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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 07-24-07, 09:51 AM   #1
Funyet
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"Twitchy" bike?

Hello,

My first post here! I've been a casual cyclist for years. I recently got hooked after participating in a week-long tour here in Ohio. I now try to get as much time on my bike as possible.

I'm beginning to notice something about my bike but I'm not sure I can adequately describe it. It feels like the steering is quirky/erratic/twitchy. Not like the wheel is bent or out of alignment, more like I'm working harder than I should need to to keep the bike going where I want it to go. This is very subtle, and it may very well just be my perception, though I seem to notice it more as I spend more time on the bike. As I said, nothing appears bent, loose or out of alignment. Any ideas?

By the way, the bike is a 2006 Bianchi Eros.

Thanks!
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Old 07-24-07, 09:57 AM   #2
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Perhaps your stem is slightly out of alignment with your front wheel. You straighten the stem but the wheels are not straight so you constantly need to make corrections. The remedy is simple loosen the bolts that clamp the stem to the steerer, realign the front wheel and stem, and retighten the bolts.
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Old 07-24-07, 09:59 AM   #3
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Another possibility is the rear wheel is out of dish significantly and does not track well with the front wheel due to it being off center in the frame.
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Old 07-24-07, 10:03 AM   #4
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Ahh, what you must mean to say is that your bike handles almost telepathically, and if you even think or give a subtle hint that you want to change direction, it responds enthusiastically!

Or, maybe it's just a bit twitchy. It's a combination of your center of gravity, how much you move your body/arms around when you pedal, and most importantly the geometry of how the bike is made.

Note that speed can definitely have affect how it feels, and a bike that's squirrelly at slow speeds may be stable at high speeds. Some "stable" (or "ponderous, unresponsive" depending on your preferences) bikes get soo stable at speed that adjusting your line through a corner can be more difficult than it needs to be.

Anyhows, reams have been written about handling and bike geometry. Without buying a new bike or fork, try 1: pedalling smoothly without pulling really hard on the bars or swaying your body all over.
2: sometimes a longer stem or wider bars will help(of course these may make you less confortable for other reasons, so change with caution).

Is this the same bike you rode on the tour? Not that it matters to the Bianchi, just curious.
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Old 07-24-07, 10:23 AM   #5
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The first thing to check is the headset compression. Hold the front brake tight and rock the bike fore and aft. Watch for slack (play) between the fork crown and the head tube, there should be none. If there is then the headset bearings should be greased and the headset pre-load should be reset.

At rest when you turn the fork and front wheel the motion should be smooth and not wobbly. If your bike feels less stable than previously the difference may be due to looseness in the headset.

The reason a bicycle continues in a straight line when hands are removed is steering trail. Trail is a function of head tube angle and fork rake offset. Modern racing style bicycles have less trail than touring bikes and most older racing bikes. The only way to change a bike's trail is by changing the fork. Changing to a fork with less offset or a longer fork increases trail. Increasing the trail will increase the bike's tendency to continue in a straight line and help it to feel more stable. Decreasing trail will help the bike change directions more quickly.

For instuctional help about adjusting or maintaining your headset go to http://www.sheldonbrown.com and http://www.parktool.com. And of course there are maintenance books available. To learn more about steering trail surf the net. FWIW here is a rake and trail calculator: http://www.kreuzotter.de/english/elenk.htm

Al
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Old 07-24-07, 10:24 AM   #6
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If you're headset's loosened up a little, maybe that could be a cause. Also front hub cones - maybe your QR skewer isn't tight enough and there's a little sideways play in the wheel at the rim?

Edit: Doh. Al beat me to it.
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Old 07-24-07, 04:39 PM   #7
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Originally Posted by tellyho View Post
If you're headset's loosened up a little, maybe that could be a cause.
More likely it's a too tight headset. That'll cause the exact condition that the OP was complaining about.
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Old 07-24-07, 08:14 PM   #8
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More likely it's a too tight headset. That'll cause the exact condition that the OP was complaining about.
I agree, too tight would also explain the problem.
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Old 07-24-07, 08:40 PM   #9
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hi all,

i agree, the headset would be the first place i'd look. i finished my build of my fondriest status with an integrated headset. i had the same type of symptom on my first ride - twitchy steering. i gave the bike a good look-over and saw that the headset cap didn't look in line with the top of the head tube. i disassebled the headset and reset it making sure everything lined up correctly. it now rides as straight and smooth as ever. we're both very happy.

have fun,
aaron
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Old 07-25-07, 07:05 AM   #10
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Quote:
Originally Posted by Al1943 View Post
The first thing to check is the headset
That would be where I would start also, Al.

... Brad
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