6 Reasons Your Rear Bike Wheel Wobbles (+How To Fix)


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Many riders are familiar with the wobble or shimmy that can sometimes occur on their bike wheels, and it’s usually not a good thing. As you ride along, the rear wheel will appear to wobble or shimmy back and forth, which can be pretty unsettling and alarming, especially for beginners.

If your rear wheel feels loose or wobbly while riding your bike, you could have either an issue with the spokes, your wheel could be out of true, an overheated hub, a broken axle, or there could be something in the tire itself that needs to be fixed.

Rear-wheel wobble, especially on mountain bikes and cruisers, can be a source of frustration and annoyance, but it’s almost always easily fixable (and preventable).

If you’ve experienced this problem yourself and want to know what causes this issue, then read on to find out six of the main reasons why your rear bike wheel wobbles and how to fix them!

Reasons your rear bike wheel wobbles

1. Missing or Misaligned Spokes

With each revolution of our wheels, a few thin wire strands (our poor spokes!) perform an unrelentingly difficult job, being repeatedly stretched and compressed.

They also transmit the acceleration and braking forces of pedaling from the hub to the wheel rim. Those skinny little strands seem almost magical when you consider that they’re responsible for supporting the weight of a fully loaded bicycle!

Spokes are an important and sensitive component of your bike’s structure, requiring regular upgrades and care.

Misaligned spokes are a common culprit for a wobbly back wheel. The tension in your spokes should be the same on both sides of the bike to prevent any imbalances that could lead to a wobble.

If the spokes on your wheels are too loose, you’ll have to constantly fine-tune them to get them to stay tight.

If the spokes are too tight, the rim, spoke nipples, and hub flanges will be damaged.

2. Damaged Wheel

One of the most obvious causes of wobbling during riding is a bent wheel or rim that creates shakiness and vibration which is transmitted to the front set of your bike. If your rim gets bent or damaged, it can cause the tire to make uneven contact with the road.

If you feel wobbling or vibration on the rear, then your rear wheel is subject to damage and needs immediate attention.

Damage to a wheel can be caused by hitting a pothole, bouncing into a curb, or being hit hard in an accident.

3. Low Tire Pressure

Low tire pressure is another big cause that results in shaking.

Every tire has a recommended tire pressure range that should be followed accurately if you want your bike to perform effectively.

Tires that are badly worn out and get frequently punctured can also cause low or high-speed vibrations.

A damaged or deflated tube may also cause wobbling because it reduces the amount of air pressure inside the tire. This causes your bike to ride very unstable and makes it harder to control your bike.

The rear wheel must be strong enough to carry all of your weight while leaning over and pedaling.

If you are taking your bike on rough or mountainous terrains, then you will want to make sure that this part of your bike can handle some weight and stress.

Deflated tire causes rear wheel wobble
Damaged, worn-out, or deflated tires are a common cause of a rear wheel wobble

4. A Bent Axle

If you’ve had any problems with your wheel wobbling or spinning out when you ride, the first thing you should do is check for bent or broken axles.

The axle is what connects your wheel to the rest of your bike and keeps it securely attached to the frame. A bent axle is caused by a harsh impact, either with another object or with something hard and rigid, such as a rock or curb.

Another sign that your axle might be damaged is if you have difficulty taking tight turns, so be very attentive when riding.

A bent or broken axle causes wobbling when pedaling because there is no balancing weight on the back of the bike’s frame. You may not realize that this is happening until you try to pedal with an unbalanced wheel and find that it wobbles back and forth every time you pedal.

When this happens, your whole body moves with every rotation of your pedals as you try to counterbalance the difference in weight between each side of the rear wheel.

This can be very uncomfortable and dangerous if you’re riding with other people on a busy road or trail at high speeds!

5. A Loose Hub

It may be some time before you realize that your hub is loose. The telltale signs of a loose hub include

  • Your riding will likely feel “odd”
  • Your corners and descents will become sloppy.
  • Shifting could be incorrect on the rear wheel
  • You may feel or hear a “clunk” that seems to originate from your suspension
  • You may discover that tightening your quick-release skewers momentarily alleviates the problem, but it rapidly returns.

Typically, this indicates that your wheel hub is loose.

When the hub is loose, the wheel bearings, whether they are ball or cartridge bearings, can wander from side to side. Even though this is a minor movement, the distance to the rim accentuates the wobble and creates discomfort.

6. Worn Out Cup-And-Cone Bearings

The “cup and cone” hub is by far the most common form of hub used in bicycle wheels.

Although this hub is easily maintained, it requires precise adjustment to minimize friction and maximize service life.

The cones are threaded conical nuts that attach to the axle, while the cups are cast as part of the hub shell. These two pieces are separated by a steel ball bearing.

Each side of the hub has a bearing, which consists of a cup, a cone, and balls.

The bearing balls will be compressed if the cones are screwed on too tightly.

Because of this, there will be too much resistance when turning the wheel and the moving parts will wear out too quickly.

The bearings will have “play” if the cones aren’t screwed in all the way, allowing the wheel to shake freely on its axis. This causes the bike to shimmy or wobble which makes it difficult to maintain your balance.

Worn out cup and cone bearings on a bike
Worn-out cup and cone bearings are a more technical issue that can be harder to assess for the un-initiated

3 Ways to Fix a Rear Wheel Wobble (Step by Step Guide)

It can be incredibly frustrating to have a problem with your bike, especially if it has to do with your brakes, steering, or, in this case, your rear wheel wobbling.

If you find yourself dealing with rear wheel wobbling, I’ve got three potential solutions for you!

1. Tension Wheel Spokes

If your bike has a loose or tight spoke, it may be the biggest cause of a rear wheel wobble.

It is important to tension the spokes in the wheel in such cases to keep the tire reliable and long-lasting.

Gear required – For this task, you need a wheel truing stand, a spoke tension meter, and a spoke wrench.

Follow the given simple process step by step to ensure that your wheel is free of wobbles!

Step 1 – Find out the Spoke Diameter

The first step is to measure the diameter of the spokes to tension them. You can use a spoke diameter gauge and find the smallest slot your spoke can fit in.

Step 2 – Measure the Required Spoke Tension

The tension meter has a conversion chart that you can use to calculate the spoke tension according to the diameter.

Lighter rims require less tension and heavy rims require more, so make sure you check with the manufacturer as the tension may vary significantly.

Step 3 – Assess Current Spoke Tension

Now you have to hold the tension meter horizontally, squeeze the handle, place the spoke between posts and release it.

Then check the measurements on the meter’s scale. You have to cross-reference this reading with the conversion chart to find out the present tension in the spokes.

Measure every spoke on the wheel and determine whether your current spoke tension is too high or low.

Don’t be alarmed if all the spokes don’t have the same average tension, 20% difference is acceptable.

Step 4 – Increase Tension

Turn the entire wheel a quarter-turn counterclockwise to adjust the tension and then repeat the measurement.

Once your spoke tension is within the acceptable range all the way around, you can true the wheel. (Source)

2. True a Bent Wheel

Rims can get damaged in several ways, including colliding with a large bump, attempting to force your bike into or out of a bike rack, or having a spoke break.

If the kink in the rim is significant enough, it will continually strike the brake pad as the wheel rotates, producing an annoying sound and slowing you down.

But don’t worry, you can easily fix this by truing the wheel yourself using only a spoke wrench, a truing stand (if you have one), and follow these 5 easy steps to get your bike back in tip-top shape!

Step 1 – Inspect the Rims and Spokes

You can begin by flipping the bike over, or placing it on a truing stand so the wheel can spin with ease.

First, check for broken spokes. If you find any, use the same method to straighten your rim, but replace the spoke as soon as possible.

Next, make sure your axle is seated in the dropouts unless you have a quick-release wheel. If the axle isn’t straight, don’t re-true the rim.

Check your brakes to make sure they weren’t damaged or the brake cable wasn’t tangled.

Step 2 – Check the Alignment

Carefully rotate the wheel while checking the size of the gap between the wheel and the brake pad. As the wheel rotates, you will notice that at some points the gap between them is varying, which indicates a buckled wheel.

Step 3 – Locate the Problem

As you slowly rotate the wheel, you will locate the part of the rim that is hitting the brake pad.

You can fix it by tightening the spokes in the direction opposite to the bend. If the rim is tugging to the left, locate the spoke on the right side of the hub that is closest to the buckle’s center.

If it is tugging to the right, locate the spoke extending from the left side of the hub.

Tightening the spokes pulls the rims away from the side it was bent to, thereby aligning it.

Step 4 – Adjust the Tension

The nipple of the spoke needs to fit into the notch of the wrench for it to be tightened, so make sure you’re using the appropriately sized wrench.

Tighten by turning counterclockwise.

If you’re not sure, produce noise by “plucking” the spoke like a guitar string. Adjust by a full turn and try a second pluck. A higher pitch indicates a tighter spoke, while a lower pitch indicates a looser spoke.

Step 5 – Add Finishing Touches

You can tweak more spokes if you think that your wheel needs more adjustment. Rotate the wheel again to check the desired results and squeeze each pair of spokes to ensure that all gaps are even and the rim is free of dents or dings.

More than five twists of the spoke wrench mean a potentially damaged wheel. After a certain number of dents, a rim can no longer be re-trued and will need to be replaced. (Source)

3. Fix a Loose Hub

To inspect for a damaged hub, first keep your bike steady, hold the wheel at its highest position and shake it.

Any play, often accompanied by a clunking sound, indicates that your hub needs tightening.

For hubs that use press-fit cartridge bearings, altering the hub tension may be impossible, which means you need new bearings. All the other hubs need their bearings tightened up again.

However, overtightening the nuts and bolts can prevent the wheel from turning freely, leading to early bearing failure.

Cone nuts are commonly used to secure hubs. Find the axle, and more specifically, the pair of nuts close to where the spokes connect to the hub.

These nuts are placed side by side so the outer nut can lock the inner one into place.

To do this, you must first loosen the outer nut, then tighten the inner nut, and finally tighten the outer nut again without touching the inner nut.

Tighten the cone nuts, then rotate the wheel while holding the hub axle in place. If you don’t feel any grating or binding sensations, then the tire is free of wobble!

Conclusion

Wobbling is a very common issue that plagues bikers, which often strikes at times when you have to act as quickly as possible.

While now you are aware of various problems associated with wobbling and different ways to fix them, it’s important to keep calm and not panic in such situations. If you’re a new learner, then these problems can help you identify the issues that might lead to an uncomfortable riding experience, so you can easily eliminate them and ride cautiously.

But as someone that’s experienced wheel wobble, I can assure you that once it’s happened the first time, you’ll do just about anything to stop it from happening again!

Martin Williams

Martin has been tearing up all sorts of trails on a range of bikes ever since he was young. He once cycled across France, and once fell into a canal on a hybrid. He writes about everything to do with cycling on our site. You can find out more about him at bicycle2work.com/about-martin-williams/

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