Cure For Shimmy? Need Bearing Headset?
09-01-12, 10:08 PM
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Cure For Shimmy? Need Bearing Headset?
My 1982 Peugeot PSVN has a bad front end shimmy at about 15-20 mph. Coasting or pedaling. A knee on the top tube stops it but it is hard to pedal that way.
I switched to a different wheelset (freshly built, true) and still had the shimmy. I've since had a mishap and the front wheel is a bit de-trued, and guess what, I still have the shimmy. I'll true the wheel but am not hopeful that the shimmy will go away.
I've read that roller bearing headsets can fix shimmy. Why is this? Is it worth trying?
58 cm, 700C, 185 lb rider. No fenders or other stuff hung on the front end.
I switched to a different wheelset (freshly built, true) and still had the shimmy. I've since had a mishap and the front wheel is a bit de-trued, and guess what, I still have the shimmy. I'll true the wheel but am not hopeful that the shimmy will go away.
I've read that roller bearing headsets can fix shimmy. Why is this? Is it worth trying?
58 cm, 700C, 185 lb rider. No fenders or other stuff hung on the front end.
09-01-12, 10:33 PM
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maybe a bent fork/frame??
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2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
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2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
2000 litespeed Unicoi Ti, XTR,XT, Campy crank, time atac, carbon forks
09-01-12, 11:20 PM
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It tracks straight, hands-off, and I've not found any misalignment. But I will check again.
I had been thinking the new wheelset would cure the shimmy.
I had been thinking the new wheelset would cure the shimmy.
09-01-12, 11:55 PM
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It maybe a bandaid.. maybe if you add front panniers Mass will dampen the situation..
fatter tires for bigger contact patch "pneumatic Trail"..
maybe ..
fatter tires for bigger contact patch "pneumatic Trail"..
maybe ..
09-02-12, 06:21 AM
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Google "bicycle shimmy" - all you want/need to know about causes and possible cures.
09-02-12, 06:54 AM
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What condition is the headset in? Is it worn, "indexed", too loose, too tight? Headsets are rarely the cause of shimmy but shimmy at 15-20 mph is pretty unusual as it is normally a higher speed problem.
In the past when "standard diameter" steel tubing was normal, larger frames were the ones prone to shimmy due to their inherent low rigidity and there were many reports of it from big riders. Now that "oversize" steel, aluminum, Ti and carbon frames are the norm, their greatly improved stiffness makes these reports much less common.
Your Peugeot certainly falls in the first catagory but the low speed of the onset makes me think there is another factor too.
In the past when "standard diameter" steel tubing was normal, larger frames were the ones prone to shimmy due to their inherent low rigidity and there were many reports of it from big riders. Now that "oversize" steel, aluminum, Ti and carbon frames are the norm, their greatly improved stiffness makes these reports much less common.
Your Peugeot certainly falls in the first catagory but the low speed of the onset makes me think there is another factor too.
09-02-12, 07:45 AM
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I had noticed a shimmy in one of my rides at similar speed. It was new (didn't shimmy before). I adjusted the headset (tightened out some looseness) and the shimmy went away. I wasn't expecting that outcome and was only adjusting the headset because it needed it.
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