Speed Wobble from Hell

I've known about the phenomenon of speed wobble for well over 25 years and know that it's not the fault of the bicycle, that it is a natural phenomenon and that it can be corrected by shifting your weight on the bicycle. A similar phenomenon can be seen, apparently, when towing a trailer in a car, or sometimes in a boat at speed.

Yesterday my younger daughter Lizzie had persuaded me to do the cycle (17 km) of the Schull Duathlon, with her doing the two runs which were 5k and 3k. You can do these as an individual or as a team. She was doing this as a part of her running training because she likes the social aspect of triathlon, having spent some years doing triathlons with considerable success.
The route climbs for about a mile or so from Schull village and then drops fairly steeply on a roughish road.
I'm pretty heavy at the moment at 15.10 and was cycling my carbon fibre road bike for the first time since my friend was ultimately fatally injured by his forks snapping last October. He died on Christmas Day.
Anyway Lizzie came in third on the run and first lady by a mile and I suppose there were about 20 teams, the rest individuals.
Off I go, not going into the red up the hill.
As I approached the top two whippets on time trial machines passed me.
Down I go into a tuck and start going downhill. Suddenly about half ways down the bike began to wobbly not mildly but violently. When it starts gently you have the presence of mind to shift and stop it. The memory of my friend's recent death entered my mind and I was petrified. I began to lose control of the bike and it veered towards the ditch. I was braking by this stage and to my amazement I managed to stop and get off the bike without mishap. I expected to find a broken frame or a puncture so violent was the oscillation. I had a good look at the bike, tested the tightness of the wheels in the forks, and gingerly remounted, having considered jacking it in. I began again and continued the descent. A mild oscillation began again and I stopped again. I gave it one more go, a little oscillation began but by this stage I'd regained my composure and shifted forward and gripped the top tube between my knees, or crossbar, as it is in Ireland and it stopped. I was okay for the rest of the cycle though I did not descend flat out. I supposed I'd lost 2 or three minutes but we still won the team prize, ENTIRELY due to how good a runner Lizzie is. I was shaken AND stirred.
What hit me in this episode was the swiftness and the violence of the phenomenon. Interestingly my son-in-law who has a summerhouse near here and who cycles a lot, and like me is a big man, has suffered the same phenomenon on this, and only on this hill.

I'd not had a speed wobble on this bike before..

LizzieChrisnKaty

Lizzie finishing.

7 comments on “Speed Wobble from Hell”

  1. Alan wrote:

    Congratulations to you and Lizzie — it is a team effort, after all. Great photo — she seems to be strolling casually, glancing at her watch, wondering what time dinner will be.

    I can get speed wobbles — shimmy — at certain speeds and weights on my (steel) tourer, but I automatically control it as soon as it starts. I've played with it, deliberately setting it off, to experiment with cause and cure.

    It also happened once in my Land Rover on a downhill coast road in Croatia, with juggernauts on my tail. Very scary.

    I have no suggestions for you and your carbon fibre bike, other than to say that you need to be able to trust your bike.

  2. Patrick wrote:

    I'd not had a speed wobble on this bike before.

    I've never had speed wobble on any bike, probably because I never exceed 30 mph (preferably 25 mph). I feel it's too risky even without speed wobble and even on a trusted bike. It's one reason I never did/will cycle competitively. Well done with the Duathlon though.

    (I thought you had decided to sell your carbon fibre bike)

  3. Kern wrote:

    I had heard about pressing your knees inward to help regain control but have never experienced the violent phenomenon you describe. It is very interesting that it occurs on one specific hill. It almost sounds like the type of oscillating motion that sometimes aflict bridges.

    Your friend's finale is very tragic, Garry. That's not how stories are supposed to end.

    We had lunch in Schull on our tour in 2010. There was a film festival of some sort going on at the time. The tourist office there told us about the sandwiches at Crookhaven Inn – the best on the penninsula, they said. Good memories.

  4. Jim wrote:

    Thats a sad tale about your friend.
    I have recently purchased two very nice 90s steel road bikes and am now considering stripping my newer ali/carbon bikes to modernise the steel bikes and to hell with the weight penalty. I too have never experienced a shimmer but my bikes are not the lightest. I'm also a big guy. I wonder if it is the disparity beween the weight of bike and rider?

  5. Garry wrote:

    I don't think it is. I've experienced minor wobbles before that I controlled easily on other bikes but the suddenness and severity of this made me panic. I havent sold bike as i think that my bike which I've never crashed is very unlikely to give trouble. If I crash it I'll have it x-rayed

  6. Roger wrote:

    I'm 9 stone and 5 foot 6 and have also experienced shimmy on 3 different bikes – all steel, 2 tourers (Dawes Galaxy was one) and a racing bike (all small 54/52 cms horizontal geometry). It can knock your confidence for some time and make you extremely cautious when descending. The last time i experienced it was on my race bike on the flat! and can only put it down to the road surface which i noticed was "dimpled". Once it starts it can sometimes come on suddenly and violently and as you tense up you can make it worse – the advice being to relax but this is easier said then done. Having checked my bike over i wondered whether it could have been excaserbated by a very small out of true rear wheel – no more than a couple of mm. I havent had it since on the same section of road.

  7. Chris wrote:

    I've had a speed wobble only once. I didn't think I was going that fast, actually. Probably less than 30mph. I think I may have been spinning out at the time and that caused it. I've been much faster since without a problem (although in hindsight I probably shouldn't have gone that much faster).

    It's a very sad story about your friend, Garry. I thought I had remembered that you were selling the carbon bike. I'm glad for you that you didn't.

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