I recently got a Nashbar 853 frame. I'm 5'9" with 32.25" inseam and will be riding a 17.5" frame.

The frame has an inner sleeve to hold the seatpost.

This sleeve is only 50mm long if I measured correctly, from end of seat tube towards the inside. I can see and reach with my fingers the vent holes for the seat stays below where the sleeve ends.

In plain English, the seat tube is straight wall all the way and the seatpost is held by a 50mm sleeve. Past below these 50mm the ID of the tube is like 29mm.

Would it be safe to run 10"-11" of exposed post with my crappy 140#?

Can I get away with a 350mm post or a 400mm one? Does it actually makes sense to run a longer post if the sleeve is only 50mm deep?

Has anyone had any problems with long posts on these frames (I'm quoting the RM Blizzard as it's basically the same frame)?

Anyone else running tall posts on these frames?

These frames have been around for so long that I think I'm more concerned that I should, but I wante to doublecheck with someone who knows.

Thanks!!

Pic of the offending one...