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Who Knows a little about Peugeot PX-10 seat tube construction?

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Who Knows a little about Peugeot PX-10 seat tube construction?

Old 12-24-09, 01:06 AM
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Who Knows a little about Peugeot PX-10 seat tube construction?

I have to admit it... I never once gave it a thought before, but today I was cleaning a late 60's PX-10 frame and noticed that there was blockage about 8" down the seat tube. I shined a flashlight down the tube and even poked a long rod down there and sure enough it ended.

It's dark down there and there is a slight amount of corrosion, so I can't exactly tell how it is constructed. I am assuming that it is designed to prevent objects or water from getting down there... and not that I have a foreign object stuck in the tube...?

Any one know how the seat tube is designed? Anyone have a diagram? Am I nuts?

Now I am going to have to take all the seat posts off all of my bikes to find out if they are all made this way or if this is unusual. Anyone know so they can save me the trouble???
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Old 12-24-09, 01:09 AM
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Stuck post with a solid end hammered down out of the way?

-Kurt
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Old 12-24-09, 01:13 AM
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I'm positive that's not the case. It seems as though it is manufactured with an internal stop. I may need a smaller flashlight to see in there better.

Originally Posted by cudak888 View Post
Stuck post with a solid end hammered down out of the way?

-Kurt
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Old 12-24-09, 01:16 AM
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That's odd. I hope it is a treasure map or something.
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Old 12-24-09, 01:19 AM
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Oh, how stupid of me...

Why don't I just check out the OTHER PX-10 I have and see if it has the same stop.

BRB, BF-CV...
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Old 12-24-09, 01:27 AM
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The other bike has the same thing... and I measured this time, 6" down.

So it's not a treasure map or a pounded down seatpost, or even old malted milk balls.

But I still would like to know how it is made...?
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Old 12-24-09, 01:35 AM
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I would imagine it is just a plug brazed into place?
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Old 12-24-09, 01:35 AM
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Originally Posted by Ivandarken View Post
The other bike has the same thing... and I measured this time, 6" down.

So it's not a treasure map or a pounded down seatpost, or even old malted milk balls.

But I still would like to know how it is made...?
Well, PX10's were made with butted tubes, right? So maybe it's just a piece of metal that could be dropped in at the top and then smashed down into the butted section of the tube?

I'm also just making this up, so..... yeah....
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Old 12-24-09, 05:01 AM
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Originally Posted by DRietz View Post
Well, PX10's were made with butted tubes, right? So maybe it's just a piece of metal that could be dropped in at the top and then smashed down into the butted section of the tube?

I'm also just making this up, so..... yeah....
Remember, butted tubing means it's thicker at the ends and not the middle, so you cannot just drop items down the tube and expect it to stop and jamb against a section in the middle. The thinner wall section at the middle will just let it drop down towards the BB shell or lower butted section, much lower than the few inches down the OP noted on his PX10. My 80's Peugeot PSV does not have this plug in it. I figure that they used to do it back then for some obscure "French" bike building design logic/purpose.........which is not surprising these days when looking back at older French bike frame
construction and component design.

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Old 12-24-09, 07:34 AM
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That's almost as wierd as the floating wooden plug in my PX10's steer tube. Nobody has ever been able to give me an explanation for that plug that makes sense to me.
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Old 12-24-09, 07:41 AM
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Originally Posted by Dirtdrop View Post
That's almost as wierd as the floating wooden plug in my PX10's steer tube. Nobody has ever been able to give me an explanation for that plug that makes sense to me.
France.
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Old 12-24-09, 07:47 AM
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Hey! My PX-10 frame has the seat tube plug as well! Mine is at depth of 6 or 7 inches and you can easily see it with a flashlight. I thunked it gently with a rod, and it thunked back, feeling soft and movable, feeling like cork or balsa wood. I'm guessing it's a block for debris or water, to prevent it flowing down to the BB. Cork makes sense because it could (wine bottle technology, how French!) be shoved down a clean new tube, and would expand when it gets past the butt area. Some softer balsas can have the same characteristic, but it's really not as elastic as cork (my model airplane days many many days ago!).

It would also serve to damp vibrations in the seat tube. This could be part of the perception of a PX-10 frame. Some think such frame tube resonance or ringing is a significant part of percieved ride quality.
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Old 12-24-09, 08:06 AM
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Originally Posted by Chombi View Post
Remember, butted tubing means it's thicker at the ends and not the middle, so you cannot just drop items down the tube and expect it to stop and jamb against a section in the middle. The thinner wall section at the middle will just let it drop down towards the BB shell or lower butted section, much lower than the few inches down the OP noted on his PX10. My 80's Peugeot PSV does not have this plug in it. I figure that they used to do it back then for some obscure "French" bike building design logic/purpose.........which is not surprising these days when looking back at older French bike frame
construction and component design.

Chombi
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85(?) Vitus Plus Carbone 7
Except that most seat tubes, including those used by Reynolds, are single butted, meaning there is no thick section at the top. The tube diameter is the same all the way down to just above the bottom bracket. So, if you put a light interference fit plug in the seat tube, you could drive it down to any depth, until it hit the butt, just above the BB shell.
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Old 12-24-09, 08:17 AM
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Originally Posted by Dirtdrop View Post
That's almost as wierd as the floating wooden plug in my PX10's steer tube. Nobody has ever been able to give me an explanation for that plug that makes sense to me.
The plugged steerer tube was to keep the fork from flying off if you cracked the steerer tube. It was more common on Track bikes where stresses are greater, although on mountain decents I would imagine theres a good amount of torque applied to the steerer.
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Old 12-24-09, 09:49 AM
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Originally Posted by big chainring View Post
The plugged steerer tube was to keep the fork from flying off if you cracked the steerer tube. It was more common on Track bikes where stresses are greater, although on mountain decents I would imagine theres a good amount of torque applied to the steerer.
That's one of the explanations I mentioned that makes no sense. The plug is less than an inch tall and is loose in the tube.
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Old 12-24-09, 11:18 AM
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Thanks for all the conversation. I am surprised that so far no one here has any authoritative information... you guys have such experience.

It's good to know that there are still some mysteries in the world to be solved... however, there are still a couple of Peugeot experts that have yet to find this thread.

I will examine the cork possibility (which I find elegant) later when I can remove the bottom bracket and see if it does the same thing going upwards.

Do you think I should get out my sawzall and open her up for science? I'm sure a cutaway section would put this mystery to bed once and for all!
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Old 12-24-09, 11:58 AM
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I have a India-made Hercules roadster frame who's seat tube was filled at least 4" with gear grease, down by the bottom bracket. Nice debris stopper.
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Old 12-24-09, 02:33 PM
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The last bottom bracket I serviced had seeds, leaves, debris. Lots of it. I tapped on the seat tube for a while and it just kept falling out. Can mice get into a seat tube? The only thing I could think of.
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Old 12-24-09, 02:45 PM
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Originally Posted by Dirtdrop View Post
That's one of the explanations I mentioned that makes no sense. The plug is less than an inch tall and is loose in the tube.
About the only (and highly unlikely) situation it would help in would be if the steerer tube's bond broke within fork crown - in which case, the front brake bolt would hold the tube equally well.

Seeing that most steer tubes break above the fork crown, the story is pure hoopla, as Dirtdrop says. Someone was having a gag at the expense of Big Chainring, IMO.

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Old 12-24-09, 02:46 PM
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Originally Posted by big chainring View Post
The last bottom bracket I serviced had seeds, leaves, debris. Lots of it. I tapped on the seat tube for a while and it just kept falling out. Can mice get into a seat tube? The only thing I could think of.
I did hear long ago of someone who supposedly found a dead mouse in a BB once - got caught on a BB lug pin, I believe.

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Old 12-24-09, 03:00 PM
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Originally Posted by Dirtdrop View Post
That's almost as wierd as the floating wooden plug in my PX10's steer tube. Nobody has ever been able to give me an explanation for that plug that makes sense to me.
Wood dowels were often inserted into steer tubes as a safety measure in the event of fork failure. I'm not sure why yours in "floating" but perhaps the wood has dried and shrunk over the years?
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Old 12-24-09, 03:02 PM
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Originally Posted by David Newton View Post
I have a India-made Hercules roadster frame who's seat tube was filled at least 4" with gear grease, down by the bottom bracket. Nice debris stopper.
It probably automatically re-lubricated the BB bearings too, when the weather gets warm enough...
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Old 12-24-09, 03:12 PM
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Originally Posted by JohnDThompson View Post
Wood dowels were often inserted into steer tubes as a safety measure in the event of fork failure. I'm not sure why yours in "floating" but perhaps the wood has dried and shrunk over the years?
Dowels, or something the length of a cork?

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Old 12-24-09, 04:10 PM
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Road Fan,

I think you win the prize. There is indeed a stopper of cork within the seat tube of unknown length. I pulled a shard of loose cork out of my other PX-10 and confirmed this. As well, it is cleaner in that bike and I can clearly see the texture of cork within the tube.


The discussion now becomes: WHY?

Is it merely for protection from debris/moisture getting into the seat tube?
Is there a performance aspect to this?
Does anyone know other manufacturers who used this method?

Quick, everybody check your late 60's era road bikes!!!

Originally Posted by Road Fan View Post
Hey! My PX-10 frame has the seat tube plug as well! Mine is at depth of 6 or 7 inches and you can easily see it with a flashlight. I thunked it gently with a rod, and it thunked back, feeling soft and movable, feeling like cork or balsa wood. I'm guessing it's a block for debris or water, to prevent it flowing down to the BB. Cork makes sense because it could (wine bottle technology, how French!) be shoved down a clean new tube, and would expand when it gets past the butt area. Some softer balsas can have the same characteristic, but it's really not as elastic as cork (my model airplane days many many days ago!).

It would also serve to damp vibrations in the seat tube. This could be part of the perception of a PX-10 frame. Some think such frame tube resonance or ringing is a significant part of percieved ride quality.
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Old 12-24-09, 05:14 PM
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Originally Posted by Ivandarken View Post
Road Fan,

I think you win the prize. There is indeed a stopper of cork within the seat tube of unknown length. I pulled a shard of loose cork out of my other PX-10 and confirmed this. As well, it is cleaner in that bike and I can clearly see the texture of cork within the tube.


The discussion now becomes: WHY?

Is it merely for protection from debris/moisture getting into the seat tube?
Is there a performance aspect to this?
Does anyone know other manufacturers who used this method?

Quick, everybody check your late 60's era road bikes!!!
Allright, Hey,Hey! (that's my end zone dance combined with a little Jack Brickhouse!). For my prize I will accept the modest gift of a mint 56 cm early '60s PX-10 frame with all the tough parts still attached ,,,

The main concrete benefit I can think of is to block debris from falling into the greased bearing. I doubt Peugeot used BB sleeves, like Campy and some of the Japanese companies did. The more I think about it the better idea I think it is to seal teh BB bearing area.

If I was their product manager I'd probably have resisted deleting the seat tube cork, even if there was a BB sleeve, if it showed any benefit to ride quality. My frame has some internal rust above teh cork, so it was containing water as well as debris. I really don't get it about the fork tube plug. I wonder if there are corks in the top and down tubes? That would be evidence of a forward-looking product tuning process at Peugeot. It's nearly weightless damping system.

Has anyone here seen the dismantling of a PX-10 frame, or have a mangled one that can be cut up?

Bottom line: No, Ivan, I don't have a really strong theory of why there's cork in there. But if my debris barrier explanation turns out to be true, add a set of wheels to my prize package, ok bud?

BTW, I know my early '70s UO-8 does not have any head or seat tube plugs in it. I just got another similar frame, which has no fork plug, but I haven't taken a good look yet into the seat tube. None of my later (early '80s) Italian frames have this. Same for my '73 Super Course and my 1980 Woodrup. Sorry, no more late '60s stuff in my stable.

Last edited by Road Fan; 12-24-09 at 05:20 PM.
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