Bending a seat post

Discussion in 'General Bike Discussion' started by photosbymark, Oct 9, 2010.

  1. photosbymark

    photosbymark New Member

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    Well I am stuck. I have Fuji Newest 3.0 that I simply don't fit. My knees are just too far forward to keep from causing knee pain and the saddle is all the way back. Its close. Pain doesn't show up till I ride several miles, but its always there.

    The bike new is about a $500-600 bike, but to get a new layback seat post I am into the bike another $100 150 to MAYBE work. Looked around and had a mountain bike with a 27.2 post with more of a setback and it was closer still, but just not enough.

    Now I found another 27.2 that looked so close, but again not close enough. Since its only a $25 post I wonder if there is a way to make my own layback seatpost. It wouldn't be the end of the world if it didn't work and damaged a $25 post so has anyone bent the post for a better fit. At 27.2 that's just a fraction over an inch so I wonder if something like a conduit bender could do the job or what tool I might need to bend it back another inch or two. Right now I have plenty of seat forward adjustment, so going a bit too far wouldn't be a problem. Way too far might be.
     
  2. worthlees

    worthlees Senior Member

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    Somewhere on another forum read an article & saw pics of a rider bending a post. Can't
    find the forum or article again. Remember though he had to heat his post and gently
    bend it about 30* bend to get what he needed . Checked fit ,etc. ,when satisfied he
    welded a small metal brace for safety on the inside bend. Hope this helps,will keep looking.
     

  3. DGM

    DGM New Member

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    I'd say don't do it.

    An aluminum post isn't designed to be bent. There's no way to know if you've cracked it while bending it. Leaving the opportunity for it to snap off while cruising along. The thought of a sharp jagged aluminum post around your bits is kinda scary.

    As for using conduit or other rando pipe, chances are it wont fit well. Seat posts come in sizes of very small increments. Most frames can only properly clamp the exact size (in this case 27.2mm) post they were designed for. One size up could become wedged into the frame, never to come out again. One size too small may not clamp tight enough, causing the post to move around, or the seat tube to become damaged.

    I would suggest either dealing with riding the wrong sized bike, and not burning time trying to make odd custom parts. Or ditch the incorrect size, and get the right one.

    Instead of spending your time and efforts trying to make this wrong sized bike fit, find a way to make a spare couple hundred bucks. Then sell your bike, combine the funds, buy something better.
     
  4. Industry_Hack

    Industry_Hack Total noob (& forum admin) Admin Staff Tavern Member

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    DGM, did you happen to notice the date of the original post? While your advice is certainly valid, the issue has probably been addressed.
     
  5. photosbymark

    photosbymark New Member

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    DGM Yes I considered those possibilities, but I had access to knowledge and equipment not available to many. I used a commercially available post to start. Even I wouldn't have tried with other types of pipe or tubing. My neighbor has basically a machine shop in his garage. (his shop is probably better equipped than some) I had access to a pipe bender that allowed bending without mangling the tubing. Had it been steel heating it would have also been a viable alternative. Did it compromise the strength? Maybe but very slightly if at all. Had the post been crushed during the bending, you bet your hind end it would be weakened. After it was bent, a VERY close inspection showed no signs of cracks. Yeah its possible, but I really don't think so. Though it could just snap, that would be far more likely with a CF (which then bending would not be an option anyway) than metal. Most metals will give some sort of warning prior to a total failure. It's far more likely to bend, and that I can feel. If it broke, my rear is far enough back that I would wind up on the rear rack, post likely between my legs. Granted the crash might make me quit laughing at the neighborhood kid that crashed a Stingray with the cool shift hand on the top tube. At least I don't think it would replicate a trip to the Drs. office either.

    I considered adding a brace, but the neighbor that has more experience with metal and machinery than most engineers felt it unnecessary. I rode it and it felt solid enough that I agreed. So far so good. Not a lot of miles o that bike since, but seems fine. Long term I am more worried about the seat post of the frame being an issue more than I am the seat post that I bent being an issue. Moving my weight back puts a different set of stresses in different ways than expected. Yet the way everything is locked in, I really don't think that will be a problem. It too should give some warning.

    Honestly I do appreciate the concern, and your post should remind us all to really think before we modify. I considered the risks and possible failures. Yet to update, the best I can say is so far so good, but I am watching it very closely. Yet still seems solid and all is well, but so far is still very much an operative part of the phrase.
     
  6. DGM

    DGM New Member

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    I keep forgetting to notice how slow this place seems to move.....
     
  7. DGM

    DGM New Member

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    sounds like you've got a good handle on things. Any pictures of the current setup? I'm curious.
     
  8. photosbymark

    photosbymark New Member

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    Nah but if you are curious, I'll go take some. The biggest pain was actually the slot for the saddle. Just bending the post back wasn't enough. Doing that left the point of the seat in a position no sane person would want to ride. That part of the post was solid aluminum though and extending the groove for the saddle adjustment was no big deal and the strength shouldn't be affected. It didn't take that much to make a big difference in saddle position. Got the weight back which I think makes the bike stop better, and it put my knees in the right position relative to the pedals. Longer cranks also might have worked, but that would have been probably half the cost of the bike. It also might not have worked and been out the cash and still have a bike that didn't work for me. The $20 seat post was certainly a practical alternative from a cost perspective.

    Yet like most things its a trade off. When I got the seat in the right position the handlebars were too far forward. I ended up rotating them back to get the balance I wanted between the weight of my hands and the weight on my butt for a fairly comfortable ride. It works, at least so far. Something might bend later, but so far so good. You won't see another one like this, and a better solution would have been to not buy and get a bigger frame. Yet I got the biggest frame available at the LBS, and it was so close to fitting problems didn't show till I started putting miles on it. The test ride felt great, it was just too short.

    I don't ride it that much, but don't get rid of it because the person that sold it to me is now a very close personal friend and it has a lot of meaning to me as more than a bike. It is still fun to take it out for a spin once in a while and though I still get some attention because of the seat post, its nothing like the attention I get on the recumbent.
     
  9. loiblb

    loiblb New Member

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    I have aThompson factory bent post on my Cannondale. It made the bike a little more of a better fit. It was not that easy to get my seat just in the sweet zone, but it worked. I think thay run around $80+-.