Can I make my 27.2 titanium post fit my 27.0 frame ?

[phoenixbikes]

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 ?

[shiggy]

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.

[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.

[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.

[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.

[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.

[kosayno]

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.

[shiggy]

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

[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.

[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.

[pvd]

It's a waste of time and energy.

Anyway: 27.2 to 27.0 Seatpost Modification | Peter Verdone Designs

[Yogii]

How much do you weight?

[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.

[TacoMan]

If you are going to modify one, pick which is the least expensive to replace.

[graviT]

I think this is a great idea.

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.

[phoenixbikes]

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.

[jeff]

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.

[phoenixbikes]

I've been posting over there in that thread for years. No luck yet.

[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.

[duncaterro]

I don't want to damage the frame or the seatpost and I don't want to risk my safety.

[ovwok]

only .004" in radius. less than the thickness of a sheet of paper. just have the frame reamed.

[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.

[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.