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I have a Jamis TAXI beach cruiser needing repair. Part of the bracket that is welded for holding the seat post clamp in place has come loose. The frame says T6 6061 aluminum.

I am having trouble finding anyone to weld the piece back on. Can it be repaired without welding? How about grinding the other half of the clamp off and using a new clamp that goes around the tube (OD 31mm+)? How about putting a bolt through the tube for a fixed position (would this weaken the tube)?

enter image description here

Pictures: https://photos.app.goo.gl/2FWGkogtMTbUZkU98

Update: I followed the suggestions and am very happy with the result. Sorry for being slow to respond. seat post with old clamp removed

new post clamp

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    Use a new collar, cut then grind off the excess, careful not to over heat the tube. Do not weld, do not drill and use a bolt.
    – mattnz
    Commented May 17, 2021 at 0:33
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    @mattnz that's an answer, and I agree with your suggested plan.
    – Criggie ♦
    Commented May 17, 2021 at 4:24
  • What worries me more is that bit that has left this gap in the seat-tube where the eyelet has broken away. I'd try to fill it up with some epoxy or similar to take the pressure of the collar.
    – Carel
    Commented May 17, 2021 at 19:25
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    @MaplePanda : the hollow-out left of the slot where the eyelet for the bolt has broken off.
    – Carel
    Commented May 19, 2021 at 6:28
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    @mattnz Thank you for the help! I have done what you suggested, and updated the photo album. Currently waiting for the new collar to arrive.
    – Old Grouch
    Commented May 19, 2021 at 16:07

1 Answer 1

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It is aluminium, it is a material that do not like welding, even less drilling through it.

In my opinion, you are left with one reasonable option only, as mentioned by @mattnz, remove the other half of the bolt clamp and then use a new clamp.

Please use the longest seat post you can find, to avoid stressing the top part of the seat tube. Given the failure you had and the laid back posture on a cruiser bike, it may be helpful to place the new clamp with the bolt in the front, not on the back.

You have also a crazy option : banana seat, as explained in this video from Youtube.com

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  • For others' reference, the OP said the outer diameter was about 31mm. You need to get a seat clamp with the correct diameter. I would guess the OP really meant 30.8? Although I think 31.8mm is also a potential outer diameter for seat tubes. In practice, get a pair of calipers and measure, or ask a bike store.
    – Weiwen Ng
    Commented Sep 17 at 22:37

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