Bicycle Mechanics - Shimming 26.0 suspension seatpost to 27.2 ?

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA
meb
02-07-09, 04:13 AM
I've got a 27.2 seattube I want to put a suspension seatpost on.
I have a couple 25.4 suspension seatposts plus a a 26.0 that was once sent me instead of the 25.4 I ordered. Thought I'd shim the 26.0 since that seatpost is otherwise unusable on any of my hardtails (all other hardtails are 25.4 or 13/16). Seems since 26.0 is such a rare size, I couldn't find the proper shim. Should just get 25.4 to 27.2 and store the 26.0 boat anchor or is there a source for 26.0 to 27.2?

joejack951
02-07-09, 02:25 PM
You could try this:

http://www.universalcycles.com/shopping/product_details.php?id=27606&category=172
meb
02-08-09, 02:10 AM
You could try this:

http://www.universalcycles.com/shopping/product_details.php?id=27606&category=172

My read on these is that they are adjustable over a range on the seat tube diameter and fixed on the seat post diameter.

Sounds like the top one is too small in seat post diameter and the bottom 2 are too big in seat tube diameter.

Am I interpretting the shim data correctly?

If so, sounds like I need the converse of these-adjustable seat post to fit a rare seat post diameter to a fixed common size seat tube.

joejack951
02-08-09, 12:21 PM
Sorry, I read the description incorrectly. Your interpretation is correct. For some reason why I first read it I thought the seatpost and seattube diameters were adjustable.

Your best bet is to find some shim stock and use it to convert your 26.0 post to 27.2 or whatever you want. .025" (.635mm) thick aluminum is available in 2024 alloy from McMaster Carr for $15 for a 12" x 12" sheet (enough for many failed shim attempts :)). It's ever so slightly bigger than what you'd ideally use (0.6mm = .0236") but worst case you'd need to lightly sand it down to get a better fit. It won't be as pretty as a purpose made shim but it should do the trick.
mike_s
02-08-09, 05:32 PM
You can get brass sheet from just about any hobby store, but 0.025 (in reality, it's probably 22 gauge, which is 0.0253") might be a touch too thick to fit. The necessary thickness is a bit less, ~0.0236". 24 gauge (0.0201") might work better, since the clamp is made to go smaller than the nominal size, but the seat tube can't get any bigger.