French frame questions

Retro Bob wrote:

If/when did French volume manufacturers (e.g. Motobecane/Peugeot) stop
using smaller seat tubes on their butted frame sets? Are/were their
downtubes different in size too ?

Not clear they ever did in butted steel.

French metric seat and down tubes are 28 mm vs 28.6 (1 1/8")

Top tubes 25 mm vs 25.4 (1")

Do I understand correctly that a French BB uses RH threads on both
cups but and an English thread BB will use LH threads on the
chainwheel side ?

That's correct. There's a lot of info on the idiosyncracies of older
French bikes on my Website at:

http://sheldonbrown.com/velos

Sheldon "Francophile" Brown
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| that they should do unto you. |
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Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon Brown wrote :
Retro Bob wrote:

If/when did French volume manufacturers (e.g. Motobecane/Peugeot) stop
using smaller seat tubes on their butted frame sets? Are/were their
downtubes different in size too ?

Not clear they ever did in butted steel.

French metric seat and down tubes are 28 mm vs 28.6 (1 1/8")

Top tubes 25 mm vs 25.4 (1")

My Motobecane Grand Jubile', which is 1977 or 1978 (IIRC,
component date codes from 1977) has Vitus 172 double butted
tubing and frame tube diameters of 28 mm ST, DT, and
26 mm TT. Yup, 26mm, I measured it thrice.

The OE Suntour Cyclone front derailleur clamps on the 28mm
seat tube just fine. The fork, stem, and BB are all metric
sized, but the rear dropouts are Suntour as well, actually,
to match the Suntour drivetrain and SR crankset.
Go figure.

Retro Bob wrote:

On 15 Sep 2004 22:36:54 -0700, (Benjamin Weiner)
wrote:



My Motobecane Grand Jubile', which is 1977 or 1978 (IIRC,
component date codes from 1977) has Vitus 172 double butted
tubing and frame tube diameters of 28 mm ST, DT, and
26 mm TT. Yup, 26mm, I measured it thrice.



SO... double butted... I'm figuring a mm each side where the seat post
goes in ... 26mm seat post ? Or does it use .8mm tubing and hit 26.4 ?

Still wondering what this stronglight seatpost I have hanging around
here that measures +/- 24mm might have fit. Early French maybe ?

Our Gitane tandem uses a 25.0 mm seatpost. Made it easy to make a
replacement when the original broke by slightly turning down a
1" (25.4 mm) aluminum rod.

Peter wrote:
Retro Bob wrote:

My Motobecane Grand Jubile', which is 1977 or 1978 (IIRC,
component date codes from 1977) has Vitus 172 double butted
tubing and frame tube diameters of 28 mm ST, DT, and
26 mm TT. Yup, 26mm, I measured it thrice.

SO... double butted... I'm figuring a mm each side where the seat post
goes in ... 26mm seat post ? Or does it use .8mm tubing and hit 26.4 ?

Still wondering what this stronglight seatpost I have hanging around
here that measures +/- 24mm might have fit. Early French maybe ?

That Grand Jubile' uses a 26.6 seatpost in a 28mm diameter seat tube,
suggesting a tube wall thickness of 0.6mm (or maybe 0.7, but usually
there's some slop). Like a 27.2 post in a 28.6mm seat tube.

Bike boom bikes come in all sorts of seatpost sizes, usually the
thicker the gaspipe, the smaller the post.

Our Gitane tandem uses a 25.0 mm seatpost. Made it easy to make a
replacement when the original broke by slightly turning down a
1" (25.4 mm) aluminum rod.

Several companies make 25.0mm posts still, I think American Classic
does. Some Look and Vitus frames require the 25.0mm post.