Author Topic: general advice on making a tour happen  (Read 9442 times)

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Offline John Nelson

Re: general advice on making a tour happen
« Reply #15 on: July 03, 2014, 10:21:01 am »
Wow, JD, I think I'd carefully inspect your frame for cracks. At any rate, your old 520 is quite different than a 520 of today.

Offline paddleboy17

Re: general advice on making a tour happen
« Reply #16 on: July 03, 2014, 12:57:14 pm »
I think shimmy is a common problem in store bought touring bikes.  If you read the fine print, they are called lite touring bikes.  Some people can get away with putting panniers on them, and some can't.  Lite touring bikes may have the mount points, but they are not really designed to take panniers front and rear.  I had a Bianchi Volpe that wiggled like an exotic dancer, and that is why I spent the big bucks on a Waterford heavy touring bike.   My base pannier pack is 15 pounds each (4X15, so 60 total), so I don't think I travel overly heavy. They do not sell ready made heavy touring bikes in bike store, although I hear good things about Long Haul Truckers.

My Waterford will flex but it immediately dampens out the vibrations.  This is what generally makes it a rock solid ride.  Once had the front wheel not fully seated, and the Waterford shimmied like my old Bianchi.  Once I re-seated the wheel, the Waterford was back to being rock solid again.

This summer I am taking a tour and I am not taking my Waterford.  I have been modifying an old steel KONA mountain bike that belonged to one of my kids.  The KONA got drop handle bars, bar end shifters, and brake hoods.  I also but one of the Schwalbe Marathon tire variants on, maybe 26x1.5.  The KONA is not as stiff as my Waterford, but it is a lot stiffer than my Bianchi was.  I had problems getting a front rack that worked but I finally ended up with a Minoura steel rack.  The Minoura clamps to the brake boss and the axel.  The KONA fork is rigid steel, but shaped like a suspension fork and has been a bear to fit a rack to.

You might try a better front rack as I believe that is where a lot of shimmy dynamics start.
« Last Edit: July 03, 2014, 01:04:43 pm by paddleboy17 »
Danno

Offline JDFlood

Re: general advice on making a tour happen
« Reply #17 on: July 03, 2014, 01:07:41 pm »
Jobst Brandt has this to say about shimmy: "Bicycle shimmy is the lateral oscillation of the head tube about the road contact point of the front wheel and depends largely on frame geometry and the elasticity of the top and down tubes. It is driven by gyroscopic forces of the front wheel, making it largely speed dependent. It cannot be fixed by adjustments because it is inherent to the geometry and elasticity of the bicycle frame. The longer the frame and the higher the saddle, the greater the tendency to shimmy, other things being equal. Weight distribution also has no effect on shimmy although where that weight contacts the frame does. Bicycle shimmy is unchanged when riding no-hands, whether leaning forward or backward." Complete article at http://www.sheldonbrown.com/brandt/shimmy.html.
I watched a friend almost go down two days ago during a shimmy at 35 mph. He stopped it by grabbing the top tube with both knees. Like JDF he was a tall guy with a big bike (steel).


EXACTLY!

Offline JDFlood

Re: general advice on making a tour happen
« Reply #18 on: July 03, 2014, 01:12:10 pm »
Wow, JD, I think I'd carefully inspect your frame for cracks. At any rate, your old 520 is quite different than a 520 of today.

No cracks, this happened when new. Although, they have changed the geometry since I bought the bike, maybe they beefed it up. But I can make it happen on any of my bikes by overloading... ok, I have not been able to make it happen on my Independent Fabrication's Independent (Fully Loaded Touring bike), but I am sure with a lot of bricks I could. As I say, this is way more common than people think.