2007 Scattante CFR Elite = wobble at high speeds



joe85748

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Sep 26, 2011
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I experienced the terrifying death wobble on my 2007 Scattante CFR Elite for the first time yesterday. Was going Mt Lemmon at about 45mph when it started. I had a very difficult time slowing down because the wobble was so violent that the tires were barely making contact with the road. I did manage to slow the bike down to about 15 to 20 before crashing.

Does anyone have any recommendations on bikes that this is less likely to happen on? I know it could happen on any bike under the right conditions but I want to reduce the risk of it happening and I don’t have confidence in the Scattante.

By the way, the bike is maintained and the road was smooth.
 
Yikes!!

I had something similar happen at Bear Mountain last season on a Specialized Tarmac SL3 with the Dura-Ace deep section clinchers. And just like you happened pretty much at the same speed - right about 47-48mph. I am usually a daredevil and hit 150mph+ a long time ago on my ZX-11. Needless to say this was TERRIFYING! I'm sorry your incedent ended in a wipe.

I was chatting with someone who had something similar on their Cervelo with the Zipp carbon/alloy hybrid clincher (404's?). This should not happen on every (any) bike. I did the same decent on my aluminum Cinelli with Mavic Ksyrium Elite's the week before and had managed hitting 53mph - bike tracked dead staright and I was laughing with hysterical joy.

My feeling is it is not your frame but maybe your wheels - what brand and model are they? Some surmised that the long valve stem on my wheels caused the imbalance. Sadly we didn't troubleshoot, like using different wheels or whatnot.

Some may say your headset needs adjusting, it is possible but that was not the case in either mine or the Cervelo's wobble.
 
The wobble can be the result of a number of things:
-loose headset
-loose QR's
-sub-optimal weight distribution on your bike
-maybe unbalanced wheels but the imbalance would have to be comparatively severe
-road defects
-???

Your best bet is to make sure everything on the bike is properly adjusted, torqued, and etc. Make sure your wheels are properly seated in the drop-outs and aren't misaligned.

Wobble is a resonant condition on the bike, which just means that at some vibration frequency, the wobble will increase in amplitude. Every rigid structure--bikes included--has a resonant frequency, and usually for a bike that frequency is outside of normal riding conditions. One thing that can most certainly exacerbate a wobble and even contribute to the initiation of a wobble is a rider who is not relaxed on the bike. In fact this is one reason why wobble's can be difficult for some to tame because when the wobble starts, the rider tenses up, possibly making the wobble worse. When you encounter a wobble the best advice is to relax and press your knees against the top tube. Getting weight on the front wheel helps. Apply rear brake, gently. Drag it a bit. Wobbles typically don't cause crashes but are certainly enlivening. Wobbles are speed dependent, so once you slow below the speed where it was initiated it should ease up. Should.

I had a monster episode of wobble descending Kitt Peak a few years ago, at about 40mph, just before entering a corner. The wobble made the line through the corner "interesting" and made corning a bit more intense than it normally is. After the corner, a bit of knee squeeze and relaxation, with a touch of rear brake killed the wobble. I finished the descent, making sure to stay below the speed at which I'd had the fun. The source of the wobble was a mechanical brain fart on my part just before the ride, a mistake which shall my remain nameless to protect my dignity.

I'd recommend doing the mechanical checks above and going back to Lemmon for test rides. Maybe just ride up to the Babad Do'ag overlook. On the way down, carefully build up speed, backing off if you start to feel the beginnings of wobble.
 
[SIZE= medium]Thanks for the advice. I have to admit that I was completely unprepared for what happened and had no idea how to stop it. I made the mistake of instinctively grabbing the handlebars as tight as I could, which put more downward pressure on the handlebars, which is what i believe ultimately[/SIZE] caused the front end to go completely out of control. Now that I know about this, I think I will have a pretty good chance of controlling it next time.
 
I've never had a severe wobble on a bicycle, but I have on a motorcycle (ran over a 2x6 lengthwise). The way to overcome a wobble on a motorcycle is to accelerate, which takes weight off the front wheel. I did just that and it worked, though I was really short on room with cars in front of me. With a bicycle, I would think the physics are similar enough that while you might not be able to accelerate out of the wobble, you may be able to shift your weight to the rear to get enough weight off the front wheel for it to go away.
 
Originally Posted by jpr95 .

I've never had a severe wobble on a bicycle, but I have on a motorcycle (ran over a 2x6 lengthwise). The way to overcome a wobble on a motorcycle is to accelerate, which takes weight off the front wheel. I did just that and it worked, though I was really short on room with cars in front of me. With a bicycle, I would think the physics are similar enough that while you might not be able to accelerate out of the wobble, you may be able to shift your weight to the rear to get enough weight off the front wheel for it to go away.
This definitely not always the case. I had a race bike that was particularly prone to nasty tank-slappers on exit from corners. On a bicycle, too much rearward bias itself can cause a wobble on a descent. Worse, unloading the front wheel compromises steering control, which is significant on a bike given that a bike doesn't have nearly the inertia--both translational and rotational--to increase stability.
 
Originally Posted by joe85748 .

[SIZE= medium]Thanks for the advice. I have to admit that I was completely unprepared for what happened and had no idea how to stop it. I made the mistake of instinctively grabbing the handlebars as tight as I could, which put more downward pressure on the handlebars, which is what i believe ultimately[/SIZE] caused the front end to go completely out of control. Now that I know about this, I think I will have a pretty good chance of controlling it next time.
That's a pretty normal response. When a rider tenses up, the natural steering damping of a relaxed grip and loose arms goes a way. Staying relaxed is something that might take some practice. Again, this is pretty common for riders.

Hopefully you and your bike weren't too beat up in the crash. Getting a scar or two is good, so long it's on you and not the bike.

Where on Lemmon were you when this happened?
 
I was somewhere in between mile 1 and 2. Not sure exactly where.

I was able to safely duplicate the problem. While riding at a moderate speed, sitting down, with my torso slightly elevated, I firmly grabbed the top of the handle bars and slightly shifted my upper body side to side. It is amassing how much the forks and front rim flexes while doing this. When I stopped moving, the wobble went away fairly quickly. When I had the accident last week, I think I was moving so fast that the wobble became self perpetuating.

If there are any riders out there that have not experienced this, I would recommend testing the flexibility of your front end like I did…in order to know what causes it. I wish I knew about this before. It would have saved me from needing to buy the extra large tube of Neosporin
 
Originally Posted by joe85748 .

I experienced the terrifying death wobble on my 2007 Scattante CFR Elite for the first time yesterday.
It seems strange that a bike with the name featuring the word scat doesn't allow the rider to "enact scat free tilt" - which is an anagram of Scattante CFR Elite...

I find the subject of 'speedwobbles' to be interesting as in close to a couple of decades of riding, the only time I've had some mild shaking on the bike was when I was descending at high speed on a cool day and was fecking freezing cold. My shaking caused the bike to 'shake'.
 
Originally Posted by joe85748 .

I was somewhere in between mile 1 and 2. Not sure exactly where.

I was able to safely duplicate the problem. While riding at a moderate speed, sitting down, with my torso slightly elevated, I firmly grabbed the top of the handle bars and slightly shifted my upper body side to side. It is amassing how much the forks and front rim flexes while doing this. When I stopped moving, the wobble went away fairly quickly. When I had the accident last week, I think I was moving so fast that the wobble became self perpetuating.

If there are any riders out there that have not experienced this, I would recommend testing the flexibility of your front end like I did…in order to know what causes it. I wish I knew about this before. It would have saved me from needing to buy the extra large tube of Neosporin
You shouldn't be seeing a lot front end or front wheel flexure while moving your body side to side. In fact, you really shouldn't see any at all since that doesn't really exert much of a moment on the bike. Have you had your wheels checked to be sure they're laced to the proper tension and that the tension is even across each wheel? Are you sure that your headset has enough preload on it? What was the moderate speed? How do you mean that you were "moving so fast"?

A self-perpetuating wobble is a type of harmonic, specifically a resonant frequency. In more precise terms, all rigid bodies have resonant modes. That is to say there are specific vibrational frequencies at which the strength of those vibrations will increase on their own. Typically real life structures are engineered so that the resonant frequencies won't exist inside or near the structure's potential range of operation. It's something, however, that isn't typically done (or may never be done) for bicycles. It would be difficult to construct tests to accurately reflect the range of conditions in the bike could operate. Luckily, for most riders on most bikes (the vast majority) and in most conditions, the resonant frequencies are way outside the conditions the bike will ever operate. Witness what Swampy said about his one single experience over a lifetime of cycling. It seems, for whatever reason, the gods hate you and have gifted you with a set of conditions that is making your downhill bicycle life more exciting.

I'd suggest having your bike inspected by an LBS wrench, and make sure the wrench knows the issues your experiencing. I'd highly recommend Fairwheel Bikes as a place to find a good/excellent mechanic, but that doesn't mean there aren't any at other LBS in Tucson. I'd avoid using Performance Bike as the mechanic source.

Wikipedia's got a good article on resonance: http://en.wikipedia.org/wiki/Resonance .
 
Joe - even though the thread has been stagnant for awhile I had to respond because in years of riding I never had that happen and only saw it once but it was a Scattante CFR Elite! I have read that wobble comes at high speed decents usually but the one I observed was on a flat section at a pretty high rate of speed. The rider was a little heavy for a road guy but I saw the wobble and it was dramatic, he got it back under control. He also bought another bike shortly thereafter. In reading about wobble they always say put your knee against the top tube and I am in the habit of doing that even without feeling any wobble. Hope you got it figured out.