ink1373

so, i've renovated an 80s schwinn world sport (i think) and i've been looking to replace the seatpost and saddle. however, the current, and presumably original seatpost, has 25.7mm stamped on it. so far i've been unable to find any modern seatposts at that size...my question is, will a 25.4 work? a 26.0? how precise do i really need to be here?

thanks in advance.

sydney

A 25.4 with a shim is a possible bet.Don't try and pound in a 26.0. Depending on indivudal tolerances,.2mm can be a go or no go. Depending on how much meat you have, a seattube can often be reamed to take a slightly larger size.

mctrek

Sydney, first of all sorry to resurrect such an old post. Question for you, what would you use as a shim, that measures 0.15mm thickness? Would you use an aluminum pop can, two layers of it maybe? Or could you have a seatpost at 26.0mm turned on a lathe to 25.7mm. I think taking 0.15mm from the wall thickness should not effect the aluminum seatpost too much.

fietsbob

seat posts are in even numbers of 10ths of a mm.. your measurement is off. its either 25.8 or 25.6..

you can find seatpost sizing shim sleeves with a 25.4 ID & either OD... OD of 25,8 is 0.2 mm in wall thickness difference .




A reaming tool that is adjustable can shave out the inside of the frame's seat tube out to the next larger size..
It must be done carefully.. with some skills & cutting oil.






...

fietsbob

Digital or vernier calipers can measure thickness of soda /beer cans to use as shims..

madpogue 

Even though it was stamped 25.7?

But now I'm curious. I have an '85-ish World Sport, now I have to go look at it....

I have a modern seat post marked 31.9 sitting in my "WTF am I gonna do with this stuff?" box.

fietsbob

Well you're stuck then.. So, what do you plan to do? Did you measure it independently, yourself.. ?

FWIW.. I Own a BridgeStone Road Bike.. it came with a 27.0 seat post,, marketplace has a lot of 27.2 seat posts..
Local Bike shop, in the off season, let me use an adjustable reamer, I carefully shaved out,
0.1 mm from the inside until a 27.2 seatpost slipped in.. then stopped cutting..

Now it fits perfectly ...






....

madpogue 

Your bike might be a World, rather than a World Sport. Are there any decals referencing the frame material? That might help indicate what model you have. I just checked an '84 World and an '85 World Sport. The '84 World is plain high-tensile steel, and has a 25.7mm seat post like yours. The '85 World Sport is 4130 chrome moly, and has a 26.4 seat post.

The 25.7 size is definitely an outlier, but on the other hand, Schwinn made a LOT of entry level bikes BITD, so it shouldn't be impossible to replace it. You'll probably be stuck, however, with the cheap heavy chrome steel pillar-style post.

Bill Kapaun

Careful use of emery cloth?