Seatpost clearance tolerance?
 

Making a custom seatpost shim for my litespeed. Trying to figure what the normal, reasonable, useful (pick your word) tolerance is for a seatpost. ID of the shim is easy- I've found that to be true to the billing, posts tend to be undersized. I can also bring a seatpost to work with me much easier than a bike with no seat.

I know for sweat or welded pipe fittings, it's .007" (ID of female fitting > OD of male of fitting) which is about .178mm. Is this about right?

Hell, anyone know the ID of a 1 1/4 straight wall Titanium tube from the early 90s? Hell, even an idea of the common wall thicknesses? The best I can surmise with my questionably accurate calipers, the wall thickness is 1.05mm

Dan- I think you already know that this project will likely be a "turn to fit" one. With the claimed dimensions only a moving target. Andy.

[Quote; ....Hell, anyone know the ID of a 1 1/4 straight wall Titanium tube from the early 90s? Hell, even an idea of the common wall thicknesses? UNQUOTE]

IthaDan; It would depend on its ID and wall thickness....

[Quote: The best I can surmise with my questionably accurate calipers, the wall thickness is 1.05mm. Unquote]'

IthaDan; Suggest find something of known size and then use the calipers to measure it. Worse case you will then know how much they are off kilter. Then just do the math to get the size of something unknown. Of course a pretty decent digital calilper with spare battery and a nice foamed snap plastic case is about $16 or so on Amazon.

Hope that helps
/K

Oh I know it'll be a make to fit kind of scenario, I was just wondering if there's any kind of convention. Now that im thinking about it though, I guess tubes have a nominal ID, and if that size post doesn't fit, the framebuilder reams the tube to fit the nominally sized post.

I have digital calipers- $8 garage sale with foam case branded with some cartridge reloading company on it..

I'm thinking standard tolerance is ~.15mm. My "25.4" Thomson post is actually 25.25 but the stock 25.4 shim is an honest to goodness inch. That's about .004". So tighter than plumbing fittings.

Generally, you would want a slip fit, i.e. 5-10 thou clearance. This way to post will go in without getting scrached too much.

Thank you.

I called Waterford about this once. They said .2mm. Just a point of reference

Great, thanks. I had a feeling it was about that.

My math was off before- .15mm is more like .006"