Q: I think I may have bought a bike that’s too difficult for me to control. The handling is twitchy and it shimmies on fast descents. The frame is very light, being made of titanium in the compact style.
I wrote to Uncle Al about this and he blamed the frame. But I’m wondering if you have any additional thoughts from your perspective. — Ken P.
COACH FRED: Uncle Al has ranted various times about the problem you’re describing. Use our website’s search function to read up on his thoughts and recommendations. Search for shimmy and wobble.
In your case, it could be any of the mechanical possibilities that Al cites. Or it could be the bike’s design and tube thinness combined with your weight and riding position. The top tube on some lightweight frames isn’t stiff enough to damp vibration, so shimmy results. Given the type of bike you bought, that’s what I’d guess.
Sometimes a bike will shimmy for one rider, while a different guy can descend on it at 50 mph with nary a wiggle. I have a bike that’s dead stable when I ride it unladen. But if I put on a rear rack and panniers, it shimmies like mad at 30 mph. For my body weight the top tube is plenty stiff, but with panniers “wagging the dog,” the bike becomes unstable.
Position on the bike can be a factor. Sitting too far to the rear with the saddle jammed back might cause shimmy. The front wheel doesn’t have enough weight on it to damp vibration. But sitting too far forward can be a problem, too. Lots of weight on the front can upset the steering response the bike was designed to produce.
That said, you should be able to ride at either end of the position spectrum without problems. There are plenty of bikes out there that’ll let that happen.
In the end, shimmy can be caused by so many factors (or a combination) that it can be impossible to sleuth out the actual cause. I think it was Eddy Merckx who replied, “Buy a new bike” when he was asked how to cure a shimmy problem.
But first, follow up with your bike shop and the manufacturer. Neither wants a top-dollar customer to be on a bike that might cause a crash. I bet they’ll do their best to remedy the situation.