First speed wobble crash
#101
What a good reminder!
Started reading this, selectively so as not to give myself a mental hurdle too (I don't think I often get above 30, so there's that), but it seems like a great reminder for me to get gloves. I have been thinking about it because I grip with my left hand and have to remind myself frequently to switch my grip to lesson the numbness I get (G.I. Joe grip) but aside from something with gel pads for that, I am reminded it will help protect my hands when I fall. Any suggestions?
#102
Scary stuff! Touch would I’ve never experienced a speed wobble on any bike. It seems to me like an unlucky combination of mass and frequency leading to an undamped resonant oscillation. If I ever experienced a speed wobble like this I would never trust that bike again. But a different rider on the same bike with a slightly different mass (lighter or heavier) might never have an issue as it would change the resonant frequency.
I agree with the poster above who mentioned that wider, lower pressure tyres are likely to help damp out this kind of resonance. They certainly feel more stable to me at high speed. My current road bike (Giant Defy) on 32c tyres at 65-70 psi is rock solid on descents. But I do hope I don’t think about this thread next time I’m bombing down a hill!
I agree with the poster above who mentioned that wider, lower pressure tyres are likely to help damp out this kind of resonance. They certainly feel more stable to me at high speed. My current road bike (Giant Defy) on 32c tyres at 65-70 psi is rock solid on descents. But I do hope I don’t think about this thread next time I’m bombing down a hill!
#103
Senior Member
Thread Starter
I have just bought the Trek Domane SL7 and have now had two cases of speed wobble in the first 8 weeks. Both around 50kph, both with cross winds but both controllable by reducing speed and both terrifying. I have been cycling for years and am used to descending at higher speeds than this. I have changed my seat position and height to take more wight off my bars and have changed my bar grip (both times happened when on my hoods). After the second time I have been reading a lot and have learnt about squeezing the top tube with my knees etc but am not looking forward to my next down hill with a cross wind. It almost makes me want to go back to my Cannondale SuperSix Evo - which was a lot twitchier but ever subjected me to a speed wobble.
I wish I had a fix for you but what works for me (slowing down) may not be the solution you want to hear.
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#104
Senior Member
If you read the sales pitch for the Trek Domane you will understand why speed wobble is more likely with the Domane then most other road bikes.
It's the IsoSpeed technology that gives it that smooth ride. It allows the frame to "move with the road". We know a stiff frame reduces the likelihood of speed wobble, And limits the amplitude as well, Sometimes enough to allow us to keep control. But too stiff makes for a jarring ride.
It might be prudent to limit your speed to 50 kph down hill. Perhaps have a 2'nd bike when you feel speedy.
It's the IsoSpeed technology that gives it that smooth ride. It allows the frame to "move with the road". We know a stiff frame reduces the likelihood of speed wobble, And limits the amplitude as well, Sometimes enough to allow us to keep control. But too stiff makes for a jarring ride.
It might be prudent to limit your speed to 50 kph down hill. Perhaps have a 2'nd bike when you feel speedy.
Last edited by xroadcharlie; 06-12-21 at 11:30 AM.
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#105
Senior Member
If you read the sales pitch for the Trek Domane you will understand why speed wobble is more likely with the Domane then most other road bikes.
It's the IsoSpeed technology that gives it that smooth ride. It allows the frame to "move with the road". We know a stiff frame reduces the likelihood of speed wobble, And limits the amplitude as well, Sometimes enough to allow us to keep control. But too stiff makes for a jarring ride.
It might be prudent to limit your speed to 50 kph down hill. Perhaps have a 2'nd bike when you feel speedy.
It's the IsoSpeed technology that gives it that smooth ride. It allows the frame to "move with the road". We know a stiff frame reduces the likelihood of speed wobble, And limits the amplitude as well, Sometimes enough to allow us to keep control. But too stiff makes for a jarring ride.
It might be prudent to limit your speed to 50 kph down hill. Perhaps have a 2'nd bike when you feel speedy.
The stiffness of the frame is not all that important as is the frequency of mechanical resonance is determined by lengths of tubing among other things. Everything on the bike is part of a system - frame, wheels, rider, location of mass etc… if it was as simple as a damper in a frame or not, or stiffness of a frame then solutions would be obvious and they simply aren’t.
You have to do a deep dive into Laplace mathematics and mechanical characterization and simulation to get this right. None of this is intuitive. In point of fact, intuitive solutions are as counterproductive as they are helpful.
Last edited by JohnJ80; 06-12-21 at 12:30 PM.
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#106
This makes me wonder about bikes like the Specialized Roubaix. Early versions of that had an undamped spring above the headset. The latest version also has a damper.
#107
Senior Member
it depends how much damping there is in that flexible part. It could actually act more as an un-damped spring, which would tend to make things worse at the resonant frequency.
This makes me wonder about bikes like the Specialized Roubaix. Early versions of that had an undamped spring above the headset. The latest version also has a damper.
This makes me wonder about bikes like the Specialized Roubaix. Early versions of that had an undamped spring above the headset. The latest version also has a damper.
None of this is due to a single cause or, by now, all of those things would have been eliminated and there would be no resonance/under damped instances in bicycles and this would never happen.
This stuff is always complex and multidimensional. That’s why it’s hard to isolate, replicate and pin down. Every time this happens, I’m sure it scares the crap out the bike manufacturer’s lawyers and engineers (been there done that - different industry). The big guys are going to have a lot better handle on simulation and analysis of what causes this in their bikes than the little guys.
#108
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One thing I've noticed lately is my bike is much less wobbly if I keep one leg down and one up (as if you are going into a turn). For some reason I seems to stabilize my bike when going downhill. I suspect either the leg is acting like a brace or the center of gravity is lowering.
Anyone else notice this?
Anyone else notice this?
#109
Blast from the Past
I've been plagued by this for quite a few years, across several bikes and across road and TT position. In my case it's always down hill and for me I think 3 components are present when it's likely to happen. There is a road surface component, certain types of regular & higher frequency bumpiness, think rumble strips or roughed up chip seal. There is a visual component. On a wide open descent I feel more prone to wobble than on a tree lined, visually closed in road. And there is a mental component. Anticipating the onset of a wobble on every down hill I'm certain leads to more tension.
Two simple things that really helped me (other than just avoiding some routes, which I do). First is having my head up on descents. Second to a much lesser degree is the standard knees on the top tube. I would also agree that at times I feel more stable with one foot down, or even pedaling.
On the positive side. My current frame, a Felt FR1, is the most stable I've felt in years. It also happens to have a very stiff front end in a sprint, coincidence or related? I'm using HED Jet wheels with 25's. Together a soft but fast feel, a lot of road roughness doesn't make it to the bars. On this bike I can actually tuck on down hills again! Something I have not had the confidence to do in a long time.
Two simple things that really helped me (other than just avoiding some routes, which I do). First is having my head up on descents. Second to a much lesser degree is the standard knees on the top tube. I would also agree that at times I feel more stable with one foot down, or even pedaling.
On the positive side. My current frame, a Felt FR1, is the most stable I've felt in years. It also happens to have a very stiff front end in a sprint, coincidence or related? I'm using HED Jet wheels with 25's. Together a soft but fast feel, a lot of road roughness doesn't make it to the bars. On this bike I can actually tuck on down hills again! Something I have not had the confidence to do in a long time.
#110
My point is this: it’s unknowable without knowledge of the entire system at resonance at that instant in time and without some knowledge of the impulse that set the system into resonance.
None of this is due to a single cause or, by now, all of those things would have been eliminated and there would be no resonance/under damped instances in bicycles and this would never happen.
This stuff is always complex and multidimensional. That’s why it’s hard to isolate, replicate and pin down. Every time this happens, I’m sure it scares the crap out the bike manufacturer’s lawyers and engineers (been there done that - different industry). The big guys are going to have a lot better handle on simulation and analysis of what causes this in their bikes than the little guys.
None of this is due to a single cause or, by now, all of those things would have been eliminated and there would be no resonance/under damped instances in bicycles and this would never happen.
This stuff is always complex and multidimensional. That’s why it’s hard to isolate, replicate and pin down. Every time this happens, I’m sure it scares the crap out the bike manufacturer’s lawyers and engineers (been there done that - different industry). The big guys are going to have a lot better handle on simulation and analysis of what causes this in their bikes than the little guys.
#112
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3 answers, damp the vibration, change the frequency, and pedaling faster can do that, 3 and most
important, loosen up. Not only will staying loose help stop the vibration, you’re not going to crash from the wobs unless you tighten up and add to the problem.
important, loosen up. Not only will staying loose help stop the vibration, you’re not going to crash from the wobs unless you tighten up and add to the problem.
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#113
Senior Member
I agree it is complex. But if you add any undamped spring into a system it is likely to make things worse rather than better if resonance occurs. Now the elastomers used in the Domane frame may well have some level of self damping so they may not be a problem. But we do know that this bike is not immune to speed wobbles, whatever the cause.
Again, it’s unknowable until all the masses, springs, damping rug and resonances are identified and the nature and frequency domain composition of the input impulse response are known.
The reason we keep seeing this stuff happen is largely because of simplistic solutions that don’t account for multiple effects simultaneously.
So no, I don’t agree. You simply have no idea what the effect of their frame components are.
#114
Do you really think Trek engineering didn’t think of that and simulate it before they committed huge money to molds for the frames? If only it where that simple.
Again, it’s unknowable until all the masses, springs, damping rug and resonances are identified and the nature and frequency domain composition of the input impulse response are known.
The reason we keep seeing this stuff happen is largely because of simplistic solutions that don’t account for multiple effects simultaneously.
So no, I don’t agree. You simply have no idea what the effect of their frame components are.
Again, it’s unknowable until all the masses, springs, damping rug and resonances are identified and the nature and frequency domain composition of the input impulse response are known.
The reason we keep seeing this stuff happen is largely because of simplistic solutions that don’t account for multiple effects simultaneously.
So no, I don’t agree. You simply have no idea what the effect of their frame components are.
I just pointed out that it's actually a spring, not a damper (although it may have some self-damping). Neither of us would know what the effect of that additional spring is, we can only speculate. My own experience of undamped springs in the automotive world is that they make resonance effects worse. I would have thought that was quite a reasonable view, no? It's one of the primary reasons why dampers even exist.
Trek engineering might not have looked that closely at resonance, presuming it wasn't a problem in their field testing. But if they did, then it didn't really help the OP and at least one other poster who had a problem with this bike.
#115
Senior Member
You've lost me now. I wasn't disagreeing with anything you've said. You stated in response to what someone else posted. "I don’t agree. If anything the damper would limit oscillations of the frame and change the mechanical resonance".
I just pointed out that it's actually a spring, not a damper (although it may have some self-damping). Neither of us would know what the effect of that additional spring is, we can only speculate. My own experience of undamped springs in the automotive world is that they make resonance effects worse. I would have thought that was quite a reasonable view, no? It's one of the primary reasons why dampers even exist.
Trek engineering might not have looked that closely at resonance, presuming it wasn't a problem in their field testing. But if they did, then it didn't really help the OP and at least one other poster who had a problem with this bike.
I just pointed out that it's actually a spring, not a damper (although it may have some self-damping). Neither of us would know what the effect of that additional spring is, we can only speculate. My own experience of undamped springs in the automotive world is that they make resonance effects worse. I would have thought that was quite a reasonable view, no? It's one of the primary reasons why dampers even exist.
Trek engineering might not have looked that closely at resonance, presuming it wasn't a problem in their field testing. But if they did, then it didn't really help the OP and at least one other poster who had a problem with this bike.
#116
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Glad you are okay, considering the circumstances. Thanks for posting this cautionary account too, and I hope you heal up fast. I try to clamp my knees on the top tube but I forget at times. This has never happened to me and I hope it never does but very interesting to read through the responses.
#117
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#118
#119
Jeez! Six or seven times and you were still gutsy enough to get back on that bike? Wow, I am so glad you were not seriously injured. That could easily have been a disaster for you.
I had these high speed wobbles two or three times on different bikes. Scary as hell but I was lucky to never go down.
High speed wobble can be caused by so many things; fork, headset, wheel bearings, spokes, wind, speed, road surface, etc... and any combination of those and other things.
The Trek Domane has yet another set of considerations that have been hinted at but (unless I missed it) have not been specifically mentioned; the IsoSpeed decouplers. Never ridden with them, and I'm sure Trek researched the hell out of the design and implementation. But aren't the ones on the Sl6 adjustable? Is there some possibility that the ones on this particular bike are a little off?
I had these high speed wobbles two or three times on different bikes. Scary as hell but I was lucky to never go down.
High speed wobble can be caused by so many things; fork, headset, wheel bearings, spokes, wind, speed, road surface, etc... and any combination of those and other things.
The Trek Domane has yet another set of considerations that have been hinted at but (unless I missed it) have not been specifically mentioned; the IsoSpeed decouplers. Never ridden with them, and I'm sure Trek researched the hell out of the design and implementation. But aren't the ones on the Sl6 adjustable? Is there some possibility that the ones on this particular bike are a little off?
#120
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#121
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Had a scary wobble at 45+ MPH, it was caused by a fork that was not rigid enough. Replaced the fork with a new carbon one from a different manufacturer and no issues.
OP get your wheels trued and maybe some new rubber. Those would be cheap first steps.
OP get your wheels trued and maybe some new rubber. Those would be cheap first steps.
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#123
Senior Member
Thread Starter
#124
Senior Member
I've never had a speed wobble, ever, and I've descended at 65 mph, lots and lots at 40+. Thing is, I ALWAYS descend pedals level, butt off the saddle, knees with death grip on top tube - and old style diamond frames with level top tubes, the real bummer about the new frame designs. Yes, that's a slightly tiring position, but nothing as tiring as skiing bumps. One should be able to hold that position for at least 30', no problem. When one tucks at speed, hands in the hooks, butt off the saddle and moved back, chin 2" off the stem, elbows tucked under the belly until they almost meet. At 40, that's about 1 mph slower than on my clip-ons.
If it's a fast corner, I'll drop the inside foot, but I still press on the top tube with the outside knee. I never stick a knee out at speed. I know people do it, but I prefer to touch the brake or sit up rather than go for aero drag with the knee.
If it's a fast corner, I'll drop the inside foot, but I still press on the top tube with the outside knee. I never stick a knee out at speed. I know people do it, but I prefer to touch the brake or sit up rather than go for aero drag with the knee.
I don't grip the top tube with my knees, I have my "butt off the saddle and moved back" but I keep the saddle stabilized in between my thighs. Also, I just take the weight off the saddle but keep almost like sitting on it. With my hands in drops only with light grip, putting pretty well no body weight on the bars.
I have elbows well bent, to let the bike pivot at BB point under me over the road unevenness. I put my weight on the saddle only when I try to increase the speed by pedaling. Essentially I let the bike do what it wants and only keep the saddle sliding side grip to steady it laterally. I believe I once felt it starting to or wanting to oscillate and maybe that's why I now keep it lightly squeezed btw legs as a precaution quite consciously.
That's also relaxed style how I drive cars, only keep light touch on steering wheel, most steering done with one hand only. My brother holds the steering wheel with both hands (as they teach you in driving school) and steers the car all the time, which before long makes me motion sick because modern cars are quite sensitive to such steering (lower profile tires transfer lateral motion quite well). I doubt a horse would like you to ride him like that
I never had serious wobble developing on bike, my top speed is ~ 40 mph and hills around where I ride are not that long that I wouldn't be able to maintain the above position. I have only ever seen the speed wobble on TV motorbikes GP races on tracks, I take it, that is the same phenomenon (it happens in almost every race to somebody and they are not able to eliminate it).
And because of that, I associate the wobble with motorbikes or bikes that are tuned up to max, like thoroughbred horses. The geometry of racing bike with its steep fork angle is like asking for something like wobble (probably wrong assumption) but weirdly it happens on Domane which has more relaxed geometry that makes it more stable (as I gather from eying it last fall as prospective buyer), than your top range typical bike.
The guy in that video
Originally Posted by rousseau View Post
At 0:28...fugging hell...
doesn't seem to go too fast at all. If that were to happen to me, I'd seriously consider selling the bike and buying something else.
Last edited by vane171; 06-20-21 at 06:07 PM.
#125
Senior Member
'Best' can well be misleading here. These riders often sacrifice safety to highest speed. Like they sit on the top tube, which is now against race regulations I understand. Here she obviously didn't keep the saddle stabilized between her thighs, else it couldn't oscillate like it does in the video.