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RADBMX.CO.UK  |  Technical & Reference Section  |  Tech and Restoration  |  Bent seat tube
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Author Topic: Bent seat tube  (Read 274 times)

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Offline ammacopij72

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Bent seat tube
« on: July 08, 2018, 04:04 PM »
Just noticed I might have a bit of a disaster here, can't get the seatpost into the tube as there is a slight bend/kink in it. Any ideas on how to resolve this without destroying the (new) powder coat lads??  "help" "help"

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Offline oldschoolace

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Re: Bent seat tube
« Reply #1 on: July 08, 2018, 04:15 PM »
 difficult to put right.  Easiest option is to find a slightly narrower post( they do vary in diameter from make to make)  and live with it. Without cutting it out and fitting a new mast all I can think of is a well greased post knocked down which may straighten it a bit.... Or get stuck :/
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Offline ammacopij72

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Re: Bent seat tube
« Reply #2 on: July 08, 2018, 05:22 PM »
difficult to put right.  Easiest option is to find a slightly narrower post( they do vary in diameter from make to make)  and live with it. Without cutting it out and fitting a new mast all I can think of is a well greased post knocked down which may straighten it a bit.... Or get stuck :/

Cheers fella, can't believe I didn't see it before getting it powdered.. The problem is compounded by the fact that I've had the layback powdered too..

Might try running some sandpaper down the tube to see if it makes it any better and then try the grease and rubber mallet technique, fingers crossed!!
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Online Jon1971

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Re: Bent seat tube
« Reply #3 on: July 08, 2018, 05:43 PM »
difficult to put right.  Easiest option is to find a slightly narrower post( they do vary in diameter from make to make)  and live with it. Without cutting it out and fitting a new mast all I can think of is a well greased post knocked down which may straighten it a bit.... Or get stuck :/

Cheers fella, can't believe I didn't see it before getting it powdered.. The problem is compounded by the fact that I've had the layback powdered too..

Might try running some sandpaper down the tube to see if it makes it any better and then try the grease and rubber mallet technique, fingers crossed!!

I would try that first mate, fine sand paper or wire wool then like you say grease and a rubber mallet. Should sort it :daumenhoch:
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Offline Taipan

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Re: Bent seat tube
« Reply #4 on: July 08, 2018, 06:37 PM »
I had an old seatpost taken off a GT pro stickered up as a GT post,I stripped it of its powdercoat it didnt have a GT stamp? but the post is deffo thinner (still strong) than the ones available today,so bitd they must have been a lot thinner,so look around for an older post maybe?
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Offline oldschoolace

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Re: Bent seat tube
« Reply #5 on: July 08, 2018, 06:59 PM »
I have a couple of these



https://m.ebay.co.uk/itm/19mm-To-62mm-Car-Engine-Flexible-Shaft-Brake-Cylinder-Hone-Bore-Honing-Tool-2756-/263481728748?nav=SEARCH

The stones are too fine a grit to do anything but polish tubing but I fook them off and glue small strips of emery cloth to the 3 feet.
Work great on seat masts, quick, easy and reach further than you would ever put a post  :daumenhoch:
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Offline ammacopij72

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Re: Bent seat tube
« Reply #6 on: July 08, 2018, 08:06 PM »
I have a couple of these



https://m.ebay.co.uk/itm/19mm-To-62mm-Car-Engine-Flexible-Shaft-Brake-Cylinder-Hone-Bore-Honing-Tool-2756-/263481728748?nav=SEARCH

The stones are too fine a grit to do anything but polish tubing but I fook them off and glue small strips of emery cloth to the 3 feet.
Work great on seat masts, quick, easy and reach further than you would ever put a post  :daumenhoch:

Fantastic mate, thanks for that!  :daumenhoch:
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Offline deeman

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Re: Bent seat tube
« Reply #7 on: July 09, 2018, 08:12 AM »
What a fooker! I had the same on a RL-20 once.....it's nigh on impossible to spot! I ruined 1 seatpost before I realised what was up. I resorted to grease and mallet technique to get another one in. It never went down as far as I would have liked.....Hope you sort it somehow  :daumenhoch:
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Offline Retrodan72

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Re: Bent seat tube
« Reply #8 on: July 09, 2018, 08:40 AM »
Gutted for you Neil especially as you’ve taken so much time to make sure every detail is spot on with this build, but like Damo said, these things are virtually impossible to spot.

On the plus side, you’re an experienced bike builder and you’ve put it out there on  :radbmxsmilie: where others can offer advice from their experiences.

I think you’ll know what to do without damaging the powder.

Good luck fella
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Offline ammacopij72

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Re: Bent seat tube
« Reply #9 on: July 09, 2018, 08:54 AM »
Cheers Lads, fingers crossed it turns out okay.....  :-\ "nono"
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Offline ammacopij72

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Re: Bent seat tube
« Reply #10 on: July 09, 2018, 12:09 PM »
I have a couple of these



https://m.ebay.co.uk/itm/19mm-To-62mm-Car-Engine-Flexible-Shaft-Brake-Cylinder-Hone-Bore-Honing-Tool-2756-/263481728748?nav=SEARCH

The stones are too fine a grit to do anything but polish tubing but I fook them off and glue small strips of emery cloth to the 3 feet.
Work great on seat masts, quick, easy and reach further than you would ever put a post  :daumenhoch:


Any specific grade of emery cloth mate?
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Offline oldschoolace

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Re: Bent seat tube
« Reply #11 on: July 09, 2018, 12:19 PM »
Depends on whats down there. A phone torch is handy to shine down the mast. I have used 120 grit in the past when i had a stuck glasfibre post but would say 180-240 would be a good starting point. Aim to go down the grades so the mast is nice and smooth then you are done
I used a 90 second araldite to bond the emery cloth, holds it well enough but is brittle enough to get off when you are ready for the next grade  :daumenhoch:

Will bung a pic of mine up
Sixteen thirty-two. What is that? A year?   No, it's your top score on Pole Position.


Offline oldschoolace

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Re: Bent seat tube
« Reply #12 on: July 09, 2018, 12:45 PM »
Here you go  :daumenhoch:


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Offline ammacopij72

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Re: Bent seat tube
« Reply #13 on: July 09, 2018, 12:55 PM »
 :daumenhoch:
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Offline WINI

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Re: Bent seat tube
« Reply #14 on: July 09, 2018, 01:13 PM »
Wait till you see my snapped off renthal in an early unstamped GT performer frame  :10_2_12:
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Offline ammacopij72

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Re: Bent seat tube
« Reply #15 on: July 10, 2018, 11:15 AM »
Wait till you see my snapped off renthal in an early unstamped GT performer frame  :10_2_12:

 :crybaby: :crybaby: "nono" "nono"
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Offline chubby

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Re: Bent seat tube
« Reply #16 on: July 12, 2018, 11:08 AM »
That snake post fitted fine, didn't notice a bend in there either Neil ???

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Offline MartyC

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Re: Bent seat tube
« Reply #17 on: July 12, 2018, 01:05 PM »
Wait till you see my snapped off renthal in an early unstamped GT performer frame  :10_2_12:

A strong mix of caustic soda will have that out in about a week!


Better to crash and burn than fade away

Offline ammacopij72

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Re: Bent seat tube
« Reply #18 on: July 12, 2018, 04:14 PM »
That snake post fitted fine, didn't notice a bend in there either Neil ???

Sent from my HTC One M9 using Tapatalk

That's cos the snake post is bent too mate!  :'(

Fingers crossed Clint's idea will sort it out...  "help"
« Last Edit: July 12, 2018, 04:16 PM by ammacopij72 »
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Offline chubby

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Re: Bent seat tube
« Reply #19 on: July 12, 2018, 04:44 PM »
Ahhhhh fook
Honestly didn't notice either were bent ..

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Offline ammacopij72

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Re: Bent seat tube
« Reply #20 on: July 13, 2018, 07:57 AM »
Ahhhhh fook
Honestly didn't notice either were bent ..

Sent from my HTC One M9 using Tapatalk

not your fault mate, only a slight kink in the seat tube and never intended to use the snake post so didnt look at it that closely. I think the issue is being compounded by the new nitto seat post being powdered too...

Fingers crossed it's all okay after a bit of fettling  :daumenhoch:
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Offline ammacopij72

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Re: Bent seat tube
« Reply #21 on: July 17, 2018, 06:33 PM »
Gonna make an attempt on the seatpost tomorrow, but have now found another problem when putting the stem in. It looks like the casting on the inside of the fork is not very round and the stem post just jams up about 40mm from where it needs to be...  :crybaby: Thumbs down

I'm thinking maybe reaming out the forks might sort it?

Just starting to piss me off now as was hoping to have this done for mk and I'm running out of weekends.... :tickedoff:
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Offline oldschoolace

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Re: Bent seat tube
« Reply #22 on: July 17, 2018, 09:16 PM »
Had the same problem when I was trying to install a linear bearing in a fork once to run a woody style roller cam. Ended up buying a blacksmiths bit with a reduced shank (about 7 quid)
Ran it in a corded drill on half speed with the forks in a vice. Went really slow at it so it didn't grab and it worked a treat if a little scary  :LolLolLolLol:
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