Nope…… not with my new frame as it ain’t built up yet but i was looking at the threads on stw along with other posts online and i think/agree wi other comments regarding the seatpost shim/insert as being the cause of the problem – it’s too short.

As you can see from the pic below the shim is only inserted 60mm into the frame

The pic below shows the shim insertion depth and the usual area of cracking which is within 10mm from bottom of shim, so i figure as the minimum insertion depth for seatposts is usually 100mm the fact that even though you may think you have 100mm of seatpost in the frame, it ain’t doing jack-$hit as the 60mm shim takes the strain and transfers whatever seatpost movement into the middle of the structural weld area rather than further down the main tube where it could be handled better, i guess a well fitted shim may also strengthen the frame so i wonder if it would be beneficial to downsize the seatpost to 28.6mm thus increasing the shim thickness?.

So if i remove the 60mm shim and replace with a correctly sized 100mm depth cane creek shim i shouldn’t have any problems but i tried very carefully to grab the outer lip of the shim and move it but i suspect that the alloy shim fitted is bonded or glued in with some form of loctite, it might crack off if i bung the seatpost and pour very hot water through the BB shell, then pack ice or use freezing spray in the alloy shim to contract it – I’ll try and contact Silverfish tomorrow to see what they say about the idea or if it would invalidate the warranty.

Just seems like the sensible thing to do as i want this frame to last a very long time

Cotic hummer frame crack-possible problem/solution?

Cotic?

I’d phone “Cotic” straight away & let them know 😯

And another ti frame cracks in the same position….

It’s not cracked NBITF.

My guess is you are correct, but you’ll certainly invalidate the warranty – but are they warrantying these frames for this failure?

As you say, it does seem a bit pish to only have a 60mm shim, you’re effectively only inserting the seatpost 60mm into the frame?.

Oops, read it properly 😳

Yeah, they are honouring the 5yr warranty for cracking frames but surely it’s financially beneficial for all involved if i can fix the possible problem in the first place. I was going to phone silverfish but i can’t find a phone number on their website so i’ll email them when i get home later.

it does seem like a bad design putting a shim in and ending it there. Ideally the shim should be tapered in thickness at the bottom to gradually reduce the stress up to the edge but I suspect that’s not been done too.

If it’s still in warranty then it’s up to Cotic really if they will allow you to do it and keep the warranty. Not sure how easy it is to get out though. There should be some sort of adhesive between the two so localised heating to the adhesive Tg should soften it to get it out.

Could it be a press fit, in which case you’ll struggle to get it out. And would the maker admit to a less thab optimum design, by telling you 100 mm would be better?

My Ti frame cracked there too, same sort of shim 🙁

mine too – sad to see manufacturers still doing this