garage sale GT

Is it possible a 1980 Super Vitus 971 Gitane Criterium required a 26.6 seatpost rather than a 26.4 because of 0.7mm thick 28mm tubing? (28-0.7-0.7=26.6)

Is it possible the lug rotated backward a bit and left a tiny bulge in the top rear of the seat tube, around the slot, because of the extra clearance?

Is it safe to try to bend or clamp it back after getting the correct seatpost or should the frame be condemned?

I don't know how thick the paint is and couldn't measure inside the seat tube anyway.

The other possibility is that Super Vitus 971 was rated for less than 220lb. I believe it was, but it may have been in order to have adequate rigidity, not to prevent failure, and I am hoping the failure was due to the wrong post. Please help if you can.

repechage

I have two Super Vitus frames, one is 26.6 the other 26.8.

If the post was too far out, it may be possible to distort it, of course the frame hould have been cooked during mfg.

Get a post that allows insertion 2 cm or so below this bulge.

You might be able to block it back, but there may not be enough room to clamp it effectively.

garage sale GT

Is the 26.6 a 971 and the 26.8 a 980?

garage sale GT

Here are some pics. As can be seen the bulge was very slight. Mostly I want to know if anyone thinks the brazing of the seatstays could have been weakened by a rearward rotation of the seat clamp lug of less than one degree. It is now clear that there was too much clearance around the post, and I just confirmed that a. it is possible Gitane mixed up parts, and b. some super vitus bikes came with 26.6 and 26.8 seatposts, as stated above.

So, how about it? If I can straighten the seat clamp lug and insert a larger seat post whch matches the ID of the seat tube, should this thing be safe to use, or do I risk seatstay failure because the lug twisted backward a bit?

luker

I don't think you could get a block in there. I also don't think that the damage is anything but superficial. Can you get a 26.6 seatpost into the frame?

repechage

Show the seat lug ears who is boss, then get access to a Park seat post sizing tool to know what size you need.
No, the seat stays were beaten up more by the way they were cut and folded closed, French production at its most interesting, light tubing and pricepoint level production tech.

As to the exact model of the Super Vitus on mine, I don't know, one was labeled as a Reynolds 753, only to be revealed by paint removal, the other was revealed after powdercoat removal, faint Super Vitus stampings to one end of the butt section of the tubes.

garage sale GT

I am more concerned about the little globs of brass holding the stays to the lug. I wonder if those could crack off the frame.

I am sure many stays are cold formed a bit during manufacture; the brazing probably stress-relieves them a bit. The ones from Gitane just aren't finished as nicely as some others.

garage sale GT

What do you mean by "block"?

I can get a 26.6 spacer and 25.4 post in there, I guess I should measure to see if it's the correct thickness.

Chombi

SV980 seatpost diameter is 26.4mm. At leat it is for Peugeot PSVs. Confirmed it with my micrometer on my 84 model. Not familiar with 971 tubing, but there could be a difference....

Chombi
84 Peugeot PSV
85 Vitus Plus Carbone 7

garage sale GT

Please tell me the OD of your seatpost.

Chombi

Uhmmmm...are you asking for seat tube diameter??? As I stated, seatpost diameter (O.D) on my PSV's seatpost (made by JPR) is 26.4mm.
I believe I saw a post here recently stating that 26.4mm is typical for 80's and earlier "metric" tubing, like Vitus SV980/983. Lots of 26.4 seatpost still available at eBay, even a few Campy versions once in a while, so there should be no problems locating one, even NOS. I would say that 27.2 and 26.4 are the two most common seapost sizes for 70's though 90's bikes. Everything else in between and out of that range will be harder to find.
I'll measure my PSV's frame seat tube outside diameter when I get home tonight and post it up if that is your question.

Chombi

garage sale GT

Yes I meant seat tube.

luker

a wrinkle or a dent can sometimes be forced out of a tube using a block...two pieces of steel that are made to fit the outside diameter of the tubing with the dent. Grease the block, clamp in a vise, and rotate the dimple out.

Quoting Repechage in part: "You might be able to block it back, but there may not be enough room to clamp it effectively. "

garage sale GT

Thanks for letting me know what he meant.

It mostly buckled outward, though, and fixed itself a bit when I forcibly rotated the seatpost against the direction which weight normally does. I was thinking of just putting the right size seatpost in, then using a hose clamp to force the tubing to conform to the seatpost. The buckling was only about 1mm from the post even at its worst.

I mostly write to see if anyone thought I should be concerned about brazing failure around the seatstays or something else which could injure me.

Chombi

The seat tube on my 84 PSV with SV980 tubing is measuring out at around 27.27mm OD. I suspect that it's closer to 27.25 OD, minus the finish/clearcoat, measured about 3-4 inches below the seat lug.
Hope this info helps.

Chombi

garage sale GT

It does, because my SV971 post is 27.88 which suggests that it is possible that your frame could need a 26.4 while mine could have required a 26.6, whether or not the tubing may be a bit too large and out of spec.

The post should fit the tubing, I think. I believe mine would have been OK if the bottom of the seatpost had been well supported, instead of pinching an oversize tube and lug around a small portion of the post and expecting it to bear all the torque of my weight.

verktyg 

Don't believe everything you think! ;-)

Here's some realities of bike manufacturing.

Many stamped steel lugs were out of round to begin with, especially seat lugs. Also the excess heat generated while brazing the seat stays on to the seat lug frequently caused the seat tubes to bulge inside the seat lug, sometimes even a little below the lug.

So, you could have an out of round lug with a bulge inside it.

When I was running a shop and building some frames in the 70s, we made a set of mandrels for rounding out the seat tubes and removing the bulges. This was something very rarely done on production bikes, even by many top name builders.

Sometimes seat tubes where machine reamed along with the head tube. VAR made a dedicated machine for production reaming plus sawing the split in the seat lug.

https://www.sheldonbrown.com/var/pages/var0007.html

Having assembled many hundreds of bikes during the 70s (mostly French) I can testify that the only time a reamer got close to most of those frames was to remove excess over spray paint in the seat tube during assembly at the factory!

Many bikes came with a seatpost 1 sometimes even 2 sizes smaller than what was optimum to fit a properly dimensioned seat tube.

For example, last year I bought an all Campy 1972 Gitane Super Corsa. On the first test ride I couldn't keep the seat post from sliding down. It didn't look right. When I checked it the post was a 25.8mm instead of the proper 26.4mm! This bike was built at the peak of the bike boom and the seat tube was that far out of round!

I have a number of French bikes in my collection made with Super Vitus 971, 980, & 983 tubing. They all have metric sized tubes.

Super Vitus 971 was available during most of the 70s. It had the same tubing wall thickness as Columbus SL tubing with .9mm-.6mm seat tubes. It was made from a high strength, low alloy medium carbon steel , originally XC35 and later XC38. SV 971 tubing had strength properties similar to Reynolds 531 and Columbus chrome moly steels.

A properly rounded and reamed SV 971 metric diameter seat tube should take a 26.6mm seatpost

28mm OD - 2x .6mm = 26.8mm with .1mm clearance room per side.

Most SV 971 bikes you see will have a 26.4mm seatpost.

Super Vitus 980 was made of a chrome moly steel and had .8mm-.5mm wall thickness seat tubes. My 1980 Bertin C37bis is made of Super Vitus 980 has a 26.8mm seatpost from the factory.

28mm OD - 2x .5mm = 27mm with .1mm clearance room per side. Thus a 26.8mm seat post.

I have a 1983 Peugeot PSV10 frame made of Super Vitus 980 that I haven't started assembling yet. Right now, a 26.6mm seat post fits but once I spread the ears on the seat lug, round it out and clean it up, I'm pretty sure a 26.8mm post will fit.

Now, to Super Vitus 983, I have three 1984 Gitanes made with it. The 2 Tour de France bikes came from the factory with 26.4mm seatposts. The ears on the seat lugs were compressed so much that they were touching. I cleaned up and rounded out one of them. A 26.6 fits a little loose. I haven't gotten to the other one yet.

My 1984 Gitane Super Corsa has the same frame as the TdFs except for the color. After cleaning, rounding and reaming, I found that a 27mm seatpost fits perfect. I didn't over ream it. The reamer runs freely below the lug so that's the tubing ID. It appears to have a .4mm wall thickness on the top of the seat tube.

Supposedly, SV 983 had .9mm-.6mm wall thickness main tubes But I think that it's thinner than that.

Now the believe part...

Most seatposts at least from the classic pre 1990s days were not accurately machined to the marked sizes - even sacred Campy seatposts. Most tend to be a few tenths of a millimeter undersize and/or are tapered. Some are out of round - wider side to side than front to back or vice versa. A few years back I measured over 30 seatposts from a dozen makers, even some NOS Campy posts and those was my findings.

BTW, I used a new 6" Mitutoyo digital caliper for speed and convenience but I have access to measuring equipment that can measure down to lightwave lengths!

There should be almost no compression of the slot in the rear of the seat lug on a proper fitting seatpost. When the ears touch, the lug is being stretched further out of round and can result in a crack forming in the rear of the seat lug or top of the seat tube below the lug.

I highly recommend getting a brake cylinder home or brush hone to smooth out the inside of the seat tube so that making minor height adjustments is easy. Also. take a small round file and remove any burs inside the seat tube to prevent the zigzag snake like marking on seatposts.

Oh, and the 27.88mm OD dimension you mentioned, if you measure the tube on a different axis or in a different location you might find that it's 28mm + a few tenths over because of the paint thickness.

Have fun,

Chas.

kepohe

Hello,

I can't post pictures because I'm new here. I have a Bernard Carre super vitus 971 ( i think build around 1980) and a campagnolo seatpost 26,8mm. The seatpost diameter is too small. When i put the screw, the ears are not touching but the space is really small.

Do you think it's possible to use 27mm seatpost with vitus 971? I read only 26,6 or 26,8mm for super vitus 971.

Thanks.

bertinjim 

kepohe -

Try and get a framebuilder or a bike shop familiar with steel framesets to ream the seat tube and then hone it. Make sure the points of the seat lug are smoothed off to prevent scoring on the seatpost. Have the framebuilder check the seatpost opening after reaming and honing using a seatpost gauge which should confirm the actual, round, opening of the seat tube. I suspect you are right and that it will be 27 mm once cleaned up..

kepohe

Ok thanks, I will try to find a shop to check the seatpost size. When i have 10 messages, i will post pictures and video about my B.Carre.

kepohe

Hey, it's ok now i can post link and picture.

So here is my B. Carré. I think end 70's or begin 80's. Rear derailler is from 1980. The frame is super vitus 1980. And the seatpost 26.8 is too small. I think i will buy a 27mm but i never see 27mm on vitus 971.









And a little movie:

bertinjim 

kepohe -

You are right, the seatpost is way too small. A properly fitting post should have both sides of the seat lug cut nearly parallel. You will need to get the Carre's seat lug sides bent back to parallel before the framebuilder/shop can even think of measuring, reaming or honing the seat tube. By the way, the seatpost bolt is the wrong type as you should be using a regular Allen bolt in the threaded clamp not half of a two part bolt.

Great bike, by the way. And yes, probably late 70s to early 80s as I believe Carre changed his stay cap style and added the Fleur de Lys crown around the mid-70s.

T-Mar

The post on kepohe's Carré has been tuned down. It may have started out as 26.8mm but there's a significant neck starting about 20mm from the top. It needs to be measured it to determine the actual diameter.

Edit: I'd gently pry the cinch slot open to the point where the sides are parallel, then see if the unreduced top portion of the post fits properly and use that as my starting point to determine post size. Going larger than 26.8mm may be the wrong direction.

bertinjim 

T-mar -

That is an excellent observation. That seatpost should be one, smooth surface from top to bottom. kepohe, pull out your digital calipers and measure the post up. Then follow T-mars instructions on post fit.

kepohe

Hello,

Thanks for all your answer. Yes the seatpost diameter is not original. My neighbour have the same campagnolo seatpost and there is no neck... I bought a 26.4 JPR and it's better now.
And Yes the screw is not good. i bought the bike like that. i bought Allen titanium screws. I'm waiting them.