Seat post bolt

Hey everyone,

I've got a old raleigh frame which I'm currently using as a singlespeed commuter. The old seatpost bolt stripped so I cut it out, however the LBS didn't have a suitable replacement bolt so I just decided to use a standard allen bolt/nut with some washers either side, but it doesn't seem to keep the seatpost tight enough. Anyone got any solutions? The bike isn't anything special so I just want a solution that works effectively in stopping the seatpost from slipping down.

Is there any way to use a modern style clamp like this:

Post a photo up of the frame in question...

I got one spare if you want you can have it, like the old raleigh one but tightens with an allen key

I think the issue is that the eyelets which the bolt goes through are coming apart from the frame. It's a cheap gas pipe frame - anybody know of any cheap DIY solutions to get the seatpost secure?
https://dl.dropbox.com/u/867382/Frame%20realignment/raleighfixed.jpg

I can't see why it would matter what type of bolt you use. If the sides of the original clamp are touching (as they appear to be) and it's still slipping you should probably double check that you've got the right diameter seatpost in. Otherwise I guess you'll have to cut a wider notch in the seat tube to allow it to pinch up more.

P.S. The black thing at the top of the photo is a light bracket and nothing to do with this problem right?

Yeah there's a light bracket on top. It looks like the "ears" of the lugs are bending when I tighten the bolts, will double check the seatpost/seattube diameter.

If you post the frame or even tubing type, someone might be able to tell you what size seatpost you need. My 531 Raleigh is 27.2mm, my gaspipe (18-30) Raleigh is 25.4mm.