marrac

Hey, I've done building my Peugeot PHE20, everything working fine except seatpost, it keep sliding down from time to time after rides. I've bought the 24mm seatpost because that was what I measured before and old seatpost also was 24mm, most of the Peugeot bikes on web also having that size, but I think it's wrong because no matter what I use, I've already tried carbon paste, new binder bolt, it keeps sliding down. Also the seatpost is kinda hard to put in, I need to force it down pretty much. so I think someone before me used a wrong seatpost size and squeezed the frame too much, because I just realised that frame is squeezed on the top like on the picture. The question is now what seatpost size I could use with the method I saw on youtube from RJ The Bike Guy, because I don't found information about size for that Peugeot model. I'm thinking about trying the smalles size that I could buy now like 25.4mm and open up the frame a little bit with screwdriver.

Mr. 66

Do you recall the tubeset of your frame? I'm not real familiar with that model. That will
help to determine the correct one. It's pinched pretty big right now you may want a steel post to help ease it back in shape to the right size.

randyjawa 

Based on your picture, the seat post is too small in diameter. Look at the slot and notice that it is noticeably narrower at the top when compared to the bottom. That, to me, suggests that you need a larger post.

When I measure for seat post size, I measure across several seat lug diameters, just to see if the seat post opening has been distorted. Once several measurements (using a Vernier caliper) have been made I use the average for size. Before doing that it would be best if you opened up the slot so that the top and bottom gap is the same.

marrac

The model is Peugeot PHE20 from 1987, but it's weird example because I've only found the photo in german catalogue but the name is Mont-Blanc, and mine is Jubilè, also was with the English threaded BB not the French one, some more info and photos in this thread https://www.bikeforums.net/classic-v...ot-jubile.html
So I'll try to open up the slot for seatpost and then measure it, there is no more information about this model more than this german catalogue here https://www.bikeboompeugeot.com/Broc...,%20PH501T.jpg

Mr. 66

The bike boom in German does tell us that your tubing is HLE and it looks to be the internal lugs.

marrac

I've tried to open up the slot today, and I think I managed to straighten up the slot, but the weirdest part is that the 24mm seatpost now slides in really nice but it have a little bit of play, but the measurement of inside the tube is again showing me 24mm, I tried with 25mm old seatpost from another bike and it didn't even go in. Does it could be something between 24-25mm? I don't know if I'm gonna find a seatpost in this size, or I could try to open up the slot even more to try fit the 25.4mm?

Sactown_Albert 

Have you considered purchasing a shim or fashioning your own?

Mr. 66

No do not try to open further, damage could incur. It's open plenty. Your next post will fit in but will have no wiggle.

I dont have experience with HLE to recall from.

marrac

Sactown_Albert I'll try to make one now.
Mr. 66 But now I don't know what size it should be if 24mm have a little bit of wiggle, and the measurement inside is 24mm. I don't think so there is smaller size than 25.4mm

DiegoFrogs

I had a Canadian built, internally lugged HLE Peugeot for some time, probably for the American market. It used a 15/16" (23.8) mm post. I don't know what size your post should be, though.

sovende

Get a seat post shim!

uncle uncle

Buy a six pack of your favorite beer. Drink one while you contemplate your life, or bicycle, or crypto currency, etc. Once empty, cut from the can a rectangle the length of the circumference of your seatpost, and with a width of about an 1". Install your seatpost with this impromptu seatpost shim, at the slotted area of your frame's seat tube. A modern beer can is about 0.1 mm in thickness, so this would give you, effectively, a 24.2 mm diameter seatpost. See if this keeps your post from slipping. If it still slips, but seems like it takes longer to slip, drink another one, and from that one, cut a shim that wraps around the diameter twice. Repeat drinking and creating shims as necessary. You can always replace this shim with a more elegant shim, once you determine the thickness you need. (Don't drink and ride.)

oneclick 

You might hit a bump and spill your drink.

dddd

My 1984 PKN10 with 24mm seatpost has this very same problem, so I found that I had to lengthen the slot downward in order to allow sufficient clamping force to be generated with a standard binder bolt.
I lengthened the slot a few mm and had to go a few more mm after that, but finally no more slippage occurs now!

I used a carbide cutter in my Dremel Moto Tool, didn't do a very straight cut and yeah this photo isn't great either, but you can see how long that the slot is.

marrac

I've tried with shim, even half of the shim, nothing work because it's way too tight to put it with the shim. The weird thing is when I tighten the bolt it seems like one half of the frame going tighter, and then when I want to get out the seatpost it's scratching the aluminium from the seatpost.
Also guys do you think it could be because original it was the 6 speed bike, and I put there Shimano Claris 8 speed group, but I put the rear wheel with little bit of force, because the dropouts are 124mm not 130mm?

zandoval 

I have three bicycles that use Beer Can Shims of varying sizes and thicknesses. I installed them as a temporary measure when seeking Seat Posts and Bars of the appropriate size. Ha... That was years ago and they still remain in use.

It's not a surprise that all three are Peugeots...

zukahn1 

Pretty sure these are spec 24.0 so the next size larger post probably won't work. One thing you could try if there's a bike coop near you is to get the shim off lesser vintage Schwinn and sand it down bit.

dddd

Nothing that you did out at the dropouts is affecting the grip on the seatpost.

What kind of indication led to the clamp seeming to "go tighter on one half"? Do the ears remain equally parallel?

The design of these frames puts the upper end of the stays right where the clamp ears need to rock inward, which forces the bolt to have to flex the stiff stay ends locally.
The problem is that the slot doesn't extend below the stays (which would allow the stays and clamp ears to come together under the force of the bolt, without bending the upper ends of the stays).

If I was approaching this problem again, I would first drill a hole just below the stay ends and then saw the slot downward to meet the hole (the 1/8" diameter carbide cutter did work for me, but it was difficult to cut the slot lower in a straight line).
Best to work slowly in either case!

marrac

When I tighten up the bolt, and the unscrew it, I see the one side of the slot just scraping off the aluminium of the seatpost like a knife, also without seatpost I just see the one side bending more than the other. I'll give another try with carbon paste because I don't have dremel tool for now, and I don't know if it safe enough to do it.

Mr. 66

I like to use a combination file, flat one side arc on the other, and use the arc to smooth the sharp edges. This prevents the scrape and scaring the post you are describing. Try to advoid twisting motions when inserting or removing.

Your post, if spec correctly, may be worn down so far that it may not hold as you need it to.

zukahn1 

Yes pretty simple just file two grove x on each side at the clamp point to stop shifting slip and clamp it down a bit.

uncle uncle

https://www.autozone.com/test-scan-a...E&gclsrc=aw.ds

You could give one of these a go too, with a portable hand drill. They are available at most car parts stores, or Horrible Fright (Harbor Freight). My thought is, with a honer, it takes the need for skillfulness out of the equation... but one needs to go slow, checking for any progress often.

marrac

It's a brand new seatpost and I have that problem with the old one also. I've tried to fit the 25mm seatpost after opening up the slot but no luck with that also, 24mm now have a gap on the lug ears side. I don't know why it going like this when I tighten up, seatpost now doesn't slip, but if I wanted to do some correction with the height I can't because it's squeezed too hard and still scratching the seatpost. It's seems like seatpost is little bit too small, but there is no other size between 24 and 25mm. I'm just ready to give up on that bike.

1simplexnut

Hi I have an 80s Peugeot parts catalogue which mentions a 24.75mm post . Maybe it is what yours should have ?

marrac

1simplexnut Nice find, but damn if it's true then im screwed, it was hard to find a 24mm seatpost haha, but I've also photo of catalogue from 87 of Mont Blanc model with same specs like my bike, and I think it came with integrated clamp for saddle, not like this one. Last thoughts that I got is just lug ears are deformed and don't clamp the right way, or inside of the tube got the paint scratched by time and it's changing the thickness.