Seat tube fix suggestions

[jointhedotz]

Hi All,

I'm in a bit of a pickle with a frame I'm currently trying to build up so thought I'd ask for some help in here.

I picked up a 95 Fisher Cronus for little enough money that I won't cry if it's scrap BUT it's a nice enough frame to warrant trying to repair imo. The issue I have is that a former owner has added a split to the top of the seat tube and bent it in to fit a thinner seat post (an ugly cheap suspension jobby at that!)

So far I've tried levering it apart from the splits with screwdrivers, using the smaller post to try and push it out from inside (if you know what I mean?).

So, how would you approach the problem?

Pics below:

 

[02gf74]

My approach would be to find post of correct diameter file end to o a short taper and slowly tap it in to splay the tube to original size.

Drill hole on post to tavlke a bar so it can be rotated. Doing it slowly and twisting post to make sure it doesnt get stuck may work.

 

[gradeAfailure]

Re:

^^^
That, then have the added slot carefully welded up, re-ream the seat tube, dress back the weld and touch up the paint. Job done

 

[focomat 1c]

Find out the correct seat tube size, and carefully measure the existing size at 90 degrees to the bike centre line ( the tube looks to be slightly oval )
Get the biggest hex bolt you have and cut it to length to just fit inside the tube. Put a nyloc nut fully onto the bolt, insert into the tube and undo the nut,
splaying the tube back to its correct dimensions. It would be preferable to slightly overdo the splay, as the welding will almost certainly reduce the diameter of the tube again when it cools. Ideally get it welded by the TIG process and put some small wedges in the top of the 'splits'. Weld from
the bottom up to the wedges, allow to cool, remove wedges and complete weld. Ream tube etc

 

[jointhedotz]

Some food for thought there, thanks guys. Will try and have a look over the weekend and report back

 

[legrandefromage]

My approach would be to find post of correct diameter file end to o a short taper and slowly tap it in to splay the tube to original size.

Drill hole on post to tavlke (???) a bar so it can be rotated. Doing it slowly and twisting post to make sure it doesnt get stuck may work.

What he said.

Proper fit post will engage the whole seattube so there little chance of a post rocking back & forth around the thin clamp area.

 

[jointhedotz]

02gf74, When you say file the seatpost to a taper......could you clarify slightly? Do you mean on the side that'll go into 'the dodgy bit' or the whole circumference of the post?

Cheers

 

[mattb]

Re:

Use an adjustable spanner to gently pry the tube back into shape.I did this on an alpinestars al-mega seat tube that got slightly damaged in the post

 

[02gf74]

Re:

Imagine pencil that has been sharpened.

So do same to post so there is tapered end. The idea is that diameter is smaller so will go past the splayed in part and will push it out to original diameter as the post goes in.

Thats the theory and should work but will be quite hard work. Do the pushing in tiny steps making sure post is free to turn, i can forsee post getting stuck so it will go neither in no out.

 

[jointhedotz]

Well, I filed the side that was uneven down a little and managed to get the post in fully but it doesn't appear to have reshaped the tube. The post got a lot of scoring on removal as well but I suspect I should have used grease, slight oversight....

Still, frame is useable now so on with the build, will just use that post and not adjust the height of the seat once fitted. She'll never be a garage queen anyway

Thanks for all the advice folks