Rear End Vibration at High Speed

If the car has rear end vibration at high speed, this generally indicates that the rear wheels are out of balance.

Reason for rear-end vibration at high speed
(1) Out of balance rear wheel.

Before explaining how imbalanced rear wheels can cause the rear end to vibrate, we need to first examine this notion of "wheel balance". A wheel consists of a rim and tire.  When rims and tires are manufactured, they're almost always somewhat flawed.

Rear Wheel Alignment Symptoms

For example, in the case of a tire, one portion of a tire's tread may be slightly thicker than a similar-sized portion of tread elsewhere on the tire. This means the tire isn't balanced in terms of weight distribution.

To balance the tire, a mechanic will strategically position/fasten lead weights to the edge of the rim, thus compensating for the manufacturing error. Now, if a rear wheel is out of balance, it won't rotate evenly as the vehicle is being driven and, consequently, it'll vibrate. At a certain speed, the vibration becomes severe enough to cause certain rear suspension components to vibrate as well - this is when it's noticeable to you, the driver.

What to do?

Have the rear wheels to be balanced. There are two methods of balancing - static, with the wheels off the vehicle, and dynamic, with the wheels on. The dynamic method is best since it takes into account the brake drum (or disk) and its influence on a wheel's balance.

How Tire Balancing is Conducted

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