Clem Seatpost Issue

[Gordon Stam]

Hey Gang. I have a 59cm Clem which takes a 29.8 seatpost. I got the tandem seat post from Rivendell in the proper size and it would not fit - too big around. Apparently my seat tube is a wee bit smaller than 29.8. I sanded down the Riv seatpost and made it fit but I would like to swap it out for something other than a single bolt design, which I finding is finicky with the seat tilt adjustment*. The only option I'm seeing is a Thompson Elite seatpost. Either that or use an adapter to fit a 27.2 seatpost, which I have and would prefer to avoid. BUT...if I get a Thompson in 29.8 I'm likely going to have to sand it down and since they only come in black that would look funky. Plus it's $100+.

Alternately Thompson makes a 29.4 seatpost and I wonder if that would fit okay. If I order one and find it doesn't work I might have a hard time returning it because of the inevitable(?) scratches it will incur in the process. 

I've measured the seat tube ID at the clamp and get anywhere from 29.5 to 29.8. The 29.8 measurement is only along the front to back axis. Nowhere else do I get 29.8.

So, Thompson and sand it down, 27.2 adapter, or live with the current post and deal with the adjustment?

Any other ideas?

*Trying to adjust the tilt yesterday the clamp seems to have sort of taken a "set". If I'm even close to where it has been it goes back to that position. Micro adjustment is just not happening.

[Laing Conley]

Use an automotive brake cylinder hone to slightly enlarge the seat tube.  I always hone the seat tubes to remove brazing residue anyway. Brazing residue is what scratches up your seat post. 

Make sure that it is not just a crimped seat tube lug first. 

Laing

Delray Beach FL

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[Gordon Stam]

Thanks Laing. That's where we are headed. I called up my LBS and they have a seat tube reamer. We ordered a new seat post, a Kalloy Uno, which apparently has a better clamp design (still single bolt), and they are going to ream the seat tube and give that Kalloy a try. 

Lately I've come to appreciate the LBS more and more. These guys sell (and speak) Rivendell so they are a real asset. 

[Garth]

Assuming you bought it new, this a Riv issue to remedy. As the seller of the frame it is up to them to deliver a bike that is to the specs that they advertise. Without that standard, there are no standards. At this point you should at least be compensated for your remedies by Riv, for the labor cost of the shop. I used to work in a shop a long time ago, it was always up to us to make sure all the parts fit in the frame as spec'd. That was all part of the purchase.

Otherwise what would be the point, forget about the details leave it up to the customer for a "surprise !" ?  Imagine if the frame builder adhered to that as a standard in building the frame !!

[Michael Connors]

I have an idea (but I haven't actually tried it). If the problem is the tube is out of round, use a stem and wedge to spread the direction that measures 29.5. Leave the binder bolt in to keep the slot from spreading.  On my 50 year old department store bike with a deformed clamp area, I just use a large screwdriver to wedge the slot wide enough to install the seat post.

[Gordon Stam]

Garth, that's a good point. It's pretty obvious but I hadn't even considered it. Yeah, I did buy the frame new, from the LBS. I'll bring it up with them and call Rivendell as well. It's something they ought to be aware of. 

[iamkeith]

Curious what Rivendell has told you, but I'm also wondering why you would go straight from 29.8 to 29.4, and not try 29.6.  That would seem most straight forward and least likely to damage anything.  They exist and, even if only in one-bolt designs, that's a small one-time, set-it-and-forget-it hassle compared to reaming a seat tube. Here's one.

https://www.thebikesmiths.com/products/kalloy-sp-359-7084?variant=41522031067296

On Thursday, March 13, 2025 at 11:19:11 AM UTC-6 lconley wrote:

[Gordon Stam]

Called Rivendell this morning and the word was that they see this situation on rare occasions. Usually the problem with the bigger Clems is seatposts that are too loose. But the word would be passed on to Grant. 

As far as the 29.6 seatpost goes I had never thought of that but interestingly enough the seatpost I sanded down ended up measuring about 29.6. But I agree with Garth above that if the bike is specified to have a 29.8 seat tube, that's what it should be. It saves time and energy down the line. For example, when I first got the frame I ordered an adapter sleeve that allowed for the use of a 27.2 seatpost, of which I have a few. In fact my first ride was with an American Classic 27.2 seatpost. However a Truvativ 27.2 seatpost (with a double bolt adjustment - like I like) won't work. Too small, likely due to the constricted seat tube. So reaming out the seat tube to it's proper dimensions ought to allow for that Truvativ seatpost to work, if I wanted.

At any rate the situation will be resolved soon and Rivendell is aware that one more Clem got out there with a constricted seat tube. 

[Gordon Stam]

Update on the seat tube - it's fixed! I now have a proper 29.8 mm seat post in there, a Kalloy Uno with a fancy "Advanced Project" graphic, whatever that means. It's a nice post, with a tich more setback that the one I got from Rivendell and a little easier adjustment. It's a tight fit, it goes in and out smoothly, but maybe a little more work is in order.

The shop didn't have a reamer that was big enough and the mechanic told me when I picked it up that had I answered my phone earlier in the day he was going to ask my permission to go at it with a file. I took that inspiration and stopped by Harbor Freight on the way home and picked up an appropriate looking file set. They worked somewhat but the the real star of the show was a cylindrical grinding tool on a cordless dremel. That and (thanks Laing!) a brake cylinder hone. The constriction was pretty much in the lug area at the top and vigorous work with the grinder eventually got the seat post to pop through, yielding a satisfying feeling of accomplishment. After that the hone was employed to smooth everything out and maybe enlarge the hole a wee bit more. I completely wore out the shoes that the hone came with so after those get replaced I may spend some more time with it to see if I can loosen up the fit just a smidge. The hone doesn't remove much steel (it does some) but as Laing mentioned it is great for smoothing out nasty burs and irregularities that scratch up the post. Plus its fun to use, and relatively cheap at $20. All you need is a drill to attach it to. Go getcha one!