gitaneusa.com Forum Index » Vintage Gitane » gitane seat post dimensions?    View previous topic :: View next topic  gitane seat post dimensions?   Posted: Tue Mar 23, 2010 7:43 pm mva0322 Joined: 11 Jan 2010 Posts: 2 Location: Sydney Australia does anyone know the actually seat post dimensions on the old gitane track bikes circa late 70's? i think it's 27.2 but i'm not totally sure? thanks in advance Austin. Sydney, Australia.   Posted: Wed Mar 24, 2010 4:13 am sandranian Site Admin Joined: 27 Feb 2006 Posts: 2701 Location: Southern California Almost assuredly not 27.2. Most likely 26.8. Best thing to do is to take it to your LBS (local bike shop) and have them measure it. _________________ Stephan Andranian Costa Mesa, CA www.gitaneusa.com   Posted: Wed Mar 24, 2010 5:58 am lofter Joined: 05 Mar 2006 Posts: 1162 probably a 26.4 or 26.6   Posted: Wed Mar 24, 2010 9:16 am sandranian Site Admin Joined: 27 Feb 2006 Posts: 2701 Location: Southern California We are all over the place! Best to take it to someone with digital calipers. _________________ Stephan Andranian Costa Mesa, CA www.gitaneusa.com   Posted: Wed Mar 24, 2010 9:58 am lofter Joined: 05 Mar 2006 Posts: 1162 yup i agree Seat Post Sizes   Posted: Wed Mar 24, 2010 1:27 pm verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area sandranian wrote: We are all over the place! Best to take it to someone with digital calipers. Even better yet, someplace where they have a seatpost diameter gage (or a shop with a good selection of seatposts). What kind of tubing is your frame made of? What model bike is it? The older Track Standard (or School model in Europe) track bikes were mostly made with the same seamed low carbon steel tubing that was used on the Gan Sport and similar bikes. They took a 25.8mm or sometimes even a 25mm seatpost. The Mexico and Super Pista models had Reynolds 531 butted main tubes (the Super Pista was all Reynolds 531). Most production French bikes made with Reynolds 531 used the 7/10 wall thickness tubing for the butted main tubes. What does that mean? The thicker "butted" section at the ends of the tubes had a 1.0mm wall thickness while the thinner sections were 0.7mm thick. Seat tube are generally only butted at one end, the bottom end that goes into the bottom bracket. See the specs from the 1980 French Gitane catalog - "Cadre compétition tout REYNOLDS 531, 7/10". http://www.gitaneusa.com/images/catalog/1980/french/Gitane_1980_Page_08.jpg 26.4mm was the standard seatpost size for frames made with metric 7/10 tubing. A bike made of Durifort or Vitus 888 tubing had 8/10 wall thickness straight gage tubing. It was 0.8mm wall thickness throughout - no butts. These frames usually used 26.2mm seatposts. The less common Durifort or Vitus 788 probably had a 0.7mm wall thickness seat tube and would have used a 26.4mm seatpost. The thinner the tubing wall thickness the lighter the frame and the more supple it is except in large frames which can be too flexible with thin tubes. Super Vitus 980 had 5/8 wall thickness - .05mm x 0.8mm in the butted ends. These frames could have used 26.6mm or 26.8mm seatposts Super Vitus 971, 983 and Columbus SL tubes were 6/9 or 0.6mm x 0.9mm wall thickness. These frames made with metric tubes usually took a 26.6mm seatpost but could have been scrunched down to take a 26.4mm. If you are a regular "set it and forget it" kind of person, stop here... On the other hand, if you are an obsessive, Princess and the Pea type like me (and Eddy Merckx) always fiddling with seat height read on... Most seat tubes on production bikes and even some custom built frames are warped out of round from the excessive heat used to braze on the seat stays. Also the seat tube inside the lug can be bulged. This makes measuring with calipers a little difficult. The seat tube is usually wider front to back and narrower side to side. From experience, I know what seatpost size should fit in what kind of seat tube. If the inside of the seat tube is smooth and the post is only off by 0.2mm diameter plus the ears on the lug aren't squeezed too tight I'll usually leave it alone except for honing the bore with a brush or brake cylinder hone. I look at the back of the slot in the seat lug. If it's pinched closed too far, it a good probability that the seatpost is too small in diameter which can result in a cracked seat tube. Cracked seat tube and lug. Too small a seatpost. If I'm putting in a new seatpost then I will usually correct the problem starting with gently spreading the ears that the seatpost bolt goes through. Also I file off any sharp points or edges where the red lines are in the picture below. This makes for smoother insertion, adjustment and removal of the seatpost. I usually run an adjustable reamer through the seat tube to open it up to the next size seatpost if it was badly crunched. If the seat tube is badly out of round, I have some tools to drive down into it to round it out a little - don't try this at home kids... After that, I ream it and hone it. Voilà , better than new! So why bother? a. you read too far down! b. because it makes fine tuning saddle height a lot easier. I've found that adjusting the height by as little as 1/8" can make a big difference in comfort for me! Most used seatposts have been sanded down at the bottom to remove the zig-zag gouges made by the sharp points in the lugs (see picture above). If not they probably need to be. This can result in a seatpost that's as small as 26.2mm at the bottom and 26.4mm at the top. Also many seatposts including the sacred Campys are out of round either to begin with or from over clamping. You can get shims to use a smaller sized seat post in a bigger seat tube. I've never used one but they are supposed to work OK. One last thing, take and put a big glop of grease inside the seat tube and rub it all around. Also coat the bottom of the seatpost with grease. This will make insertion and adjustment easier plus help keep dirt and moisture out of the bottom bracket. _________________ Chas. SF Bay Area, CA USA ============== 1984 Criterium 1969 TdF 1971 TdF 1974 TdF 1984 TdF x 2 Bikes 1970 SC 1971 SC 1972 SC 1984 SC 1984 Team Pro 1985 Professional 1990s Team Replica   Posted: Thu Mar 25, 2010 12:51 pm logarto Joined: 18 Feb 2008 Posts: 56 What he said. Both of my Vitus 980 Gitane frames are using 26.4s now and also came with 26.4s stock but always looked like they really wanted 26.6. And the Columbus tubing Gitane frames were always speced for 26.6 Some of the older Columbus SP (english diameter) frames like my 1973 Olmo needed 27.0 to accomidate the 0.7 (single butted from 1.0) seat tube. I suspect that during the 1980s these got honed out a little bit in production to accept the much more common 27.2 size. The smaller french tubing diameter created minor problems for the Suntour "endless band" family of front derraileurs due to the slightly smaller outside circumference. Does anybody remember the vintage of Kleins that wanted 27.4? I finally took advantage of one of the new superlight carbon/titanium seatpost designs that come in 25.0 with a shim or package of shims for modern frames. Looking to use it with my old round tube Centurion carbon, but the sucker is so light and thin in the clamping mechanism that now I'm flat afraid to ride it at all before I shed a few lbs myself. I've broken a crankarm that I knew beforehand was suspect (Sachs New Success,) but I was using it because it was new and free and I loved the way it looked. This under extremely fortunate circumstances and barely 600 yards from my house; the one other part that got ruined from the low speed trip over the handlebars was an ancient Open4 CD front rim that was rusting in all the ferrules, something that should have never happened in this climate and hasn't happened to me with the same rims made at approximately the same time. As lucky as that all turned out to be, it's still a soboring experience when you consider that the youngest driveline components I had on any bike at the time dated back to 1991 or thereabouts. Now I do use modern cranks on some of my older bikes and put up with the disposable Isis and Octalink bottom brackets. I immediately retired my notoriously flimsy Profile handlebars and stem too. After that little misadventure I'm really not all that inclined to push the seatpost failure envelope that close to the old family jewels. Having a Look pedal walk right off the spindle is the second worst thing that's happened to me mechanically in the last 20-25 years.   Posted: Fri Apr 16, 2010 12:39 pm Frenchbuilt Joined: 18 Apr 2007 Posts: 443 Hi it would seem that with all of the filing honing and reaming that there might be some areas where very little metal is left. I cleaned up the inside of my seat tube and there are some areas that seem very thin ( at the slot) with everything back to 26,4 mm. Thanks, Dan Seat tube wall thickness   Posted: Fri Apr 16, 2010 10:10 pm verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area Dan, I'm very careful with thin wall tubing like Super Vitus 980 and similar dimensioned tubes. The first thing that I do is make sure that the seat tube and lug are as round as possible without damaging anything like the seat stay brazing. The seat lug on my 1969 Tour de France was so out of round that when I reamed it after trying to correct the shape, I cut all the way through the tubing wall to the brass in one spot. Another reason why seatposts need to be inserted at 3" into the seat tube. _________________ Chas. SF Bay Area, CA USA ============== 1984 Criterium 1969 TdF 1971 TdF 1974 TdF 1984 TdF x 2 Bikes 1970 SC 1971 SC 1972 SC 1984 SC 1984 Team Pro 1985 Professional 1990s Team Replica Final result   Posted: Sat Apr 17, 2010 7:27 pm Frenchbuilt Joined: 18 Apr 2007 Posts: 443 Cleaned up carefully and once oval now takes 26,4 Had old Simplex post and added seat. Around 75 mm in tube as you recommended which just fits me. Thanks, Dan gitane seat post dimensions?     gitaneusa.com Forum Index » Vintage Gitane You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum All times are GMT - 8 Hours   Page 1 of 1   All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First  Select a forum Gitane USA----------------Vintage GitaneGitane RacingModern GitanePro Racing - Classics/Giro/Tour....Owner Gallery   Powered by phpBB © 2001-2004 phpBB Group Designed for Trushkin.net | Themes Database.