Seat tube issues

[Rick]

So you think Thomson makes the 27.4 post precisely for situations like mine? How nice of them

I don't think they are "nice"; I think they want to make a profit.
And so they wouldn't be making a 27.4 as a standard size unless there were a significantly large demand; which means there must be quite a few other people with the same size tube as yours.

Custom bicycle frames are not a big enough market to demand custom tube sizes from the tube manufacturers, so they have to use commonly available tube sizes. Maybe 27.4 is a standard industry inner diameter for Ti tubes. I don't know this is true, I am just speculating to find a logical explanation of your situation.

[breezerboy]

Sure, I could give the 27.4mm a try, but that's no really the point. I shouldn't have to be doing this on a brand new £1000+ frame....right?:(

The point is, you should use the right diameter seat post for the bore of your seat tube. If the spec stated 27.2 but the measurement is for 27.4, use a 27.4.

Whether it's a defective frame or a typo on the website spec we cannot say unless you give us the manufacturer/supplier. If their supplied Ti post is 27.2 you may be able to reject the frame/post as defective due to incompatibility. If they supply (or pay for) a 27.4 post it solves the problem, works perfectly and you need to stop complaining and ride it.
27.4 isn't, or at least wasn't an uncommon size, especially on superlight frames. Waterford used them for years, and as well as Thomson you could get American classic and Dura Ace seatposts in 27.4 amongst others.

As for it being £1000+, that's irrelevant. Any frame, at any price should be correct.

So the first issue: if using a compact chainset (Red 22), one of the bottle cage bosses on the seat-tube is in the way of the craze-on clamp (Red 22). I contacted the shop i bought the frame from, and the manufacturer of the frame suggested to them I get an aftermarket braze-on clamp that allowed the front mech some adjustibility. OK, fair enough, but still quite annoying considering how expensive the frame is, and the fact that SRAM (and maybe the others) have these important measurements online available for who ever wants to see them.

These frames are designed to take a braze-on clamp, so any picture of it, including the ones on the manufacturers website, is shown with a braze-on clamp.

Do they specify a specific clamp? Several different designs are available, some with no adjustment, some with huge adjustment. Not being able to use your chosen clamp is not reason to call the frame defective, just not as you would have specified it had you had the choice. If no clamp will give correct front mech setup, you may have reason to reject, but only if they had expressly stated that it would be compatible with the components you are using prior to purchase.

I'm assuming from the price this is off the peg rather than custom. I'm only asking because custom may have given you more reason to reject as it doesn't appear to suit your needs. Of course, it being several months after purchase doesn't help either way.

[Calnago]

I agree that seat tube is out of "acceptable tolerance" for a 27.2 seatpost. I'd be rather upset as well. You should be able to use any 27.2 post of your choosing, not forced into using a "fat" seatpost because they over bored the seat tube. I didn't even know Thompson made a 27.4 seatpost but that's not the point. Seems like quality control is an issue here, not you being "nitpicky".

[CharlesM]

Still not sure why we can't know the brand and the shop...

As long as you have measured right, You have a frame that's not suitable.

The proprietary seat post thing is bull5h!t.


This is either the shop and manufacturers issue and they should refund you...

Or it's your seatpost that's off and you're not measuring it correctly.

[ridingmakesmehappy]

Sorry again for this very late reply! I've been non-stop with xmas shenanigans.

So here is an update: shortly after my last post I called up the shop. The reason they hadn't replied to my earlier emails was because they were still waiting on the manufacturer to get back to them. So they called the manufacturer up there and then, and spoke to higher management, and they agreed that this issue had gone on long enough and so agreed to give me a full refund! I am very happy

OK so based on some of your questions and suggestions I feel like I haven't explained a few of my previous point properly. So in regards to the internal diameter of the seat-tube. The frame specifications are for a 27.2mm seatpost and I was using a 27.2mm seatpost and the manufacturer was offering me a 27.2mm seatpost. No doubt in the past manufacturers have designed frames to take a 27.4mm post, but this is not one of them. Also, I said the average diameter was approximately 27.4mm, but what I should have said is this:

T 27.32, 27.52, 27.43 average 27.42
B 27.60, 27.50, 27.42 average 27.51

So the T means Top, the top of the seat-tube, and B means Bottom, a little further down the seat-tube. As you can see, I took 3 measurements for T and B, at different angles to get an average. The important thing to take away from this is the relatively LARGE range in the diameters. So yes, I could have attempted to use a 27.4mm post, and no, it would not have worked.

Here is another set of measurements I made with 2 of my other bikes to compare to; note the consistently smaller range:

Specialised Langster
T 27.34, 27.28, 27.28 average 27.30
B 27.25, 27.34, 27.40 average 27.33

Cannondale F600
T 27.22, 27.39, 27.30 average 27.30
B 27.23, 27.33, 27.26 average 27.27

There is another point that I need to make, if I haven't done so already. Something inside the seat-tube was chaffing the crap out of my seat-post. I'm not sure how to upload pictures on here, when I find out, I'll post one! And yes, the frame is off the peg, although there is an option for a custom build.

As to why I don't want to name the shop or the manufacturer; my worry is that my experience will be taken out of context. The reality is that both shop and manufacturer have a good reputation, else I wouldn't have bought what I bought. And in all honesty, everyone gets a few hiccups, even the ones with a good reputation. Also, the shop I bought it from don't know me personally as I had them post the frame over to me. So in their eyes, I could have been some random punk trying to scam or mislead them, something I reassured them I wasn't.

I guess the message to take away from this, now that it is all over, is that you should persevere when your gut instinct is telling you not to settle.