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  1. #1
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    Wobbling/shaking during descent

    2011 Specialized Allez. I did my first double century yesterday and bike was performing without issues even during descent even at speed. More than half way through the ride during a steep descent while going 40+ MPH, the bike started to wobble/shaked so bad that I could barely control it and almost ate the pavement but managed to stop.
    I checked the wheels, spoke and headset and they were tight. Pretty scary moment so I decided to slow down a bit during descent and it happened again around 25 MPH. Slowed down to 15 MPH and it happened again. With about 70 or so miles to go, I get worried whenever I see a descent and had to really slow down almost to a crawl. Any ideas on what would caused this? taking the bike to shop tomorrow.

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    Bianchi Goddess Bianchigirll's Avatar
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    CONGRATS!!!! a double century that is great!

    do you have alot of miles on this bike? did you have a handlebar bag or some other gear you don't normally carry? did you have a flat? maybe the wheel was put back a tad off center. did you change your position for decending? such as early in the ride you decended on the hoods later the drops? how is your front tire?
    Bianchis '87 Sport SX, '90 Proto (2), '91 Boarala 'cross, '93 Project 3, '88 Trofeo, '86 Volpe, '89 Axis, '79 Mixte SOLD, '99 Mega Pro XL Ti, '97 Ti Megatube, , '90 something Vento 603,

    Others but still loved,; '80 RIGI, '80 Batavus Professional, '87 Cornelo, '86 Bertoni (sold), '09 Motobecane SS, '98 Hetchins M.O., '09 K2 Mainframe, '89 Trek 2000, '?? Jane Doe (still on the drawing board), '90ish Haro Escape

  3. #3
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    Yes, congrats on the double century,

    High speed wobble is a common problem on road bikes, with multiple possible causes from simple ones like loose headsets, to complex ones like slight frame mis-alignment. Usually if it happens while coasting it occurs only at or above a certain speed, and can often be solved with simple measures like riding slightly lower tire pressure, or by coasting in a tuck with the pedals horizontal and your knee against the top tube to dampen any harmonics.

    Since yours happened at various speeds, and started only halfway through the ride, I suspect it's not a classic case of high speed wobble, and that something changed. My first guess is that your headset loosened, possibly from cups settling in the frame (common on new bikes). It could also be that a wheel went out of line, or that it might be related to brake pulsing if you used the brakes.

    Another possibility it that there was always a slight tendency to wobble that you've always controlled, but with fatigue you're ability to manage it got worse.
    FB
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    Quote Originally Posted by Bianchigirll View Post
    CONGRATS!!!! a double century that is great!

    do you have alot of miles on this bike? did you have a handlebar bag or some other gear you don't normally carry? did you have a flat? maybe the wheel was put back a tad off center. did you change your position for decending? such as early in the ride you decended on the hoods later the drops? how is your front tire?
    Bike has 2700 miles, only had a light on top of the hood which I've had before w/ out any issues. At first, I thought I had a flat but didn't. I always descent on the drop and both tires are new with a 100 miles or so

  5. #5
    Senior Member Ira B's Avatar
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    If wheel bearings and headset are adjusted correctly and tight, frame is not damaged or bent I would double check that the spokes are tensioned correctly, wheels are true, and installed/ lined up properly. The rear wheel in particular can be easy to install a bit off center and can make a bike a real handful at high speed.
    Yep, THAT Ira

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    FB, took the bike to bikeshop today and mehanic checked the everything...headset, wheelset and frame alignment and they are all good. He even took it on a short steep descent and could not replicate the problem. He's keepin the bike and will do another test on long steep descent to try to replicate the issue

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    Senior Member Ira B's Avatar
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    Quote Originally Posted by Dirt-Eater View Post
    FB, took the bike to bikeshop today and mehanic checked the everything...headset, wheelset and frame alignment and they are all good. He even took it on a short steep descent and could not replicate the problem. He's keepin the bike and will do another test on long steep descent to try to replicate the issue
    I am curious if you drove to the ride start point and have had the wheels on and off?
    Maybe one was installed out of line during your ride but is now installed properly making the problem go away?
    Yep, THAT Ira

  8. #8
    Senior Member volosong's Avatar
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    "Dirt-Eater" ... let's hope you don't become an "asphalt eater". I've posted several times the past few weeks about the "death wobble" that I experienced for the first time on a new bike I purchased. Being new, nothing was wore out. Bike just came out of the shop from a full work up, so it is assumed that everything was adjusted properly.

    This high-speed front wheel wobble seems to happen quite frequently, and there is no one cause for it. It is a combination of things that when resonating at just the exact harmonics, create the wobble. One of the major causes is the geometry of bikes these days. "Lively", I call it. The rest is technique ... or lack thereof. The only change I made on my bike is to put the next size longer stem on it. That acts to shift my weight slightly forward, making me more balanced on the bike. And, I make sure that I keep my weight forward on the descents, not back like I normally did with my older bikes where I shifted by weight back. Finally, I keep one knee next to the top tube ready to press against it if the wobble starts. That interrupts the harmonics and minimizes any wobble. Don't tense up either. That is the first instinct, but the best is to hold the bars loosely.

    It seems that the one time I experienced that wobble, hitting an unevenness in the road was enough to start the bike shaking. A crack or something. No debris, as the road is pretty clean. But, there are cracks all over the road. Now, on descents, I don't try to break any speed records and most of my focus is on the "feel" of the bike. I'm feeling for the least amount of shaking so I can put a stop to it right then. When my confidence improves and I can control any onset of the wobbles, then I'll go for a speed record.

    Funny thing about that wobble, (my version of it). It only happens on non-powered descents. For me, the wobble occurred at around 33-38 mph, (can't remember exactly, but somewhere around there). Not all that fast for a descent. Next time out, before I had the stem changed, I went on the same route. I kept it pretty slow on the descent, but on the long run in, a seven-mile uninterrupted, slightly downhill, wind-to-the-back run, I easily exceeded 42 mph and did not experience any wobble at all, or even a hint of it. The only difference is that on the descent, I was coasting ... on the power run, I was hammering pretty intensely.

    It is a very scary situation. You've had your bike checked out. Now, work on your technique. Do a search in the various sub-forums. In response to my initial query, a couple of people posted links that told me a lot about the situation and how to mitigate it. Then go out and "practice". Be one with the bike. "Listen" to it. Try to bring on the wobble, then employ what you learned to see how fast it goes away. It isn't always caused by the bike, sometimes it is us and our improper technique for today's bike geometry. Good luck.

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    D-E, My congrats also!

    Most of the causes for a speed wobble that I can think of won't happen in the middle of a ride and then worsen (15 MPH is darn slow for a speed wobble) as the ride continues and then not show up in diagnosis afterwards. I'm wondering if one of the tires, in particular the rear increased pressure or perhaps the front lost some air enough to change it's profile enough from the other tire's profile and cause unstability. Was it very hot?

    Brad

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    Thanks for all the input guys. It may have been my technique..hmmm. I've done high speed descent before without issues but on a little smoother surface. This particular surface is a little rough with some tiny gravel. I've kind of new to road biking since I'm a mountain biker. I did feel the bike wobble a little and it got worse and worse as the speed picked up. I'll keep in mind regarding using the thigh againts the top tube to stabilized the bike. I've experienced some minor wobble before and was able to control but this time it was just too much, even my friend who was behind me and saw the whole thing got really scared.

  11. #11
    Senior Member volosong's Avatar
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    Quote Originally Posted by Dirt-Eater View Post
    ...I'll keep in mind regarding using the thigh against the top tube to stabilized the bike...
    Just to clarify ... use the inside of your knee. Don't think your thigh is physically able to touch the top tube before you knee will. And, a knee (or thigh) against the bar will not "stabilize the bike" ... it interrupts the harmonics that are in effect at that particular time. You want to change the harmonics that cause the wobble. "Stabilize" is the wrong word here, if it means the same to me as it does to you.
    Last edited by volosong; 05-23-11 at 08:10 AM.

  12. #12
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    One thing that I haven't heard mentioned is whether the lbs checked the dropout alignment on your front fork - it must be perfect. And if it's not and you have a carbon fork, replace it. I've found mis-aligned carbon forks to be the cause of "wobbles" on several bikes in the last couple of years.

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  14. #14
    Bianchi Goddess Bianchigirll's Avatar
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    Quote Originally Posted by Dirt-Eater View Post
    Bike has 2700 miles, only had a light on top of the hood which I've had before w/ out any issues. At first, I thought I had a flat but didn't. I always descent on the drop and both tires are new with a 100 miles or so

    2700 miles on 2011 bike WOW are we going to see you at the RAAM? I wish I could help more with your issue. OH did I miss this in the post is this a carbon or Alloy bike? have you notived and black smudgy looking stuff near any frame joints?
    Bianchis '87 Sport SX, '90 Proto (2), '91 Boarala 'cross, '93 Project 3, '88 Trofeo, '86 Volpe, '89 Axis, '79 Mixte SOLD, '99 Mega Pro XL Ti, '97 Ti Megatube, , '90 something Vento 603,

    Others but still loved,; '80 RIGI, '80 Batavus Professional, '87 Cornelo, '86 Bertoni (sold), '09 Motobecane SS, '98 Hetchins M.O., '09 K2 Mainframe, '89 Trek 2000, '?? Jane Doe (still on the drawing board), '90ish Haro Escape

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    Quote Originally Posted by FBinNY View Post
    Another possibility it that there was always a slight tendency to wobble that you've always controlled, but with fatigue you're ability to manage it got worse.
    Sounds like your mechanic has hit all the usual mechanical suspects. I'm guessing it's the fatigue factor, multiplied by how tense you got after that first incident. You likely tensed up, probably because you were slightly fatigued. Next downhill, you tense sooner, and set up that bike/rider resonance sooner, which makes you even more tense on the next downhill.

    You can damp that out with the knee on the top tube trick, but the real solution is to loosen up. Sometimes that's not possible (me, downhill at 35 mph, 15 mph headwind, 40 degrees), but if you can relax that death grip on the bars, it'll let up.

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    I did some research and I experienced the so called " speed wobble or others call it death wobble". it's uncommon but it does happen. There wasn't necessarily wrong with the bike but other factors may have contributed i.e fatigue, there was also cross wind and it was a little chilly going down. At least now with some input from you guys and little research, I would know how to react if does happen again.....1) GET OFF THE SADDLE, 2) SQUEEZE KNEE ON THE TOP TUBE, 3) RELAX GRIP ON HANDLE BAR which I did and probably saved me

  17. #17
    Senior Member volosong's Avatar
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    Glad you are now informed and have more confidence. When it happened to me, I "knew" for sure I was going down. As I was twiddling with the brakes, I was moving over to the side of the road with the intent of side-swiping the road cut. Figured that would be better than sliding along the asphalt at 30+ mph. Before I crossed the white line into the road cut, I was able to slow down enough to stop the wobble.

    Of course, I stopped completely and inspected the bike. All the usual suspects; flat tire, loose headset, loose quick-release, loose handlebars, etc. Nothing seemed wrong, so I continued down the hill ... at a snails pace. Once off the hill, no hint of the wobble.

    Next time out, I was on the lookout for it. I think it might have started happening again, but the inside knee to the top tube seems to have stopped it, if it indeed was starting. I'm just a wimp now on descents ... at least until I regain full confidence in my bike handling abilities. Good luck. I wouldn't wish this on my worst enemy.

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