UKC

Did a long and fast downhill on the road a few days ago, then as I braked at the bottom my front wheel started violently wobbling side to side. This coinsided with a change in surface (smoother tarmac) and with every press of the brakes it got worse to the point I thought my front wheel was coming off - terrifying!

Just about kept it under control after a fight with the handlebars and got myself to stop. Checked everything after to find it was all surprisingly solid. Never happened before or since.

Just wondering if this has happened to anyone else and as to why it could happen? And most importantly how I can reduce the chance of it happening again?

All I can think (I'm no engineer!) is the flex in the carbon frame/forks started to resonate with braking and the vibration from the road - starting some kind of bouncy positive feedback loop? I have a PlanetX Pro Carbon bike.

In reply to Swampi:

Speed wobble

https://cyclingtips.com/2011/03/speed-wobble-when-the-bike-shakes-its-head/

In reply to Swampi:

https://m.youtube.com/?reload=7&rdm=2leyxq5cc#/watch?v=JVgjiB4Y6a0&...

This might help.

I've had speed wobble from shivering on descents!

In reply to Swampi:

Motorcyclists call it a 'tank-slapper'.

In reply to Swampi:

Have you checked the wheel cones are tight?

In reply to xyz:

Thanks all.

Definitely sounds like a case of speed wobble. At least I know how to stop it now by gently bringing my weight to the front of the bike. Although we'll see how easy that is while going 80kph as my headset violently shakes!

In reply to Swampi:
Had a Planet X Pro Carbon once as a hire bike on holiday and thought the frame had a lot of flex - found it a bit sketchy down hill, but fortunately not to the point of speed wobble.

In reply to Swampi:

I had a similar experience on my cyclocross. 85 kph down a bumpy 1:5. My front wheel shook and my teeth began to chatter. When I looked down it was my belly hitting my double chin!