• 11-26-2012
    phoenixbikes
    Can I make my 27.2 titanium post fit my 27.0 frame ?
    I have an old 1993 Kona Explosif. It takes a 27.0 post, and finding one in titanium is not easy or cheap. I have a 27.2 titanium seatpost though. Is it possible/relatively safe to remove .2mm. I'd like to use the post with a Hite Rite. Is it feasible to modify the post and/or the frame ?
  • 11-27-2012
    shiggy
    Quote:

    Originally Posted by phoenixbikes View Post
    I have an old 1993 Kona Explosif. It takes a 27.0 post, and finding one in titanium is not easy or cheap. I have a 27.2 titanium seatpost though. Is it possible/relatively safe to remove .2mm. I'd like to use the post with a Hite Rite. Is it feasible to modify the post and/or the frame ?

    No. Not feasible. Just use a proper size post and forget about ti.
  • 11-27-2012
    phoenixbikes
    It seems like .2mm is insignificant, but I don't want to damage the frame or the seatpost and I don't want to risk my safety.
  • 11-27-2012
    Canaboo
    I don't know how thick the wall diameter is on your Ti seatpost is but .2 is very insignificant. I have turned several 27.2 Aluminum or alloy posts into 27.0 or 26.9.
    It is rather easy to do it precisely if you have any hand skills at all. I used a metal file to rough the entire surface that will be inserted and then wrapped emery paper around the post and spun it to polish it. Start with coarse and work your way through the grit grades until the post is polished. Check the fit periodically.
  • 11-27-2012
    disease
    I don't know how thick the walls are on your seatpost. Syncros titanium seatposts have 0.035" walls. Reducing one of them by 0.2mm in diameter will reduce the wall by 0.004", bring it to 0.031(or less, since seatpost diameters are usually less than their nominal diameter). If you are not heavy, and the seatpost is not extended very far you may be okay, but you are pushing the limits.

    Aluminum posts are much thicker than titanium or steel ones, so the comparison is not relevant.

    Buy a new seatpost.
  • 11-27-2012
    JaquesN
    Is reaming the frame to 27.2 not an option? Or have I misunderstood and that's what you are proposing? I have reamed out .1mm per side and not had a frame crack. YMMV.
  • 11-27-2012
    kosayno
    Quote:

    Originally Posted by disease View Post
    I don't know how thick the walls are on your seatpost. Syncros titanium seatposts have 0.035" walls. Reducing one of them by 0.2mm in diameter will reduce the wall by 0.004", bring it to 0.031(or less, since seatpost diameters are usually less than their nominal diameter). If you are not heavy, and the seatpost is not extended very far you may be okay, but you are pushing the limits.

    Aluminum posts are much thicker than titanium or steel ones, so the comparison is not relevant.

    Buy a new seatpost.

    Reducing the diameter by .2mm=reducing each wall .1mm. Insignificant amount. I like Canaboos idea.
  • 11-27-2012
    shiggy
    Quote:

    Originally Posted by Canaboo View Post
    I don't know how thick the wall diameter is on your Ti seatpost is but .2 is very insignificant. I have turned several 27.2 Aluminum or alloy posts into 27.0 or 26.9.
    It is rather easy to do it precisely if you have any hand skills at all. I used a metal file to rough the entire surface that will be inserted and then wrapped emery paper around the post and spun it to polish it. Start with coarse and work your way through the grit grades until the post is polished. Check the fit periodically.

    Notch failure is a very real possibility with ti. I would not touch it.

    Reaming the seat tube is a possibility but you also risk frame failure
  • 11-27-2012
    Canaboo
    If there is a danger of notching by using grades of emery paper to polish then being too-ham handed for the task is very likely. I'm assuming that the average guy can wield a piece of sandpaper without endangering any limbs.
  • 11-27-2012
    phoenixbikes
    I did a bit of machine shop work in college and do a fair bit of modification to my own bikes on a regular basis. I think maybe taking .1mm from the post, and reaming the seat tube out .1mm might do the trick.

    I also have a 2008 Redline D440 29er that takes a 27.0 post. I run a Dean titanium post on that bike. I am thinking it might be a better candidate than the Kona to ream the seat tube for the 27.2 ti post.
  • 11-28-2012
    pvd
    It's a waste of time and energy.

    Anyway: 27.2 to 27.0 Seatpost Modification | Peter Verdone Designs
  • 11-28-2012
    Yogii
    How much do you weight?
  • 11-28-2012
    rafirafi123
    This truly falls into the category of "bad ideas". There's a reason that the wall thicknesses of the seatpost and the seat tube are what they are. Reducing them is a bad idea. Imagine how you would feel if your seat post failed on a fast descent. And then rest easy knowing that it won't, because you scrapped this bad idea and bought the correct post.
  • 12-04-2012
    TacoMan
    If you are going to modify one, pick which is the least expensive to replace.
  • 12-06-2012
    graviT
    I think this is a great idea. :rolleyes:

    A quick web search shows a few titanium posts with wall thicknesses of under 1mm. If yours is similar then your "insignificant .2 mm" is at least 10% of the total wall thickness. Of course that is if you are capable of removing exactly .1 mm over the entire area of the seatpost and don't accidentally remove a bit more in one area.
  • 12-06-2012
    phoenixbikes
    Quote:

    Originally Posted by Yogii View Post
    How much do you weight?


    I am 6'4", 225 lbs. The seatpost has a fair amount of extension. The 27.2 actually does slide into the frame a bit, without forcing anything. It's probably that the tube is a bit fatigued, so reaming might not be a great idea.

    Damn, I want this to work. :madman:
  • 12-07-2012
    jeff
    Quote:

    Originally Posted by phoenixbikes View Post
    I have an old 1993 Kona Explosif. It takes a 27.0 post, and finding one in titanium is not easy or cheap. I have a 27.2 titanium seatpost though. Is it possible/relatively safe to remove .2mm. I'd like to use the post with a Hite Rite. Is it feasible to modify the post and/or the frame ?

    Post over in the VRC forums "For Trade Only Thread". Dollars to donuts there's someone over there hoarding 27.0 Ti posts.
  • 12-07-2012
    phoenixbikes
    I've been posting over there in that thread for years. No luck yet.
  • 12-07-2012
    whydomylegshurt?
    Do you ever adjust your saddle height? If not, soak a 27.2 ti post in liquid nitrogen. Carefully install it to the desired height and let it warm up. You will have a very strong seatpost to seattube connection but you probably won’t ever get it back out.
  • 12-12-2012
    duncaterro
    I don't want to damage the frame or the seatpost and I don't want to risk my safety.
  • 01-03-2013
    ovwok
    only .004" in radius. less than the thickness of a sheet of paper. just have the frame reamed.
  • 01-03-2013
    phoenixbikes
    Did just that about a few days ago. The post moves, but not freely enough to use a Hite Rite. I am going to sand the inside of the tube to see if I can get the post to go up/down without any friction. I want to use my Hite Rite, but it's going to take some elbow grease to get it working properly.
  • 01-03-2013
    ovwok
    had the same problem with a road frame once. Go to a good auto parts store and pick up a brake cylinder ball hone (flex hone), run it in and out on a drill with some WD40 or something to stop the stones from plugging up.