masi61

I am getting ready to build up a nice, used Klein Performance frameset that I got off eBay last week. It takes a 27.4 seatpost.

Obviously this is not a common size so I understand that there are going to be limited choices. I have seen American Classics came in that size, but I've never been a fan of the minimalist saddle rail clamping head of this design. Campagnolo made a 27.4 but they are expensive and most likely too short (I'm 5'11-1/2" but the bike is like a size 54 so I'll likely need a post more like 330mm), Thomson does make a 27.4 post in this size and length but it might be out of production now. There were 3 on eBay when I checked in 3 different lengths, all black.

I think I had seen an occasional Syncros or maybe Control Tech in the 27.4 size on eBay in the past but none are popping up now. I would love it if I could use a modern Ritchey twin rail clamping carbon post in 27.4 but I don't believe they are made.

Can anybody think of any other 27.4 options? I'd appreciate any tips on 27.4 posts I that I'm overlooking? What would be really cool if there were a way to get a titanium seatpost in that size (for its shock absorption quality to soften to oversize aluminum tubes.

TenGrainBread 

FWIW the claimed ability of a rigid seatpost to meaningfully "absorb shocks" is probably nonsense. It's a very small and rigid component, no matter the material. Nobody has ever done any scientific studies on this oft-repeated claim. I've had two titanium seatposts and they offered no noticeable difference in comfort from aluminum.

The 90s Dura Ace seatposts came in a 27.4 also. Pretty expensive on ebay. What's wrong with the Thomson?

masi61

I like their zero setback post but am going for some set back here. Thomson’s angled set back post is not going to come in a 27.4, plus that abrupt angular look in their setback post is not the vibe I’m after.

I would respectfully disagree with your assertion that different posts can’t differ in comfort. The more post exposure you get, the more length you have to tune your ride a little. The difference between a stiff post and one with some compliance is a bit difficult to quantify but from what I have read (and personally experienced) - it only amounts to like 1mm of travel to make a difference. I’ve not used a titanium post yet but I’ve heard that they can reduce some chip seal buzz.

TenGrainBread 

Fair enough on the aesthetics of the setback Thomson. I don't like how it looks either.

I had an idea. Waterford used to build a ton of frames with 27.4 seat tubes and supplied various high end seatposts for them since this was somewhat unique. Why don't you give them a call and see if they have any deadstock seatposts in storage?

masi61

Thanks for the suggestion! I will check with Waterford.

thinktubes 

Have you considered getting a 28.0 and having a machinist turn it down?

steelbikeguy

I had a frame builder do a little touch-up work on a frame, and it ended up changing from a 27.2mm seat tube to 27.4mm.
I was not amused...
This was when the American Classic posts were still in production, so we settled on him coughing up the money for one of these posts.

Fortunately, I've got a lot of experience with these, and have no bad results. Some folks do have issues, though. I'm about 155 pounds, so maybe that's why I've had better luck?

My Raleigh Team also uses 27.4mm, and currently sports an American Classic. I wouldn't mind putting something a bit more Italian looking on it, though. I'll keep an eye on this thread, in the hopes that someone uncovers a crate of 27.4mm Super Record posts in the basement of a bike shop one day.

Steve in Peoria

masi61

I did consider reaming it out using a Cal-Van expanding reamer tool and cutting fluid. But if the next size up is 28.0, that size I would think would be even more obscure. Funny thing is - when I put the jaws of my metric dial caliper down into the bore of the seat tube - the 27.4 dimension registered on the dial when the jaws were placed on these 2 different strategically placed football shaped blobs of aluminum solder.

TenGrainBread 

Someone was soldering your seat tube? What do you mean?

JohnDThompson 

Or a 27.2 post and a shim. Less risk of removing too much material that way.

Kevin stafford

27.2 with a soda can (or beer can) shim should work.

scarlson 

If you want to go this route, as a machinist I have to warn you that this seat post business isn't as precise as you might assume. The posts I've measured with my micrometers often measure 0.1mm under what is marked. In other words, for example many 27.2 posts (from some not-shabby brands at that, including SR and Campy) measure 27.1. The frame is also often out of round. So it would not be a guaranteed outcome by any means even if it were turned to some precise diameter. Come to the shop with the bike and oversized post, however, and I could get you set up right in short order by my favorite method for one-offs like this: measurement-guided trial and error.

In a situation with a damaged frame or an odd/unavailable size, I usually buy a post in whatever spec is a little big and then ream the frame to get a nice slide fit. Within reason, of course. It's riskier on a welded aluminum frame, and pretty much a no-go on a bonded frame. Then I stamp the post (up top where it can't wear off!!) and the frame to ensure that nobody ever forgets the size.

If I were you, I'd think about using an adjustable reamer as others have mentioned, especially since you mention blobs of "solder" (weld?) inside the tube. What is the diameter if you *don't* put your calipers on those lumps? Anywhere close to 28?

A used Chadwick & Trefethen can be had for short money on Ebay, just make sure you're getting the right size. I think mine cost $30 or so. Even if it's dull it will cut aluminum easily. There's extensive documentation available on these reamers, which come in numbered "nominal" sizes but some also should list fractional inch lower and upper limits that can be mapped to the numbering system as well. You can drive it with an adjustable wrench on the square-drive, and it's quite user-friendly to set up taking nice light cuts until the thing fits.

masi61

There were flat globs of what appeared to be solder on the interior of my seat tube. I can photo but it appears to be a non-issue since the Thomson post that I ultimately purchased (in 27.4mm size) fits fine.

jetboy 

older thread now but cannondale has 27.4 posts