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Here we see a 740iL motor mount compared to the mounts for an E28 M5. Unlike the stock E30 M3 mounts and the 740iL mounts, which look essentially the same left to right, the E28 mounts are decidedly different from left to right. This is not entirely strange, as the left and right motor mounts experience substantially different loadings during use - one being predominantly in compression, while the other is in tension when accelerating hard. Motor mounts are also subject to significant shear loads during cornering and braking (this loading is magnified with sticky R-series tires). This important fact is often overlooked, and is what leads to the particular "shear failure" of E30 325is mounts. Note that one of the E28 motor mounts is for all practical purposes identical to an E30 325is mount - basically a rubber cylinder. The E28 mounts are not fluid filled. |
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The E28 mounts are also shorter than the stock E30 M3 mounts by 1/4". They are therefore the same height as the 740iL mounts, as is shown in the picture above. note also the extremely long mounting studs on the E28 mounts. These should be shortened before adaptation to the E30 M3 chassis. |
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One of the E28 motor mounts has a unique hexagonal shape. These mounts come in different colors (which are painted on, they are not molded into the rubber). The color is an indication of the stiffness of the mounts. The color/stiffness combinations are not available to me at this time. I also cannot comment on the motor mounts recommended by Rick Stormer - those from the 1992 E34 535. I have not seen these mounts but when i do i will report on them here. |
Note: All of these alternative motor mounts are stiffer than the stock E30 M3 mounts. They are not uniquely "tuned" to damp out the vibrations of the S14 engine. Thus if you decide to use alternative mounts, be prepared for additional harshness within the cabin, both at idle and at higher RPM's. You can also expect stiffer mounts to exact a larger toll on the already under spec'd subframe pickup points. |