Bicycle Mechanics - Loss of Power Mystery

Strangest thing -- pedaling along, switched to the middle chain ring in order to begin an ascent after stopping for traffic to clear. But when I tried to start up again, the sprocket just kept turning, with no resistance and no power to propel me forward. After a few minutes of playing around with it, I shifted back onto the big chain ring, and power was restored. I returned home without incident. This morning, I thought I felt a similar loss of power for just an instant, which then disappeared and I had no further problems. This has never happened to me in 30 years of biking, and this is a good Trek racing bike (2100) with about 3000 miles on it. Any advice or ideas much appreciated.

Obviously a hiccup or brownout in the freehub.

Obviously a hiccup or brownout in the freehub.

I'm more familiar w/ latin when dealing w/ bike problems. Can anyone define these Greek terms and suggest how I might address the problem? :)

clean it

I'm more familiar w/ latin when dealing w/ bike problems. Can anyone define these Greek terms and suggest how I might address the problem? :)

inside of the freehub there are two or more teeth (pawls) that act like a ratcheting system. this allows the wheel to spin freely backwards and then engage or ratchet when you start to pedal. Over time lubrication can dry and cause the pawls to stick. the springs which enable the ratched can also snap.
It could even be a loose axle which is causing a sidewards pressure on the pawls which make them stick. Good luck. Try searching how to remove and tune your freewheel. Your LBS can fix this as well.

Thanks, Hiccuphell. Your name bespeaks an intimate familiarity w/ this problem. I re-packed my rear wheel a few months ago, but will try again, and, if that doesn't work, it's back to lbs.

If you pack the cassette with grease, use a very light grease like white-lithium. Then use a thicker grease for the bearings like boat-trailer bearing grease (has good tack & adhesion without too much viscosity).

it sounds like it may be worn ratchets. Im not sure how most other hubs work here but my Hugi's have 2 replacable ratchets with springs pushing toward eachother. So when this happens you replace ratchets, which are $15 i think. But it has not happened to me