Rear Motor Mount

JDM_DOHC_SiR said:

Yes it fits perfectly

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lurker_j said:

That Cusco mount has a durometer rating of 90, but is hardened rubber in an aluminum housing, I wonder how different that one feels

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How's the vibration from the cusco rear motor mount? I'm not super concerned about noise if there's so much benefit to the Si's performance.

NVH at idle due to aftermarket motor and transmission mounting is because of a lack of compliance at high frequencies, basically, what you want from a bushing that reduces harshness is for it to have significantly non-newtonian behavior at high frequencies. firm, solvent resistant rubbers such as buna-n, flourinated compounds like kalrez, etc. are very good at converting high frequency movement into heat, reducing the passage of vibration into the cabin. however, these materials are expensive (in OEM automotive terms) to work with.

on that same note, the kinds of polyurethanes that are marketed by superpro, proflex, energy suspension, etc. are quite bad at converting high frequency vibration into anything but high frequency vibration of the assembly. that said, they are an extremely cost effective way to get excellent low frequency behavior, much better than cheaper varieties of hard, durable rubber formulas.

at the high end in OEM automotive applications, up until today, fluid filled bushings end up being the best of both worlds. the fluid serves as the non-newtonian bit that prevents transfer of high frequency impulses from the powertrain, but the fluids can actually be tuned to be effectively non-compressible at low frequencies, which provides you with a much more rigid bushing at low frequencies vs rubber alone.

the final option, which is very likely to be the way forward these days, is to use polymer composites for the housings around the bushings. modern polymer composites have exactly the property of being damping at high frequencies but rigid at low frequencies. (fyi, billet aluminum is terrible at this -- steel tends to be a bit better but it depends heavily on the geometry of the part). when you're designing the composite and geometry, the polymer housing can actually be more effective at tuning response than the rubber or rubber-like polymer (ie, polyurethane formulas). i think why we're seeing PP/PA+GF in new damping strut designs (see: OEM endlinks).

if you're looking for a torque strut with better low frequency behavior but without an increase in NVH, i think polymer composite designs are definitely the things to look at. that said, when you invest in tooling for billet metal parts, you only need to order 10s to 100s of pieces. with injection molding tooling (high quality, that is..), you need to order thousands of pieces, hence, i would tend towards OEM parts, eg with PU/window weld cavity fillers to tune response.

as an aside, a friend of mine also has a really clever design that uses chromoly with a solid bushings on the motor side and a removable rear bushing that rotates on two axes and whose elastomer is a set of o-ringes on the sleeve of the subframe end. with this design you get to use your own bushing duro, and can run very high durometers (think 90+ viton) while retaining lower resistance against axial movement.

I got the HardRace RMM in and compared it side by side with the OEM mount. It is actually lighter than the OEM mount, just bulkier. The rubber feels about the same as the OEM mount too with a similar design with some open space inside the mount. The shell of the OEM mount feels like metal as opposed to the hardened plastic of the HardRace mount. I'm really curious to see if this is an improvement over the OEM mount now. I know my current Hasport one does it's job as far as transferring power to the wheels and keeping the engine from shifting too much, but the rattle is a bit much everytime I am coming from a dead stop. Here are some pictures of the mounts side by side. Also, the inside of the HardRace mount has this weird soft black plastic in it that came ripped in mine. It is definitely not hard enough to make for any structural integrity, so I'm not worried about it, but I'm wondering if it was also just a manufacturing thing they forgot to cut out from the rubber.

I put the hard race mount in today. The chassis vibration is gone but I also feel like I lost some of that extra power to the wheels. It almost feels like the stock mount again. At this point idk if it’s benefits are more psychological or not. If you want a night and day difference, go hasport. If you want a tiny bit more performance I guess without the chassis vibration, the hard race works.

After driving around with it a bit more, starts and stops are much less unstable than when just using the OEM mount, so this Hard Race mount is actually worth the upgrade IMO. It is a good middle ground street upgrade, but if you really are trying to squeeze all the power to the ground, get the harder mounts.

lurker_j said:

After driving around with it a bit more, starts and stops are much less unstable than when just using the OEM mount, so this Hard Race mount is actually worth the upgrade IMO. It is a good middle ground street upgrade, but if you really are trying to squeeze all the power to the ground, get the harder mounts.

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Sounds like a great option for those that don't want there teeth rattled out. Thanks for the review.

Thanks for the review! Wonder how the Type-R falls within these two options.

I just installed the Hasport 62A version recently and the only time it's negatively noticeable is 800-1100 RPM. The car idles smoothly enough after being driven around for a few hundred miles and "breaking in" the mount.

ApexEight said:

Wonder how the Type-R falls within these two options.

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I have had the following mounts and this is how they are from my usage of them from OEM feel to Rattle City


Stock OEM 1.5L rear mount
Stock Type-R rear mount
3M Window Welded OEM 1.5L rear mount
3M Window Welded Type-R rear mount
Hardrace rear mount
Hasport 62A rear mount
Everything else that's 62A+

I currently like the 3M Window Welded Type-R rear mount the best keeps the vibrations to a minimum and does not transmit any weird vibration... only going in reverse

The Type-R mount is a direct swap with non-Type-R mounts???
Or is that just a comparison to give perspective of the different RMM options?

ck42 said:

The Type-R mount is a direct swap with non-Type-R mounts???
Or is that just a comparison to give perspective of the different RMM options?

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As far as I know, it's the same. When I bought mine, the Hasport one is the same for Type Rs and all the other 10th gen civics

REBELXSi said:

As far as I know, it's the same. When I bought mine, the Hasport one is the same for Type Rs and all the other 10th gen civics

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Good to know then. Thanks!

So the hardrace is a tad more expensive than the TypeR rear mount.

To install this, is it as easy as putting the car on jacks and just simply swapping the mounts without propping the engine?
I see Lurker's mont comparison but does the HardRace RMM only transmit ANY vibration at a barely noticeable RPM, like say 1000-1500 and that's it? No extra idle vibrations?

I installed the Hardrace MM today along with the TypeR underbody chassis brace.

After driving a few hours, here are my impressions:
The slop shifting into gears is nearly gone. Shifts are crisp.
Throttle response feels like it improved ever so slightly
The engine sound got a little louder, especially as the RPMs climb. This may be the "vibration" people talk about? It sounds like the engine sound frequency reverberates a little more.
I did NOT notice any actual chassis vibrations at any RPM, which is fantastic.
When letting off the clutch pedal, that sudden vibration feel (which I would assume is the engine & trans bouncing around) is less noticeable.
I don't dump the clutch or do burnouts so I can't comment on wheel hop.

At this point I can't think of any negatives vs the stock mount. Highly recommended.

What is the part number for the Type R RMM? Thanks! (I searched the numbers on the picture above, but got nothing...)

Edit: I may have found it. 50890-TGH-A01