gitaneusa.com Forum Index » Vintage Gitane » 1984 Team Pro Seatpost Diameter Goto page 1, 2  Next    View previous topic :: View next topic  1984 Team Pro Seatpost Diameter   Posted: Fri Aug 22, 2014 2:53 pm CurtEgerer Joined: 14 Sep 2013 Posts: 39 Location: United States 26.4mm correct? I test fit a 26.4 and it felt loose. It will probably tighten down but seems like a 26.6mm would be a better fit ....   Posted: Fri Aug 22, 2014 4:48 pm sandranian Site Admin Joined: 27 Feb 2006 Posts: 2701 Location: Southern California I thought it was 26.4 _________________ Stephan Andranian Costa Mesa, CA www.gitaneusa.com Seatpost Size   Posted: Sat Aug 23, 2014 12:52 am verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area 1984 Gitane Team Pro frames were made of Columbus SL tubing which should have had a 26.6mm seat post. Read below to see "the rest of the story" Check out my posts in these 2 threads: http://gitaneusa.com/forum/viewtopic.php?t=1536&highlight=seatpost http://gitaneusa.com/forum/viewtopic.php?t=1348&highlight=seatpost Almost all French steel frames were made with metric diameter tubes. Seat tubes had a 28mm outside diameter. Better quality bikes had frames made with "double butted" tubing. This was advertising hype because only the top and down tubes were double butted (thicker at the ends). Seat tubes were only butted at the bottom ends where they go into the BB shell. The 2 most common seat tube wall thicknesses on better quality production frames were 1.0mm x 0.7mm and 0.9mm x 0.6mm. Most French production bikes made of Reynolds 531 tubing had 1.0mm x 0.7mm wall thickness. Some high performance French frames were made with thinner tubing. The wall thickness was 0.9mm x 0.6mm. These included Columbus SL, Super Vitus 971, Super Vitus 983, and lighter gage Reynolds 531 tubing. Super Vitus 980 and Reynolds 531SL tubes were even thinner 0.8mm x 0.5mm. Here's the details on figuring seatpost sizes: 0.7mm wall thickness seat tube - 2 x 0.7mm = 1.4mm 28mm diameter -1.4mm = 26.6mm Allow for 0.1mm per side clearance = 26.4mm seatpost. 0.6mm wall thickness seat tube - 2 x 0.6mm = 1.2mm 28mm diamete -1.2mm = 26.8mm Allow for 0.1mm per side clearance = 26.6mm seatpost. Here's some additional information: Seat lugs and tubing were not always round. In addition the heat used to braze on the seat stays frequently caused the seat tube to bulge inside the lug and/or the seat tube and lug could warp out of round. Last edited by verktyg on Sat Aug 23, 2014 12:52 pm; edited 1 time in total _________________ 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: Sat Aug 23, 2014 6:26 am sandranian Site Admin Joined: 27 Feb 2006 Posts: 2701 Location: Southern California Just checked my 1984: Columbus Tubing. 26.4 seatpost. Fits perfectly. But now I am starting to doubt...and will remove it later! _________________ Stephan Andranian Costa Mesa, CA www.gitaneusa.com   Posted: Sat Aug 23, 2014 2:51 pm Frenchbuilt Joined: 18 Apr 2007 Posts: 443 my team pro has 26,6. Generally, you can see if the seat post is clamping down too tight by checking the gap left (in clamp lugs where bolt passes) after tightening. If there is no gap and the two sides touch, the post is too small and risk of over stressing the clamp (paint wrinkles on TDF type stamped pieces) Just as a note, my Peugeots PX and PY 10's have the same Reynolds seat post tubes and take 26,6 posts. I always just assumed that they ran a ream down the tube to open up a bit since their build quality was awful. Seatpost Sizes   Posted: Sat Aug 23, 2014 3:02 pm verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area sandranian wrote: Just checked my 1984: Columbus Tubing. 26.4 seatpost. Fits perfectly. But now I am starting to doubt...and will remove it later! Frequently bike manufacturers including some of the top name holey of holies frame builders never took the time to properly size seat tubes. It just a simple job of tapping a steel mandrel into the top of the seat tube to remove any bulges and round out the hole then running a reamer down the tube to finish the job was all that was needed. voilà! the seatpost fits smoothly in the seat tube... About the only time a reamer was used in the seat tubes of most production frames was on the assembly line. A hand reamer was frequently used to remove excess paint so they could get the seat post to fit. It you look into the seat tube of most frames you'll see lots of paint that was never touched by a reamer. I suspect that bike manufacturers kept undersized seatposts on the assembly line to use in bulged or out of round seat tubes. Here's a good example. When I put a Brooks Pro saddle on a newly purchased "all Campy" ~1972 Gitane Super Corsa, something didn't look right. As purchased: After I fixed the problems: I checked out the Campy seatpost and it was 25.8mm instead of the correct 26.4mm. It most likely came from the factory that way! The seat tube and lug were so out of round that the very uncommon 25.8mm seatpost was all that would fit! I corrected the problem and all is in fine now. Here's a link to one of our own, LeicaLad's vintage British frame showing how far out of round the seat tube was: http://www.bikeforums.net/bicycle-mechanics/800942-seat-post-into-newly-refinished-c-v-frame.html Automotive brake cylinder bristle brush hones are invaluable for smoothing the insides of seat tubes and stems. A smooth bore allows for easy adjustment of seat and stem height. _________________ 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: Sat Aug 23, 2014 4:24 pm CurtEgerer Joined: 14 Sep 2013 Posts: 39 Location: United States Chas, when does the book come out? I truly enjoy and learn so much from your posts. Thanks! The calipers say 26.55mm for my frame.   Posted: Sat Aug 23, 2014 5:45 pm verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area CurtEgerer wrote: Chas, when does the book come out? I truly enjoy and learn so much from your posts. Thanks! The calipers say 26.55mm for my frame. Ah shucks... Thanks BTW, it's difficult to "accurately" measure inside diameters with calipers. They're OK for measuring ODs but you have to double the "resolution" when using a slide caliper - they're just not that accurate. If the calipers have a resolution of .001" or .025mm (smallest reading) you have to figure the accuracy is .002" or .050mm. The top opening of the seat tube is usually different than say a 1/2" or 3/4" down in the tube. That's hard to measure with calipers. Micrometers are far more accurate. A bore gage or inside micrometer is the best way to get accurate inside diameter measurements. http://ecatalog.mitutoyo.com/Inside-Measuring-Instruments-C1330.aspx Most better shops had a seat post sizer that let them accurately guess the seatpost diameter. They could also be used to "eyeball" how out of round the seat tube was. One last point for now, I always apply a liberal amount of water resistant grease to the inside of the seat tube and the outside of the seatpost. It prevents rust and electrolytic corrosion from forming between the aluminum seatpost and the steel tube. Plus it can reduce the amount of water that can seep down into the BB bearings. If you have smoothed out the inside of the seat tube, the grease makes minor height adjustments smooth and easy. I find that sometimes a height adjustment of as little as 1mm is enough to make riding more comfortable. (not a tale of the princess and the pea)! For me it's the balance between the pressure on my butt and my legs. Eddy Merckx used to adjust his seat height while on his bike throughout a race! I'm not Eddy... (I have to get off the bike) _________________ 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 Leave it alone   Posted: Sat Aug 23, 2014 5:53 pm verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area sandranian wrote: Just checked my 1984: Columbus Tubing. 26.4 seatpost. Fits perfectly. But now I am starting to doubt...and will remove it later! Sandman, (When was the last time you heard that! Where's wisey?) If it ain't broke, don't fix it... If you don't change your seat height very often then leave it alone unless you have the tools to do the job right and a 26.6mm replacement seatpost. My 1984 Team Pro... Not exactly all correct components but period correct. BTW, Greg Softley at Cyclomondo in OZ has "repop" French language Columbus tubing decals for all of you 1984 Team Pro owners. http://cyclomondo.net/ http://cyclomondo.net/page7.htm _________________ 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 Leica Lads solution   Posted: Sat Aug 23, 2014 7:42 pm smilingroadrunner Joined: 10 Aug 2007 Posts: 278 Location: Salina, Ks. Thanks for the earlier post and link Chas. I like the tool Leica Lad utilized, I had a recent issue with the seat tube on the 1972 TdeF that I'm working on for my new Daughter -in- Law. It was not ovalized to the degree his bike demonstrated. I had an older "beat up" seat post that I utilized and brake hone to do the final smoothing. Works great, but admittedly the Plum bob was a neat idea. I Like Steel !!! _____________ C.A. Salina, KS   Posted: Mon Aug 25, 2014 2:06 pm CurtEgerer Joined: 14 Sep 2013 Posts: 39 Location: United States RE: Columbus decals. My originals are in fairly poor shape, but I'm undecided on replacing them with repops. My fork decal is only on the left side. Many of the period race fotos I have from 1984 also show no right fork decal (others do). Any idea on what is 'more correct'? PS: my 85 Pro has only a rightside 531 fork decal.   Posted: Mon Aug 25, 2014 3:48 pm verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area CurtEgerer wrote: RE: Columbus decals. My originals are in fairly poor shape, but I'm undecided on replacing them with repops. My fork decal is only on the left side. Many of the period race fotos I have from 1984 also show no right fork decal (others do). Any idea on what is 'more correct'? Yes... Is it wrong... or just French? Here's a Team Pro (actual team bike) and the Columbus decals are on both sides. _________________ 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: Sat Sep 06, 2014 3:13 pm CurtEgerer Joined: 14 Sep 2013 Posts: 39 Location: United States As a follow-up: I purchased a 26.6 post. Used a brake cylinder hone (thanks for the tip Chas) purchased at Horrible Freight for $6. That worked very nicely. Greased the post and it slides in perfectly.   Posted: Sat Sep 06, 2014 8:07 pm CurtEgerer Joined: 14 Sep 2013 Posts: 39 Location: United States This is the hone I used: Brake Cylinder Hone   Posted: Sat Sep 06, 2014 10:02 pm verktyg Joined: 14 Jan 2007 Posts: 2814 Location: SF Bay Area CurtEgerer wrote: This is the hone I used: $6.00? That's great! They usually sell for around $20-$25 USD. Glad it worked for you. The brush hones are usually cheaper and are more readily available. That's why I frequently recommend them. The nice thing about a brake cylinder hone is that it should fit easily into the steering tube to clean up the bore. I recommend cleaning out the crud in the seat tube and fork steerer before honing. Also, I use a solvent like kerosine, paint thinner (not lacquer thinner which will damage your paint) or light weight oil to lubricate the hone. Clean out the seat tube and steerer after honing then lube things up for corrosion protection and ease of adjustment of the seatpost and stem. This afternoon while out riding, I adjusted the seat height on my bike. I lowered it about 1/8" (3mm) and it increased the comfort on my derrière immensely. The smooth fit made it easy. ONE LAST THING... (Columbo Chas.) Release the trigger on the drill so the hone stops spinning before you get to the top of the tube so that you don't damage the paint when you remove the hone! Last edited by verktyg on Sun Sep 07, 2014 2:51 pm; edited 1 time in total _________________ 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 1984 Team Pro Seatpost Diameter     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 2   Goto page 1, 2  Next 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.