Jez Higgins

Freelance software generalist
software created
extended or repaired


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Thursday 17 July 2008 Wobble be gone!

Been pedalling around on my (still feels like) shiny new bike for just over a year now. It's ace, and I love it, and you should all go and get one for yourself.

Recently, as I've started to do more miles more quickly, I've had one tiny doubt. At higher speeds, say over 20mph, there seemed to be a bit of a funny feeling in the back wheel. It was certainly something a bit odd going on at 30mph. But I didn't know what. At that kind of speed you can't been looking back under your leg at your wheel. I checked there wasn't a loose spoke. I confirmed the wheel wasn't buckled or distorted. I made sure the tyre was seated properly right round the rim. Everything was fine. I went over everything agin. And again. Everything was still fine, but there was still something odd going on at the back end.

Last night I did a bit work on the bike, fitting new brake blocks. Since I was at it, I had a good look at the chain, cassette and what-not, and checked the gears. I adjusted the front changer slightly, and to make sure it was ok I picked up the bike and turned the pedals by hand. I let go of the pedals to change the gear, and the bike suddenly started bucking in my hand. I cranked the pedals again, faster, and let them go. The whole thing was kicking like a mule, forwards and back and forwards and back. I'd been right, there was a wobble. A massive great wobble.

And then I had a vision. A vision of Judith Hann. She was telling me about a wheel balancing device designed for use on Army Land Rovers. Even a slight imbalance could cause a wheel to wobble, she explained. My wheel must be heavier on one side than the other.

I looked at the wheel again. I knew it was true and the tyre seated. The only asymmetry was in the reflector attached to one of the spokes. I took it off. I cranked the pedal, and could immediately feel the difference. When I let go of the pedals and let the wheel just spin, the bike was still and steady in my hand. It seemed amazing that a piece of plastic weighing only a few grams could make such a difference, but it clearly was. I whipped the reflector off the front wheel too.

Riding out this morning, the bike felt so much better at speed, smooth and stable. Hurrah!

So, if you have reflectors on your wheels you have three choices

  • go slow
  • have two on each wheel, on opposite sides
  • take them off

Did everybody else know this already? Am I a twit for not realising sooner?


Tagged cycling


Jez Higgins

Freelance software generalist
software created
extended or repaired

Older posts are available in the archive or through tags.

Feed

Follow me on Twitter
My code on GitHub

Contact
About