Speed Wobble Explained: What Causes Speed Wobble, And How Can You Stop It?

Speed wobble – also known as “death wobble” or just “shimmy” – is a terrifying phenomenon for cyclists in which the front end of the bike begins to shake uncontrollably, usually while descending at high speeds.

Scientifically speaking, speed wobble is caused by “the oscillation of the steering column at the resonant frequency of the bike and rider”.¹Tomiati, N., Magnani, G., & Marcon, M. (2020). An experimental investigation of the bicycle motion during a hands-on shimmy. Vehicle System Dynamics, 1–17. https://doi.org/10.1080/00423114.2020.1762902

However, this definition isn’t especially useful for cyclists out on the road, as it doesn’t tell you what triggers speed wobble, what steps you can take to avoid speed wobble if it’s becoming a regular occurrence, and how to react if a speed wobble starts while you’re cycling.

‌Speed wobble is something that I’ve unfortunately experienced multiple times in my bike racing career – and while I’ve been lucky in that it’s never caused a serious accident, it has certainly knocked my confidence when descending at speed during the races in which it happened.

Down the years, I’ve picked up plenty of knowledge both on the triggers of speed wobble and how to avoid and react to it – and today I want to share that experience with you to help you descend safely. I’ll be covering:

What Is Speed Wobble In Cycling?

In simple terms, speed wobble is when the handlebars, front wheel, and even the front end of the frame begin to weave or shake without input from the rider.

Speed wobble typically occurs when riding downhill at speed. In my experience, the faster you’re travelling on the bike, the more violently the front end will shake when a speed wobble starts.

I’ve also heard cyclists refer to speed wobble by other names such as “speed shimmy”, “high-speed wobble”, or even more ominously as “death wobble”.

It’s not unique to cyclists either; speed wobble can also happen to motorbikes, skateboards, and even the landing gear of aeroplanes.

It’s an awful experience to have on the bike, and can very easily result in a total loss of control and then a crash. For that reason, it’s essential to understand the causes of speed wobble, how it can be avoided, and how to react safely when a speed wobble starts.

What Causes Speed Wobble?

As stated previously, in scientific terms speed wobble is caused by vibration or oscillation of the bicycle’s steering column at the resonant frequency of the bicycle and rider.

Let’s break that definition down.

Resonant frequency is a complicated concept, but can be thought of as the “favorite” vibration speed of an object that makes it respond more than any other.

Imagine you’re pushing someone on a swing. If you give little pushes at the right moment, the swing goes higher and higher. That’s because you’re hitting its “resonant frequency” – the perfect timing that makes the swing move the most.

All objects, from guitar strings to buildings to bicycles, have their own specific resonant frequencies. If you keep pushing or shaking them at that exact rate, they respond a lot.

This can be desired, such as the noise made by a guitar’s string being plucked, or undesired, such as a bridge shaking violently in the wind – or the speed wobble of a bicycle.

So, all bicycles have a particular resonant frequency, unique to each bike and rider combination, which will make them start to wobble. That means the next question is what triggers that wobble.

For bicycles, this can be anything that happens to accelerate the front wheel to one side. This could be something significant, such as a sudden jerking steering motion by the rider or a gust of wind, or something almost unnoticeable such as worn bearings or a minute change in the road surface.

See the example in the video below, in which the rider deliberately triggers a speed wobble by knocking the bike’s head tube to one side:

Here are some of the most common triggers that can cause speed wobble that you should be aware of:

Bike Maintenance Issues

There are any number of major or minor mechanical issues with the bike that could cause enough movement of the front wheel to trigger a speed wobble. Here are some of the most common that I’ve encountered:

• The tire isn’t seated properly
• A wheel is out of true
• The headset bearings are worn
• The fork or frame is bent
• Misshapen tires
• Incorrect tire pressure

Any of these could cause the front wheel to move to one side with enough speed to match the bike’s resonant frequency, triggering a speed wobble.

Weather Conditions

The next factor that heavily affects speed wobble is weather conditions, the most significant of which is wind. A strong gust of wind can easily generate enough front wheel movement to trigger speed wobble.

This is particularly common if you use deep-section aero wheels. The larger the surface area of the wheel, the more it will catch the wind.

Disc wheels take this to the extreme and are extremely susceptible to speed wobble, which is partly why it is extremely rare to use a front disc wheel outside of the controlled conditions of the velodrome – even while time trialing.

Another potential weather-based trigger for speed wobble is riding in the rain.

If you start going over pockets of water, the wheel can shake because the drag of the water creates movement. If this vibration comes close to the resonant frequency, it can trigger a speed wobble.

Terrain

Although it seems obvious, the terrain you ride on also makes a big difference to speed wobble. You can expect a lot of turbulence when riding on rough roads at high speed, increasing the potential for speed wobble. 

You can also get speed wobble from seemingly smooth roads too. Some methods of laying concrete can create a barely noticeable lumpy feeling, which can trigger a speed wobble, especially if the bike and rider’s resonant frequency is unusually low.

Rider Control

Good descending skills on a bike require silky smooth handling with slow, precise movements at high speeds.

Just watch Tom Pidcock descending at the Tour de France – he looks graceful and utterly in control at all times, even while hurtling past other elite professional cyclists.

The jerky, jolting movements that might be made by a less experienced cyclist riding at speed can shift the front wheel at enough speed to come close to the resonant frequency, triggering a speed wobble.

Furthermore, less experienced riders are less likely to remain calm under pressure or know the tricks to counter a speed wobble once it begins – more on that below!

Speed Wobble In Mountain Bikes Vs Road Bikes

It’s also widely acknowledged that bikes that are less stiff or have less effective damping are more susceptible to speed wobble.

This means that mountain bikes are far less likely to experience speed wobble than road bikes, because the suspension and lower tire pressures help dampen out the oscillations before they reach the bike’s resonant frequency.

Furthermore, the different contexts the bikes are used in also play a role.

The trails used by mountain bikes are generally too rough and uneven for any vibrations to hit a stable equilibrium, making them much less likely to amplify into a speed wobble. The lower speeds mountain bikes tend to reach also reduce the likelihood of speed wobble.

Speed Wobble In Modern Vs Vintage Bikes

Meanwhile, amongst road bikes, different frame materials and designs can also make a difference.

For example, carbon fiber is a stiffer material than steel, so a modern carbon road bike is less likely to experience speed wobble than a vintage steel road bike. More modern bike frame designs also tend to be stiffer in general than older ones as technology and materials have advanced.

To get technical, bike frames with a head tube or torsional stiffness greater than 75 Nm per degree are considered to be relatively safe from speed wobble.

Many steel frames, especially those built before the 1990s, are either close to or below that figure, whereas good-quality modern racing bike frames built from carbon fiber typically have a stiffness of about 90-100 Nm per degree, and that number can even go as high as 140. (Check out these charts if you’re interested!)

So, if you’re a vintage bike lover, learning how to react to speed wobble is especially important!

How Can You Prevent Speed Wobble?

So, how can you prevent speed wobbles from happening altogether?

Here are my top tips – some of which have been learned the hard way from personal experience!

#1. Ensure The Bike Is In Full Working Order

First and foremost, ensure that your bike is in full working order.

Check the wheels are true, the tires are seated properly on the rims, you have the correct pressure in the tires, and the frameset is straight and in good condition. 

It’s easy to miss small problems that don’t arise until you start going at higher speeds. I once bought a bike that seemed perfect until I started riding it quickly, then it made awful noises and wobbled.

I later found out the previous owner had crashed it, and hadn’t informed me during the sale – and I hadn’t noticed the telltale signs when I inspected it prior to purchasing it.

If you are unsure about any components of your bike or feel it’s not working the way it should, I highly recommend taking it to a bike shop for a full health check. It might cost $100 or so, but it is worth it when it comes to safety and peace of mind. 

#2. Don’t Ride In Poor Conditions Or Terrain

If you go out in high winds or ride on poor terrain, then you are asking for trouble.

Although sometimes it’s unavoidable, it puts your chances of speed wobbling way up. If you live in a place with regular high winds and are having issues with speed wobble, consider training indoors on gustier days.

Another solution might be using a different bike for the worst days. An aero-time trial bike with a disc wheel will be awful in the wind. A mountain bike with low-profile rims and a bigger weight will handle it much better. 

#3. Don’t Push It

Speed wobble is less likely to occur – and easier to counter when it does – at lower speeds.

There’s no denying that flying down a descent at lightning speed is one of the greatest thrills in cycling, and it’s easy to get carried away once you start stringing high-speed corners together.

But if you’re not in a racing situation, I’d strongly urge you to knock off that last 10% or so of speed to remain completely within your limits to keep yourself and other road users safe, and reducing your chances of speed wobble in doing so.

How Can You Stop Speed Wobble Once It Starts?

Even with all the maintenance checks, experience, and care in the world, speed wobble can still catch you by surprise.

Because a speed wobble can only be sustained when the bike is at an equilibrium, the key to stopping speed wobble is to change something about the system of the rider and the bike.

Note that this also means speed wobble can only start while you are coasting. This is because you are in a state of equilibrium, which you don’t reach when pedaling.

Here are the key steps to take to safely counteract a speed wobble, so you can navigate your way out of the situation safely.

#1. Relax

Once you notice a speed wobble setting in, the worst thing you can do is to tense up and slam on both brakes.

If the speed wobble started while your hands were off the handlebars, gently take hold of them again – this may be enough to stop the wobble in itself.

If your hands were already on the bars when the wobble started, lightly loosen your grip and relax your arms to a point where you still have grip, but your arms are working like suspension and dampening the wobble.

You can start feathering the brakes here to begin slowing you down, but do so gradually and cautiously. Beware that the brakes may actually increase the wobble, so be prepared to allow the bike to freewheel again if necessary while you get the vibrations under control.

#2. Stop The Wobble

Next, we need to stop the wobble so everything feels much less erratic and we regain control. There are a couple of ways you can do this:

Clamp The Top Tube With Your Knees

The first way is to put your feet level (3 o’clock and 9 o’clock on the pedals) and use your knees to clamp on the top tube. This should help stop the wobble.

If you need extra support, raise yourself just off the saddle slightly.

Drop a Leg

Another great way to stop speed wobble is to drop one leg to the 6 o’clock position on the pedal, then apply pressure downwards.

This centralizes the bike and stops the speed wobble fairly quickly. 

#3. Slow Down

Finally, it’s time to come to a complete stop, if you need to. With less wobble, you can put the brakes on stronger, bringing your bike to a halt. Then you might want to take a minute to let the adrenaline get out of the system.

Alternatively, if you’ve managed to stop the wobble and dropped to a safe speed, you may feel fine to continue riding without stopping completely – though it might be sensible to stop and check your bike to see if there’s an obvious problem that caused the speed wobble.