My first speed wobble....

[Salty seadog]

Experienced my first speed wobble today. It was on the mtb with nobbly tyres. Happened at a fair speed, 20mph plus, whilst riding no handed and coasting. As soon as I touched the bars (even lightly with just one finger) it stopped, it also stopped if I braced the top tube with one knee, (whilst still no handed) our started pedaling..

I repeated the wobble many times after to trace a cause. I have ridden no handed on all my bikes many times including this one and never had it. I tried on different road surfaces but it was always the same, when up to a brisk pace and freewheeling no handed the wobble started every time. Any input from me, pedaling, leaning a knee on the top tube or touching the bars stopped it.

ETA. The bike has had no recent changes.

I did have a strong wind behind me and to the left. I was going north, the wind was from the south west.

Any idea why this behavior would suddenly start. I've have this bike 6 years without issue?

 

[Yellow Saddle]

https://www.cyclechat.net/threads/speed-wobble.198346/page-3

That link may help.

It is no use looking for the exact reason why it started to shimmy. It is more useful to understand why and that the parameters for when it will wobble/not wobble are so narrow that a small change in weight, tyres, tyre pressure, wind, terrain, road surface and many other things contribute to the specifics of a specific wobble.

But basically, it didn't suddenly start. It was always latent and conditions on the day were right.

 

[Drago]

My Raleigh Chopper was travelling at about 650MPH when then transonic buffeting set in.

 

[gbb]

Been through this myself lately after a fair lay off the bike. I suffered speed wobble almost every time I started any downhill, once I'd barely started gathering speed, usually It occurred about 20 mph I suspect.
I very very occasionally got it on different bikes in the past when I was really fit but I
I suspect most of the last episodes were down to me....loss of concentration, skill, confidence, whatever. It's virtually stopped happening now, I occasionally start to feel a slight shimmy, lightly brake and that brings it under control, then accelerate away.
I've checked my bike over and over, headsets fine, nothing get loose, changed tyres, all sorts.
One thing I did find although I can't be sure...I was cleaning get the bike and had the front wheel out. When I refitted it, I struggled to get it to sit in the dropouts properly. It went in eventually but I do wonder if it had been slightly skewed and set off a gyroscopic effect at speed.
Just a passing theory for my wobble.

 

[HLaB]

I suffered a bad speed wobble on a TT last year, sprinting on the ski poles Doh I won't do that again I put it down to lack of weight over the front wheel and hitting a small bump that was enough to get the wheel of the deck and set it in motion. Touch wood, since when sprinting I've done it the base bars rather than ski poles it hasn't happened again. Learning from ME maybe riding no handed downhill isn't a good idea, its better to have more weight over the front wheel.

 

[Ming the Merciless]

My Raleigh Chopper was travelling at about 650MPH when then transonic buffeting set in.

Was it an all you can eat buffet?

 

[Lilliburlero]

I had a couple of scary speed wobbles on fast, curving down hills on my new road bike a couple of months ago. With a sportive around the Peak District coming up, I decided that I`d better have a look at sorting the problem out and found this https://cyclingtips.com/2011/03/speed-wobble-when-the-bike-shakes-its-head/.

"3. Incorrect weight distribution is a very common cause of speed wobble. Quite often, speed wobble has just as much to do with the rider as it does with the bike. If speed wobble starts occurring, many people will intuatively put their weigh towards the back of the bike instead of putting their weight towards the front to actually stop it and dampen it out. The best thing to do to get out of a wobble is to weight one of your legs down at the 6/12 o’clock position, put some weight on the front end by bending your elbows (use soft hands – don’t grip handlebars firmly!), and take some weight off your seat (to take the pivot point away) which puts more weight back on the handlebars, which puts more weight on the front wheel. This will usually bring stability back to the bike and correct the oscillation. The reason it’s suggested that the pedals be in the 6/12 o’clock position (rather than the 3/9 o’clock position) is because this will bring your body weight into a better balanced position which will calm the bike down."

It worked for me and I now do it before the problem occurs.

 

[Drago]

Was it an all you can eat buffet?

All the legs you can break, as it turned out.

Attempting to break the sound barrier with a pillion passenger was, in retrospect, doomed to failure.

 

[johnnyb47]

Have you got any slime tubes fitted by any chance. I only ask because they make my wheels quite unbalanced with the slime inside,

 

[screenman]

I had a blowout at speed on the wheel barrow, I was not pushing it no handed at the time.

 

[Salty seadog]

Have you got any slime tubes fitted by any chance. I only ask because they make my wheels quite unbalanced with the slime inside,

No, and never experienced before ever, had the bike 6 years now.

 

[Drago]

I used slime tubes for years on my commuter, and beyond the additional rolling mass they bring I never had a problem.

 

[Welsh wheels]

I don't know a lot about speed wobble, but I suspect it's quite hard to define exactly what it is and when it's taken place.

 

[Yellow Saddle]

I don't know a lot about speed wobble, but I suspect it's quite hard to define exactly what it is and when it's taken place.

I think you'll find the opposite. You identify it by the smell in your pants.

 

[Welsh wheels]

I think you'll find the opposite. You identify it by the smell in your pants.

Fair