Expanding a Seat Tube

[blown240]

I had the idea of using an exhaust tubing expander to get a 31.6 seat post to fit in my new Beast project. I realize this is probably a stupid idea, but I wonder if it would work? I am going to have the seat stays off anyway, and its just mild steel so I could weld up any cracks....

I would have to expand it about 3mm

 

[dracothered]

I think you would be better off with a seat post shim or bigger diameter seat post.

 

[blown240]

I guess I worded my post wrong. I want to expand the frame to fit a larger post. The frame is 28.6 and I have a 31.6 dropper post I want to use.

 

[RustySprockets]

No, you worded it right, but doctoring a seat tube like that isn't something I'd recommend. I think you're asking for trouble. BTW, the smallest expander I could find was still TOO BIG to fit inside your original seat tube. Do you have a micro-sized one?

 

[blown240]

Harbor Freight has an expander that goes down to 1-1/8. But yeah, its probably asking for trouble...

http://www.harborfreight.com/tail-pipe-expander-69550.html

 

[SSG]

MY $0.02, buy or fabricate the correct seat post and don't wreck your frame. I'm pretty sure your seat post wont expand as easily as thin wall exhaust tubing.

 

[Sinner4]

I have take older bikes where the seat tube will only work with 22.2, replaced the whole seat tube where a modern 26.2 will fit. 1" EMT. If your Beast dosen't mind. Cut out the old and weld in the new seat tube that will fit your large seat post.

 

[kingfish254]

I have take older bikes where the seat tube will only work with 22.2, replaced the whole seat tube where a modern 26.2 will fit. 1" EMT. If your Beast dosen't mind. Cut out the old and weld in the new seat tube that will fit your large seat post.

This would be much safer.

 

[Sinner4]

Here ya go, the expanded view's....
1 inch emt for that 26.2 post and the second, a donor huffy for the tube.

 

[blown240]

I haven't be able to find a steel tube with a 31.6 ID.

Any ideas?

 

[dracothered]

Why not just get a different seat post?

 

[blown240]

Because I have a nice kind shock i950 dropper post in 31.6. But if I can't find the right tubing I will have to get another post.

 

[SSG]

Would this work? http://www.onlinemetals.com/merchant.cfm?pid=15341&step=4&showunits=inches&id=250&top_cat=197
also this if you want fancy http://www.cycle-frames.com/bicycle-frame-tubing/COLUMBUS-LIFE-SEAT-TUBE-31.7-X-8-5.html
Finding the seat lug that matches your seat tube and your top tube might be the tough part.

 

[blown240]

Thanks for the link!