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Discussion Starter · #1 ·
I am not a "high speed" kind if rider/racer. I'm pretty comfortable up to about 40mph, start disliking speeds greater than 45mph, and really hate it at 50+mph.

I was on a Cannondale SuperSix, it kind of bobbled around a bit at high speed, the sensation was as if I were really cold and shivering, but I this happens in all weather conditions - cold, warm, hot. I wasn't actually shivering, that's just what the bike felt like. Anyway, I blamed the bike.

I'm now on a new Specialized Venge and it does the same thing. So the problem might be me!

I clinch the top tube with my knees. I try to relax. But I'm pretty tense at high speed. I've tried pushing forward on the bars and pushing down on the bars, tried moving forward to put more weight on the front, tried scooting back a bit, but the bike seems to bobble a bit and it really makes me nervous. This occurs on many different roads and the friends I ride with tell me "yeah, road might have been a little bumpy, but no big deal".

Any thoughts on what I might be doing and how I can fix it?
 

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It sounds like maybe you are focused on constraining the bars. To ride loose it might help to picture the bars floating in your hands like your hands encapsulate the bars but do not grip them, so-to-speak. It's similar to the way your legs ride loose over bad terrain. Maybe look further down the road as well.
 

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The phenomenon, variously called "shimmy" or "speed wobble", is much discussed and not completely understood. It's a resonance effect, and a too-tight grip on the bars by a nervous rider is definitely one of the things that can contribute. But it's different on every bike, affected by things like frame elasticity, wheel weight, weight placement, and others.

You say you grab the top tube with your knees. Are you sitting on the saddle when you do that? Try standing, with cranks level (I assume you're coasting rather than pedaling at 40+ mph), lift your butt off the saddle, shift weight back, with body low and arms almost straightened, hands in the drops. And as craiger suggested, look down the road, not down at the bike.
 

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Instead of clinching the top tube with your knees, just lean one of them into the top tube. No need to hold it tight, just slight pressure with one of your legs. Legs at 3 and 9 o'clock and lean the 3 o'clock (forward) leg against the tube. And like the other fellows said, light on the handlebars.

Are you in the drops?
 

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My understanding is that this is an issue of weight distribution. I had this happen often, on a bike I used to ride prior to getting a real fit. Turns out the seat was 1cm too far back - so much that I never sat on it - which I imagine must've had quite the effect on weight distribution front/rear.

This has not happened since getting a fit. Velodogs question about you being in the drops is also, essentially, a question of weight distribution. Drops effectively shift your weight forward.
 

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My understanding is that this is an issue of weight distribution. I had this happen often, on a bike I used to ride prior to getting a real fit. Turns out the seat was 1cm too far back - so much that I never sat on it - which I imagine must've had quite the effect on weight distribution front/rear.

This has not happened since getting a fit. Velodogs question about you being in the drops is also, essentially, a question of weight distribution. Drops effectively shift your weight forward.
Oh holly bajeebees.
I would not even consider doing anything over 40 not in the drops. You don't have a full wrap around on the hoods. Even if you hook a few fingers, it's still not very strong.

Balance your weight in the drops, chew your stem and hold on for the ride.

AND DON'T LOOK AT YOUR COMPUTER!!!!

look at the road
 

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Oh holly bajeebees.
I would not even consider doing anything over 40 not in the drops. You don't have a full wrap around on the hoods. Even if you hook a few fingers, it's still not very strong.

Balance your weight in the drops, chew your stem and hold on for the ride.

AND DON'T LOOK AT YOUR COMPUTER!!!!

look at the road
Damn, that's some bad advice. What happens when you hit a bump? Get low but not that low...that's just stupid.
 

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Instead of clinching the top tube with your knees, just lean one of them into the top tube. No need to hold it tight, just slight pressure with one of your legs. Legs at 3 and 9 o'clock and lean the 3 o'clock (forward) leg against the tube. And like the other fellows said, light on the handlebars.

Are you in the drops?
This - one knee on the top tube, light grip on the bars - practice. I think geometry and bike fit might play a role, but don't know enough of that to provide useful help. I have one bike with Zipp 303's that will shimmy bad in wind at high speed, but using he above technique has pretty much knocked it out.
 

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Damn, that's some bad advice. What happens when you hit a bump? Get low but not that low...that's just stupid.
I hit the underside of my chin a couple of times on the steerer top cap when hitting bumps, it was not fun, don't do that any more.
 

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Instead of clinching the top tube with your knees, just lean one of them into the top tube. No need to hold it tight, just slight pressure with one of your legs. Legs at 3 and 9 o'clock and lean the 3 o'clock (forward) leg against the tube. And like the other fellows said, light on the handlebars.
This is exactly what I do. Clinching both knees to the top tube really isn't nearly as stable. Plus with one knee pressing hard it makes it much easier to swoop in and out of turns (changing knees depending on swoop, of course).
 

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My understanding is that this is an issue of weight distribution. Turns out the seat was 1cm too far back.
It MIGHT be an issue of weight distribution, but that is probably quite far down the list. And certainly moving the seat 1 cm would not shift weight distribution much - you move much more than that on the saddle when descending.
 

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It MIGHT be an issue of weight distribution, but that is probably quite far down the list. And certainly moving the seat 1 cm would not shift weight distribution much - you move much more than that on the saddle when descending.
Welp, file that under correlation does not imply causation then.
 

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Discussion Starter · #14 · (Edited)
The phenomenon, variously called "shimmy" or "speed wobble", is much discussed and not completely understood. It's a resonance effect, and a too

That sounds like what I'm experiencing - a shimmy / wobble at speed.

More info about me: I'm a bit over 6'1" tall, about 170 pounds, ride a 58. According to my LBS, I could have gone either 58 or 60. The 58 felt better to me, so that's what I purchased. My Cannondale had the older (dumb) ENVE 45s. The new Venge has the Roval 50s. Perhaps the larger frame size contributes?

I ride with guys who are much more confident and skilled at high speed descending (Cat 1/2, some local and regional Pro riders, Gregory Daniels, some former National Champions, and some speed demons who are always seeking new PRs/KOMs), so I'm always trying to keep up. Thus, I'm very conscious of aero and always in the drops over about 35mph, typically don't look at my cyclo-computer until I start getting nervous, mostly looking down the road.

I practice the "super-tuck" when alone (not in a pack) at speeds from 30-35mph. It scares me death, but my goal is to scare myself so I feel less scared at 45+ on the seat. That may not make sense to others, but it makes sense to me -- do something REALLY scary and other stuff becomes "no big deal".

Anyway, when I say I clinch the top tube with my knees, it is while my butt is on the saddle. I don't understand why clinching with both knees would be less stable than pressing one knee, but am willing to try it.

"It sounds like maybe you are focused on constraining the bars. To ride loose it might help to picture the bars floating in your hands like your hands encapsulate the bars but do not grip them, so-to-speak. It's similar to the way your legs ride loose over bad terrain. Maybe look further down the road as well." seems like good advice. I ride/race mountain bikes very successfully and understand the importance of riding confident/loose, but am not there yet on the road bike. Something about asphalt that amps up my anxiety.

Moving forward or backward on the seat has not solved the problem for me.

I didn't have an opportunity for anything over 40mph this weekend, so I tried some of the suggestions, didn't have a speed wobble, but it typically starts at about 45mph, so not having the issue when I don't usually have it anyway is not conclusive.

Traveling for work this week, so I'm open to more feedback and next chance to implement will likely be Saturday.
 

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I practice the "super-tuck" when alone (not in a pack) at speeds from 30-35mph. It scares me death, but my goal is to scare myself so I feel less scared at 45+ on the seat. That may not make sense to others, but it makes sense to me -- do something REALLY scary and other stuff becomes "no big deal".
As someone who is reasonably comfortable coasting at 45-50 mph (on known roads and in good conditions), and who does not experience your sense of panic at high speeds, I have to say that makes absolutely no freaking sense to me. But if it works for you, great.

I'm not going near that "super-tuck". That stuff is crazy, IMHO.
 

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The phenomenon, variously called "shimmy" or "speed wobble", is much discussed and not completely understood. It's a resonance effect, and a too

That sounds like what I'm experiencing - a shimmy / wobble at speed.


I practice the "super-tuck" when alone (not in a pack) at speeds from 30-35mph. It scares me death, but my goal is to scare myself so I feel less scared at 45+ on the seat. That may not make sense to others, but it makes sense to me -- do something REALLY scary and other stuff becomes "no big deal".
Instead of trying to scare yourself "straight", so to speak, maybe just put that effort into relaxing on the descents and not thinking about crashing. Get in the habit of touching a leg to the top tube whenever you are coasting on a downhill. If you turn the crank for a curve, switch to the other leg. Create good habits by acting in a controlled manner, exorcise fear, don't introduce more.

Any unease, most highly, transfers itself into a death grip on the bars, contributing to the shimmy.
 

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...typically don't look at my cyclo-computer until I start getting nervous....
I think that says a lot right there, for some reason you are getting nervous, tense up, and the rest is inevitable.

I would concentrate on the basics before worrying about being super aero and not sure if scaring yourself when trying not to be nervous is the best way to go about it. At this point in time you are probably waaaay overthinking everything which is just contributing to your anxiety about it all.
 

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Any unease, most highly, transfers itself into a death grip on the bars, contributing to the shimmy.
This has been my experience as well. Once when a bus was passing me closely (major potholes to my right, nowhere to go without crashing), I got my bike to shimmy on flat ground when I wasn't going much more than 21 - 22 mph, because I had a death grip on the bar.

There's lots of factors involved, though, so your situation may be different. Just something to try - relaxing your grip, I mean.

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This has been my experience as well. Once when a bus was passing me closely (major potholes to my right, nowhere to go without crashing), I got my bike to shimmy on flat ground when I wasn't going much more than 21 - 22 mph, because I had a death grip on the bar.
The exact same thing happened to me, a semi truck on my left shoulder and a curb less than a foot to the right of my tire. I'm lucky I didn't snap my bars I held them so tight, and a shimmy like I've never experienced.
 
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