Anyone ever reamed a seat tube?

I have a 30.0 seat tube and can't run most of the adjustable seatposts on the market because they are usually 30.9. I'm not a fan of shimming a 27.2 seatpost. Anyone here had their seatpost reamed to 30.9?

 

That is quite a lot to take out. You would be risking the integrity of the frame. Reaming is typically done to clean it up not change sizes.

 

0.45mm. It's a 34.9mm seat tube. It's not a lot and worth the slight risk IMO.

 

It comes down to the wall thickness not seat tube diameter. Based on you statement the wall of the tube is about 2MM thick and you would be removing over 10% of the material. Not trying to be a jerk just making sure you know what you are getting into.

 

Yup. Most bike manufacturers use 34.9mm seat tubes with 30.9 seat posts. With enough seat post insertion, I don't buy it that it'll be any weaker than any other manufacturer. And I'm not a clyde.

 

It sounds like you've done your research and have already come to your own conclusion.

I've reamed a seat tube, but it was to clean up the tube so I could use the specified seat post size.

 

Shimming is not really a big deal. I didn't want to do it on my tracer, but bought a gravity dropper for the HT, last year no one else made a 27.2. Just put one on the kids Kona with a 30.0 shim. Works just fine.

If you decide to sell that frame somewhere down the line - I dunno, just seems like too much, and to take a risk when a shim will work fine.

 

what was involved with reaming your seat tube? still got all the tools involved?

reval, point noted. the kind shock ones seem to be the one i want and i think side to side play would annoy me on the other brands. the way i figure it, its relatively low risk, and honestly, my frame doesnt have much resale value anyway.

 

A brake hone from auoozone and some WD 40 makes good even work of it. Ive done it to 2 different bikes and no issues. I went up from quite a bit because I didnt want to have to wait or buy another thomson LOL...

Works great slap it on a drill and make sure to tape papertowels to the frame to catch the little mess it makes but it works perfect....

 

I have some seat tube reamers that I use frequently but it would take forever to take off .45mm.

And you'll spend forever using this method and wear out a lot of ball/brake hones, and you'll screw up the seat tube trying to take out .45 mm.

 

If you're asking me, the reamer was a bike shop tool when I was an employee there several years ago. The reamer had adjustable cutters so you could remove material evenly and gradually. I'm not sure what brand it was.

McMaster-Carr sells adjustable reamers if you can't find a bike-specific item.

http://www.mcmaster.com/#adjustable-diameter-reamers/=9mhoxq

 

You just built a custom frame right? Did you have to ream out the seat tube?

 

Why not split the difference? Ream .2mm out of the tube and sand down .2mm from the post
or, just take it all off the post. I'm assuming the adjustable post is cheaper than the frame haha.

I think the most worrisome part would be the process of reaming. It would be possible to take too much material off, gouge the inside of the tube, have the reamer bind causing the drill to go all wild, etc...

 

The reamer I used was turned with a wrench by hand...no worries about a drill twisting your wrist off.

The high-end seatposts that the OP wants to use probably have really thin walls that won't allow much material removal without weakening. Still, splitting the difference might work well.

Another idea: try contacting a custom framebuilder and get his/her input. I've exchanged a couple of e-mails with Mark Norstad from Paragon Machine Works and he was very helpful.

 

Yes, but only to clean up the tube from distortion caused by the welding.

By the way, there is usually a 0.2 mm tolerance (i.e., a 27.4 mm ID tube is used with a 27.2 mm post).

What frame do you have?

 

Just get a gravity dropper and shim it!
having used joplins, and command posts, the gravity dropper is far more robust and comes in 27.2 (shim it)

 

Also note that many ti and steel frames have built-in internal shims, but most people don't know it. There's nothing wrong with shims when used/installed properly.

 

+1 on the shim.

You can pick up a 27.2 to 30.0 shim for less than $10. You'll forget about it after you install it. Integrity would probably be fine if you reamed it correctly, but I don't see the point when a much simpler option exists.

 

is the gravity dropper pretty good? i was doing the research last night and the 3inch drop is almost perfect i think.

i have an iron horse 6point.

 

Get more than you think you need.... 4" is ideal. Get it up where you need or down out of the way...