STBO Stirrup: the Hornets' Nest

Bike from the Dead · Sep 29, 2024

I picked up a decent 2x4 and some additional hardware so I can straighten out this frame over the weekend.

I also ran by storage earlier today to pick up a frame to practice this frame-adjusting technique on before I try it on Stirrup. I got this 24" AMF step-thru for free last year, and it just became a parts donor for some other AMF bikes I'm working on. It's down to just the bare frame now, and it's not one I plan to rebuild anytime soon, if ever.

I also grabbed two 24" rear wheels, one with a coaster brake, and one with a cassette, so I can practice adjusting the stays, not just for alignment and straightening, but also to expand or narrow the space for either kind of wheel. Hopefully I'll be able to try this technique out tomorrow morning.

Bike from the Dead · Oct 3, 2024

Okay, I've hit a snag with this project. Yesterday, I tried to practice cold-setting on this frame, but no matter how much pressure I put on my plank of wood, I just could not get this frame to open up beyond my initial ~11.5cm measurement. I tired adjusting the frame on the floor and on my work stand, but it didn't matter either way. I know the seat stays on this frame are a little thicker than on Stirrup, but I would think that doesn't matter. So... is this frame just built different, or do I just have chicken arms? Honestly, I'm not that strong, but I would think that I could adjust this frame with enough leverage. Any ideas as to what I can do?

Wildcat · Oct 3, 2024

They spring right back where they were originally because the tubing is strong. I would take the 2 x 4 and slide it up to where the tire sits then hammer it foward, which widens the dropouts considerably.
On that frame I would line up the 2 x 4 between the seat stays and chain stays at the same time and widen them both together that way. I would widen them well past the width I needed then remove the 2 x 4 to see how much width it still had. Once it's wide enough, then the dropouts need to be lined up as they will point outwards.

Bike from the Dead · Oct 3, 2024

Wildcat said:
They spring right back where they were originally because the tubing is strong. I would take the 2 x 4 and slide it up to where the tire sits then hammer it foward, which widens the dropouts considerably.
On that frame I would line up the 2 x 4 between the seat stays and chain stays at the same time and widen them both together that way. I would widen them well past the width I needed then remove the 2 x 4 to see how much width it still had. Once it's wide enough, then the dropouts need to be lined up as they will point outwards.

View attachment 280926

You wouldn't happen to have a more visual example of how to do what you described, would you? I'm afraid I don't understand what you mean.

Wildcat · Oct 3, 2024

Put the 2 x 4 between the stays and force it forward, opening up the stays.

Wildcat · Oct 3, 2024

I also used a wide mallet and hammered it up into the stays and did the same thing, then clamped the dropouts to get them straight.

Bike from the Dead · Oct 3, 2024

Wildcat said:
View attachment 280940

Put the 2 x 4 between the stays and force it forward, opening up the stays.

Wildcat said:
I also used a wide mallet and hammered it up into the stays and did the same thing, then clamped the dropouts to get them straight.

View attachment 280941

Oooooh. Okay, I think I get it now. Thanks! I'll see if that works for me.

Pondo · Oct 4, 2024

Another thing to try would be to use the 2x4 the way you originally did but put a block of wood or something between the 2x4 and the seat tube. You might not have enough room to push the 2x4 down the way you have it sitting directly on the seat tube. You may have to use your body weight a bit on the end of the 2x4 as well. I would recommend putting a block under the seat tube near the top to support it at about a similar height to the bottom bracket so the seat tube will be less likely to twist.

Pondo · Oct 4, 2024

This is how I like to set mine up. You can see I have a 2x under the bottom bracket shell and a 4x under the top of the seat post tube for support. Then position the long 2x4 to where it's just under the dropout for max leverage.

Before I make any adjustments I measure the distance between the dropouts. Then I kind of bounce on the end of the 2x4, in a controlled manner, a few times and measure again. When I've got it spread half way to the new dimension I flip the frame over and do the other side. You might do the string to check for alignment 1st as one side may need more adjusting than the other.

If you need to bring it back in a little you can just set up your lever under the bottom dropout and use the same process.

You don't want to go back and forth too much like I did with this frame. On already weak tubing it can make it weaker. I wasn't worried about it on this old frame. It's a 24" and I plan to replace the rear triangle with a 26" at some point. I've had to do some rear triangle adjusting on most of my build off frames so far and this method works pretty well for me.

Bike from the Dead · Oct 4, 2024

Pondo said:
This is how I like to set mine up. You can see I have a 2x under the bottom bracket shell and a 4x under the top of the seat post tube for support. Then position the long 2x4 to where it's just under the dropout for max leverage.
View attachment 280973

Before I make any adjustments I measure the distance between the dropouts. Then I kind of bounce on the end of the 2x4, in a controlled manner, a few times and measure again. When I've got it spread half way to the new dimension I flip the frame over and do the other side. You might do the string to check for alignment 1st as one side may need more adjusting than the other.

If you need to bring it back in a little you can just set up your lever under the bottom dropout and use the same process.
View attachment 280974

You don't want to go back and forth too much like I did with this frame. On already weak tubing it can make it weaker. I wasn't worried about it on this old frame. It's a 24" and I plan to replace the rear triangle with a 26" at some point. I've had to do some rear triangle adjusting on most of my build off frames so far and this method works pretty well for me.

That might work. When all else fails, make a bigger lever!

Bike from the Dead · Oct 10, 2024

I tried @Pondo's wood-stacking technique on my test frame yesterday, and I finally managed to open up the rear triangle a bit. And by a bit, I mean I opened it up by almost exactly 2.5cm... in one move. I spaced the dropouts wide enough to just squeeze this 6-speed wheel inside, but I also misaligned the frame enough to see with the naked eye. To be honest though, I had to press both knees down on my lever just to make anything happen; this thing was stubborn! That said, I don't think I cracked the frame anywhere. Now I need to practice fixing and aligning this frame...

STBO Stirrup: the Hornets' Nest

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