rnorris

A number of months ago I had my most serious bicycling accident to date. It occurred on a local bike path when a rider coming fast from the opposite direction took a turn wide and clipped my left handlebar, throwing my front wheel into a wild wobble. I didn't go down immediately and tried to hold on for a second or two, then instinct took over and I hit the brakes. Went down hard right then on my right side and got a ride to the hospital with a broken collarbone, two cracked ribs, and more than a little road rash. (The wonderful human being who hit me fled the scene).

Realize now that hitting the brakes was probably the wrong thing to do, and I wonder if I might have been able to damp out the wobble with my upper body and shifting my weight rearward, perhaps aided by a quick push on the pedals. Have any of you been able to do this, or have other tips for recovering from the "death wobble"?

Thanks,
Bob Norris

NoRacer

Maybe some of this may help?

https://www.sheldonbrown.com/brandt/shimmy.html

webist

Quite helpful. Thank you.

filtersweep

Just curious, but how long did the wobble last before you went down?

rnorris

Thanks for the replies. The article by Jobst Brandt is interesting. It's describing spontaneous shimmy that originates through frame geometry and riding dynamics (learned about that as a 50-lb. 9 year old on a Stingray bike with high handlebars, kissed pavement then too) but once it starts the dynamics would be the same as an impact induced shimmy like the one I had. The article mostly tells how to prevent shimmy, but makes the interesting point that it can't be stopped by shifting weight fore or aft- so it's harder to get out of it than I thought.

My pre-crash wobble was very short, a few seconds at most, but long enough to be amazed that I was still upright after being hit like that. The stabilizing effect of the wheelspin was too strong for the wobble to take the bike down until I slowed down. My head was flopping around too much for me to see anything, so I suppose it's better that I crashed before I hit someone else, or a tree.

Roody

The instinct is to clamp tight with your hands and brake, but sometimes that is the worst thing to do. Try to hold the bars lightly and steer yourself out of trouble. Shimmying usually occurs at high speeds, wobbling at slow speeds, although I'm not sure if that's the official definitions.

Sluggo

I don't buy Herr Brandt's analysis of wobble, but I don't think that is what is going on here.

This is a case of impact pushing you to one side, over-correct one way, over-correct the other way, etc... You may have been able to wrestle it into control eventually if you had not hit the brakes, or not. It is pure reflexes. Riding mountain bikes and/or cyclocross and crashing a lot helps prevent crashes in this sort of situation, but it is no guarantee (and not necessarily a good trade).

Roody

You sound like you know what you're talking about so answer me this. If you do brake, you will be going slower when you crash? That's a good thing, no?

One thing's for sure, I've fallen so many times that I'm finally getting pretty good at it!

slvoid

Act like you're slapping the handle bars back and forth with your hands, cept your handle bars are smacking your hands, which are held firm but not a death grip. Don't hold it tight, that only increases the oscillation since you set up a feedback loop with your own muscles. Same as on a motorcycle w/o a damper.

filtersweep

I have never bought into that resonant frequency argument either- too many different frame materials and geometries to have shimmy at such consistantly narrow bands of speed. ALso, I would expect the air in the tires to somewhat insulate the frame from absorbing that energy, and road vibrations are more random, like white noise, rather than a wave that will oscillate. (I think riders white knuckle it, and literally shake their bikes themselves.) But I am no physicist. Of course, people will point to motorcycles and on and on and on....

I have seen plenty of people go down in races after touching tires. Sometimes it looks like the front end of the bike is turned into jelly... exactly as you describe. It isn't the frame that oscilates. I don't think there is any time for the frame to absorb that much energy- especially as the frame is isolated from the front wheel by the headset.

lyledriver

I've had success in situations like this by quickly locking up the back wheel, and steering into the direction of my body's travel.

Once you get your front wheel in the right direction, and under your centre of mass, you can ride out.

LittleBigMan

Watch out for front tire blowouts, too. If your front flats, don't use the front brake. Use your rear only. If you're going downhill, look for a place to "out." Don't be tempted to try that front brake!

Roody

And there was a timely reminder in Winter Cycling to avoid the front brake on ice.

bandregg

We just had a racing coach talk to us about bike handling during crits and his advice was counterintuitive: steer into the direction you were hit from. This comes from what to do when you touch someone's wheel from behind (the situation where you'll go down). When you touch someone's wheel you're thrown away from it and you also think "I need to steer away" which send you down quickly. It's better to steer back in the direction that you touched in to compensate for being pushed away and work from there.

The other thing he said which is definitely true: you should practice this! Get some friends, find a grass soccer field and ride around bumping each other, touch wheels, brush handlebars. This is good practice for regular riders as well as racers. You never know when you're going to need these skills.

Toyman991

It sounds like the dynamics involved are very similar (if not indentical to) kissing the rear wheel of a rider ahead of you. I was able to recover from this situation by unclipping and dabbing my feet on the pavement to keep from going down. Maybe I was lucky but it worked (once) for me. John

GGDub

My experience is the only way you figure out how to keep the bike upright, is to learn why it went down in the first place. It all comes down to your balance and how quickly your body can react. Most people know intuitively what to do, they just don't react fast enough (sometimes, obviously, you can never react fast enough). You can read all the articles you want but the best way to learn how to avoid crashing unfortunately, is to crash. I second what was said above, mtn biking and cyclocross racing are great ways to learn how to avoid crashing and they give you a softer landing than road

Roody

Well those rocks and roots don't always give you a soft landing.

Sluggo

Wanna buy a bridge?

Yes, it's generally a good thing to be going slower when crashing. However, as someone else noted, the front brake especially can compromise control when on the edge, and can make it more likely that you can't pull out. I am not sure grabbing the rear would help, but it's less likely to do harm than the front.

Practice is good. Anyone for a game of polo?

Eatadonut

Well, don't take my advice as sage - it sounds suicidal to me, but has worked no less than 5x since I started riding about 18 months ago.

When I get hit, or start the death wobble, I grab the rear brake and lock up, and let my bike fishtail just a little bit. I find that the really forceful swing that I induced, combined with lots less speed, will kill any wobble. It's a lot easier to pull out of a purposeful fishtail than a surprise wobble.

Obviously, that's not what you want to do in a race, it slows you down, and would probably crash you into someone else, but it works fine for me in a campus setting.

rnorris

The situation I was in was most like the high speed wheel touch described by Toyman991; the front wheel was shimmying fast and violently, say 2-3 cycles per second. The bars were shaking me like a dog shakes a rat, couldn't see more than a blur and don't think I could have steered the bike anywhere until I got the shimmy under control. But it wasn't getting any worse, and I had time to realize "hey, maybe I can get out of this". Chose the wrong way, though.

The geeky side of me wonders if this was a lesson in precession, like what happens with a spinning top after you knock it- goes unstable and eventually tips over.

The suggestions of going loose with upper body, braking carefully with the rear brake only, and getting feet down make the most sense so far. The instant I started braking (with both brakes) the shimmy got worse until the bike jacknifed.

Great ideas, guys.

-Bob Norris

huhenio

My last spill had something of a speed wobble into it, and it was roughly 15 to 20 violent wobbles. I had the chance to unclip before I went down ... so I think 5 to 10 seconds

Crunchie

Whether you buy his claims or not, the key sentence in the Brandt article is:
Shimmy (to this non-physicist) is related to center of gravity. As Brandt suggests, it can start with hands off the bars, butt firmly on the seat (well, the seat on my bike is above the handlebars). So, to end shimmy, lower your center of gravity.

My first experience with spontaneous shimmy was several years ago on a 45 mph descent (oh, craaaaap!) and neither a death grip on the drops nor careful braking would stop it until I'd come almost to a halt. Headset adjustment didn't help either. What did help, on subsequent occasions, was to do just what Jobst recommends, although one could wish he'd been more emphatic: I did a little jump *down* onto the level pedals, and the shimmy stopped immediately! After a couple more successes and a little regained confidence, a friend suggested gripping the top frame bar between my knees, and along with unweighting the saddle (most of my weight on the pedals, some on the handlebar, none on the saddle), the dreaded shimmy has not reappeared, even with my hands at the stem. This is on a road bike, don't know how it would work with suspension. Hopefully induced shimmy would respond similarly.

Put your pedal to the mettle,

Crunchie

slagjumper

Past summer I was riding down a paved descent on my hard tail mountian bike. I was going about 32 and my hands where off the bars. It freeked me out, but once I put my hands on the bars it stopped. Surprised the crap out of me.

I'll have to try and induce the shimmy again, (keeping the hands on the bar) and try Sheldon's suggestion:

Unloading the saddle (without standing up) will stop shimmy.