geva

I crashed my bike
I think i lost control.
but I can't remember anything from that ride.
I think it's happened because of speed shimmy....
(my coach saw me crashing, and he told my handlebar was wobbling like crazy)
I crashed on 71 kph in a descent.
I lost control....

I know I will come back to the saddle.
but it wont be on my cervelo R3.
I don't trust them anymore.

can you please suggest what will be my next bike?

I want them to be fast, stable and light.
but I still don't really know what my budget is....

dvdslw

Sorry to hear about your wreck and I hope you're ok! I would think the wobble was wheel related and not bike related, Cervelo make some of the finest road bikes out there. Obviously from the looks of the front wheel there's no telling now if it failed but you were going pretty fast and possibly ran over something, hit a pot hole, or had unforeseen damage to the rim before your ride to give you the wobble which sent you flying? I've ridden a few bikes with an out of round front wheel and they seem to ride pretty good until the speed increases and then it starts wobbling. The faster you go the worse the wobble. If that was the case then any bike you were on with that wheel would have ended up the same.

rpenmanparker 

While it is impossible to know for sure, speed wobble (or death wobble) is usually not the fault of a wheel or any other individual part of a bike, but rather a systemic failure of the entire bicycle. Various stiffness characteristics (or the opposite -flexibility), weight distribution, vibrations from the road, speed, etc, all combine to produce the resonant harmonic vibration that results in the catastrophic outcome. It is not thought to result from something being loose like a headset or hubs. In fact things being too tight can be a contributing cause since that allows the vibration to be transmitted undamped throughout the frame. The best analogy for it is the catastrophic failure of a bridge when an army is crossing it in lockstep or when a windstorm starts it vibrating. There is just a resonant frequency that when reached throws the structure into violent oscillation.

The one corrective action that is routinely recommended is to clamp the top tube between your thighs to dampen the vibration before it gets out of hand. Of course that is a lot harder these days than in the past due to sloping top tubes.

There is no way to test a bike for this characteristic a priori, because you can't predict what frequency it will take to start the oscillation. Some say too much trail is a cause, others say too little.

In case you are wondering, yes, I have unfortunately experienced the phenomenon, and it isn't any fun. I was only going about 32 mph on a downhill (actually an overpass) and was able to ride it out to the bottom when the natural slowing on level ground damped out the oscillation. Good thing I was wearing my brown shorts.

A new bike is a good idea, but there is no accurate way to predict which one would be safe.H

ere is an article by Jobst Brandt about it: Shimmy or Speed Wobble by Jobst Brandt

rpenmanparker 

One more thing. My problem occurred on concrete pavement that was cut with the parallel lines (about 1") that help drain water off. I think those set up the vibration.

Jaeger99

Never heard of this before, and I almost wish I hadn't.

dalava

^^this.

It could happen to any bike, so it's not specific to a Cervelo R3.

geva

the road was pretty good and dry.
no potholes on there.
the first time i notice the wobble i used the powertap front wheel.
so, i suspected he was the problem. so i changed him to the ksyrium sl.
well, i think it's didn't helped me...
i heard that the r3 is known for this kind of problem.

this is the descent where i crashed (i didn't make this vid.)
you can see the place were the accident occurred in 3:36 to 3:50

merlinextraligh

A little bit late after your crash, but there's no reason to crash from a speed wobble. They are entirely manageable. As mentioned above, clamping your knee to the top tube will kill the vibration.

Also, most anything you do to change the frequency can stop it, i.e. shift weight back, loosen elbows.

The worst thing you can do it tighten up, which you likely did.

You can also stop speed wobbles by changing your speed. You can actually pedal through them and they'll stop as you reach a higher speed, of course you can also gently slow to stop them

Key is to know that they are controllable and will not crash the bike.

The rider however can crash the bike by tightening up and overreacting.

I've ha speed wobbles above 50 mph and lived to tell the tale.

rpenmanparker 

It is, I think, preferable to try to put weight over the front end, not back it off. This helps stabilize it. But I agree that when in a harmonic vibration, just about any change will help get you out of that regime except a death grip on the bars.

njkayaker

Just to be clear, Cervelos don't have this "characteristic" in any general sense.

It's possible that there are things related to this particular bike that lead to the problem but that could be the case for any bike.

rpenmanparker 

All bikes have this problem and at the same time no bikes have this problem. It is completely situational. Rider weight, position, road conditions, speed, wind, etc. No bike that has experienced the death wobble has ever been found to be flawed, per se. Okay, so I exaggerate. I don't know that for a fact. What I know is that no bike I have ever heard of (and many have been written up in knowledgeable articles) has ever been found to be defective in a way to cause the problem.

njkayaker

71 kph (44 mph) isn't that unusual.

The problem you had isn't characteristic of Cervelos at all.

We really don't know what caused the problem but it wasn't the bike being an R3.

Note that I don't care that you might want to go with some othe brand (there are lots of good bikes out there) but don't be fooled into thinking that the same exact thing couldn't happen with another brand.

Keep in mind, also, that whatever your particular problem was, it not usual at all. That is, there isn't any reason to expect you'll ever have the problem again (assuming things are properly maintained).

njkayaker

Yes.

I'm just making sure that it's clear that it's not a Cervelo specific problem (if I was, I'd see it on nearly every ride I do!).

rpenmanparker 

Another good article on the subject, this one by Tom Kellogg of Spectrum Cycles: Spectrum Cycles | Geometry

And a pod cast on the topic: The Outspoken Cyclist ? 08/6/2011 « WJCU

holden west

Good advice in this thread. I recently experienced a speed wobble as I passed 60 kmh on this hill. My legs were already clamping the top tube and simply moving my hands out from the tops to the drops quickly stopped the shimmy before it got really bad. I agree when it quickly gets going it can be startling and unfortunately the instinct is to freeze and tense up--the opposite of the cure.

rpenmanparker 

Likely moving your hands put more weight on the front wheel as recommended by some.

TexMac

Sorry about your crash.
As per bikes, i ride this one below;
Giant Propel Advanced 3 review - Cycling Weekly

Clipped_in

Great comments. I've survived a shimmy at ~50mph as well. In my experience, upper body tension is the number one thing that exacerbates and prolongs the problem. If it happens simply tuck down, relax your upper body, and clamp the top tube between your knees (as has already been suggested).

bt

it's the bike. those pencil thin seat stays can't hold up to any kind of shimmy.

glad I sold mine.

rpenmanparker 

If it were about the rear end, you might be right. Alas, no.

bigdo13

sorry about your wheel mano...

**** happens, to err is human... you'll be back at it in no time... best thing is that you weren't seriously injured or even killed...

dtrain

Rational or not, life is too short to ride a bike you don't trust. Your riding style might make it even worse (if you feel tense). Hopefully you are on the mend.

znomit

My trek used to do this now and then when set up for rando rides (small handlebar bag), and a heavy maxis refuse tyre on a dyno wheel. Steep hills and crosswinds. Scary as hell. No problems since I ditched the bag and switched out tyres.

bt

you're on the right track op.

get another non cervelo frame

geva

i barely survived.
i crashed into a guardrail.
i broke some bones in my face and shoulder. and i lost lot of blood.


thank to my coach and friends i'm alive!
thank to my family and friends i'm back on my legs!


thank god i dont remember the pain or the crash itself.


and now i'm recovering...
it will take time.
but i will be back...(!)