bobwysiwyg

I need to replace the seat post on my grandson's Expedition. I can't find any info on the diameter. I tried Sheldon Brown's data base of seat post info, but the Expedition was not one the models listed. Any help would be appreciated. Oh, and I'm guessing it's a 2013 or 2014.

mixteup

A digital caliper is your friend, here .......

bobwysiwyg

Sure would.. if I had one, and if I had a post to measure.

mixteup

You can get a plastic one for about $10, but this one is a little better -

https://www.amazon.com/Stainless-Mil...ateway&sr=8-10

If you had one, you could measure the ID of the seat tube -
It might give you a place to start, if no one comes through with exact knowledge.
I don't know how anyone can work on any kind of machinery, without some way like this to measure things -
It would drive me crazy not to have one. But that's just me, I guess

bobwysiwyg

.. just trying to get an answer, I do very little that requires such a tool. Thanks for your input though.

JoeTBM 

@bobwysiwyg
This lists a 27.2 if that helps

https://www.specialized.com/us/en/ex...entry/p/106321

and this is the same size post

https://www.specialized.com/us/en/ex...sport/p/106353

bobwysiwyg

Thank you. Just what I was looking for.

fietsbob

a good caliper has 3 ways to measure things , inside, outside and depth.

Crankycrank

Take it to your local bike shop or a Co-Op if you have one nearby. Have them measure and insert post to be sure it's the right size as they come in fractions of a millimeter differences so easy to get it wrong. If you're trying to keep costs down shops and Co-Ops will sometimes have cheap spares exchanged from new bikes or used posts.

Andrew R Stewart 

So the old post is either missing or isn't marked with it's diameter? Since a spec chart doesn't account for real life manufacturing tolerances/distortions trial fitting a post is the only real way to insure the best choice. Since wishing to return a scratched, but "new" post after it didn't fit isn't always allowed (the scratches diminish the post's value to it's next owner) having a shop test fit before buying is a smart way to both get the right size the first time and also develop a relationship with your LBS. All the shops I've worked in have had a selection of test posts that can be scratched without worry or cost. Andy

Andrew R Stewart 

BTW one can use a strip of paper, a pen and a simple metric rule to get pretty close to a diameter measurement. Wrap the strip of paper around the object. make a mark on it where the end of the strip is on it. Lay the strip flat on a surface and now measure from the strip's end to it's mark. Take this measurement and divide by 3.1415 to get what is very close to the object's diameter. By doing this one reduced the error to aprox. 1/3 of a direct measurement. This will get one within the ball park to then begin the test fitting of trial posts. No fancy measuring tools needed. Andy

JoeTBM 

Andrew, not trying to be a wiseguy here and have always enjoyed your wisdom but if you are going to express pi (π) as a four digit decimal it is 3.1416. Also the op expressed that in posting #3 that he did not have the old post so there is nothing for that strip of paper to wrap around.

Andrew R Stewart 

Joe- My posts are not only intended for the OP but also for those reading. And I think you, too, agree that one tenthousandth difference in the value one uses for pi is vastly less then the width of the pen or pencil used to mark the end of the circumference.

Or did I miss you attempt at humor? Andy