Serotta Legend Seat tube Question

[cmbicycles]

I recently picked up a legend ti frame (painted under the seatpost collar)and have been picking through my stuff to build it up. I assumed it would take a 27.2 post and a 31.8 seatpost clamp... although once I received it I found it takes a smaller clamp, roughly 29.4mm +/- (tube wall thickness measures about 1.1-1.2 mm). Either way I had problems getting a post to go in without an abnormal amount of persuasion.

It started gouging the 27.2 post I tried to put in, even with the clamp pulled off the frame. After I looked more closely it appears one side of the tube, at the seat clamp slit, is flared out slightly instead of being completely round and I am assuming this is where the problem stems from. Any ideas on an easy way to fix this?

The clamp that came with the frame is stamped 33, but measures closer to 30.0 diameter, so not sure the stamping is the intended size. I have no idea how this happened or could have happened, it was shipped with the clamp on, and the prior owner said they had a Thompson post in there with no problem... but my Am Classic ti post, and a few other posts wont go without some persuasion.

I was thinking I could file/dremel the slit in the tube, or use a flex hone, and see if that helps with the scratching issue, though not sure how effective it would be with titanium.
Thanks for the thoughts and suggestions

[buldogge]

The tube sounds like it has been pushed out-of round by tightening in a too small seat post. Thomsons run pretty undersized IME.

Use a seatpost gauge and work it in to the 27.2 position and tighten down the proper seat post clamp (31.8-32.0)…alternatively, use a sacrificial post…old steel, cheap Kalloy, whatever.

-Mark in St. Louis

Originally Posted by cmbicycles

I recently picked up a legend ti frame (painted under the seatpost collar)and have been picking through my stuff to build it up. I assumed it would take a 27.2 post and a 31.8 seatpost clamp... although once I received it I found it takes a smaller clamp, roughly 29.4mm +/- (tube wall thickness measures about 1.1-1.2 mm). Either way I had problems getting a post to go in without an abnormal amount of persuasion.

It started gouging the 27.2 post I tried to put in, even with the clamp pulled off the frame. After I looked more closely it appears one side of the tube, at the seat clamp slit, is flared out slightly instead of being completely round and I am assuming this is where the problem stems from. Any ideas on an easy way to fix this?

The clamp that came with the frame is stamped 33, but measures closer to 30.0 diameter, so not sure the stamping is the intended size. I have no idea how this happened or could have happened, it was shipped with the clamp on, and the prior owner said they had a Thompson post in there with no problem... but my Am Classic ti post, and a few other posts wont go without some persuasion.

I was thinking I could file/dremel the slit in the tube, or use a flex hone, and see if that helps with the scratching issue, though not sure how effective it would be with titanium.
Thanks for the thoughts and suggestions

[happycampyer]

Serotta was pretty exacting with their tolerances, so 27.2mm was 27.2mm. I know of several Serotta dealers that wouldn't carry certiain seatposts because they were not always exactly 27.2mm. I bought an Ottrott used that the previous owner had managed to crimp the seat tube out of round at the collar, and the shop had to get a special tool to ream it. I would take the frame to someone you trust, and have them inspect it. Titanium is not easy to work with.

Regarding the front derailleur clamp, the seat tube of a Legend is swaged, so it is wider at the bottom than at the top. All of the Legends/Ottrotts I have owned have taken a 34.9mm clamp. I would take a pair of calipers to the seat tube where the clamp should go to get a precise measurement.

[cmbicycles]

Originally Posted by happycampyer

Regarding the front derailleur clamp, the seat tube of a Legend is swaged, so it is wider at the bottom than at the top. All of the Legends/Ottrotts I have owned have taken a 34.5mm clamp. I would take a pair of calipers to the seat tube where the clamp should go to get a precise measurement.

I know it takes a 34.9 F der clamp, it came with one mounted. The seatpost collar was the measurement that threw me. The seat tube wall thickness measures 1.1-1.2mm, so double that and add it to the seatpost diameter of 27.2 and you get 29.4-29.6... which seems an odd collar size to me, but I haven't owned a serotta before so that's why I mentioned it. Thanks

[happycampyer]

Doh, of course you were talking about the seatpost clamp.

[oliver1850]

Do you have the Serotta seat collar? They were made to specific diameters for the intended frame.

I can measure ST OD on a couple of (older) Legends if it helps, but your math sounds right to me. I think all Serottas in that era used a "27.2" post. That said, actual size of nominally 27.2 posts can vary quite a bit. I have a Cannondale carbon post that's labeled 27.2 but measures on the small side for a 27.0. Clamping that post tightly enough to prevent slippage might deform the ST enough to make normal 27.2 posts a difficult fit.

I would probably work a cheap 27.2 around in it with plenty of lube and hope to free up the fit of the post you actually want to use. You can of course go straight to ream/sand ID, but you're removing material that was intended to be there if you do that.

You might try to find a burr on the ST ID. Most likely place would be the edge of the slot, but if someone snagged a post in it, it could be anywhere. Careful cleaning and inspection of the ID of the ST might turn up a burr that could be filed out.

[93legendti]

Fwiw, when I used Campy Chorus Ti posts in Serotta's, the fit was really tight and it took some force to get the post in and out, leaving the post scored (sic?). Easton posts fit nicely, which is what I usually used.

[Saint Vitus]

Originally Posted by 93legendti

Fwiw, when I used Campy Chorus Ti posts in Serotta's, the fit was really tight and it took some force to get the post in and out, leaving the post scored (sic?). Easton posts fit nicely, which is what I usually used.

Glad I'm not the only one with this issue.

[93legendti]

Originally Posted by Saint Vitus

Glad I'm not the only one with this issue.

I could have sworn I was doing something wrong, but how hard can it be to put the right size seatpost in a bike?

I just changed the 27.2 seatpost in my Concours. From an FSA carbon which was very tight, to a Uno carbon which went in just right.

[Ahneida Ride]

I use a Thompson in Legend ...

[Saint Vitus]

Originally Posted by 93legendti

I could have sworn I was doing something wrong, but how hard can it be to put the right size seatpost in a bike?

Same here, but I didn't want to buy another post if I had a quality one already. So I ended up wet lapping the post to clean up the gouges (it was rough looking) as well as doing the same inside the seat tube. I noticed that gouging seem to occur around the seat stay welds. Even with copious grease the post is still tight but now I could reasonably insert it and adjust height.

[cmg]

Bontrager, easton ec70, shimano dura ace sp7410 njs and FSA slk posts will be slightly less than 27.2. Campy modern post 2000-on will be slightly larger 27.289+ same goes for dura ace sp7410, no njs logo 27.2+. i have 2 custom bikes that won't fit the campy modern post so i know the pain. i took the ti bike and couldn't find a shop that would ream it for a 27.2. Not if i didn't buy it from them. so let the suffering begin. enjoy....

[pbarry]

If it's ovalized, reaming is not the best solution. A proper mandrel might make it more round--Buldogge's recommendation for using a sacrificial steel SP is right on. Find the correct clamp and a slightly undersized post, and all should be good. Use carbon paste if there's slippage...

[Brian Smith]

Originally Posted by pbarry

If it's ovalized, reaming is not the best solution. A proper mandrel might make it more round--Buldogge's recommendation for using a sacrificial steel SP is right on. Find the correct clamp and a slightly undersized post, and all should be good. Use carbon paste if there's slippage...

It's hard to offer complete advice without knowing what is wrong with the frame, or indeed what size tube and posts are being discussed. I would, however, disagree in general that an undersized post and some goop is the best solution for an oval seat tube. To me this is like a post-accident automobile's bumper fallen cover affixed with duct tape as a solution, in that the underlying damage is the real issue. Something sharp is causing the scratches on the post being inserted. That something should be identified.

cm - DKG was a supplier to Serotta for clamps in the 30mm sizing, if the frame is of the age that I am imagining and used that clamp, and they are still being offered here:
DKG Sizing Page

It is likely, in my experience, that whether the tight fit and scratches are due simply to a past over-tightening of the clamp, perhaps to accommodate a 27.1mm post, then remedied by manipulating the tube above the slot and sweetening the edges of the slot, or whether they are due to the interior surface of a weld such as the seat stays, a reamer may be required to achieve a nice sliding fit.

If you were anywhere nearby, or wanted to ship it, I'd offer to have a look at it and see about fixing it. This is not an un-heard of issue.

[pbarry]

Good on you Brian for the offer. Without seeing the frame, we are all just speculating here.