Funny that you would have almost the opposite issue!

I am 99% sure that "Trifox" are painting and selling the frame but aren't the designer/manufacturer. I reckon the seatposts are not meant to be painted at all (how many carbon seat posts are?), and by putting several layers of paint and clearcoat on the seatpost, they are effectively increasing the diameter, which leads to the poor fit, and the lack of grip on the seatpost, which is causing all these issues. I also had plenty of other minor problems with the paint job, which support that conclusion - there was paint inside the brake bosses which needed to be scraped out to get the brakes installed, there was also clearcoat over the dropouts which needed to be cleaned out to get the QR skewers to grab properly, and the paint around the headtube/headset went all the way in to the bearing seats(?) and chipped and crumbled away when I installed the bearings.

Even more evidence is this Oz Cycle video . At 14:00 he mentions that the clamp and seat don't mate properly because the fit is too tight - he files away some of the wedge clamp to fix it but I think he should have sanded off some of the paint on the seatpost instead. He also had problems with paint overspray in other areas too.

I also suspect that the min insert line on my seatpost is actually totally arbitrary, and they've just painted a random line on the seatpost, so I might be fussing over nothing, But I have no way to know for sure.

Funny, that when I mentioned any of the above to Trifox support (when they were still talking to me) they told me no other customers had ever had any issues with the seatpost! From discussing and reading online, it actually seems that every single customer has had one or more problems with their seatposts!

Just to follow up in case anyone is considering buying this frame, here's the Canyon geometry for an Endurace CF (using this frame because Canyon include the seat height in their geo charts):

You can see that the minimum saddle height of the M size. is 20 mm higher than the maximum saddle height of the Trifox X16 size 54, which maxed out at 720 mm, and the maximum saddle height of the Endurace in size S, which is smaller than the Trifox in every way, is still 80 mm higher than the Trifox X16 size 54. This is because of the ridiculously small seatpost:

What's ridiculous is that even the XL (size 58) Trifox frame's max saddle height of 760 mm is less than the XS Canyon frame, with a max saddle height of 766 mm...



I went back and forth with the seller and they told me that they didn't believe it was too short, and I needed to fully build the bike up to test it (i.e. install pedals, saddle and bars, not just insert seatpost in seat tube and measure). I also contacted my bank about a chargeback, but they told me I had to work with the seller. While building the bike up I noticed a crack in the seat tube:



Sent this through to the seller too and he said "no it is not broken", "that is not crack", "is actually design of frame", etc., etc. He still refuses to accept a return or refund me, but now his reasoning is because I've installed components on the bike... but the only reason I did that is because he refused to accept a return until I put components on the frame...

Trifox claim they have a 3 year warranty, asked about that a few times, no response. A few days later the seller messaged me asking why I don't just sell the frame on to someone else, when I told him I wasn't going to sell a cracked CF frame that could never fit anyone (due to the tiny seatpost), he just repeated that it's not cracked and there's no longer seatposts available.

Absolute disaster, and unfortunately, my bank don't seem to care about the crack, and they have indicated that because I ordered the wrong size (not true), I probably won't get a refund, although they (or Mastercard) haven't made a final decision.

I bought this frame after seeing Trace Velo, Hambini and Oz Cycle give great reviews for Trifox frames. I’m 178 cm tall and I ride a Medium Giant TCR Advanced (2016). I compared the geometry to their geo chart, and bought a Trifox X16 size 54. The geometry chart is only 1-2 mm different at most, basically identical. It was only after assembling the bike that I realized that there was a major issue: I have normal length legs for my height (inseam 83 cm), and on my TCR, the seatpost is about 20 mm from maximum height/minimum insertion. The maximum distance from BB to saddle rail on my TCR is about 780 mm, and I have it around 745 mm (depends on saddle and pedal stack, obviously).

On the Trifox X16, the maximum distance from the BB to the saddle rail is just 720 mm, so the saddle at maximum height is 30 mm too low for me. The seat tube on the Trifox is actually 5 mm taller than the TCR, but the distance from saddle rail to min-insert line on the Trifox seatpost is just 240 mm, 60 mm shorter than the TCR seatpost! Basically, I need the seatpost to be at least 30 mm longer (40 mm really, to be safe with different saddles and pedals). You might think I just need the next size up, but the size 56 only has 20 mm more seat tube length, and 20 mm more still isn’t enough, and the 56 has too much reach for me anyway (I’d need a tiny stem). The frame is the right size for me in reach/stack/etc., the seat post is just extremely short.
I tried to explain all this to the Trifox support guy, but they don’t seem to understand my issue (or don’t want to). I asked several times if there was a longer seatpost for larger sizes, they said no. To be honest, I don’t see how anyone my height or taller could possibly fit on this frame, or the size 56 or 58, with the tiny seatpost. I sent them dozens of photos and tried to explain the issue several times over the course of a week. These are some of the pictures I made for them to explain the issue:

https://i.imgur.com/t4XzKuh.jpg
https://i.imgur.com/yLNsSor.jpg

Then I realised that the Trace Velo guy looks quite tall – So I went to his build video and he says he ordered the size 58, which has 522 mm seat tube length (C-T). Using that measurement, and a photo of his bike setup, you can measure his seat post extension at 280-285 mm in the below photo. But, the seatpost I have, only has 240 mm maximum extension? So, Trace Velo either has a longer seatpost, or, he has his seatpost set up 45 mm BEYOND the minimum insertion line (measured from two different videos):

https://i.imgur.com/YxTl9Vs.jpg
https://i.imgur.com/0oBgHEj.jpg

I’m 99% sure he is actually just clamping the seatpost way below the minimum insertion. I contacted Trifox support again and explained all of the above, I asked how Trace Velo (who they sponsored to promote this frame) managed to get 285 mm of seatpost extension and sent them the above photo. They replied with this (my measurements on the right, theirs on the left):

https://i.imgur.com/iwfVZ2g.jpg

The dimensions they have added to the left side are completely wrong. He clearly doesn’t understand how to read a geometry chart or measure their own bike frames. I sent them this to explain that the dimensions they had marked as '240' and '280' were completely wrong:

https://i.imgur.com/QJYmuIc.jpeg

At this point I said if he wasn’t able to supply me a longer seatpost, explain how Trace Velo got a longer seatpost, or help me in any way, I wasn’t able to use the bike frame at all, so I asked for a refund.

Surprise surprise, they refused, and have stopped responding. I ordered through Aliexpress thinking it would give me a bit of protection, but after appealing to Aliexpress, they also denied me, unfortunately I think the issue (correct size frame, but seatpost too short) is too technical for them to understand across the language barrier, and they don’t understand why it renders the whole frame unusable.