Mountain Biking - Help with seat post

I have a Infinity Mayhem bike at school and I am trying to figure out the seat post size. My bike seat has been stolen in the past so I'm using an old bike seat that does not fit. There is no way for me to take my bike to the bike shop so im trying to search the size of my seat post on the internet but no luck so far. I was wondering if anyone here knew the seat post size for the Infinity Mayhem?

Thank you

Take it out of the seatpost and the size is usually stamped on the end.

Sorry, I forgot to add in my post that my bike seat was stolen and I'm using a seatpost that does not fit.

Anyone? Please help.

Sorry, I forgot to add in my post that my bike seat was stolen and I'm using a seatpost that does not fit.

so it doesn;t fit...
likely that iff'n you got the non-fit post inserted at all, then its prolly too small... not too big
iff'n you were able to close the binderbolt/seat clamp and it held the post reasonably, then it was likely not way too small...
so likely it was maybe the next size smaller...
so pull it out, check the size on the post (if no size visible, mic the post) and then go to the LBS and see if they have a 'used' post one size larger you can try to insert. expect the bigger post to be really, really hard to insert at first, since you've already clamped the seattube down some to fit the smaller post...
But iff'n its right, it'll eventually go down properly... if properly greased.
Then do the right thing and buy a new proper sized seatpost from the LBS who 'loaned' you the used test post...
when you leave the bike 'exposed', run a cable thru one seat rail and hook to U-lock or whatever your main lock setup is. A little more hardware to carry, but beats havin to replace the post and seat yet again.

Ok thanks. Lets assume that the seat post size for my bike is 27.0. Would a 26.8 seat post work?

Ok thanks. Lets assume that the seat post size for my bike is 27.0. Would a 26.8 seat post work?

Really, no. I wouldn't. You should use the correct size that fits you seat tube.

The only way to properly use an undersized seat post is to add a shim.

The only way to properly use an undersized seat post is to add a shim.

I've used an old inner tube before with success. YMMV

I've used an old inner tube before with success. YMMV

Success is subjective.

That is not the correct way to do it.

If you like it, then go ahead. Good luck.

I've used an old inner tube before with success. YMMV. . . and your "advice" is a little late. Like to think the OP solved this maybe two years ago at least.

. . . and your "advice" is a little late. Like to think the OP solved this maybe two years ago at least.

And if he 'solved' it by using the innertube method, by now the seat tube would have deformed, ovalized, or failed. That is, if the bike had been ridden any appreciable amount.

Aw hell, after 2 years now that bike probably has been ham-fisted into oblivion.

Success is subjective.

That is not the correct way to do it.

If you like it, then go ahead. Good luck.

Maybe not the correct way but it worked without damage. We're not talking a big difference in size here.

^I had much higher hopes for the post of a 7-year veteran of the site with only 34 posts in total. What a let down.

Wow lmao I can't believe this topic is still going on. I ended up using a seat clamp/bolt thing...2 years ago. Thanks guys. LOL