I've used the shim method on seat posts, but as you move the seat post the shim seems to squirm around and get out of position, it gets to be a hassle. An old machinist's trick to give some purchase on a too lose shaft is to take a center punch or a carpenter's nail set and ping a couple dimples around the shaft. A little edge of metal gets pushed up around the dent that will hold the shaft in place until you tighten the set screw or whatever. Too tight and just file down the erupted metal. It may not be prudent to put slight dents on a good post's shaft, even below the visible part, but it is one way to enlarge the diameter slightly. I have done this on solid shafts, never on a tube. I'd approach it delicately to avoid distortion, do a little test down at the bottom first.
Dennis Young Hotaka, Japan
>
>> I have a bike with a 26.2 seatpost. I measured the seat tube inner
>> diameter (at the lug) with calipers and measure just a hair larger,
>> say 26.25 on average. I think it is safe to say that a 26.4 would
>> not fit.
>>
>> The seatpost feels loose in there. The problem is that as soon as I
>> loosen the seatbolt, the seatpost just slides right down, making it
>> hard to make small adjustments.
>>
>> Has anyone experienced this, and have a good cure?
>
> You have at least a couple choices -- you could shim your present post
> with a thin piece of metal, say a slice out of an aluminum beer or soda
> can. This is probably the easiest and least expensive option. You could
> try other posts to find one that fits better and buy that one. Or you
> could ream the seat tube to accept a 26.4mm post and use that.