LOOK695 Posted September 27, 2015 Posted September 27, 2015 What causes a bike to speed wobble? Happened on a fast downhill which is on a training route and had been ridden 100s of times. Top end bike, no changes to bike fit, bike in good condition, no wind, road service good, speed wobble, rider down with two broken ribs
Disylizzy Posted September 27, 2015 Posted September 27, 2015 When it starts to vibrate and then it oscillates without being dampened, it gets worse and worse. A quick google search shows that any number of things could have cause it. Can be something as simple as rider's position on the bike, to a technical problem with the bike itself - more specifically steerer or front wheel. Look up speed wobbles for motor bikes, lots more posts on that. Should have similar results for a bicycle.
'Dale Posted September 27, 2015 Posted September 27, 2015 What causes a bike to speed wobble? Happened on a fast downhill which is on a training route and had been ridden 100s of times. Top end bike, no changes to bike fit, bike in good condition, no wind, road service good, speed wobble, rider down with two broken ribsAs you approach the speed of light.....????
LOOK695 Posted September 27, 2015 Author Posted September 27, 2015 As you approach the speed of light..... Us roadies always trying to go as fast as possible
David Marshall Posted September 29, 2015 Posted September 29, 2015 It is unusual to come down from a speed shimmy. It's the fright that normally kills you! Often you can break the motion by standing or steadying the top tube with your knees. If it is a bike you are familiar with and it hasn't happened before I would be worried. Time for a detailed inspection. (Skewers, dropouts, fork, headset, spoke tension, wheel cracks etc.)
ahmedbadat Posted September 29, 2015 Posted September 29, 2015 i used to get it alot and it was very very scary till someone on the hub told me about squeezing the top tube with my knees and now i dont get it anymore.
LOOK695 Posted September 29, 2015 Author Posted September 29, 2015 It is unusual to come down from a speed shimmy. It's the fright that normally kills you! Often you can break the motion by standing or steadying the top tube with your knees. If it is a bike you are familiar with and it hasn't happened before I would be worried. Time for a detailed inspection. (Skewers, dropouts, fork, headset, spoke tension, wheel cracks etc.)Thanks for the reply. I have inspected the bike (not my bike), and there is no sign that it was involved in a crash. Only the shifters were moved out of position and the seat has some marks on it.
LOOK695 Posted September 29, 2015 Author Posted September 29, 2015 i used to get it alot and it was very very scary till someone on the hub told me about squeezing the top tube with my knees and now i dont get it anymore.I also squeeze the top tube with my knees. How do you position your legs in a curve? Normal would be outside foot down
rudi-h Posted September 29, 2015 Posted September 29, 2015 i got a slight speed wobble on the jock this year, coming down from Kaapsehoop at 89km/hr. scary stuff that, but can't tell you why it happend or what to do to prevent it. maybe governing my bike at 88 km/hr is the answer...
ahmedbadat Posted September 29, 2015 Posted September 29, 2015 I also squeeze the top tube with my knees. How do you position your legs in a curve? Normal would be outside foot downnot sure i understand the curve part but all i do is put both crank arms horizontal and squeeze the top tube with my legs. hope it helps
Hennie VR Posted September 29, 2015 Posted September 29, 2015 When it starts to vibrate and then it oscillates without being dampened, it gets worse and worse. A quick google search shows that any number of things could have cause it. Can be something as simple as rider's position on the bike, to a technical problem with the bike itself - more specifically steerer or front wheel. Look up speed wobbles for motor bikes, lots more posts on that. Should have similar results for a bicycle. Even better.............Youtube it.............can be very entertaining until it happens to you. Question: Was the rider riding with hands on the bars when he/she had the wobble?I have never experienced a speed wobble whilst having my hands on the bars.
Barker Posted September 29, 2015 Posted September 29, 2015 not sure i understand the curve part but all i do is put both crank arms horizontal and squeeze the top tube with my legs. hope it helps Sounds like grabbing onto the seat with your a$$ manoeuvre.
Pure Savage Posted September 29, 2015 Posted September 29, 2015 Just do as the world champion does...
Cheese Posted September 29, 2015 Posted September 29, 2015 Happened to me a few times , most recently at Dome2Dome . Has not happened to me for a while. From all the reading I have done it is mostly rider related, position on bike, Relaxed or not . As everyone says google it. For me it goes a lot with confidence, happned to me a couple of years ago and I had a bad time descending for a while , did all the things you read on the web and I seemed to be fine, however last Thursday it happened , and since then I am not relaxed. As you are not relaxed it happens more easily. So try to do the leg thing , get the weight of the saddle and onto peddles and you should be OK.
Cheese Posted September 29, 2015 Posted September 29, 2015 Just do as the world champion does...Jip, Weight on the front wheel, Top tube between his legs. Low centre of gravity. That about the best position.
Pure Savage Posted September 29, 2015 Posted September 29, 2015 Jip, Weight on the front wheel, Top tube between his legs. Low centre of gravity. That about the best position. You can also put in a few pedal strokes as well apparently.
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