Sobeisdead

I have a Steel DeRosa currently with a 27.2 seat post which works fine however I've had people tell me that I'm using the wrong one since the "ears" touch. I personally think that's just the design but unsure. Any thoughts?

Rolla

These make it easy to verify the inside diameter of the seat tube. Your LBS should have one you can use.

masi61

Pinched in like that is not by design. If that HED seatpost is a 27.2, is there a chance that the seat tube had been previously reamed to 27.4mm?

Lombard

If it works fine and doesn't slip, why the concern?

Iride01 

The ears shouldn't touch. So maybe your have the wrong size seat post or the top of the tube and other parts involved have stretched or for some reason the inside radius of the seat tube near the top has gotten larger. Maybe someone incorrectly reamed it.

Another tell is the gap narrows in the slot cut into the seat tube.

However if your saddle is maintaining it's proper height and not slipping, then maybe everything has just enough of what it needs. So then you can just ignore all of us that think it's wrong and thumb your nose at us! <grin>

One issue you might possibly have if the seat post is undersize is that no matter how tight the clamp, the bottom of the seat post might rock back and forth inside the tube as you pedal and cause some squeaks or clicks you may never find.

Sobeisdead

It could be. The frame did come from ebay but they did have all the details like frame size, head tube, backspacing, bb type and of course the seatpost diameter. Everything else checked out so I didn't question the seatpost. I did try a few others and the 27.2 is the one that slipped in with a bit of resistance.

I just don't want this to be a future problem with the bike but i guess if it works it doesn't need fixing .

PhilFo 

What probably happened is that someone had the wrong size post and they rode with it anyway. You can see the paint cracks in there suggesting that someone put in a slightly larger post, torqued down the binder bolt and slightly bent the collar. After that, you now have the condition that the collar wants a larger post but the appropriate size post now allows the slightly pinched ears to touch. It's good strong steel, so you could have a good shop carefully bend them back. You could also remove the paint from between the ears on the collar which will give you another .5mm so they aren't touching.

JohnDThompson 

Some of the lighter gauge tube sets came with 27.4mm ID seat tubes, e.g. Reynolds 753.

well biked

It's very possible to overtighten the bolt and distort the seatlug, as in the photo, even with the correct seatpost diameter. Or maybe the seapost is too small in diameter,, and the seatlug has been distorted to keep the seatpost from slipping. Regardless, the people who have told you that it shouldn't look like this are correct.

Sobeisdead

any recommendations?


I also did do some research on the bike also on Sheldon Browns bike index and found that the DeRosas from that time had a 27.2 seatpost diameter.

tFUnK

It shouldn't look like that but there are reasons why it currently does (already mentioned above). If it's not slipping I wouldn't worry about it.

Iride01 

If you ever decide to try new seat posts out, then make certain that the slot cut in the seat tube is open and the side fairly parallel to each other when you try new posts for size. Otherwise you'll not be able to feel the proper fit. The tapered sides of a really large punch can help you open it up to where it needs to be. If you just pry with a screwdriver or something then the seat tube opening might become oval instead of staying round.

But if everything is working together and you aren't having an issue, then there is no reason to change the current setup.

Sobeisdead

Thanks a bunch guys for all the Info, it is greatly appreciated!!

Hondo6

Don't believe the OP ever stated explicitly that he'd/she'd measured the seatpost itself.

I'd be especially interested in knowing the measured diameter where it's clamped - especially if it's a CF seatpost.

I understand over-torquing CF parts where they are clamped is "not a good thing". And I also understand alloy is often easier to deform than steel.

LV2TNDM

This was my first question. Seatpost actual diameters can vary considerably. So determining the actual diameter of the post is the first step.

Even so, that clamp has flexed enough to cause the paint to chip. Not good. I'd work on getting a better fit so that collar clamps properly. Reaming the seat tube out to fit a 27.4 may be the best option, depending on what 27.4 seatposts are available. The other option is knurling the existing seat post, but this is not an ideal solution (or possible with CF). But would remedy any slipping if the OP were having this problem.

zandoval 

Had this problem a couple of times. On my older bikes who knows just what size seat post they originally had. Especially the French ones. My solution is to first make sure the top of the tube is round and not deformed. I also clean and sand out the top of the tube also using a screw driver to separate the dog ears. I then wrap tape around a dowel to check sizing till I get a good snug fit to both the upper and lower part of the tube. Often they are not the same. I buy a seat post that fits the lower part of the tube and if I have to, I use a beer can shim at the top. On one old bike the dog ears were so deformed and stretched out I used a hack saw blade to open up the space between them.

A few times I have had to buy a 1mm larger aluminum seat post and then resize it using the old file and sandpaper technique.

Youtube: Seatpost Size - From Wrong To Right

grumpus

I'd remove the post, insert a large flat bladed screwdriver between the ears from the inside and pry gently* until the faces are parallel, also the slot. Check with a finger for any bumps or jaggies around the slot that need tapping/filing out of the way (there may be a slight ripple around the edge of the lug, but no more than that). Then try a 27.4 seatpost. Or a larger 27.2 seatpost - the current one may be undersized.

* Warning - possibility of paint damage, but you already have some touching up to do so no big deal.

Keefusb

I would remove the binder bolt, carefully open the space between the "ears" and the seat post slot with a screwdriver or similar. Check the consistency of the seat tube inner diameter using calipers. The cheapest and easiest way to get a better fit is to either fabricate or buy some round shims and shim the seat post near the top of the seat tube. Before re-inserting the post and shim(s), clean up any old grease or crud from the inside of the seat tube, and then run some emery cloth around the inside of the seat tube to remove any burrs or sharp edges.

A quality seat post is also a must for these kinds of situations. I recently purchased a cheap no-name alloy seat post for a nice steel road bike. After just a couple of hundred miles, the post began to bend near the top of the seat tube. Aluminium tends to break before it bends excessively, so a new quality seat post (I ended up using a NOS Profile seat post that is identical to one I have been using for 20 years on another steel road bike I have) was very important. After several hundred more miles, the Profile seat post is doing a great job without bending.

grumpus

A caliper may not give a useful reading - you really need to use a bore gauge to reach below the distortion at the top of the tube.
The problem with most shims is they don't reach far down the seat tube - ideally the shim would support all of the inserted section of the seatpost. So perhaps the easiest way to get a good fit is to accurately measure the frame and get a decent seatpost that's the right size.

Keefusb

Using a caliper to make several internal diameter readings at various points around the top of the seat tube will tell you how far "out of round" the tube may be. Too far out and it will likely need to be reamed or require additional work to make it round again.

If the measurements show that a reaming may be needed, and you don't have a reamer, using shims may still be the cheapest and easiest way to resolve the problem.