almost hospitalized, bicycle speed wobbles at 48 MPH
 

A buddy and I hit Devil's Lake hills today for a ride to train for a race in 4 weeks. We wanted big hills to climb to build up endurance as the race has some of the biggest hills Wisconsin has to offer. On a decent I was in my aero bars and then switched over to my drop downs once I blew past 30MPH. I tucked in further to take advantage of the downhill section. Once I approached 48 MPH my handlebars started to wobble back and forth violently about 30 degrees. I death gripped the handlebars and grabbed a hand full of rear brake to try to slow down but I was overpowering it too much. I then grabbed a ton of front brake and eventually slowed down to 20 MPH and the head shake stopped.

My buddy was behind me and saw the whole thing. He claims there was smoke rolling out of my tires and brakes and thought for sure he was going to have to scrape me off the pavement.

It was a scary moment I do not wish to repeat. My bike is an Italian steel Bianchi from 1987. I love the bike but am now scared to push it hard on the down hill sections. I think it is due to the natural frequency of the fork. Back in the good old days of motorcycles I remember guys putting steering dampers on the motorcycles. I wonder if they make something for bicycles?

Should I try a steering damper, different fork or just get a different bike?

Anybody else have this happen? What was the result?

Here to live for another ride.

Speedy:)

Have had that happen on a motorcycle at 70 or 80 mph. Scared the crap out of me.

I didn't hit the ditch either.

Glad you're OK.

Why not just slow the f*ck down?

Just sayin'...

cause it defeats the purpose of shaving your legs....

it may be time to consider a new bike if you are pushing those speeds, new geo and angles really make a huge differance. im riding a Bianchi C2C and love it!

Heh heh @ slow down.

Not being knowledgeable about high level cycling, this is probably a useless question/approach, but thinking about the world of car wheel/tire balancing/truing, is there any type of super sophisticated computer wheel/tire/tube balancing and truing that you could have done to make sure that front wheel/tire combination doesn't have even the slightest bit of imperfection/microscopic wobble?

See, I told you it's probably useless. http://forums.pelicanparts.com/suppo...ool_shades.gif

An old (and now dead) friend used to do wheel work for a few minor TDF riders... he used a set of forks and did it by hand spinning and tightening to balance the wheels... then he'd test using a power drill to rotate 'em at *really* high speed to confirm balance. Not sure what speed he got up to, but there were many chants of "Need more power!!!"

Wow.

I've had my Bianchi a tad over 40 mph a couple times. Maybe I'll consider that the max.

I still have all my leg hair thank you. To slow down kind of defeats the purpose of a race or race preparation. To race is to push the limits of man and machine and to find a solution to what ever is holding you back, hopefully before it injures you. In this case the speed wobbles are holding me back and will continue to be an issue in the future. I am not going to get any slower.

Speedy:)

have done the 48 coming off mt pisgah outside of asheville- even when everything is just fine, it is stunning

was behind my buddy coming down that slope 2 years ago when he got the death wobble- no smoke, but scary as ****!!-our group talked a lot a bout it on the rides following- believe he googled "death wobble" and concluded no brand was safe- some thought that shifting weight on the bike was best....

all i can tell you is that we will never slow down on the bikes, anymore than we will when we think we have a great line coming into our favorite corner in our 911s - fun is fun

hope that wobble was your last experience like that

I don't know if this helps, but I get high speed wobbles every time I race my XR1200. Well, these are at about 130 MPH. When they start, I just relax my grip on the bars and start moving my butt backwards, and increase pressure on the footpegs, by weighting them with my calf muscles. That usually calms things down. The idea is that I am moving the movement of the bike away from the ends, and towards the middle, by use of force. Same thing might work for bicycles?

Is the race a triathlon? If not, why have aero bars on the bike. I've never had a steering damper on a road bike, and the only one I had that could get sketchy at high speed downhills was a Landshark that used steel tubing that was too thin for the size. I had a Davidson with 75 degree head angle that CW would say should be twitchy but it was stable as a rock downhill.

I've never experienced head shake on my bicycle (1997 Serotta), even at > 50mph, but I've read in various bicycle mags that you're supposed to clamp the top tube between your knees when it happens.

Do a basic frame alignment check. Simple string method and also check the headstock bearings / bearing load.

Happened to me as well on a motorcycle back in 1986. Brand new GSXR-1100 and didn't matter that they came stock with a damper. 130 mph and an instant violent shake... most scary. Within a week a major service bulletin was issued. The culprit: Early release bikes had incorrect pre-load headstock bearings.

I've had what I can describe as high speed "surging" before, where the presta valves throw the wheels out of balance at that speed...but never a death wobble...

when that happens try gripping the frame top tube with your knees it will stablize the wobble

That's nuts on those things.

Does it happen when you lean into a turn? I don't think its the Bianchi or its age. Check the frame and the fork it maybe out of whack. Was it ever in an accident? I really think you wheel is out of true for this to happen. Check the skewer to make sure its tight to the dropouts. Also, like someone said earlier, check the head set. put your fingers on the headset where the fork crown meets the bottom of the headtube and slam on the front brake while you push the bike forward. There should be no movment there. It should solid. Head set maybe too tight also but I don't think it will cause that kind of violent shaking. A 30 degree shake is way, way too much.

No. Scooch your ass back on the saddle and add some weight over the rear wheel with a little weight down on one of the pedals. if you try to stabilize your bike by the top tube with your legs, you will fall because you just shifted all your weight forward where the shaking is going on.

You need a stiffer frame if you want to go much over 35mph: that old Bianchi: Not good ! !
I got in that situation on my 80's Bottechia, which I promptly sold.

Many bikes later I got a carbon stayed Ti- main triangle Colnago, which is very confident inspiring. Was well over 45 mph with no problem... Now my full carbon BMC will be put thru the test this summer.

I have to respectfully disagree with you on the steel frame. If its a quality tubing Bianchi, it should be very stable. I have raced many old steel frames from the 80s through the 90s. We were nuts on the downhill. Never any issues. Just make sure the wheels are true. without a bend fork, or both fork blades are true not out of wack.