Weird Crash
Last Post 10/31/2019 06:25 PM by Cosmic Kid. 40 Replies.
Author Messages
6ix

Posts:300

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10/20/2019 12:13 PM
Was on descent yesterday with a very strong crosswind.  Got up to a little over 40mph when i made the decision to basically brake to a near complete stop as it felt unsafe.  had knees clamped on top-tube and was bracing myself.  While decelerating, my bike went out of control.  The wheels seemed to be oscillating and violently shaking the bike even as I braked.  Felt like both wheels had turned oval and I had blown out the tires (I hadn't.  Wheels were perfectly true.)  I ended up crashing in the ditch and breaking my hand in three places. 

I'm not super light at 158 lbs and was on my Chapter 2 Rere with the latest Mavic Cosmics.  I've experienced crazy crosswinds before even to the point of having to put a foot down.  But I've never had my bike suddenly start bobbing up and down so violently that i lose control. 

This took me forever to type since hand is in cast. 
Orange Crush

Posts:2646

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10/20/2019 02:29 PM
Sorry to hear that 6ix. Heal well.

Where you cold? I've had similar sensations basically caused by intense shaking of my body due to cold.

As it happens I did a 12k descent in torrential rain and frigid temperatures yesterday (it was supposed to be dryish) but I only started feeling really cold at bottom.
6ix

Posts:300

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10/20/2019 05:54 PM
nah, wasn't cold at all. mid 60's, i think. I have been cold enough to shake before and that isn't what happened. Something bizarre happened with the aerodynamics of the wheels causing it to violently bob up and down even though i was trying to come to a stop. Might shoot this over to Zinn at Velonews.
smokey52

Posts:297

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10/20/2019 06:29 PM
resonant frequencies? https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)
79pmooney

Posts:2213

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10/20/2019 07:05 PM
What model Cosmics? I went to their website and see that the Cosmic name covers a huge array of rim depths and shapes. Being an aero geek (specifically from the lift side of the equation, not so much the drag) I want to know exactly what rim shape acted so badly. (I was fascinated by sail theory since I was a kid The two most important books I owned were "Theory of Wing Sections" by Abbott and Von Doenhoff and Sailing Theory and Practice" by C. A. Marchaj. Still have them.

I wonder if your particular rim was alternating between attached flow and creating lift and detached flow, creating far less lift.

Ben
79pmooney

Posts:2213

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10/20/2019 07:06 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:07 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:08 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:12 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:14 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:15 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:15 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:16 PM
Bah!  Double post
79pmooney

Posts:2213

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10/20/2019 07:18 PM
Bah!  Double post
huckleberry

Posts:546

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10/20/2019 08:41 PM
For god's sake, Ben!

; )
79pmooney

Posts:2213

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10/20/2019 10:25 PM
huck, I get lousy service here. (I absolutely refuse to go Comcast and they and the local phone co have a monopoly.) When it's busy, I get the try again button but cannot see if the issue in outgoing or just incoming. Seems outgoing was working just fine today!
6ix

Posts:300

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10/21/2019 07:43 AM
They are the Mavic Cosmic Pro Exalith. The latest model with the somewhat blunt leading edge. Their marketing materials state "The new Cosmics are so much better in the wind; gone are the sudden jerks from the front wheel of old. Crosswinds can be countered through the bar or by simply shifting your body weight."

I used to believe that.
79pmooney

Posts:2213

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10/21/2019 11:41 AM
I struck out trying to find a cross section of the rim. I did see somewhere that it is a NACA foil section (well, an approximation of one since none of the NACA sections are symmetrical front to rear and none start or end with a bicycle tire!)

I wonder if 1) the actual tire is super critical to the aerodynamics and 2) if the combo was working alternately as an airfoil and not. (Mavic does claim aerodynamic properties for that rim and that the ride is "dynamic". Sadly, you found both to be true so you probably don't have the basis of a claim against Mavic. (Mavic in court "But our rim behaved exactly as advertised.")

6ix, what is the depth of the front rim and what tire were you using? Interesting to see if the final cross-section is significantly different with your tire vs the Mavic recommended.

One challenge Mavic has is that they offer so many different rims. Aerodynamics are very specific to shapes with small differences potentially having large effects. Really, they should test each rim with a variety of tires so they can warn consumers that this tire and that tire do not do well with this rim but that takes many expensive wind tunnel runs. (Two dozen runs per rim perhaps to cover a decent range of tires. Times their probably 3 dozen rims offered. Say $1000 per run for wind tunnel time. Most of a million dollars.)

Contact Mavic. If they are a responsible company, they will want this as a data point that might lead to changes that keep someone else out of a ditch and maybe they will have a sweet gift for you.

And most important - right hand or left? Your dominant? (Ben - right thumb, right wrist twice, right collarbone twice. Totally right handed. Know the routine a little too well.)
6ix

Posts:300

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10/21/2019 12:04 PM
Thanks for the help Ben. Rims are 45mm deep and 25mm wide. Running 25mm Conti GP4000 II tires. Nothing special and fortunately they escaped unscathed. I guess it must have just been a freak aerodynamics issue but I may mention to Mavic just so they are aware of the potential. I can replay the whole incident in my head and the wild up and down oscillation was truly bizarre.

Got the fiberglass cast put on this morning. I'm a lefty and it's unfortunate my left hand but i only use it for writing and drawing. sucks that part of my job is sketching!!!

Oh, and painkillers suck something fierce. No idea how the pro's were taking Tramadol and not barfing everywhere.
Orange Crush

Posts:2646

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10/21/2019 03:53 PM
This is very strange indeed. I've had several times where I needed to come to a (near) complete standstill on downhills due to fierce crosswinds I didn't think I could hold but never anything like that.

Closest I've come to actually having a bike swiped from underneath me was summiting Ventoux. Our climbing speed on 2nd summit that day alternated from >30 kph to < 5kph depending on wind direction and on very last part it was cross. Scary $4it.

Maybe you just need to put on some weight and problem solved?

I just came off a bout with gout. Worst pain I've ever experienced by several orders of magnitude (they say it is the only type of pain coming close to that of child labor). The painkillers were accordingly strong but none of the potential side effects.
79pmooney

Posts:2213

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10/22/2019 12:48 AM
I rode Jessica in a storm with a crosswind so hard I needed most if the road. Wanted to stop but didn't trust that I could without crashing with that wind at my side. Missed the first driveway to pull into and had to brave that gust cycle another 1/4 mile before the next driveway appeared. The rest of the ride, while the wind was at my side, I made it a point of stopping as soon as the gust started to build. (Classic gust/lull cycles so familiar to us sailboat racers but at storm intensity.)

Now I have used Mavic Open Pros in front and the somewhat deeper Velocity Aeros in back. A very well behaved combo, even in those winds.

Ben
zootracer

Posts:679

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10/23/2019 11:58 AM
I wonder if you are descending at a good clip and encounter a heavy sidewind that applying your brakes at full force trying to come to a complete stop is a wise idea. I used to have those funky Rolf Vector Comp wheels on my '99 Klein. I live in the foothills and the roads are somewhat sheltered from the wind. When I did hit a crosswind it would almost blow me off my bike. I would apply my brakes to gradually slow my bike down. Just saying...
6ix

Posts:300

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10/24/2019 08:05 AM
Yeah, I agree now that braking hard perhaps wasn't wise but I'd committed to slowing to a crawl in order to safely get down the hill. It was already dangerous. I kinda wonder if that back-fired on me as I started to lose control once I'd applied the brakes. In regards to aerodynamics, what in the ever-living-hell happened? Sure, at 45mm deep those Cosmics aren't low-profile by any stretch but they are leaps and bounds more stable than the older v-shaped rims from the 90's and 2000's. Big difference.

Regardless of the depth, what would cause things to start oscillating and bouncing up and down? Some weird physics at play.
Cosmic Kid

Posts:2900

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10/24/2019 08:52 AM
A lot of things could have caused that speed wobble...even a minute amount of play in the headset could kick it off. Wheel slightly out of true, tire not seated correctly, etc. At those speeds and in those conditions, everything gets magnified.

There was an interesting podcast on the TrainerRoad pod a few weeks ago about speed wobbles. Could be worth a listen to see if anything sounds like it could have been the cause.

One of the guys I ride with got a new Giant Propel earlier this year.....was going down some descents out in western IL and could not get the bike to stop shaking. They checked everything and nothing came up funky....but could not get rid of the shakes. LBS eventually forced Giant to take the bike back and they put him on a TCR instead....no problems with that bike.
Just say "NO!" to WCP!!!!
Cosmic Kid

Posts:2900

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10/24/2019 08:53 AM
Hope you are healing well, 6ix!!
Just say "NO!" to WCP!!!!
zootracer

Posts:679

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10/24/2019 09:17 AM
6ix...I had my first bad crash in 2000. Descending at a reasonalble clip (30MPH). I slowed to around 15MPH in order make a hard left turn at an approaching intersection. My bike ('99 Klein) started wobbling and shaking. Next thing I remember is my wife standing over telling me I had been involved in a crash riding my bike. I don't recall anything. Motorist found me laying on the roadway unconcious. They obtained my phone number and called my wife (I lived about .7 miles away). I was transported to the hospital by ambulance, my chest hurt. I had fractured 4 ribs and received a concussion. When I was discharged from the hospital about a week later I inspected my bike. The front wheel was flat, it was scuffed up. I remember hitting a rock just as I started the descent. However the tire getting scuffed could have happened when I went down. The bike never did that shaking thing again. I've had flat tires since on the front wheel while descending, never caused the bikes to shake like that incident. the Klein is long gone, on my third bike since then.
Hope your hand mends o.k. I fractured two metacarpals in my right hand in 1995. I was fighting a combative DUI arrestee at the hospital who was trying to escape and was trying to pull my pistol out of its holster (I was a CHP at the time). I hit him in the jaw with my right fist which shattered my right hand. My hand eventually healed but I can not straighten out the middle finger (must be irony in that). I guess the surgeon I had was not the best, although he had been an M.D. in Vietnam. The doctor in the ER, who helped contrain the arrestee along with a male nurse (the guy went beserk) said the jaw is the strongest bone in the body. I said I should have used mace. The doctor said if I had the mace would have gotten into the ER's air conditioning vents and they would have had to evacuate the entire ER. The fractured hand was the only injury I sustained in my 27 year career. I've had three bad crashes while riding. Besides the fractured riibs, fractured my right hip in 2005, fractured left elbow in 2011. Riding my bike has turned out to be more dangerous than a career as a police officer.
Be careful out there, cycling is damn dangerous as I discovered.
6ix

Posts:300

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10/24/2019 09:48 AM
My last crash was in late 2007 but i've gone down three times since july! What the hell?!

My headset has a wee little bit of play. That's the only thing i can possibly think would contribute. Maybe at that speed (40mph+) combined with crosswind (45mph+), things get pear-shaped really quick.

Yeah, the fourth metacarpel is broken into three pieces. My hand will forever be borked but I don't see it affecting my ability to draw as I rest the pencil between index and middle finger. Sure can't do that with this cast on!
Orange Crush

Posts:2646

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10/24/2019 02:42 PM
A bit of play in headset would do the trick and definitely make crash less weird. Three times since July?!
Cosmic Kid

Posts:2900

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10/24/2019 07:44 PM
Yup...I would definitely think it was caused by the headset play.

I’d start from scratch on it now...get new bearings dropped in (could be pitted) and get everything tightened up properly and you should be good to go.
Just say "NO!" to WCP!!!!
Cosmic Kid

Posts:2900

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10/24/2019 07:44 PM
Note to self - don’t fook with zoot....he’s a bad ass!!!
Just say "NO!" to WCP!!!!
zootracer

Posts:679

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10/24/2019 08:31 PM
CK Not a bad ass but definitely a very old ass..
SideBySide

Posts:444

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10/25/2019 01:59 AM
Bummer, I hope you heal well and quickly.
6ix

Posts:300

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10/25/2019 08:42 AM
Sounds like it was really the result of poor handling skills in extreme conditions combined with a headset with just a wee little bit of play. I'd purposely left it like that because i couldn't find a happy medium between it being overly loose and creaking/ticking when fully tightened. Still a freak accident but in looking back could have been so much worse. That's a busy highway.

Thanks for all the help fellas!! I'll try to keep the rubber side down more often next season.
zootracer

Posts:679

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10/25/2019 09:20 AM
Don't feel bad, I fractured my hip back in 2005 trying to climb my own driveway in the wet. Not the brightest thing to do....
79pmooney

Posts:2213

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10/25/2019 11:56 AM
zoot, I remember that. Back in the VeloNews days. I broke my thumb riding out the driveway to my parents' house the winter after I had hung up my racing numbers for good. Dirt driveway. Well below freezing but dry. At night. I didn't ride with a headlight in those days because I was very aware that there were so poor that 1) cars didn't notice them and 2) at speed I overran the beam so they were useless. Here, it would have served well!

My tire found a 4" deep frozen rut. No problem (and in fact I didn't even know) until I needed to make a minor balance correction. Fell to my left. Broke racing rule #1 (as I was no longer racing ). Don't let go of the handlebars until after you hit the road; a rule that had served me very well. Put my right hand down. Jammed my thumb. Didn't really notice; my knee hurt a lot more! Pulled my mitten off to mess with the quick release and saw at first glance that my thumb was wrong. The break was well back, in my palm.

That ride was to go in-town to donate blood platelets. The only other time I had missed an appointment there was 14 months before when I was in a coma. (No driveways involved there.)

Ben
Orange Crush

Posts:2646

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10/25/2019 01:00 PM
6ix - I've had that very issue of a creaking headset on my commuter. Messed around with it for a bit but like you could never quite get it right between removing the creaking and having it sufficiently tight. I can't for the life of me remember how I finally solved it but trust I must have replaced it ultimately. It's been a few years ago. Best not to cheap out on this kind of stuff.

Had a few crashes this year myself but all of them were "fun".
1. Trying to squeeze too fast through a gate on a gravel trail spinning out. This was a beer sprint to local brew pup. My entire left leg was a very deep purple for many weeks.
2. Several spills in loose sand in Oregon that Ben witnessed. On the last one the top tube of my bike sheered off. It remained surprisingly compliant though on a 20k downhill but was making death sounds all the way.
3. Being unable to lift my front wheel up beyond a reasonable doubt to get over a bridge curb. Clearly getting old (timing) and not enough upper body strength. Crashed on both hands and knees. This was a few week ago on the maiden voyage of the replacement frame I got from Specialized.That replacement frame is sweet (stiff).

That's enough for 2019 I'd say.
longslowdistance

Posts:1895

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10/25/2019 10:31 PM
FWIW, I've been reading these notes and still am confused. Left Right shimmy is well know to all of us, loose headset, out of balance front wheel, side wind, pavement issues, coming from a cold rider, or whatever. As a medical person who rides, I am certain that certain of us are more prone to the left right shimmy due to genes (blame your parents).
But up and down as described by the OP, I just don't get that.
6ix

Posts:300

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10/27/2019 02:37 PM
Was inspecting my frame today and found an impact fracture that was hidden underneath the chainstay protector.  It passes the coin test and I don't see a crack forming.  Think the chain just smacked it really hard and chipped away the top gel coat layer.  Even so, thankfully there is a carbon repair shop here in Boulder I'm taking it too.  More money down the drain. This sport is quickly becoming far too rich for my blood.