curing ovens, inert gases, and specially designed mixers are involved. I can't get into the specifics because there are a lot of trade secrets that I can not talk about (seriously).

Those delrin inserts are machined from solid stock. The delrin stock is expensive and this is why they are $300. If you were to buy polyurethane stock then you would be in the same predicament as with delrin. It is also expensive for the stock. Not to mention that you would not know the properties of the polyurethane stock (aside from hardness) because the suppliers do not offer it. I can tell you that the cheapest supplier that I know of offering solid polyurethane stock would charge around $200 plus shipping for the amount of material needed to make the cradle bushings. You could always contact us, we can make you some nice chunks of polyurethane for less than $200.

54inches

iTrader: (4)

Don' forGet MAgIC.

swiss

iTrader: (3)

To clarify, you feel that filling the voids in the stock cradle bushings would lead to a catastrophic failure?

Cadzilla

iTrader: (3)

I did it. Spent $30 total I believe.

I shot some 3m window weld in the voids, let it dry in the same shape as the stock bushing, filed it down flat, then used the washers to sandwich it. With 2 washers it was way way too firm- so much so that all slack in the driveline whatsoever was sent upstream to the flywheel. The throttle response was great when you hammered it but in stop and go it was very hard to modulate...I came to the conclusion that there is slack in that cradle for a reason- to allow some of the movement of the diff and let you shift in peace. Ultimately I backed it down to one washer on top/bottom, and it was fine. Without having tried the aftermarket options, I feel it produced an adequate result with no add'l nvh.

I contemplated the spectres for many years, but I don't like how they and other aftermarket bushings basically fuse the cradle to the frame. The fill method kept those 2 parts (and vibrations) separate using the urethane as the buffer layer.

I know it may not the most effective solution but I was only looking to take out the side to side wiggle/slop in the rear end during relatively slow cornering, and it accomplished that nicely. I think the 3m stuff is 65a which was very similar to the stock rubber if not harder. If you're looking to eliminate wheel hop with cradle bushings, forget it.

I posted several of these pics before but I can't find the thread. sorry about the pic sizes. I've resized them using the photobucket editor, which works about 10% of the time.


sliced off the lips of existing bushings





templates







urethane dried but crude. I sanded them down nice and flat/uniform after these pics were taken





sandwiched with 2 washers. I eventually went to one, but never got more pics. You can see that the washers don't actually touch the cradle, but that urethane now fills the whole cradle void.

FuzzyLog1c

iTrader: (4)

I assume that the original mount would hold (as best it can), but the filler material might suddenly split or shear under torsional strain caused by hard cornering (1.1G+). If that occurred, the rear subframe would suddenly shift, throwing the back end of the car wide. The natural reaction to that is going to be abruptly letting off the throttle, which may make the car want to swap ends.

Bowtie70SS

iTrader: (10)

Well Cadzilla I guess my title "new idea" is blown out of the water. I guess the design difference of a solid rear axle and a independant are the reason the vibrations/harmonics are transferred. Cars with unit bodies have had their rear frame rails attached (welded) to the body/floors and rear suspensions mounted to them. Maybe 4 mounting points are not enough if you are trying to make a more solid connection to the car.

etcts-v

Love the creativity of finding your own solutions, this is what makes the community on here so badass!

Personally a huge fan of RevShift mounts, affordable, durable and overall great company which is why I'll stick with their solution for the rear cradle. But that's just me.

FuzzyLog1c

iTrader: (4)

Now, if we could only get them to develop a 8.8 kit that cost $2500...

etcts-v

Amen!

Cadzilla

iTrader: (3)

have you even taken the cradle apart yet? With no bushings at all, it's still not going anywhere. The bolts hold the cradle to the frame. The (stock) bushings barely serve a purpose.
wrong, sorry..

FuzzyLog1c

iTrader: (4)

Then prove it. You saying "it isn't so" doesn't make it so.

And the glowing reviews of the Revshift bushings, post install, clearly indicate that replacing the stock bushings does something significant.

Fuzzy_Wuzzy

iTrader: (8)

This would be the pin in the haystack case. Worst case the rear would shift maybe 1/2" (and i really doubt you would get all 4 filled materials to fail at once. If you cannot handle that I would recommend not driving your car so hard, I would expect more issues from dirty roads than filling stock bushings.

Are the Revshift bushings better - YES
Is filling the stock bushings bad - NO
Will it last - To be seen...
Is it better than the Revshift bushings - I Doubt it, especially since you still have the soft stock bushing in there.

I think all Cadzilla is saying is that the cradle will still be in the car, there is physical restraint besides the bushings.

FuzzyLog1c

iTrader: (4)

Have you ever felt the stock bushings kick out sideways during a 1.10-1.20 G power turn? Happens to me two or three times per week on my drive to work when it's warm enough to get enough grip. The first couple of times it happened, I thought I had lost all traction in the rear end and let off on the throttle. The resulting weight shift almost put me in the ditch. Now that I know what to expect, it's only unnerving, not dangerous, but I wouldn't want to know that that situation might be lurking around the corner.

But maybe I'm just paranoid.