[slimjw]

I had my first experience with the dreaded death wobble last weekend when I came in a little hot on a sweeper during a descent. Ride was on my new BMC and though it hasn't been officially fit yet, its dimensions are similar enough that I duplicated the saddle position from my older Pinarello and it has certainly felt comfortable enough for rides of 3 hours or so.

One thing I did change though, was the stem length. I was using a 110cm stem on my older bike (which I recently changed to a 120) and am running a 120 on the BMC. There is also a slight difference in total HT height between the bikes and am currently riding it with zero spacers.

I have been trying to eliminate the variables from the scenario so as not to repeat it. It seems certain I came into the turn too fast (partially due to not being used to the decrease in braking effectiveness with my Easton carbon clinchers vs my normal aluminum wheels) but I can't remember if I caused the wobbles by braking too hard under speed while trying to get the bike under control or if they were happening anyway.

I have read some of the previous topics about this and it happened to fast for me to remember to clamp the TT with my legs or shift my weight or any of the usual recommendations.

So, although I think rider error contributed a lot to this incident, I've done the same descent at similar speeds on my other bike and never had any wobble. I'm wondering if the new longer stem and decreased stack height would contribute at all due to a different weight distribution? All other fit factors being equal I would have less weight on the front wheel with the longer stem, right?

I should also say that so far, at speeds up to 40-45 on straight downhills I haven't experienced any wobble.

 

[Coolhand]

Stem normally has nothing to do with it assuming you installed it properly.

 

[Kerry Irons]

Death grip

I had my first experience with the dreaded death wobble last weekend when I came in a little hot on a sweeper during a descent.

Most likely it was you gripping the bars as hard as you could when you got spooked by your excess speed. That changes the resonant frequency of your "body-bike system" plus any twitch of your arms provides a forcing function for the oscillation. Stem length (alone) is the most unlikely cause.

 

[jlwdm]

Most likely it was you gripping the bars as hard as you could when you got spooked by your excess speed. That changes the resonant frequency of your "body-bike system" plus any twitch of your arms provides a forcing function for the oscillation. Stem length (alone) is the most unlikely cause.

+1

Jeff

 

[Mr. Versatile]

IME one of the sure fire things for stopping a speed wobble is to push a knee against the top tube, or clamp the top tube with both knees. I was on a downhill last week with a little turn at the bottom. I started into the turn between 35-40 mph & the bike started to wobble. I was on my new bike & it's the 1st compact frame I've owned. I went to clamp the top tube with my knees & I couldn't find the $##$^%$$#@ thing. My knees are both above the top tube with the pedals at 3 & 9:00. I finally found it & recovered from the wobble. I'm laughing about it now, but I wasn't then.

 

[martinrjensen]

clamping the top tube

Remember to try it next time!
Definitely clamping the top tube with your thighs will stop the high speed wobble. All that has to happen is that you get into a high speed wobble and don't forget to clamp, and then (this is important) live to remember the tactic, and you will always try it instinctively in the future.
I had that problem and for some reason remembered the advice on this forum, and clamped, and it saved me from a sure crash. I don't think I would have died even though a car was going to be involved, but it was going to be ugly, that's for sure. As it was, it was a good learning experience.
Remember, what doesn't kill you, makes you stronger.

 

[froze]

Mr Versatile has the answer for your problem. This problem pops up today on modern bikes, and it doesn't occur all the time, it occurs at random times and most of the time rarely. If it happens everytime your ride then you have a problem that needs to be addressed, but from the sounds of it it was a fluke. I would try to repeat the situation again and see what happens, and let us know what happened.

 

[Mike T.]

110cm stem..............recently changed to a 120

I went from 100 to 130mm and didn't experience the dreaded wobble, nor did I expect to. This subject has been beaten to death for a long time. I was reading about it 24 years ago when my Vitus 979 had the problem. Do a search for Lennard Zinn's writings on the subject.

 

[EricH_NJ]

I should preface this story by saying I’ve been married and divorced. I am no stranger to fear.

I experienced the “death wobble” for the first time this weekend and under the worst possible circumstances.

About 30 miles into my Sunday ride I was descending Rt. 579 into the town of Bloomsbury, NJ. I have done this route 4 times in the past and have never had a problem. At the steepest section of the hill (about -18%) there is a 45 degree left turn that if you overshoot brings you to a guard rail with a fairly steep fall on the other side.

My bike has been working fine all day so I figure as I approach I’ll alternate back and front brakes to slow myself. I’ve done this before and it’s always turned out fine. I start with the back brake and get almost no resistance. This is not good (doing almost 40 and running out of room). I figure, no problem, front brake does most of the work anyway, I should be able to slow enough to make the turn. Start working the front brake…. Death Wobble starts.

I tried everything I could to stop it. I stood up… I tried clamping the top tube between my knees… Tried relaxing my arms and grip… I even tried moving from the drops to the hoods. Nothing worked. It felt like everything was going in slow motion and as I approached the guardrail I clicked out and planned to just try and maintain as much control as possible over the impending crash. I could not steer and was headed for the edge. By the grace of God I was able to stop two feet before hitting the rail.

The back brake turned out to be a cable problem. If it had been my front brake I would either be dead or eating through a straw. I checked my headset, my wheels for true, and my fork. All were fine.

The only difference on this descent in relation to previous times down the same hill was trying to slow solely with the front brake. I’m not sure if this was the cause, a contributing factor, or just a very bad coincidence but wonder if anyone else who has been through this has been using only the front brake on a steep descent when the problem began.

 

[Kerry Irons]

Front brake shudder

The only difference on this descent in relation to previous times down the same hill was trying to slow solely with the front brake. I’m not sure if this was the cause, a contributing factor, or just a very bad coincidence but wonder if anyone else who has been through this has been using only the front brake on a steep descent when the problem began.

Likely there was a bit of brake shudder on the front wheel and that triggered the shimmy. Clean the rims with a ScotchBrite pad, and apply a little sandpaper to the brake pads.

 

[froze]

Just for informational purposes. What kind of bike do you have, ie road, touring etc, what's it made of, ie steel, carbon fiber etc; what brand and model is the bike; what brand of wheels and how many spokes, is the front wheel radial laced, bladed or round spokes; brand of fork are you using; did you change anything on your bike recently?

 

[Mr. Versatile]

Although the front brake does the lion's share of the work, IME the rear brake not only helps slow, but also acts as a stabilizer. As an engineer Kerri could probably address this much better that I. This is just a wild guess on my part. Maybe using the front brake only puts all the stress on the front of the bike; headset; fork, front wheel. By applying the rear brake and assuming the rear wheel is still in contact with the pavement, it also puts some stress on the rear of the bike; chain stays, rear wheel, seat stays. As I said I'm about the farthest you can get from being an engineer, and this is just a wild guess on my part. My experience has been that when using the front brake only my bikes feel significantly less stable than when I use both brakes together.

 

[froze]

Although the front brake does the lion's share of the work, IME the rear brake not only helps slow, but also acts as a stabilizer. As an engineer Kerri could probably address this much better that I. This is just a wild guess on my part. Maybe using the front brake only puts all the stress on the front of the bike; headset; fork, front wheel. By applying the rear brake and assuming the rear wheel is still in contact with the pavement, it also puts some stress on the rear of the bike; chain stays, rear wheel, seat stays. As I said I'm about the farthest you can get from being an engineer, and this is just a wild guess on my part. My experience has been that when using the front brake only my bikes feel significantly less stable than when I use both brakes together.

I'm no engineer either so I need further explaination. I've ridden bikes with front and rear brakes for at least 40 years, I've applied front first, rear first, all at once and never once from a cheap road bike to expensive road bikes have I ever felt a destabilization effect in any combination of brake application. I've even come down steep mountain grades in So California out of Lake Arrowhead, Fraser Park, Wrightwood and on and on and alternated brakes then as well and never had any odd effects. So is this something pecular with CF frame bikes, because none of my steel, AL or TI frames ever did this, or is this just a thought process your pondering?

 

[Mr. Versatile]

I've experienced the wobble on aluminum, steel and carbon fiber bikes. I might be dreaming, but I'm just relating my experience. I have 48 years of adult cycling plus 30 years of motorcycling, and IME the instability I've felt when using the front brake only applies to both vehicles. I'm dead sure I felt this. As far as speculating why this happens I may be completely full of $hit.

 

[mrcookie]

I wonder if there was a bit of pucker factor when the rear brake was applied to no avail, thus causing the aforementioned deathgrip, which, along with other factors such as kerry mentioned, could have made things worse?

 

[Gnarly 928]

Some bikes wobble, some do not. I won't keep a bike that had done the wobble on me any more. I did keep a custom steel frame I had built to race on because the builder admitted he made an error when he selected the fork, and he replace it with a stiffer one....but for many years, I raced that bike but never totally trusted it..I still have it today..

I've had many high end modern bikes...Ti, Alu and carbon. When I get one that wobbles, I get rid of it right quick...Who needs that? Some brands never wobble...or at least owners who I have asked say their _____________ (fill in the blank) has never wobbled. Some brands are notorious for it...Giant comes to mind from a few years back...Everyone who's raced on had encountered that awful feeling.

Why would you ever ride a bike that you had to clamp the top tube between your knees to survive on? My 'steel' race bike never again wobbled after I got the proper fork...but I certainly remembered that terrifying experience of being not in control while descending a steep mountain pass...and I never fully trusted that bike...but I couldn't afford another at the time...Now, with Ebay and Craigs list...I get an unstable frame...I off it and get a different brand...

Just me, but that is what I do..."life is too short to ride a wobbler"

 

[froze]

I wonder if there was a bit of pucker factor when the rear brake was applied to no avail, thus causing the aforementioned deathgrip, which, along with other factors such as kerry mentioned, could have made things worse?

I'm at a complete loss. I know I've heard of a few, and I mean a very few, who have experienced a wobble, but most people that I knew or know, including myself, that raced or otherwise never had any wobbles ever. I know one time coming out a mountain pass I was doing over 60mph and never felt a thing. One of the guys that I knew experienced a wobble was riding a Vitus lugged AL bike at around 45mph but he never touched the brakes until the wobble occurred then he tried to slow down; but if your remember that Vitus was a noodle frame. Another person I knew had a Peugeot (model I forget) steel job, but he constantly complained about frame flex, got a wobble, but again no braking action was involved when it started. The only other that I can remember details was a guy who has a AL Klein bike with either a steel or AL fork I can't remember, he replaced the fork with a ultralight CF fork, shortly after he experienced two wobbles, both times no brakes were being applied, he switched back to the old fork and never had the problem again.

Again I'm perplexed over what causes these wobbles. From the people I knew I can't come up with any reason for it other then poorly made frames in 2 of the cases. But did those 2 frames have poorly made forks? Is that why the Klein got the wobble after a superlight CF fork was put on and then never reoccurred after the old fork was put on?

 

[temoore]

I had this happen once on my Giant carbon. After changing the wheels, it seemed to be less susceptible to wobbles. Grabbing the top tube did help make the bike feel less likely to go into a wobble, as did lessening the weight on the handlebars, which grabbing the top tube with the thighs allowed.

 

[froze]

Still perplexed, maybe no one has an answer. The experiences that I know of "seemed" to be related to either the fork or a noodly frame, so could it these uber light frames and/or forks are the problem? And/or could it be low spoke count wheels that are allowing the wheel to oscillate more then higher spoke wheels such as 32 spokes and up?

One poster, Gnarly, mentioned he wouldn't keep a bike that got a wobble, I agree with him! But what kind of bikes do you have Gnarly? Are the wheels low spoke count? Are the frames ultra light?

Is it possible that maybe a side wind catches bladed spokes in such a manner that it sets up a wobble?

It can't be argued for an out of balance tire because the vibration from that, known as a harmonic imbalance, would occur all the time at a certain range of speed.

 

[Gnarly 928]

Still perplexed, maybe no one has an answer. The experiences that I know of "seemed" to be related to either the fork or a noodly frame, so could it these uber light frames and/or forks are the problem? And/or could it be low spoke count wheels that are allowing the wheel to oscillate more then higher spoke wheels such as 32 spokes and up?

One poster, Gnarly, mentioned he wouldn't keep a bike that got a wobble, I agree with him! But what kind of bikes do you have Gnarly? Are the wheels low spoke count? Are the frames ultra light?

Is it possible that maybe a side wind catches bladed spokes in such a manner that it sets up a wobble?

It can't be argued for an out of balance tire because the vibration from that, known as a harmonic imbalance, would occur all the time at a certain range of speed.

I have had a few really light modern frames that were just too light, too fragile for my taste. One was just twitchy, it never really wobbled, but the front end felt unstable and I got a look at a "cut a way" of the frame at a pals shop...I sold that one right quick, even though it was fun to ride uphill.

I had another, spanish build, that was also real light, but the rear end hopped around corners and it sounded like a bongo drum. That one felt like it was going to wobble at any time...never felt good going fast downhill and certainly felt dangerous on rough corners or in Crits.

All these bikes I've owned over the past 4-5 yrs, they were all ridden with the same sets of wheel and approximatly the same fit dimensons.

I have about 4 sets of wheels, not counting TT wheels, covering the range of configurations...some high spoke Zipp 303s, some low spoke Reynolds, some Reynolds low profile carbon climbing wheels, even some alloy clincher wheels with plenty of spokes and low profile rims... They do not cause wobbles...it's the frame and the geometry, in combo that causes that...In my own opinion.

In the 'race' to "out-light" all the other brands, makers sometimes go too far and unstable handling is the result, or fragile bikes that aren't very 'real life' friendly. Some of them just keep the same geometry and make everything lighter and lighter....till they start breaking or causing them warrantee problems..

Right now, I have an Eastern-Made Colnago and a Ridley Noah...they both come in at a porky 14.6 lbs (+/-) with pedals and wheels...not the lightest bikes, but they do everything with no fuss....so I like em. Why would I want to save 1/2 a lb but always have to think, as I start over the top of a climb..."Oh boy, watch out now, here comes the descent...." or ..."Where is my torque wrench, my water bottle cage is a little loose...I need to tighten up my seat post collar...don't go too tight....Ooops, the frame just cracked..." or pick the thing up by the saddle and have the bars slap the top tube and break it...Or have it feel like at any corner, it could go into the Death Wobble?

My requirment for a Keeper bike is one that dissapears under me as I ride...I forget the bike and can concentrate on the ride...If the bike is constantly calling for my attention...it is not for me...

A big fat soggy steel bike...I would always be noticing that...A feather light noodley one...that would get my attention at the crest of every mountain as I started off downhill, wondering..One with odd-routed cables and finicky components would take up my extra time during stage races, time I would rather use with my team or in bed or eating...