The Speed Wobble: Surviving the Terrifying Cyclist Experience

When you’re speeding down the pavement at 25 miles an hour on two wheels, the last sensation you want to feel is that you’re losing control. If your bike gets caught in a speed wobble, though, that’s exactly what it will feel like.

Although “speed wobble” may sound like the name for a fun kiddie coaster at your amusement park, in all reality, it’s anything but fun for the unsuspecting rider.

“It’s one of the most terrifying experiences to a cyclist,” says longtime cycling coach Darryl MacKenzie. “It’s almost as if it’s a horse that’s trying to buck you off. And it happens quickly, with little or no warning. You can be riding all your life and not get one of these, but if you do you better know what’s happening and what to do.”

If you’ve never heard of a bicycle speed wobble, you’re probably curious at this point. So, just what is it — and how do you stop it? Coach Darryl has the answers.

What Is a Speed Wobble and When Does It Happen?

The bicycle speed wobble — some call it a shimmy — only happens when you’re going very fast downhill. It usually starts somewhere between 25 and 35 miles per hour, and it’s exactly what it sounds like: Your bike begins to wobble aggressively side to side, seemingly for no reason.

It’s not very common — most of the time, you’ll race downhill with no issues — but that’s why it can catch so many cyclists by surprise. When it happens, you can easily panic, thinking that your wheel is about to fall off or you’re riding too fast on a flat tire. At that speed, though, you do not want to overreact.

In his decades of cycling, Darryl has experienced a speed wobble fewer than10 times, so he estimates it’s happened once every 20,000 miles or so. But it’s scary every time, and it’s not always clear what’s causing it.

How to Stop a Speed Wobble When It Happens

So, what do you do when a speed wobble strikes? First, let’s reiterate what we already said: Don’t panic. If you stay calm and focused, this won’t lead to a crash. It may have started suddenly, but you won’t be able to make it stop immediately. This takes patience.

Now that you’ve got your head on straight, the next step is to clamp your knees firmly against the top tube. This will help to reduce the rate and intensity of the wobble because you’re minimizing wind turbulence and providing some counter-pressure against the bike.

Next, lean forward to lower your center of gravity and keep your pedals level — at the three and nine positions on a clock. This will increase stability and prevent you from putting too much pressure on either pedal.

Finally, resist the urge to slam on the brakes. The wobble actually gets worse as the bike slows down, so an aggressive, sudden stop is not going to help. This is tough because braking is likely your first instinct when this happens. Go easy on the brakes and bring the bike to a gradual stop. You can even try alternating gentle pressure on the front and the rear to see if either one helps reduce the wobble more. 

How to Prevent It

When you’re able to pull off the road and stop, you can check your bike for any immediate signs of a cause. More than likely, however, there won’t be anything obvious. It’s not entirely clear what causes a bicycle speed wobble, and most of the possibilities need a mechanic’s eye to spot.

That being said, there are a few things you can look for. Here are the seven most common factors that could contribute to a speed wobble, from most to least likely:

1. A loose or worn headset: This critical point where your fork and frame connect sees a lot of motion, making it a likely spot for components to loosen or experience wear and tear. You can tell if it’s loose by standing over the bike, squeezing hard on the brakes and trying to move it forward and backward. If the headset moves, it needs to be tightened. To find signs of wear, though, you need a mechanic.
2. An unbalanced front wheel: Anything that causes uneven weight distribution on your front wheel could be suspect. Darryl has seen this when cyclists put their computer sensor’s magnet on the same side of the wheel as the valve stem, which is already the heaviest spot on the tire. Moving the magnet to the opposite side (180 degrees away) evens out the weight and can fix the problem. A quick way to check for balance issues is to remove the front wheel, hold it in front of you and spin it very fast. If you feel your hands moving up and down at all, you might have an imbalance.
3. Alignment problems: There’s a chance your front and back wheel are not tracking precisely in the same line, and this can cause issues at high speeds. A mechanic can spot this easily with a jig.
4. Fork issues: Your fork could be cracked or out of balance, and this can throw things out of whack when you’re going fast enough.
5. A bent frame: This is basically the same problem as the alignment. Darryl once had a bike that caused five different wobbles on one century, and this was the culprit. Fortunately, the manufacturer sent him a new bike.
6. Bad tires: Any weak spots or damage to the tire could be enough to shake up the bike. The good news is, it’s easy to change a tire.
7. A loose skewer: The skewer is the rod that fits inside your axle (on rim-brake bikes) and is tightened with a cam lever. If this isn’t tightened down properly, it can cause your wheel to wobble. This is easy to tighten by hand if it’s causing problems.

Checking out all of these factors may lead you to the source of your speed wobble and help you prevent it from happening again. Sometimes, though, it can still happen out of nowhere. Be sure you’re ready to stay calm and in control when it does.

Look for more insights from Coach Darryl over at his website.