Bike Wobble
67
Member
1216 days
xt4 posted 26 weeks ago.
This exact same thing happened to me at about 40mph a few years ago on a Specialized Transition Elite. Scared the hell out of me, and left me with zero confidence descending. I had the bike looked over top to bottom, the wheels trued, everything I could think of. Went back out there and had the same problem.
I did some research, and there seems to be a high speed phenomenon that's hard to diagnose. It could be an imperfection in the wheels, or even the frame - something slight, even material, and not "fixable". In certain conditions, the bike carries a slight vibration, generally not noticeable unless your descent gets especially long or especially fast. In those cases, the vibration increases and stability decreases the further/faster you go.
A suggestion I read - and what helped me - was to position myself very far back off my saddle when descending, so my center of gravity was further back on the bike. Also, I'd pin my left knee to the frame of the bike (just, squeeze my legs together until my knee was pressing against the top tube). The theory is that changing the center of gravity and "dampening" the frame vibration/absorbing it more through the body keeps the wobble from increasing with velocity through the frame. It worked for me - no more wobble. But, I have to say, it wasn't until I was on entirely new bike that I was confident again on fast descents. Something like that gets in your head - at least for me.
Good luck and ride safe!
687
Member
319 days
jsk85 posted 26 weeks ago.
I've had the same experience...am still on the same frame and don't have confidence descending above 45mph which is usually when the wobble sets in for me. Luckily there aren't many huge hills in this area to worry about descending faster than that...and the ones that are big enough usually have an intersection at the bottom, so I'm already braking in anticipation of cars
1192
Member
348 days
TriSooner posted 26 weeks ago.
Probably imperceptible imbalances in the wheel and/or tire that are exaggerated at high speeds and very high RPMs. Probably not much you could do except maybe true the wheels. That’s why we ‘balance’ our car tires so at highway speeds they don’t vibrate as badly. At least you didn't go down.
3354
Member
1413 days
RV posted 26 weeks ago.
Ya speed demon!
I also heard that squeezing your legs together into the top tube will help maintain control.
RV
It takes a long time to get good. - Scott Molina
Slow is smooth; smooth is fast. - Rich Strauss
139
Member
1141 days
NotAsFast posted 26 weeks ago.
I used to have speed wobble. Usually caused by imbalance on the wheels, much like your car.
The easiest way to see if you wheels are out of balance is to put your bike up off the floor and see if your wheels rotate to one point then return back till one part of you wheel is always at the bottom. This at speed causes a uneven weight distribution which cases vibration and eventally wobble. You can solve it by taping small lead weights under the rim tape if it is bad. The other reason could be an unbalanced tire or finally you may have a hop in you rim. Which any LBS can diagnose and remove.
I balance all my wheels before mounting the tires, and I also make sure there is no hop in them as well. I also check my tires after mounting for balance and if it is excessive I take the tire back and exchange it.
I have a few hills I hit 45+ on and dont have any issues with vibration or wobble.
Hope this helps.
386
Member
1266 days
triNick posted 26 weeks ago.
Glad to hear that I'm in good company. It scared the hell out of me the first time. I was amazed I was able to control it and come to a complete stop. The guys behind me said it looked scary. I didn't do much on-the-road riding since that had happened, mostly bike trainer stuff. Then in March going down hill again in Italy it happened again, holy crap that was scarier! No shoulder, on coming traffic and biker and car behind me... My coach was behind me and saw it, he also said it looked scary. This time it was on a road bike and not my tri bike. We checked the bike out and nothing seemed loose. I had also checked my tri bike after it happened and we didn't find anything. I thought it might have been related to the 404's I had on.
He did give me 2 good tip that I incorporated a few day later when it felt like it was going to happen again. He told me to hug my bike frame with my knees to help control the bike and to sit farther back. It seemed to work.
I still haven't recovered from these two incidents when going downhill now days, especially when it windy. I freak just a little bit...
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549
Member
314 days
jhudalla posted 26 weeks ago.
I was getting speed wobble as well when I first got my sworks tarmac, at speeds over 45mph the front wheel was going nuts, I too crapped my pants a little bit. Apparently the Ksyrium ES rims have a hub issue that requires them to be tightened every now and then. I got a little wrench from the bike shop (for free) and it tightened the hub, solved the problem.
Weary is the path that does not challenge.
I was on a very long, fast downhill today and the bike began to wobble uncontrollably, The shimmy and shake began with the front tire and the rest of the bike decided to follow along, making the whole bike very unstable. I was very close to going down before I got it under control.
The bike was serviced and race checked 2 weeks ago. I run Michelin Pro 2 tires on an '05 QR Kilo. Have I inadvertantly discovered the bikes top speed or could it be something mechanical?
Needless to say I rode the brakes on the downhills for the rest of the race and no further port-o-pottie stops were necessary for the balance of the bike leg.
john
Pain is inevitable. Suffering is optional.