Merlin Titanium

[Tom Kunich]

Here's a really interesting fact:

I could not get the 27.2 carbon seatpost to go into the Merlin seat tube I tried several aluminum seat posts and had the same trouble. So I got a Richey 27.0 seatpost and it fits correctly. Now, there is no deformation of the seat tube and Merlin lists the seatpost as 27.2.

Do you suppose that they normally ream the seat tube out to 27.2 and forgot to do that on this specific bike? After all, mistakes can be made and wouldn't it be a little silly to depend upon the seat tube to be exactly the correct dimension?

[Frank Krygowski]

I'm sure mistakes can be made. Some people make many, and thus have so, so many problems.

- Frank Krygowski

[ritzann...@gmail.com]

Seems to me any higher end bike shop, such as Andy's, would have frame tools. They could easily ream out the seattube to 27.2mm. But Tommy lives in Oakland, the Bay area, so he is out in the wilderness and there are NO high end bike shops within a day's drive of him. Poor Tommy. He will just have to learn to live with his problem and suffer.

[John B.]

But why? Both 27mm and 27.2mm seat posts are available. Why not just
use the correct size that fits the existing frame. Amazon has both
sizes for about $15.00.
AND... for as little as $8.99 you can buy your very own set of digital
calipers to measure seat tubes with. Both I.D. and O.D.
--
Cheers,

John B.

[AMuzi]

More probably someone tightened the seat binder sans post,
deforming the top of the tube.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[AMuzi]

I'll bet 5c that the slit at the top of the seat tube has
sides not parallel, i.e., the top is pinched in. This is
usually from someone tightening the seat binder without a
post in the frame.

Easily rectified, but people over react and start cutting,
reaming, sanding, making larger problems out of small ones...

[ritzann...@gmail.com]

Ahhhhh. Experience speaks. Would you fix this problem by putting a pole inside the seat tube and prying it out wider? Or using a wedge in the slit to widen it and the seat tube diameter?

Just a nickel bet? I think you would be safe to lay a dime or even a quarter on this one.

[Tom Kunich]

On Wednesday, May 4, 2022 at 8:45:56 PM UTC-7, AMuzi wrote:
> On 5/4/2022 7:46 PM, Tom Kunich wrote:
> > Here's a really interesting fact:
> >
> > I could not get the 27.2 carbon seatpost to go into the Merlin seat tube I tried several aluminum seat posts and had the same trouble. So I got a Richey 27.0 seatpost and it fits correctly. Now, there is no deformation of the seat tube and Merlin lists the seatpost as 27.2.
> >
> > Do you suppose that they normally ream the seat tube out to 27.2 and forgot to do that on this specific bike? After all, mistakes can be made and wouldn't it be a little silly to depend upon the seat tube to be exactly the correct dimension?
> >
> More probably someone tightened the seat binder sans post,
> deforming the top of the tube.

That was the first thing that occurred to me so I looked and it was overly tight for the entire insertion length. You should have seen me trying to get the 27.2 out to insert the 27.0. I did look at the cutout that allows the seat tube to collapse with the binder bolt. It was parallel Also the 26 slipped in normally all the way down the seat tube like a seat post usually does.

[Tom Kunich]

The 27 slipped in like a normal seatpost. I have three titanium bikes here and that was the only one with problems. And if it were a bent or out of round seat tube it would not have been tight all the way down since I had to FORCE the 27.2 seatpost in with the seat binder all the way loose. It isn't as if I haven't built a couple of bikes in the past and run across problems such as the seat tube being deformed.

[Luns Tee]

On Wednesday, May 4, 2022 at 9:00:29 PM UTC-7, russell...@yahoo.com wrote:
> On Wednesday, May 4, 2022 at 10:51:29 PM UTC-5, AMuzi wrote:
> > I'll bet 5c that the slit at the top of the seat tube has
> > sides not parallel, i.e., the top is pinched in. This is
> > usually from someone tightening the seat binder without a
> > post in the frame.

> Ahhhhh. Experience speaks. Would you fix this problem by putting a pole inside the seat tube and prying it out wider? Or using a wedge in the slit to widen it and the seat tube diameter?
>
> Just a nickel bet? I think you would be safe to lay a dime or even a quarter on this one.

The last time I had to address a seatpost insertion issue, I was fortunate that the seatpost binder wasn't a loose nut and bolt, but with the nut integrated into the ear on the seatpost. I literally put a nickel in the slit, and ran the binder bolt into the nut from the backside, pushing on the nickel to open up the slit. The nickel is thicker than a either a dime or quarter, and more importantly, is what I had in my pocket at the time.

This opened things up enough to insert the seatpost through the clamping area, but it did get a little stuck going deeper. Dried/hardened grease in the seat tube from under the previous seatpost was getting in the way. A few seconds with a brake cylinder hone took care of that.

[Luns Tee]

It takes only a slight amount of deformation to interfere with insertion, slight enough there's no way to see it directly. If you look from behind the bike, the main deformation isn't of the tube ends closing in left/right, but rather of the corners of the tube folding forwards into the opening away from you. The binder bolt pinches at about 8mm away from the ~1mm tube wall, and the bending moment of the pinch force against this distance pushes the corners of the clamp forwards. With a seatpost in place, it resists this forward push, but without a seatpost, the tube end is easily deformed enough to cause trouble.

[Tom Kunich]

Well, as I said, there was no deformation in the seat tube with the clinch nut fully loosened. By eye it was perfectly round and multiple seatposts fit in without showing any out of round And the markings on the seat posts that had to be jammed into the whole were all the way around the seatpost. Any deformation of the seat tube would have shown as irregular scars on the seat posts.

Think about it. Do you suppose that they make titanium tubing with exactly 27.2 mm ID? I more suspect that they don't worry too much about the ID and then simply bore the seat tube to the exact diameter.

[AMuzi]

Calipers are cheap. Meatware is a different matter.

Seat tubes are commonly not round and often not the same
size at the top as 50mm or 100mm in. Your average guy, new
to measurement, will easily use his new caliper to take the
wrong dimension (to two decimal places!!) draw the wrong
conclusion and wreck the piece with a reamer. Sadly not an
uncommon scenario.

A better path would be to slip a 27.0mm post in it, see if
there's play when inserted 100mm. That's a good indication
you have a deformed seat tube top and not the 'wrong' size
post. Much simpler than multiple snap gauge readings and
fully adequate for a bicycle seatpost.

https://www.ctemag.com/news/articles/measuring-snap

Understatement of the year from that link, "My experience is
that The L.S. Starrett Co. in Athol, Massachusetts, makes
good stuff."

[AMuzi]

On 5/4/2022 11:00 PM, russell...@yahoo.com wrote:
> On Wednesday, May 4, 2022 at 10:51:29 PM UTC-5, AMuzi wrote:
>> On 5/4/2022 10:22 PM, russell...@yahoo.com wrote:
>>> On Wednesday, May 4, 2022 at 8:50:03 PM UTC-5, frkr...@gmail.com wrote:
>>>> On Wednesday, May 4, 2022 at 5:46:26 PM UTC-7, cycl...@gmail.com wrote:
>>>>> Here's a really interesting fact:
>>>>>
>>>>> I could not get the 27.2 carbon seatpost to go into the Merlin seat tube I tried several aluminum seat posts and had the same trouble. So I got a Richey 27.0 seatpost and it fits correctly. Now, there is no deformation of the seat tube and Merlin lists the seatpost as 27.2.
>>>>>
>>>>> Do you suppose that they normally ream the seat tube out to 27.2 and forgot to do that on this specific bike? After all, mistakes can be made and wouldn't it be a little silly to depend upon the seat tube to be exactly the correct dimension?
>>>> I'm sure mistakes can be made. Some people make many, and thus have so, so many problems.
>>>>
>>>> - Frank Krygowski
>>>
>>> Seems to me any higher end bike shop, such as Andy's, would have frame tools. They could easily ream out the seattube to 27.2mm. But Tommy lives in Oakland, the Bay area, so he is out in the wilderness and there are NO high end bike shops within a day's drive of him. Poor Tommy. He will just have to learn to live with his problem and suffer.
>>>
>> I'll bet 5c that the slit at the top of the seat tube has
>> sides not parallel, i.e., the top is pinched in. This is
>> usually from someone tightening the seat binder without a
>> post in the frame.
>>
>> Easily rectified, but people over react and start cutting,
>> reaming, sanding, making larger problems out of small ones...

> Ahhhhh. Experience speaks. Would you fix this problem by putting a pole inside the seat tube and prying it out wider? Or using a wedge in the slit to widen it and the seat tube diameter?
>
> Just a nickel bet? I think you would be safe to lay a dime or even a quarter on this one.
>

If that's the problem, you're much better off re forming the
seat tube to round (using a slightly smaller post) than
removing material.

[Tom Kunich]

The difference in diameter between 27.2 and 27.0 is 8 thousands of an inch. Hardly the sort of thing that you could feel play in on a seat post. In my experience MOST seatposts are tighter at the top than deeper in the seat tube. Plus, the 27,0 seatpost tightened right up without a problem.

[AMuzi]

+1
Re form minor deformations, remove crud, use a tube polisher
or a fine grit hone (such as a brake cylinder hone) all good
techniques.

Anyone considering a reamer ought to go back and measure,
pause to reflect, measure again and then go get competent
professional advice.

[AMuzi]

+1

[AMuzi]

> "there was no deformation in the seat tube..."

If there was no deformation of the seat tube, and if the
bore were clean, your 27.2mm post would have slipped into a
Merlin of its own weight.

[Sir Ridesalot]

Back in the 1980's I read or was told that a well fitted seatpost would SLOWLY drop into a seattube when the seat binder bolt was loosened.

Far too many people reach for a reamer, file or other cutting tool far too soon when faced with an overly snug seatpost.

Another thing that I was told was that it could be quite risky to ream a thin walled 27.0mm seattube out to 27.2mm. Doing so could result in unduly thin seattube walls.

Cheers

[Lou Holtman]

If the bore is exactly 27.2 mm and round a seatpost of exactly 27.2 mm and round would not ‘fit’. You need some play in the order of 0.03 mm.

Lou

[AMuzi]

Try it in another frame. A 27.0 post rocks noticeably in a
27.2mm frame even when the top portion is tight.

[AMuzi]

In theory, no problem at all, assuming quality tube (which a
27.0 bore would be anyway). In practice, the setup for that
is artful and guys do shoot reamers out the side of seat tubes.

[AMuzi]

> If the bore is exactly 27.2 mm and round a seatpost of exactly 27.2 mm and round would not ‘fit’. You need some play in the order of 0.03 mm.
>
> Lou
>

Yes that's true. For bicycle purposes seat tube bores are
slightly oversize.

[John B.]

At one time L.S. Starrett and Brown and Sharp were the only two
micrometers allowed in some of the better shops (:-)
--
Cheers,

John B.

[AMuzi]

I've never been disappointed with anything by Starrett
(after the price shock ebbs).

[John B.]

Well, Massachusetts minimum wage is now $14.25 an hour and Japanese
Minimum wage is something like $8.00 an hour and Chinese minimum is as
high as $3.90/hour, in Beijing, and apparently as low as about half
that in other provinces.
--
Cheers,

John B.

[AMuzi]

I do own some very nice Mitutoyo tools, I'm not slighting
Japanese precision instruments. But Starrett really is
exceptional. I doubt minimum wage laws much affect price in
that category.

[John B.]

No but it may be an indication of relative costs (and therefore
relative sales prices :-)

Japanese tools, like all Japanese products have come a long way. I
remember the first Japanese micrometers that the A.F. issued. Good
looking and seemed to work well until one of my boys somehow got a
tiny bit of steel in the threads and the micrometer "locked up". Since
the thing was no good any more we clamped it in a vice and twisted the
thimble loose and found that neither the thimble or the sleeve were
hardened steel.

But the Japanese learn fast and I'm sure that today's tools are as
good as anyone else's.
--
Cheers,

John B.

[Lou Holtman]

0.2 mm play is 'enormous' in that application.

Lou

[Tom Kunich]

Uh, think about that. What with someone saying that the seatpost should slide in of its own weight - .03 mm is a thousands of an inch and there's NO seatpost that is so accurate that it would be able to slide into the seat tube of its own weight with a thousandths clearance! Even with the 8 thou clearance of the 27.0 the Ritchey seatpost wouldn't "slip" in.

[AMuzi]

On 5/6/2022 8:04 AM, Tom Kunich wrote:
> On Thursday, May 5, 2022 at 4:06:06 PM UTC-7, AMuzi wrote:
>> On 5/5/2022 3:49 PM, Lou Holtman wrote:
>>> On Thursday, May 5, 2022 at 10:17:31 PM UTC+2, AMuzi wrote:
>>>> On 5/5/2022 1:18 PM, Tom Kunich wrote:
>>>>> On Thursday, May 5, 2022 at 11:07:55 AM UTC-7, Luns Tee wrote:
>>>>>> On Thursday, May 5, 2022 at 10:28:05 AM UTC-7, cycl...@gmail.com wrote:
>>>>>>> On Wednesday, May 4, 2022 at 8:45:56 PM UTC-7, AMuzi wrote:
>>>>>>
>>>>>>>> More probably someone tightened the seat binder sans post,
>>>>>>>> deforming the top of the tube.
>>>>>>> That was the first thing that occurred to me so I looked and it was overly tight for the entire insertion length. You should have seen me trying to get the 27.2 out to insert the 27.0. I did look at the cutout that allows the seat tube to collapse with the binder bolt. It was parallel Also the 26 slipped in normally all the way down the seat tube like a seat post usually does.
>>>>>> It takes only a slight amount of deformation to interfere with insertion, slight enough there's no way to see it directly. If you look from behind the bike, the main deformation isn't of the tube ends closing in left/right, but rather of the corners of the tube folding forwards into the opening away from you. The binder bolt pinches at about 8mm away from the ~1mm tube wall, and the bending moment of the pinch force against this distance pushes the corners of the clamp forwards. With a seatpost in place, it resists this forward push, but without a seatpost, the tube end is easily deformed enough to cause trouble.
>>>>> Well, as I said, there was no deformation in the seat tube with the clinch nut fully loosened. By eye it was perfectly round and multiple seatposts fit in without showing any out of round And the markings on the seat posts that had to be jammed into the whole were all the way around the seatpost. Any deformation of the seat tube would have shown as irregular scars on the seat posts.
>>>>>
>>>>> Think about it. Do you suppose that they make titanium tubing with exactly 27.2 mm ID? I more suspect that they don't worry too much about the ID and then simply bore the seat tube to the exact diameter.
>>>>> "there was no deformation in the seat tube..."
>>>>
>>>> If there was no deformation of the seat tube, and if the
>>>> bore were clean, your 27.2mm post would have slipped into a
>>>> Merlin of its own weight.
>>>> --
>>>

>>> If the bore is exactly 27.2 mm and round a seatpost of exactly 27.2 mm and round would not ‘fit’. You need some play in the order of 0.03 mm.

>>>
>>> Lou
>>>
>>
>> Yes that's true. For bicycle purposes seat tube bores are
>> slightly oversize.
>
> Uh, think about that. What with someone saying that the seatpost should slide in of its own weight - .03 mm is a thousands of an inch and there's NO seatpost that is so accurate that it would be able to slide into the seat tube of its own weight with a thousandths clearance! Even with the 8 thou clearance of the 27.0 the Ritchey seatpost wouldn't "slip" in.
>

They do when dry and clean.

[Tom Kunich]

Well, I've never seen one that would. Though using the exception of "dry and clean" does seem to be stretching thing don't you think? You couldn't have it clean if there were every a prior seatpost. At least in my experience. None of my other bikes have offered any excessive force to insert the seatpost. Well, let me correct that. That titanium seatpost I had would not insert but it was .3 mm out of round.