So you have just conquered a steep hill and have started flying down the other side. As you pick up speed, the unexpected happens.
You are not doing anything wrong, not even pedaling, but your bike starts to wobble. This wobble gets more severe the faster you go.
Your handlebars violently shake from side to side, and you are doing everything you can to stay on your bike. The only thing you can do is slow down or come to a complete stop to recompose yourself.
What you have just experienced is speed wobble. This terrifying phenomenon has slowed many cyclists down, fearing being thrown into the nearest hedge.
In this article, we will cover:
- What causes speed wobble
- How the bike moves with speed wobble
- How you can prevent speed wobble from happening
Let’s look at how to keep riding smoothly!
What Causes Speed Wobble?
Speed wobble is when your bike’s steering oscillates at a frequency that is too high for you to react to. You can also get speed wobble when riding a motorbike or a skateboard.
When a bike gets speed wobble, something has caused the front wheel to accelerate to one side. Simple things can do this from a gust of wind, a bump in the road, a wheel that isn’t true, or event the rider sneezing.
There needs to be a couple of factors that need to be just right (or wrong) for speed wobble to occur. You need to be going at the right speed, and something needs to set it off at the right time. The speed wobble needs to be at the natural resonant frequency of the bike and rider.
Speed wobble is more likely to occur on less stiff bikes or ones with low-level damping. This is why it happens on road bikes more than mountain bikes. Mountain bikes suspension removes unwanted oscillations and uneven terrain, and slower speeds make it hard for a mountain bike to reach a stable equilibrium.
The good news about speed wobble is that it can only oscillate so much. The speed wobble cannot exceed its limit, so the oscillations don’t grow enough to throw you off your bike.
Speed wobble only happens when you are coasting. This is because you are in a state of equilibrium, which you don’t reach when pedaling.
How The Bike Moves With Speed Wobble
When your bike oscillates below 6Hz, your bike starts to weave. At these lower frequencies, the front and rear of your bike appear to move together.
You will not experience the frame bending or twisting, as it moves with the steering assembly. However, when you reach the speed wobble frequency, everything becomes more complicated.
Nicolò Tomiati did a study by placing six sensors on an experimental bike to see how it moves during speed wobble. The study revealed that the oscillation’s amplitude decreases the closer to the rear wheel you go. This is because the front of the bike has the most freedom to move, thanks to the steering assembly.
The study also revealed that the oscillations at the seat stays are out of phase with those on the top tube. This means that when the front of the bike is accelerating in one direction during speed wobble, the rear is accelerating in the opposite direction. Therefore, the bike twists beneath you.
There is also quite a lot of torsion in the steering assembly. The fork twists upwards slightly in the direction the wheel is facing during speed wobble. Also, the handlebar bends downwards in the same direction.
How To Stop Speed Wobble – 5 Steps
Now we know why speed wobble happens and what is happening; how do we stop it once it starts?
#1: Don’t Panic
The first thing to do is not panic. It is easy to say that from behind a laptop, but it can be terrifying when it happens. If you keep your head in the game, it is pretty easy to bring your bike back under control.
If your speed wobble started when you were not holding onto the handlebars, gently return your hands to them. Simply doing this should stop the speed wobble.
#2: Clamp Your Knees Around The Top Tube
But what if your hands were already on the bars? In this case, try not to grip your bars tighter, as this can make things much worse. Instead, continue to grip them firmly and clamp your knees around the top tube.
Doing this adds damping to your frame and effectively increases its stiffness. This increases the resonant frequency, which means you will need a higher frequency for your bike to get speed wobble. So doing this should stop the shimmy.
#3: Lift Off The Saddle
Another way to stop speed wobble is to slightly raise yourself off the saddle. This reduces the stiffness, decreasing the system’s resonant frequency.
#4: Slow Down
It is easy to panic when you get speed wobble and grab the brakes. But you should avoid the front brake if possible. Gently apply the rear brake while bringing yourself into a more upright riding position.
Sitting up on your bike will increase your drag through the air, slowing you down.
However, if the road you are riding on is steep or has lots of curves, slowing down can be tricky. This is because you can use your brakes effectively when cornering. They may even increase your speed wobble at first!
The critical thing here is to remain calm. Try the other methods stated above to destabilize the oscillations before using your brakes.
#5: Don’t Jump Off!
Some people may be tempted to jump off their bike when they get speed wobble. But there is a good chance you will be going pretty fast, and with nothing but a thin layer of lycra to protect you, you are likely to get hurt.
Also, intentionally or not, falling off your bike puts you at risk from other vehicles and objects. The time it takes you to slow down enough to stop speed wobble isn’t very long, so stick with it if possible.
What If You Get Speed Wobble Too Often?
Getting speed wobble occasionally is one thing, but what if it keeps happening?
If you keep getting speed wobble, you need to do something to change the system’s resonant frequency.
You can discourage the scary equilibrium of speed wobble from happening again by making a change somewhere. You will need to you the process of trial and error to find out what the problem is.
If you increase or lower the stiffness of the system, you should be able to prevent speed wobble from happening again. This is also the case if you increase or decrease the system’s mass.
The ultimate solution is to change your bike’s frameset. The frame and fork are the most flexible parts of the system, so changing these parts is a good option; however, this is not a cheap fix.
A more affordable way is to start swapping other components. The other parts of your bike contribute to the stiffness of the system. If you were thinking about upgrading your wheels, tires, handlebars, or stem, do it. This may be what stops your speed wobble.
Tires with a softer compound are better at damping and are relatively inexpensive components to replace, and they may completely eliminate speed wobble.
Check Your Bike
Before you buy yourself a set of fancy carbon wheels to eliminate the shimmy, check your current wheels. They may need truing to straighten the wheel out. Any imperfections in your front wheel could potentially promote lateral movement, causing speed wobble.
Some people may suggest that you adjust your bearings tighten spokes, amongst other things. However, doing this won’t make a difference unless it alters the mass or stiffness of the system.
Look At Your Riding Position
Often speed wobble occurs when the rider sits high up on the bike or when their weight is shifted too far forward or back.
As we said earlier, preventing speed wobble is a case of trial and error. There is a good chance it will come with a cost, but try adjusting your riding position first. If that doesn’t work, try a new set of tires before spending money on more expensive parts.
When you speak to anyone who has experienced speed wobble, they will do pretty much anything to stop it from happening again.
Time To Upgrade?
If you are looking at upgrading your bike, check out the blogs below for some great tips for improving your cycling experiences:
In the market for some aero bars? This guide should help you out.
Or some clipless bike pedals for your road bike?