Hey, Velodiva, how about a ride report?
 

I thought you would have posted one by now -- whassup?

Velodiva & I signed up for the Berkeley Hills Road Race, held on Mother's Day. The weather was cool but beautiful and I was feeling really confident. I didn't have a shred of nerves; in fact, I was eagerly anticipating this ride. Vdiva seemed ready as well, and after much picture taking by our friends Smooooth and Sassy (too young for this forum, barely) and Hermes and Cgallagh we began the promenade from the San Pablo Reservoir parking lot to the main road.

We're on the main road with some rollers and moving along at a good clip. I stay in the middle of the pack (pretty much a first for me; I tend to hang off the back) and pay close attention to the upshifting and downshifting sounds, watching the wheel in front of me, and having fun. We're picking up speed on a long, sweeping descent and I'm still in the pack, keeping up and enjoying the draft. Suddenly my front wheel begins shimmying something awful. :eek: I'm in my drops, weight on my hands, which I thought were relaxed. So I relax my grip more and my handlebars begin shimmying as well! :eek::eek: So I holler that I was slowing, since I can't let go, and feather my brakes until I can stop. A quick once-over reveals no apparent rim, tire or spoke problem, nor was my headtube loose. :wtf: :notamused: Sadly, I watch the pack ride toward the first turn and the rest of the race, while I turn around to go back to the start.

Before I began pedaling again I looked at my Cateye and saw that my speed down the hill was 40.4 -- a personal record for me on a half-bike. And less than 7 miles into the race. Dang! However, I was and still am satisfied with my decision. Better disappointed than, well, you know...

The LBS couldn't find anything wrong either, so they called Orbea and negotiated a brand-new '09 pistachio-green Orca frame and forks for me. :love: Whoo-hoo! It should be here by early next week.

Velodiva had a very different outcome and I hope she shares it with us. That woman is fierce! :thumb:

Speed shimmy may require you to change the vibration mass of the bike quickly to avoid going down. The regular way is to grab the top tube with your knees..:eek:..not always your first thought as your life passes before you and sometimes not even what you dare do while holding on for dear life. The second way is to press up slightly off the saddle and unload your weight from the frame.

Conventional wisdom is that you must practice this..:roflmao2:..before you need it in a race. If you dare (and its a little like getting back on the horse) you will have to find a hill that you can use to approach the oscillation speed gradually, and practice slowing back out of the shakes till you can do it without raising your blood pressure 100 points. If you go fast enough, you are going to oscillate again at some unknown speed with just about any frame/wheel/headset/rider size and you must be prepared to deal with it.



Ask your racing coaches for advice.

That frame or Forks obviously has some flex in it somewhere. The method of gripping the top tube with the knees works- but as I ride compact frames- I find that cure difficult.

We have had a front wheel shimmy on the Tandem a couple of times at speed- and it was frightening. Found that a change of tyre worked on the Tandem. That was when it was used on the road- and there is no way you can put Frame flex into the equation on a Dale MT 2000. That frame is solid.

It does sound as though it could be a known Orbea problem though if your LBS has ordered a new frame. Think you made the right decision to abort the race. It may have been a problem you overcame once- but if it had occured again- you may not have been as lucky.

Great idea - I should try this with Specialized and see if I can get a new Tarmac every year...

I had this same issue with my steel bike. Had ridden it for years and down some pretty steep hills - never a shimmy. A few seasons back I felt a little shimmy and it got worse. I took it to the shop - nothing wrong. I then went on a club ride, first descent and I thought I was going in the ditch, it shook like crazy. At lunch one dayy I want to the one man LBS run by the local sage - the recognized expert in the area, even by every LBS within 100 miles - told him every thing I had been through. He cited many studies and much data and then said - move your seat up a few cm. I went home and was floored by what I found - my seat had indeed slipped back to the end of the rails. I moved it up to the marks I put on it many years prior and tightened it back up - no more shimmy.

A timely topic on speed shimmy. As I said in my post of a couple of days ago (74 miles Around Lake Tahoe), I experienced THE SHIMMY for the first time and remembered the knee-to-top-tube trick. It worked. There seem to be as many ideas on this as there are ideas on this. I did have brand new tires and had recently changed the position of my saddle. Hmmmmm. At 43.3 mph, I really don't want to experience that again.

And oh, Red, didn't want to hijack the thread. You definitely made the right decision. What a mess that could have been from the middle of the pack. I like the idea of a new frame every year, too.

And by the way, our vacuum cleaner does the shimmy, too, albeit at a much slower speed. :roflmao2:

Thanks for all the advice. I won't be trying to re-create that shimmy with any of my bikes. If it happens again I have a way to control it (I hope, and based on what you have told me here). Risk management is what I call it -- there's enough risk in racing as it is.

Stapfam, I think you were spot-on w/your comment about Orbea knowing about a problem like this, given how quickly they offered a new frame.

This sport is full of learning, isn't it?

Please note the giggler smiley in the practice session. It is not something that one "wants" to practice. Good luck with the new frame.