Educate Me On Seat Tube Shims In A Ti Frame
Hello,
Happy Thanksgiving everyone! I hope that this post is in the right place.
I have a 2005 titanium Litespeed with about 93K miles on it. It has a Ti seat tube with a shim that was honed/reamed to a snug fit. No issues with the seatpost slipping or any frame cracks in all those miles.
I recently received a new Ti frame and was surprised that the seatpost just dropped right into the frame! It also has a Ti seattube with what looks like an aluminum shim insert construction.
I took some caliper measurements and the seattube opening measures 32.13mm for a 31.6mm nominal seatpost. This is a diameter difference of .020" (0.5mm).
I have been in contact with the builder who claims that .020" is "within tolerance". Their original response was that the insert was reamed to the correct size before the slot was cut and that the top of the seattube may have expanded after the slot was cut. I don't know that I buy this argument as the seattube O.D. is round within a couple of thousandths and the diameter is the same within .005/.010" above and below the top tube. I don't have a bore gauge but based on my O.D measurements I would assume that the seattube bore is as sloppy all the way to the end of the insert shim.
While the builder doesn't consider this a problem I would like a second opinion. Hopefully there are some builders here with Ti experience. My main concern would be frame cracking of the seatpost due to metal fatigue as the post wobbles back and forth in the loose bore. Is this a valid concern or not? About the only thing that I could guarantee is that if there was no flex there would be no frame cracking!
I am also curious on what should be the proper process for installing a seatpost shim in a Ti frame. I am assuming that the insert shim is aluminum. Is it press fit or glued? If it is decided that this shim should be replaced and properly sized what special skills and tools are required to do it properly? Could a builder that only does steel frames do it or should I find someone with Ti experience (much harder)?
Thanks,
Steve