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Speed wobble
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 2014-07-21 6:17 AM |
Extreme Veteran  5722   |  Subject: Speed wobbleThis isn't mean to scare people from descending fast. It's meant to make people aware of something referred to as speed wobble and what to do. I was riding a very hilly course this weekend. I came to this nice smooth descent, quite steep, and got up to about 42mph in aero position and my bike started to wobble. I thought I was going to crash. I thought maybe I had blown a tire I stopped, checked everything, nothing wrong. I continued, twenty minutes later, boom, same thing. A bit slower, maybe 40. (I looked at my Garmin). I stopped, removed my wheels, straightened them. Nothing seemed wrong. I continued, but like a big wimp. Applying brakes on downhills to not get too much speed. Brought the bike to the LBS, they check it out. Nothing. The top mechanic, who is extremely knowledgeable said "probably, speed wobble". Googled it and sure enough that was it. Be aware of it, Know what to do if it happens. It is the scariest thing I have ever experienced on a bike. http://cyclingtips.com.au/2011/03/speed-wobble-when-the-bike-shakes... |
| 2014-07-21 7:01 AM in reply to: marcag |
Extreme Veteran 1986   Cypress, TX | Subject: RE: Speed wobble Clinching the top tube with your knees helps immensely. |
| 2014-07-21 7:12 AM in reply to: GMAN 19030 |
New user 246 madison, Wisconsin | Subject: RE: Speed wobble I got it at 54mph in the Collegiate Nationals. Pretty sure I dumped a load in my shorts. Hitting the pavement at that speed would be less than fun. |
| 2014-07-21 7:19 AM in reply to: marcag |
Master 3205 ann arbor, michigan | Subject: RE: Speed wobble I had this happen to me on one of my prep rides at Lake Tahoe last year. I started to descend and got in to the 40s and my bike got incredibly unstable. For a moment I got pretty frightened but then I remembered reading about this in the past and thought that I was probably experiencing the dreaded "speed wobble". I slid backwards a CM or so on my seat with very little change. I then pressed one of my knees against the top tube and it instantly went away. I was glad that it happened on a training ride so that I had experienced it and could be prepared if it happened on race day. I believe that the theory is that at a certain speed your bike hits an oscillation frequency that makes it suddenly unstable. By changing your position slightly or pressing your knee against the top tube you change the bike subtly and the wobble goes away. |
| 2014-07-21 9:03 AM in reply to: wannabefaster |
Extreme Veteran 5722 | Subject: RE: Speed wobble Originally posted by wannabefaster I had this happen to me on one of my prep rides at Lake Tahoe last year. I started to descend and got in to the 40s and my bike got incredibly unstable. For a moment I got pretty frightened but then I remembered reading about this in the past and thought that I was probably experiencing the dreaded "speed wobble". I slid backwards a CM or so on my seat with very little change. I then pressed one of my knees against the top tube and it instantly went away. I was glad that it happened on a training ride so that I had experienced it and could be prepared if it happened on race day. I believe that the theory is that at a certain speed your bike hits an oscillation frequency that makes it suddenly unstable. By changing your position slightly or pressing your knee against the top tube you change the bike subtly and the wobble goes away. Yes, that is the theory. There is a thread on ST with Cervelo's lead engineer and he says exactly that. Gman is right, the top tube trick is a solution. Shifting weight is another. I had never head about it and it was scary. I posted this for awareness. Let me tell you, it's scary |
| 2014-07-21 9:03 AM in reply to: GMAN 19030 |
Extreme Veteran 5722 | Subject: RE: Speed wobble Originally posted by GMAN 19030 Clinching the top tube with your knees helps immensely. Do you do that as a preventive measure or when the wobble actually starts ? |
| 2014-07-21 10:36 AM in reply to: marcag |
Extreme Veteran 1986 Cypress, TX | Subject: RE: Speed wobble Preventative when speeds start approaching 40mph. |
| 2014-07-21 11:18 AM in reply to: GMAN 19030 |
Champion 7036 Sarasota, FL | Subject: RE: Speed wobble Originally posted by GMAN 19030 Clinching the top tube with your knees helps immensely. x2 Mark
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| 2014-07-21 3:42 PM in reply to: marcag |
Veteran 576 Maple Grove | Subject: RE: Speed wobble Originally posted by marcag Originally posted by GMAN 19030 Do you do that as a preventive measure or when the wobble actually starts ? Clinching the top tube with your knees helps immensely. Can you pedal through it? Obviously, at that speed you'll be pushing 115-120 RPM on a compact crank set, but I've hit those speeds on a couple of occasions and anticipated it, but never noticed it. I thought it was because I pedaled through it. |
| 2014-07-21 4:04 PM in reply to: rdailey1 |
Extreme Veteran 5722 | Subject: RE: Speed wobble Originally posted by rdailey1 Originally posted by marcag Originally posted by GMAN 19030 Do you do that as a preventive measure or when the wobble actually starts ? Clinching the top tube with your knees helps immensely. Can you pedal through it? Obviously, at that speed you'll be pushing 115-120 RPM on a compact crank set, but I've hit those speeds on a couple of occasions and anticipated it, but never noticed it. I thought it was because I pedaled through it. I don't think I was pedalling. When I hit 50watts in the hardest gear I figure it's god's way of telling me to take a break. It is the scariest thing I have ever experienced on a bike. |
| 2014-07-21 4:17 PM in reply to: marcag |
Champion 9407 Montague Gold Mines, Nova Scotia | Subject: RE: Speed wobble The knees on top tube is preventative and will often work. You can also try relaxing your grip (which is pretty much impossible) as this can also sometimes help. I've heard of people sliding forward on their saddle and/or sitting on the top tube as well but I've never tried these methods. Shane |
| 2014-07-21 6:25 PM in reply to: gsmacleod |
Master 2759 Los Angeles, CA | Subject: RE: Speed wobble Thanks!!! I felt this too and got scared I had to slow down a bit. >.< |
| 2014-07-21 9:02 PM in reply to: marcag |
| 504 | Subject: RE: Speed wobble Well known in the skateboard community. The scars I have on my hips prove it. Don't think I'll ever have the problem on the bike, as I'm not that fast  |
| 2014-07-22 10:11 AM in reply to: skibummer |
Expert 3126 Boise, ID | Subject: RE: Speed wobble
Thanks for the post. I have had little twitches here and there but never got into a full wobble. Had a few 50+mph descents on the tt bike, no issues. Glad to know how to fix it if I ever do get a good wobble going. This happens in the motorcycle world as well, leads to some pretty gnarly crashes. |
| 2014-07-22 10:52 AM in reply to: Aarondb4 |
Pro 6582 Melbourne FL Gold member | Subject: RE: Speed wobble Originally posted by Aarondb4 Is this specific to certain brands/models of bikes? I've never experienced this on either of my Felt tri-bikes and have been up to 50mph on downhills.Thanks for the post. I have had little twitches here and there but never got into a full wobble. Had a few 50+mph descents on the tt bike, no issues. Glad to know how to fix it if I ever do get a good wobble going. This happens in the motorcycle world as well, leads to some pretty gnarly crashes. I experienced this on my old Honda Interceptor in the mid 80's doing 130mph coming out of mountains outside Boise ID. Yes I thought I was toast when it occurred, one of the scariest times in my life. |
| 2014-07-22 11:00 AM in reply to: Donto |
| Oakville | Subject: RE: Speed wobble Originally posted by Donto Originally posted by Aarondb4 Is this specific to certain brands/models of bikes? I've never experienced this on either of my Felt tri-bikes and have been up to 50mph on downhills.Thanks for the post. I have had little twitches here and there but never got into a full wobble. Had a few 50+mph descents on the tt bike, no issues. Glad to know how to fix it if I ever do get a good wobble going. This happens in the motorcycle world as well, leads to some pretty gnarly crashes. I experienced this on my old Honda Interceptor in the mid 80's doing 130mph coming out of mountains outside Boise ID. Yes I thought I was toast when it occurred, one of the scariest times in my life. I've had the speed wobble on my Trek 2.1 road bike a few times while riding in the clip-ons but never on my Felt TT bike. As posted above, I have read that it has to do with harmonics of the frame and hitting a certain wavelength/vibration (?). By pressing your leg against the top tube you apparently alter the harmonics of the frame and the wobble stops. Either way, I agree scary as hell when it happens.
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| 2014-07-22 11:31 AM in reply to: marcag |
Expert 2192 Greenville, SC | Subject: RE: Speed wobble pretty sure putting power on the pedals prevents the wobble since the applied load is constantly changing the loading on the frame and thus constantly moving the natural frequency of the frame inside some range. every time i have gotten it has been on a fast decent while not pedaling, and that's pretty much seems to be what everyone else says too. knee on the top tube works because it dampens the frame vibration and puts it out of the harmonic or natural range for the frame. when you hit a triangle(instrument) it vibrates. this is exactly what causes frame wobble. the bike is moving along at just the right speed and transferring force in a certain pattern to excite the frame and cause it to shake. |
| 2014-07-22 1:44 PM in reply to: marcag |
| 265 Denver, Colorado | Subject: RE: Speed wobble Good thing im slow! ...A nice article on a topic i definitely wasn't aware of |
| 2014-07-22 1:46 PM in reply to: 0 |
Extreme Veteran 5722 | Subject: RE: Speed wobble Originally posted by Brian W Good thing im slow! It wasn't a fast/slow thing. I was going downhill. It could happen to any of us. I plan to do some testing next week to see if I can reproduce it Edited by marcag 2014-07-22 1:47 PM |
| 2014-07-22 1:50 PM in reply to: marcag |
Expert 2192 Greenville, SC | Subject: RE: Speed wobble Originally posted by marcag Originally posted by Brian W Good thing im slow! ...A nice article on a topic i definitely wasn't aware of It wasn't a fast/slow thing. I was going downhill. It could happen to any of us. I plan to do some testing next week to see if I can reproduce it great idea, what could go wrong |
| 2014-07-22 1:58 PM in reply to: Clempson |
Extreme Veteran 5722 | Subject: RE: Speed wobble Originally posted by Clempson Originally posted by marcag Originally posted by Brian W Good thing im slow! ...A nice article on a topic i definitely wasn't aware of It wasn't a fast/slow thing. I was going downhill. It could happen to any of us. I plan to do some testing next week to see if I can reproduce it great idea, what could go wrong maybe I should rephrase that :-) I will test at high speeds using the techniques discussed and be sure I can descend at high speed without it occurring If I don't report back, it re-occurred :-) |
| 2014-07-22 2:00 PM in reply to: marcag |
Expert 2192 Greenville, SC | Subject: RE: Speed wobble that sounds much safer |
| 2014-07-22 2:02 PM in reply to: Clempson |
| 92 | Subject: RE: Speed wobble Originally posted by Clempson Originally posted by marcag Originally posted by Brian W Good thing im slow! ...A nice article on a topic i definitely wasn't aware of It wasn't a fast/slow thing. I was going downhill. It could happen to any of us. I plan to do some testing next week to see if I can reproduce it great idea, what could go wrong Top 3 ways to make sure it goes wrong... 1. Do it in front of other people and preferably people that are better looking. 2. Video it 3. This might just be a Texas/Redneck thing, but just before you start down the hill, look over to your buddies and say, Y'all watch this S#!T. Be careful but try and video your experiment. :-) Ron |
| 2014-07-22 3:53 PM in reply to: 0 |
| 39 | Subject: RE: Speed wobble When I was a kid a friend was telling me how he went down a "big" hill without using brakes. I misunderstood which hill he was talking about and went to the biggest hill in town. I almost made it to the bottom of the hill before I experienced a speed wobble. Needless to say I still have the scare on my chin from when I hit the pavement. Lesson learned the hard way. Edited by tjudson 2014-07-22 3:54 PM |
| 2014-07-22 3:57 PM in reply to: WaterRat |
| 201 Hereford, England | Subject: RE: Speed wobble Originally posted by WaterRat Originally posted by Clempson Originally posted by marcag Originally posted by Brian W Good thing im slow! ...A nice article on a topic i definitely wasn't aware of It wasn't a fast/slow thing. I was going downhill. It could happen to any of us. I plan to do some testing next week to see if I can reproduce it great idea, what could go wrong Top 3 ways to make sure it goes wrong... 1. Do it in front of other people and preferably people that are better looking. 2. Video it 3. This might just be a Texas/Redneck thing, but just before you start down the hill, look over to your buddies and say, Y'all watch this S#!T. Be careful but try and video your experiment. :-) Ron 4. Hold my beer and watch this! |
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