Do you measure the length of the post to the bottom of the clamp?

I have just bought a new frame and require a 350mm seat post. I then bought one and the length of the post upto the clamp is 327mm which is too short. Are seatposts usually measured to the rails?

Thanks very much!

bottom of post to rails usually though as ever there'll be some companies that do it differently.

Ooh, never really thought about that. I would have thought it's the maximum length that can be inserted in the frame. I could well be wrong….

EDIT: Just measured my Thomson, which is 330mm from end to seat rails. Others may measure up differently.

Wot clubber said

Hindsight is a wonderful thing 😉

I knew I should have asked on here first – Thanks for your help!

You'd have been better buying a 400mm anyway, as it sounds like you'll still have too little in the frame.

Yep, it's length of whole post, not to minimum insertion mark.

I'd say the frame is maybe a touch too small for you if you need 350mm of post sticking out!

Sorry i shoudl have been a bit clearer – I dont need 350mm sticking out!

The frame takes a 30.9mm post so lined up a 27.2mm post from another bike and decided that a 350m post would be ideal. However I was measuring to the top of the post not the rails. The 'missing' 23mm from my measurements therefore puts the post above its max.

Thanks for your help

If you're using a shim then the length of the post below the shim is almost irrelevant as it won't be in contact with the seat tube.

Make sure you use a shim that drops as far down into the frame as possible.