Engine snail mount bush alternative

I'd completely forgotten about this old thread. Very glad it was brought back up. And very timely for the recent discussions on this part. :)
 
Jonohhh said:
Howdy, just checking in to ask how the bushing is holding up? I'm currently putting an E36 LCA bushing in my snail mount and I am a little conflicted about the orientation I should install it.

The bushing is designed to be soft within a fairly tight range and then hit a (hard but not solid) travel limiter after some amount of deflection.

As oriented, I feel I should not put the left side up (the direction that the load is applied to) as there is nearly no travel before it hits the solid portion (meaning it would permanently rest on the stop and transmit extra vibration).

The right side being up is slightly better, as some travel is permitted, but it's soft enough to be deflected to the stop with my hands alone.

I'm considering putting top or bottom facing up as it's fairly stiff in that direction and should have enough rubber to still isolate vibrations fairly well. It's not designed to be loaded in that direction - but neither is it designed to be loaded consistently in the other direction as in the E36 it simply manages thrust loads from the front wheels.

Also, thank you Janis for the nice find, sourcing a Febi/Bilstein part was cake compared to the alternatives (especially considering the rush). Lemförder is my go to but this will likely hold up just the same.

View attachment 63079
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It has been a long time since I've installed these bushings in a BMW front end. If I recall, isn't this side (red arrow) placed at the bottom on the BMW?
PXL_20220625_044856092.jpg


If using this bushing for a X engine mount I would think having the heaviest supporting side (red arrow) facing down would be best. The snail mount serves mostly to hold the engine weight up at that end.

Regarding BMW suspension bushings. The same basic dimensions of bushes were often used on more than one model size platform. But the rubber was wider, fuller, and denser to adjust for the added weight of heavier platforms. For example on my 5-series cars with aftermarket performance suspension and wide wheel/tires, the stock bushings were too soft. They allowed too much movement of the control arm leading to shimmy and shake. By installing 7-series bushings in the 5's suspension (a direct fit) it cured that issue. So it might be possible there are other BMW bushings that are the same basic dimensions but have heavier rubber inserts....if that is needed for use in a X engine mount.
 
Dr.Jeff said:
It has been a long time since I've installed these bushings in a BMW front end. If I recall, isn't this side (red arrow) placed at the bottom on the BMW?
View attachment 63085

If using this bushing for a X engine mount I would think having the heaviest supporting side (red arrow) facing down would be best. The snail mount serves mostly to hold the engine weight up at that end.

Regarding BMW suspension bushings. The same basic dimensions of bushes were often used on more than one model size platform. But the rubber was wider, fuller, and denser to adjust for the added weight of heavier platforms. For example on my 5-series cars with aftermarket performance suspension and wide wheel/tires, the stock bushings were too soft. They allowed too much movement of the control arm leading to shimmy and shake. By installing 7-series bushings in the 5's suspension (a direct fit) it cured that issue. So it might be possible there are other BMW bushings that are the same basic dimensions but have heavier rubber inserts....if that is needed for use in a X engine mount.
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In the E36, the bushing here doesn't bear much vehicle weight at all- at least statically. The primary lower control arm which is L shaped with 3 attachment points bridges the spindle to the chassis, and then the end of the L has this bushing which serves to manage thrust loads on the front suspension. Vehicle weight pretty much all goes through the strut assembly, cornering forces go through the two ball joints, and then thrust is controlled by this one piece.

The reason for its soft design with hard travel limiters is for this purpose specifically. By making the bushing soft in a small range, impulses and vibrations from bumps and expansion joints get filtered out by the bushing, but larger forces like braking don't result in undesired deflection as the bushing hits its internal bump stop.

To do this, the "bridge" of the bushing faces up and down as thrust deflection turns into a lateral movement at the arm, so the travel limiters on each side makes sense.

They moved onto a more advanced suspension design with the e34 that they then used on most everything until recently. The same basic design is still in use on the 3er.

There may be (and probably are) other applications where this bushing does handle vehicle weight, and there's also an alternative design for this bushing (as you suggested) which would admittedly be far better for this application. However, oriented the way I plan to, I think it'll hold up decently long. Won't hurt to try as they came in a set of two for $30 iirc.


pic01.jpg
alternative design below
Screenshot_20220626-144652.png
 
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Jonohhh said:
In the E36, the bushing here doesn't bear much vehicle weight at all- at least statically. The primary lower control arm which is L shaped with 3 attachment points bridges the spindle to the chassis, and then the end of the L has this bushing which serves to manage thrust loads on the front suspension. Vehicle weight pretty much all goes through the strut assembly, cornering forces go through the two ball joints, and then thrust is controlled by this one piece.

The reason for its soft design with hard travel limiters is for this purpose specifically. By making the bushing soft in a small range, impulses and vibrations from bumps and expansion joints get filtered out by the bushing, but larger forces like braking don't result in undesired deflection as the bushing hits its internal bump stop.

To do this, the "bridge" of the bushing faces up and down as thrust deflection turns into a lateral movement at the arm, so the travel limiters on each side makes sense.

They moved onto a more advanced suspension design with the e34 that they then used on most everything until recently. The same basic design is still in use on the 3er.

There may be (and probably are) other applications where this bushing does handle vehicle weight, and there's also an alternative design for this bushing (as you suggested) which would admittedly be far better for this application. However, oriented the way I plan to, I think it'll hold up decently long. Won't hurt to try as they came in a set of two for $30 iirc.


View attachment 63112 alternative design belowView attachment 63113
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Do you happen to have the BMW part number for that alternative one?
 
So after one heck of a time getting the new bushing in, I finally got it seated properly. The snail mounts inner diameter surface area and tolerances made for one of the most gnarly press fits I've ever had to deal with - both for getting the bushing out and the new one in. Heat was required to get it out, and heat in the mount with a frozen bushing were required to get the new one in. I'm glad the bushings came in packs of two because the first one got absolutely obliterated.

And here's where I admit to doing something a little sketchy.

Of course, the bushing is narrower where the center sleeve is, and could potentially make it possible for the engine/bushing to slide one way or another on the sleeve. (As Janis mentioned).

Starting with pressing the sleeve in, I used rubber cement to attempt to bond the sleeve to the inner diameter of the bushing. The fit was very tight as is, but I figured the rubber cement couldn't really hurt it as my factory bushing seemed to be bonded to the sleeve in some way as well.

But to top it off, I used a section of 5/8 inch hose, cut to the exact length and press fitted it over the sleeve. It was also bonded to both the sleeve and the BMW bushing using rubber cement.

If you look at the BMW bushing you'll see there's a fairly substantial recess around where the sleeve goes. That turned out to be a good thing- as the hose I used was sized perfectly to be a tight fit on both the sleeve and on the inner diameter of that recess- also providing ample contact area for the rubber cement.


We'll see how it holds up, but I highly doubt this thing is going anywhere. When installed it won't look all too bad.

PXL_20220628_043952319.jpg
 
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Jonohhh said:
So after one heck of a time getting the new bushing in, I finally got it seated properly. The snail mounts inner diameter surface area and tolerances made for one of the most gnarly press fits I've ever had to deal with - both for getting the bushing out and the new one in. Heat was required to get it out, and heat in the mount with a frozen bushing were required to get the new one in. I'm glad the bushings came in packs of two because the first one got absolutely obliterated.

And here's where I admit to doing something a little sketchy.

Of course, the bushing is narrower where the center sleeve is, and could potentially make it possible for the engine/bushing to slide one way or another on the sleeve. (As Janis mentioned).

Starting with pressing the sleeve in, I used rubber cement to attempt to bond the sleeve to the inner diameter of the bushing. The fit was very tight as is, but I figured the rubber cement couldn't really hurt it as my factory bushing seemed to be bonded to the sleeve in some way as well.

But to top it off, I used a section of 5/8 inch hose, cut to the exact length and press fitted it over the sleeve. It was also bonded to both the sleeve and the BMW bushing using rubber cement.

If you look at the BMW bushing you'll see there's a fairly substantial recess around where the sleeve goes. That turned out to be a good thing- as the hose I used was sized perfectly to be a tight fit on both the sleeve and on the inner diameter of that recess- also providing ample contact area for the rubber cement.


We'll see how it holds up, but I highly doubt this thing is going anywhere. When installed it won't look all too bad.

View attachment 63216
Click to expand...
So no modification/alteration of the Fiat mount housing, Fiat inner sleeve, or BMW parts were necessary?

Could the sleeve from the second (destroyed) BMW bushing be used to make a pair of spacers for either side of the Fiat sleeve (instead of rubber hose)?

If you wish to make the rubber bushing even more supportive then you can fill the voids with urethane adhesive, as is used for installing windshields. I guess it would depend on how the BMW bush compares to the Fiat one in terms of support. And how firm the result is desired.
 
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