Braddanman

I have an 84 Peugeot with a seat post that is fixed with a pointed allen key bolt that goes directly from the back of the seat post tube into a groove in the seat post. The original brochure doesn't give it a brand name but just says alloy micro adjustment post (I would have thought all seat posts were micro adjustable) but it does have JPR engraved upon it. My problem is that when I ride it's always creaking which annoys the hell out of me. It took me ages to find out where this noise was coming from, at first I thought there might be a crack in the frame! It was only after I took the seat post out and refixed it that the noise stopped but after a couple of days it's back.
When I took the seat post out the holding bolt was bent (and still is a bit) I guess the weight of everything must just be pushing the end down and bending it.
So how do I stop this noise? I have two thoughts, first, I think that maybe it's a bit dry in there and I just need to line it with a bit of grease but my main thought is that as I've never moved the height of the post in years and therefore won't in the future could I change the holding bolt for a non tipped (normal) one and actually tap a thread into the seat post to hold it in place?
I know that if i do this there will be no future "micro" adjustments for me. What do you think? Are there any alternatives?
Thanks

Chombi

Sounds like you might have a 1984 Peugeot PSV like mine with the weird allen head set screw for the seat post height adjustment. Vitus used a similar setup on their bikes, but they did it with more robust parts that stood up better with use.
Just a warning, I wouldn't really mess around too much with that set screw because this setup by Peugeot is the weakest part of that bike. One over-eager turn of the allen key can spell disaster with the set screw frame tube boss cracking on you or the screw or boss threads stripping. You pretty much just carefully set these things up once and try to avoid goofing around with it as much as possible. All I can think of that you could do to ry and stop the creaking is clean up the seatpost and seat tube as much as you can and hopefully what grit might have been contributing to the creaking will be eliminated, then VERY carefully retighten the set screw to the proper seat post height. Also, carefull inspect the set screw boss and seat tube for any cracks that might also cause some noise. Finding any cracks will be certaily bad news as it will question the bike's integrity for riding safely.
Your best bet to avoid future problems is to try and locate a 26.4 OD expanding wedge seatpost that was used a year later by Peugeot on their mid level bikes (when they figured out that their previous setup was no good), including later "Triathlon" named version of the PSV. They are very hard to come by but do appear at eBay once in a while, if you spot one, grab it asap!
Tapping threads on a new hole on the seatpost tube back and going for a through bolt solution sounds good, but remember, you only really have one chance of getting it right or risk having an irreversably ruined and very hard to find JPR seatpost with the proprietary set screw centering groove if you don't, never mind the bad positioning resulting on the bike.
Can't really blame the bike for having such a weird seatpost setup........it's French, afterall!

Chombi

RobbieTunes

It's French.

All they do is complain.

The seat post is no different.

Braddanman

Thanks for your comments, it seems that I have resolved this annoying problem.
Yes it is a PSV. I never considered that I could overtighten it and damage the frame. I was a bit worried when I noticed a small bulge just next to the boss but when I took the post out and checked inside all was smooth. It must be just some of the brazing. I also noticed that the seat post is smaller than the tube more than I would have expected considering that it's only the point of abolt that's holding it in place 50mm below the top of the frame.
I've taken the post out cleaned and greased everything but also put a shim from a drinks can in place to stop the top from moving about. I also sprayed oil into the seat clamp and also the rails of the seat where they fit into the lugs.
I don't blame the French for trying out new designs and I think it looks quite good but at least road test a new design thoroughly before bringing into production. I guess the ultimate solution is to find one of those expandable wedge seat posts you mentioned.
Anyway, one or all of the above have given me a quiet ride. FOR THE TIME BEING!