Tight Ti Seatpost/tube

[SleepyCyclist]

Early Merlin Extralight - 27.2 post.
Thomson fits fine, but others are a struggle.
Can I safely hone the seat tube? Ball hone vs ?
Other suggestions?

Thanks, M

[mktng]

if the thomson post fits fine.
could it be that the other posts are the issue. not the frame?

[jtbadge]

if the thomson post fits fine.
could it be that the other posts are the issue. not the frame?

Thomson posts seem to be slightly undersized compared to other manufacturers, especially when there is a thick anodizing/finish on the other manufacturer's post makes them run over size.

[Veloo]

May I ask which others are not fitting?
I had similar issue. My FSA Metropolis seatpost was not fitting. I automatically assumed it was the seat tube.
I got a wrench to hone it. He pointed out that a Thomson fit fine. When I asked the frame builder he also said he checked with a Thomson but I had already honed it by then.
It was the FSA seatpost being a bit off in diameter. I can still fit other posts in the tube but I wish I wasn't so quick to assume it was the seat tube.

[SleepyCyclist]

eriksen ti sweetpost - fits but really really tight
campy ti - no chance
american classic - very tight
american classic ti - no chance

[RWeb]

I have an 80’s Merlin mtb. All my previous seat posts, like three, all fit very tightly. Currently I have a Moots on it. I have to use a pry on the built in clamp to be able to slide the post.

[Veloo]

Hard to imagine these being out of spec.
Do you have (access to) a good vernier?

eriksen ti sweetpost - fits but really really tight
campy ti - no chance
american classic - very tight
american classic ti - no chance

[SleepyCyclist]

I agree - hence the thought to use a hone in the seat tube. Just never done that before so wanted some advice.



Hard to imagine these being out of spec.
Do you have (access to) a good vernier?

[Veloo]

I had to hone the eccentric BB shell on the same bike.
I didn't end up using a ball hone. If I recall correctly, I think I went to Home Depot and got a rotary stiff metal bristle thing. Maybe the paint stripping type of rotary head. Can't find it right now to take a pic.

I just went slowly and kept checking to see if the BB would fit into it.

My mechanic did the same thing with the seat tube and his ball hone. Did a few seconds, checked the post, repeat.

[HenryA]

If the post of your choice is bare Ti, I’d work on it to make it fit nicely rather than work on the frame. (Bare so you can match up the finish) Its much easier to work on the outside of the post than down inside a tube. And then there’s the old saying about modifying the cheapest part.

Sandpaper backed with duct tape and shoe shine away until it fits just right.

[FriarQuade]

These kinds of long slip fits are hard to measure.

Vernier calipers are crap, regardless of what any of you retrogrouches say. They are the down tube friction shifter equivalent of the metrology world.

Measure your seat post with a 4 digit micrometer and go from there. Trying to measure your Seat tube is futile since it's very likely not parallel or straight. Once you play princess and the pea with your seat post you know what you need to do, find a new seat post that's true to size, find an oversized seat post or re-size the seat tube. Doing anything before you have an accurate read on the post that isn't fitting is asking for trouble.

[cmg]

eriksen ti sweetpost - fits but really really tight
campy ti - no chance
american classic - very tight
american classic ti - no chance

If you take a caliper to the above posts you'll discover there not all 27.2. The campy will be 27.289 - 27.299 for example. You can use a dura ace njs post their 27.00 or so. I took a reamer to my Ti frame, used the campy post as the goal, once it fit I stopped reaming.