clamp the top tube with your knees. You can stick a new fork on w/ more rack and solve this problem. Is your headset loose?

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

You say you've never been at this speed on this setup-------try relaxing your hands. A tight grip will make your front end wobble at high speeds. As mentioned earlier it could also be a bad headset, either out of adjustment or plain shot!

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Paul

"clamp the top tube with your knees. You can stick a new fork on w/ more rack and solve this problem. Is your headset loose? "

Ditto.

I crashed last year due to speed wobbles. I was going 80kph (50mph) when i got the wobbles. After talking to many people after I can confirm that most people suggest clinching the top tube with your knees and soft hands also.

I was having major wobbles on my 5200 last year. It happened on Ksyriums and Hed3's, plus I used 4 different sets of tires. The headset was going bad on mine. Like the others said, soft hands and knees to the tube help a ton.

I think Slowtwitch has an article on this very topic. DE's solution is to unweight the saddle, as this will change the weighting enough to put an end to the wobble. I've had 'em; sure were scary.

I had a wobble and then my inner-tube blew up.

Wobbles are a manifestation of a structural resonance in the bike, and it is an indication that something has been designed/manufactured/assembled/marketed in a fundamentally flawed way. The bicycle industry is in its infancy as far as research/development of products is concerned, and we should be adequately aware of the stickers mentioning tha danger of riding bikes -- they're there for a good reason, to protect the manufacturers from lawsuits.

All the suggestions offered are good ones and could prove helpful, but the long term solution is to find out the root cause of the wobble: did you change a component? (even tyres can precipitate an uncontrollable oscillation). Unfortunately, it's a trial-and-error thing, and these kind of trials can prove rather dangerous as you found out. It's also the kind of trials during development that manufacturers should be undertaking, but don't expect any changes anytime soon on that front.

John

your theory seems to neglect the fact that he was going 75km/h+ on a 23mm wide tyre, on a tri bike that already has funky handling...



i hit 92km/h coming down a mountain in jasper...knees were clinched on the top tube, and the handling was still kind of sketchy...



i don't think that most tri bikes are made to be ridden @ that speed, due to the weight displacement, etc



however, that's just my opinion

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"Anyone can work hard when they want to; Champions do it when they don't."

Ever been on a ladder that started to wobble? The bike is somewhat similar to a ladder laid on it's side (at least, most bikes are). Not fighting the ladder is the way to calm it down, same with the bike...you need to have a soft grip, shift your weight some (usually toward the front, but you need to avoid grasping the bars harder), and grab the top tube with your knees....that's like having someone grab one side of a wobbly ladder...it works really well unless the person on the ladder has a death grip! It gets back to soft hands again. Sometimes none of this works very well if you have a bad headset/tube/tire problem.

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Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)

Of all the forums (fora?) I've been on, this is absolutely the first time that there has been a "high speed wobble" thread where everyone seems to understand the nature of the problem! Not a single "is your frame aligned", or a "are your wheels balanced" suggestion!

Congratulations to all!

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"Go yell at an M&M"

Ready2run,

I have the same setup as you (KM-40 with 404s). I experienced something simular at Ironman Brazil last year going down some of the hills. The problem was my headset had become loose. After tightening the headset everything worked just fine. Check your headset.

So your argument then is that manufacturers should have stickers on their bikes saying something to the effect "This bike has not been tested at speeds over 40mph; riding at higher speeds could excite structural resonances in the frame, which could result in uncontrollable instabilities that can lead to fatal crashes".

Whatever your argument is though, it all comes down to the manufacturer having to specify what is/isn't allowed on their frames. Unfortunately though, the vast majority of manufacturers are simply artisans who have no understanding of engineering principles and modern methods of designing/simulating/testing, and therefore fail to comprehend the behaviour of their creations in the real world.

Last year a member of our club crashed badly on a long downhill stretch when his Trek 5200 started wobbling uncontrollably; he was in a coma for two weeks, but fortunately he came around and is riding again. If this can happen to Trek bikes, I shudder to think how other smaller manufacturers design their frames.

I come from a motorcycle background, and these issues are unheard of in that industry, where riding (and racing) is done at very high speeds -- and where 90km/h can be reached in first gear. But there, a badly designed product that leads to fatal crashes can lead to very expensive litigation (remember three-wheeled ATVs?)

John

This is the very same reason why I panick downhills before. My bike wobbled like that about 2-3 times in the last 4 years and I got scared to death. I mean screaming for dear life.. It happened on 3 different bikes so after talking to people we concluded that the girl was the problem, not the bike.. I am still scared and hearing things like this freak me out but I certainly learned NOT to grip hard, it is very dangerous. Once I start shaking, the bike gets out of control.. Now I go down (NOT at 50mph) and repeat to myself: "shoulders down, fingers loose..." over and aver again, it helps..

marisol
if you want to add some more comfort get a fork that has more rake. my friend's bike shook like an earthquake going faster than 45. more rake and he was able to go 55 no problems.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

Not to sound like a newbie, but what is a fork that has more rake? I don't know what is on my aegis and my road bike has a profile BCS... thanks for the suggestion..

Thanks for all the advice. I will get the headset checked out and hope it is something that straight forward. I will also try to relax my hands as I know when it happened I squeezed like a mofo - can't wait to practice this one :o)

> i don't think that most tri bikes are made to be ridden
> @ that speed, due to the weight displacement, etc

Weight displacement? Sounds a lot like the signature of one of those moronic Profile posts hack jobs to me ...

I have the strange feeling that most people riding tri bikes that actually fit claim that the weight distribution is the same as that of a road bike. It should be anyway.

Dre'

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marisol the rake is how many degrees a fork is bent, for lack of a better term, forward. If you look at your fork you'll see that it is not completly straight from top to bottom. there is some offset which enables your bike to be rideable. it basically moves the front wheel forward increasing your wheelbase. I think there is some info in the teck section on this somewhere. pm me if you have more questions.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

More rake = longer wheel base...think of driving a DeVille -vs- a Miata...you make your wheel base longer and you will have a more stable bike.

On newer bikes I bet that most of the time speed wobbles are due to the rider more than that of the fork...with CAD and all the years of worrying about it, I just cant think of many noodle forks that are new on bikes I would be to concerned with really. That being said...if you take 30oz of fluid, a gel flask, a computer, a bag for tools and strap them all to the tiller that is hanging fore of the bars...that will have a HUGE effect on the handling of your bike.

Myself, I am dumb...at IMLP I was spinning out a 54x11 on the Keene Hill at 55+ mph....in the rain. I keep my handle bars as light and clutter free as I can and have never had an issue (Ouzo Pro Lite fork).

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What if the Hokey Pokey is what it is all about?

Do you not have a bottle between your aerobars? 55mph in the rain on that hill... wow.. I think I would die of a heart attack:-)

Bottle between the bars....

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What if the Hokey Pokey is what it is all about?

:-) I was asking because you said you keep you handlebars clutter free...

I have nothing but shift and brake levers on my bars.

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What if the Hokey Pokey is what it is all about?