If you remember when the 2007 Mazdaspeed 3 was released, you may recall the rave reviews from the automotive press. If I recall correctly, they called it the “Wild Child” in the Mazda lineup. It boasted huge power for a FWD platform and enthusiasts were quick to buy and modify them for even more thrust.
Unfortunately, Mazda’s 2.3 liter direct-injected, turbocharged torque-monster was a bit TOO powerful. How so? The stock rear motor mount is very, very soft relative to how much power the motor makes. Even on startup and shutdown you can see how much the motor moves around. Hell, you can pretty much rock the motor back and forth with your hands while it’s bolted in. Such a soft mount translates to unwanted movement that exacerbates wheel hop and torque steer.
In response, the aftermarket has come up with many, many mounts over the years. Some companies offer several choices of stiffness to appeal to a broad amount of people. The stiffer mount works better to limit movement and lessen wheel hop/torque steer, but that translates to a cabin loaded with vibration. Cobb came into the rear motor mount game pretty late, but hopefully that means they have perfected what others have been doing for a while. Unlike the other companies, Cobb offers one mount in one configuration and one stiffness…done. While the competition has chosen urethan bushings ranging from 60-90 durometer, Cobb’s mount is 85. To offset some of the added vibration, Cobb’s mount has several holes drilled through the bushing. They claim that this feature offers the performance benefits of the stiffest mounts while keeping the vibrations tolerable.
Recently, I had the opportunity to install Cobb’s new rear motor mount for my 2011 Mazdaspeed 3. Not surprisingly, the Cobb piece is beautifully machined. It really is a shame that such a nicely finished part is tucked away out of sight. It’s a pretty straightforward affair involving 5 bolts in total. A vertical bolt attaches the mount to the subframe and a horizontal bolt attaches to a bracket on the transmission. The transmission bracket has 3 bolts that must be loosened to swing the bracket out of the way for removal of the old mount and installation of the new Cobb piece.
Once installed, I was shocked at the amount of initial vibration while the car was just cranking to start – it really shook the entire car! After reading about motor mount upgrades for a while, many people have mentioned that the start is the worst and that the urethane breaks after a few hundred miles once it’s flexed/loaded on and off. I’ll admit, I was skeptical…the initial vibrations and idle were annoying but thankfully there was no drone on wide open throttle.
After some 600 miles and a short road trip weekend along lots of different roads, I’m pleased to report that the mount has definitely calmed down. On a cold start, you can feel a bit of vibration during cranking but it’s nothing like that first start. As a frame of reference, I used to have an Ingalls engine torque mount on my old 2006 Civic SI and the vibration during start-up is very similar. In fact, I really don’t notice the mount at all except during start-up and if I blip the throttle at idle while stopped (which is super-douchey anyway). Nothing in the cabin rattles at idle with or without the AC and there is no squeaking or rattling while shifting or loading the car with power. On the road, torque steer and wheel hop are very much improved and replaced with a bit more wheel spin as the power is getting right to the ground.
I’m really happy with the mount so far. I’ll admit, I do have minor concerns about the longevity of the bushing itself. Over time, I’m wondering if the drilled sections of the urethane may crack with the constant flexing. I’ll inspect the bushing itself and check that the mount is properly torqued during oil changes.
As a sidenote, this mount fits all 2007-2013 Mazdaspeed 3’s as well as Ford’s new Focus ST (not surprising considering how many OEM parts on my car are marked “FOMOCO”).
Kwame
Z1 Performance
Jonathan
Corner Balance 
