Old 07-01-14, 11:01 AM
  #23  
thebulls
Senior Member
 
Join Date: Dec 2003
Posts: 1,005

Bikes: SOMA Grand Randonneur, Gunnar Sport converted to 650B, Rivendell Rambouillet, '82 Trek 728, '84 Trek 610, '85 Trek 500, C'Dale F600, Burley Duet, Lotus Legend

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by jeirvine View Post
Yup. Here:
http://www.bikeforums.net/long-dista...l#post15322546

"AVOID '81 Trek 610/613/614 and '82 Trek 613/614 because the Ishiwata CCL fork crown does not have a proper lug point so it is a failure vector."

Edit: the knowledge base here never ceases to amaze me. Thanks.
I think the bike in the OP's photo is an '81 600 series Trek -- the '82's and '83's were not made in that color, and the headtubes were painted a contrasting color, which this isn't.

The failure mode looks exactly the same as my '82 Trek 614.

My statement about "does not have a proper lug point so it is a failure vector." is a little cryptic. If you look on the inside of the leg on any well-made bicycle, the fork crown lug either has a lug point that extends down the leg, or is at least semi-circular. That's to prevent a stress-riser at the fork crown. On those Ishiwata CCL semi-sloping fork crowns, the lug is perfectly horizontal on the inside of the fork leg. That creates a stress riser, which results in more metal fatigue at that point, increasing the likelihood of eventual failure. That's what it looks like on the left leg of the bicycle in the OP's photo--horizontal tear in the leg. We can't see the inside of the right leg, but I bet it looks the same.

On my Trek 614, I was riding to work and the front end felt like it was more "flexy" than usual when I stood on a hill, and I found the crack before it caused a problem. I rode home and took the front wheel off and discovered the crack. I tore one of the fork legs off by hand but left the other there so you can see how the crack developed. You can see that there is some rusting inside the leg, but the rust is not a contributing factor, it's just surface rust. The crack had developed for some time, as you can see in DSCN1251 to the inside-rear of the torn-off right leg. But the metal is still bright in the front of the crack and all around the outside of the leg.


Attached Images
File Type: jpg
DSCN1251.jpg (106.8 KB, 995 views)
File Type: jpg
DSCN1250.jpg (95.4 KB, 957 views)
thebulls is offline