Hi there,

Trying to build up a (rigid) MTB for the summer, using parts I already have. (26er or 29er: have wheels and forks for both) The only part I need is a frame... (and maybe headset if frame had oversized head tube)....

At 5ft 8, I seem stuck between 16 inch or 18 inch. I've picked up a 16 inch On One Inbred frame (26er) for cheap but before I build it up, have measured my cycling inseam (book jammed into crotch method) + the length of the seat tube. My inseam is 80cm to pubic bone height.

On an old 26er 90s XC MTB which is 18 inch, I have around 20cm of seat post showing for full leg extension (for light trail use). So I'm thinking that on a 16 inch frame, I would end up with at least 25cm. This bike has an almost horizontal top tube and very low front end - 90s xc fit not v. comfy! Otherwise I'd just use this with a V on the rear as it's a decent cromo jobby.

On One's sizing puts me firmly in the 16 inch range, while other brands put me in the 17 - 18 inch range.

Not being an avid modern MTBer, just wondering if their sizing is on the assumption that people run their saddles a bit lower on MTBs.

Anyway, 25cm would seem like a lot of seat post!

Any thoughts appreciated!