Custom seatpost or modify seatpost

[SillyBilly]

Hi all. I have a Tifosi Auriga Disc 2018. It has a D-Shaped post. Unfortunetly I need a longer post. My bike is an XL with a 300mm post. I am needing a 400mm. Unfortunetly Chicken Cycles (the distributor/owners of the Tifosi) no longer have stock.

Does anyone have any suggestion on what I might be able to do to make the post longer? Does anyone know of a custom seat post maker??

Thanks.

[richardfm]

Try googling d-shaped seat post 400mm. Here's one example https://www.rosebikes.com/rose-d-shape- ... th-2710239

[Brucey]

if you can't source a new seatpin, you may be able to graft something onto part of the extant seat pin. If you really went to town, most of the visible parts of the revised seat pin could be of aero cross-section.

[richardfm]

if you can't source a new seatpin, you may be able to graft something onto part of the extant seat pin. If you really went to town, most of the visible parts of the revised seat pin could be of aero cross-section.

Can you suggest a safe method of doing this?

[Brucey]

my idea was to cut the visible part of the extant seat pin in two, about 4" down. Next, take an Al sheet ~1.5mm thickness and cut a piece off about 150 x 250mm. This is to become your aero section. Now, abrade near the long edges and fold it lengthwise, such that the fold is a gentle curve of 180 degrees, the abraded surfaces are facing one another, and the internal dimension is sufficiently large to accommodate the shaft of the original seat pin. Next, make some shaped wooden pieces to fill the gaps/smooth the transition. Trim the Al part so that the ends are horizontal when installed, but leaving 'sideburns' that can sit alongside the original shaft. Use epoxy resin to secure the rough-hewn wooden pieces to the original shaft. Shape the wooden pieces to fit the aero profile, allowing about 3" joint overlap.Taper the 'sideburns' down to ~0.5mm along the far edge. Using more epoxy resin, secure the aero section, bonding the trailing edge at the same time. Dress the outside of the part so as to smooth the transition between aero and 'D' sections.

You should be left with a slightly heavier (and longer) aero seat pin, retaining the adjustability of the original 'D' shaped item. Obviously the length of the aero section determine the lowest saddle position, and the highest is determined by this and the length of the lower 'D' shaped piece. A variation which allow a slimmer aero section and uses less of the 'D' section is to bond a ~1.6mm wall thickness Al tube inside the 'D' and inside the aero section. This method has the advantages of requiring no 'sideburns' and allowing the use of drilled holes in just two wooden transition pieces. If you think strength is likely to be an issue, the lower tube can be replaced with a steel version in this design. In any event, I would recommend that the tubes are bonded to the wooden transition pieces before they are shaped to fit inside either the 'D' or aero sections. However, this design uses a slightly shorter aero section, leaving more of the original 'D' section exposed at the top.

Either scheme should be more than strong enough and should not be too difficult to do, well within the likely skills of the average DIYer. However, as with any use of adhesives, scrupulous cleanliness and surface preparation are vital.

[SillyBilly]

@Brucey, that was my train of thought too. I was considering a different carbon post that might fit around my D post, and then resin bonding it in place.

[Brucey]

that'd work too, but it might be best if you stuck pieces of wood to the 'D' first, then SG'd them so that you would have a nice round shape to slide inside the CF seatpin and bond.