A vibration felt at 55 mph may not be a tire problem. Mazda has revised motor mounts available which may help remedy this problem.Google+
Car Problem Reports
Mazda Mazda3 Vibration Felt at 55 mph
Mazda Mazda3 Problem
Engine Affected: 2.0L 4 Cylinder
Average Mileage: 65,855 mi (15,000 mi - 130,000 mi)
Visitor, 2005 Mazda Mazda3, 55,000 mi
heavy vibration begins over 60 and gets worse as speed increases - bought new tires, didn't help, double checked balance and alignment at two shops - didn't help - new front rotors and pads - didn't help. Next step is checking mounts -
Driving at around 60 MPH I feel that the body (not the steering wheel) vibrates. Al 4 tires repalced and balanced including dynamic (on the car) blancing and still the problem not fixed.
Visitor, 2005 Mazda Mazda3, 90,000 mi
We picked up a shimmy/vibration at 70 mph, and it was intermittent, sometimes to the point of slowing down to 20 mph to get it to stop. We thought it might be the roads, but we got all 4 tires replaced and the alignment done and no change. It's really bad in a side wind (this could be wind getting under the hood and yanking it around), but we're tired of spending money on it. Our tires also had severe wear on the outsides.
Visitor, 2008 Mazda Mazda3, 67,000 mi
I started feeling vibration when I got up to 55. My tires are not even a year old and I get them rotated every 5,000 miles. I noticed vibration about a week after they rotated them so I brought my car back to the tire shop a couple weeks later to check the tires out. They said that the tires were fine and not out of balance or anything. I had the tire guy drive my car and he felt the vibration but couldnt explain it. Now it is even worse and started to vibrate between 65 and 70. I got on the freeway and it is on a sharp corner the whole front end started shaking so hard I thought my motor was going to fall out. Someone told me that it sounded like a lose motor mount. The vibration is in the whole body of the car....almost bouncy and sometimes the steering wheel just vibrates. Still not fixed
Visitor, 2011 Mazda Mazda3, 2.0L 4 Cylinder
viabration at 55mpr
Visitor, 2007 Mazda Mazda3, 70,000 mi
shaking at 55mph....5 different mechanics swore it was my tires
did the front and rear shocks/struts
balanced tires 5x and aligned the car
HOPING it is the motor mounts!
Visitor, 2007 Mazda Mazda3, 50,000 mi
Rumbling coming into steering column starting at about 60mph. Still searching for the cause.
Visitor, 2008 Mazda Mazda3, 80,000 mi
Vibration right 60 mph and gets worse as speed increases. Rebalanced tires three times with no change.
I am too feeling the vibration at speed of 60mph
Visitor, 2006 Mazda Mazda3
vibration at 55 mph,had tires ballanced and re-ballanced. Dealer cannot say for sure engine mounts will solve the problem. Said, best to live with the problem.