"SPEED WOBBLES" - how common are they?

[Roadrat77]

I've been a cyclist since we'll before i left school and have commute-cycled and cycled recreationally probably thousands of miles in my time but a couple of weeks back I experienced my first ever (thankfully, and last hopefully) "speedwobble" while descending at approx 50kph on a busy dual carriageway - not an experience to be repeated I can assure you - I know this phenomenon is rare and difficult to explain but my question is: just how common are these things and how many of you have ever actually had one?

 

[neil_merseyside]

I had a bike that would shimmy if I had my Rixen and Kaul Contoura bag loaded with anything heavier than a jersey, but a knee against the top tube killed the harmonic easily enough. Still have the bike and bag but they don't play together any more!

 

[sleuthey]

I had one 2 months ago at 15 kph so more of speedless wobble. It resulted in me elbowing a 2012 VW van on my left and the wing mirror snapped clean off and was left dangling by the wiring loom. It was parked alongside raised kerbstones and I had no way of making a note. I reported it when I got home and 14 days later the police wrote to me saying they had closed the file.

 

[Roadrat77]

I had a bike that would shimmy if I had my Rixen and Kaul Contoura bag loaded with anything heavier than a jersey, but a knee against the top tube killed the harmonic easily enough. Still have the bike and bag but they don't play together any more!

First I knew was the rear-end went really mushy - blown rear I thought then the whole bike just turned to jelly underneath me. Not good in the middle of a load of traffic that had just come off the M5 at Halesowen. How it didn't have me off I will never know. Jumped off fully expecting a broken spoke or skewer or possibly even a weld had snapped - it was that bad. Absolutely nothing, the bike was A1.

 

[Smokin Joe]

I had it happen once at little more than walking pace on a Raleigh Dynatech. I had just pushed off outside my house and the front started to shimmy like no tomorrow, fortunately at that speed I was able to come to a stop instantly. Even though barely moving it was an alarming experience.

 

[Twilkes]

I've never had it, 6ft5 and 100kg, and I think the additional weight over the front wheel is what prevents it, or at least increases the speed/frequency required for it to occur. A knee to the top tube is generally said to stop it, and pedalling helps reduce/prevent it, from what I've read. There was a video of a guy who would ride no handed and then bash the bars to induce a no-hands speed wobble to demonstrate how it happens - the wobble generally has a limited range so it shouldn't be enough to throw you off the bike, but it happens too fast for the rider to self-correct.

edit: this page has some videos on it: https://cyclingtips.com/2020/07/bicycle-speed-wobbles-how-they-start-and-how-to-stop-them/

 

[Twilkes]

I don't think the low-speed examples above are speed wobble or shimmy as per the article, as there wouldn't be enough energy in the system to instigate it, must be something else going on there.

edit again: although there is an example on the page of wobble that didn't stop until sub-10mph.

 

[Roadrat77]

I don't think the low-speed examples above are speed wobble or shimmy as per the article, as there wouldn't be enough energy in the system to instigate it, must be something else going on there.

edit again: although there is an example on the page of wobble that didn't stop until sub-10mph.

I was touching 50kmph and approaching a busy island and just starting to brake In a cross-wind when I had it. I must be the only rider in Brum with brown bib-shorts......

 

[Peter Salt]

Lucky enough not to ever experienced one. At least not up to about 88km/h. 90 is when I remind myself that I put the bike together myself

 

[Dogtrousers]

Never happened to me. Happened once to a friend, who descends a lot faster than me. I saw him way ahead on a long descent behaving strangely, then caught up after he'd pulled over.

 

[oldwheels]

I have had it at just over 40mph a few times with the same bike on the same downhill stretch. It was an old Dawes but never had it on any other bike.
On reflection I got a shimmy at anything over 20mph with the same bike and a loaded BoB trailer.

 

[Gillstay]

Got thrown off a motorbike once by this and it turned out the forks were off a 1936 one and the frame off a 1937 and the factory changed the head angle at this time. So we upped the castor angle and all was well.
Had it in the Alps chasing Italian cars down the passes with luggage on. So stopped using the Specialized hybrid and took the Orbit tourer instead. Rock steady.
From the motorbike, we also tested and found out that touching either brake will kill it as it changes the castor angle sufficiently.

 

[Ming the Merciless]

It will happen with certain frames and weight distributions. If it happens again a knee against the top tube can sometimes cure the wobble enough to take it out of the scary and dangerous moment. All to do with harmonics getting magnified at speed.

 

[LarryDuff]

I have had one twice, both times when descending at speed.
Second time I knew to clamp the top bar with my knees and it stopped quickly.
After I swapped the 28mm front tyre to a 25mm it hasn't happened again in the 4 years since.

 

[roley poley]

scary when it happens .i had this descending Otley chevin but had read that putting your knee to the top tube would cure it which it did ...god bless shared information from others who were there before me