Old 09-13-12 | 01:30 PM
  #13  
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Andrew R Stewart
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Joined: Feb 2012
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From: Rochester, NY

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Not sure about trusting the charts for any one bike. I know of many small but real differences from claimed specs to the actual ones. Also if a tube has a ripple in it after an impact then the length on that part of the tube has changed. Unless you're saying that the tube stretched so the ripple could exist and the angle not change. Not likely, espically with the ripple on the underside of a tube is in the compression zone. I don't know of a typical head end impact that has a force acting on the frame which after compressing the fork rearwards then pulls it back out past the original point (remember springback). So my take is that if there's a ripple there's an angle change.

Now how much and how important (to the bike's handling0 is an angle change is a different story.

Lastly be careful how you measure a bike's geometry. It's easy to confuse center points, centerlines and whether the measurement is based on the two dimensional or the three dimensional. The below comment about wheelbase-chainstay=front center doesn't mention BB drop as an example. Andy.


Originally Posted by miamijim
I had a frameset with similar visible damage awhile back and the head tube angle measured with 'spec'. I dont know what the original angle was so I looked up what it might be by comparing various geometry table and what I measured was close enough not to bother tinkering with. Steel is unique in that it springs back a touch after an impact which expains why you'll see damage without a compromise in head tube angle.

Another way to check is to measure the wheelbase and chain stay lengths. A typical road race wheel base may bee 1005mm with chainstays of 400mm which means the distance from the BB center to fork ends would be 605mm.

go through a bunch of old frame geometry charts and calculate average dimensions of what similar frame sizes to your have and measure yours in comparison.
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