How to alighn a frame with out a table and not make things worse?
06-14-23, 08:34 AM
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How to align a frame with out a table and not make things worse?
I've got a nicer for me bike that needs some rear triangle adjustment. I figured I'd get it close enough for now with string and a Park gauge.
Google took me to an RJ the bike guy youtube video demonstrating the Sheldon 2x4 method and it looked like the seat tube was bowing significantly when force was applied.
The other recommended method is to clamp the bottom bracket in a vice with sacrificial cups screwed in and push and pull the dropouts. this seams like the bending change will be primarily in the chain stays, which will have to be over bent to pull the seat stays over into alignment. That seems like it would be adding unnecessary stress to the structure.
What I'm thinking of doing is clamping the bottom bracket in a vice, padding the seat tube with a hose and attaching a full leangth piece of angle iron on top to act as the fulcrum for the 2x4. I would still be levering off the seat and head tubes, but I think the seat tube would be protected from bending and the support from the bottom bracket would make the adjustment more controllable.
Anyone think that's worth doing verses just clamping the bottom bracket? Or am I overthinking how to move the triangle over a couple mm to get the wheel centered and the bike rideable.?
Google took me to an RJ the bike guy youtube video demonstrating the Sheldon 2x4 method and it looked like the seat tube was bowing significantly when force was applied.
The other recommended method is to clamp the bottom bracket in a vice with sacrificial cups screwed in and push and pull the dropouts. this seams like the bending change will be primarily in the chain stays, which will have to be over bent to pull the seat stays over into alignment. That seems like it would be adding unnecessary stress to the structure.
What I'm thinking of doing is clamping the bottom bracket in a vice, padding the seat tube with a hose and attaching a full leangth piece of angle iron on top to act as the fulcrum for the 2x4. I would still be levering off the seat and head tubes, but I think the seat tube would be protected from bending and the support from the bottom bracket would make the adjustment more controllable.
Anyone think that's worth doing verses just clamping the bottom bracket? Or am I overthinking how to move the triangle over a couple mm to get the wheel centered and the bike rideable.?
Last edited by bark_eater; 06-14-23 at 02:47 PM.
06-14-23, 11:16 AM
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My general statement is moving the dropouts will result in the same amount of stress no matter how you do it. You just don't want to apply any point loads. If I understand your proposed method, it sounds pretty good. I have used the "put the frame on a rug and yank the dropouts one at a time while standing on the seat tube" method. I probably supported the seat tube a little or did it at the top of the steps, I don't remember. Worked just fine. I forgot I had done that until just now. I have more controllable methods now.
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06-16-23, 07:45 PM
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I've got a nicer for me bike that needs some rear triangle adjustment. I figured I'd get it close enough for now with string and a Park gauge.
Google took me to an RJ the bike guy youtube video demonstrating the Sheldon 2x4 method and it looked like the seat tube was bowing significantly when force was applied.
The other recommended method is to clamp the bottom bracket in a vice with sacrificial cups screwed in and push and pull the dropouts. this seams like the bending change will be primarily in the chain stays, which will have to be over bent to pull the seat stays over into alignment. That seems like it would be adding unnecessary stress to the structure.
What I'm thinking of doing is clamping the bottom bracket in a vice, padding the seat tube with a hose and attaching a full leangth piece of angle iron on top to act as the fulcrum for the 2x4. I would still be levering off the seat and head tubes, but I think the seat tube would be protected from bending and the support from the bottom bracket would make the adjustment more controllable.
Anyone think that's worth doing verses just clamping the bottom bracket? Or am I overthinking how to move the triangle over a couple mm to get the wheel centered and the bike rideable.?
Google took me to an RJ the bike guy youtube video demonstrating the Sheldon 2x4 method and it looked like the seat tube was bowing significantly when force was applied.
The other recommended method is to clamp the bottom bracket in a vice with sacrificial cups screwed in and push and pull the dropouts. this seams like the bending change will be primarily in the chain stays, which will have to be over bent to pull the seat stays over into alignment. That seems like it would be adding unnecessary stress to the structure.
What I'm thinking of doing is clamping the bottom bracket in a vice, padding the seat tube with a hose and attaching a full leangth piece of angle iron on top to act as the fulcrum for the 2x4. I would still be levering off the seat and head tubes, but I think the seat tube would be protected from bending and the support from the bottom bracket would make the adjustment more controllable.
Anyone think that's worth doing verses just clamping the bottom bracket? Or am I overthinking how to move the triangle over a couple mm to get the wheel centered and the bike rideable.?
While I do face and chase the shell before alignment I don't use cups during. If I'm clamping in a bench vise I'll pad the faces with small 1/4" thick steel plates. Andy
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