Chain and seat stays.

[John Gialanella]

Can 1970 Schwinn Paramounts P-13 bikes take rear Campagnolo hubs with either 120 mm width or 126 mm width or are the drop offs on the seat and chain stays different widths. The one on my bike is 120 mm and would a rear campy hub of 126 mm be too wide.
Thanks John.

 

[juvela]

-----

stock spacing on a 1970 Paramount is 120mm

better not to force opening to accept 126mm OLD hub

if you wish to mount 126mm hub frame should be cold set



-----

 

[John Gialanella]

Thank you for that information, that is what I thought that they were 120mm. I was looking at this new set of rims with Campagnolo high flange hubs. I will have to ask seller if the rear hub is 120 mm and also if it is English thread, not French or Italian thread.
John.

 

[juvela]

-----

should you elect to open the rear spacing to the 126mm dimension suggest to have it done by a framebuilder or at least someone experienced in making the adjustment...

the non-drive side stays will move with greater effort than the drive side ones due to chainstay dimpling


-----

 

[Eric Amlie]

The non-drive side stays will move with greater effort than the drive side ones due to chainstay dimpling.

Thanks for that!
I've cold set a couple of frames over the years but never considered that.
Important indeed.

 

[juvela]

-----

the steel tubes have a measure of springyness to them such that it is is necessary to make an adjustment slightly past where one wishes things to end up and then remeasure

generally best to content oneself with adjusting in increments of modest size until goal achieved

within a few adjustments one quickly begins to get a "feel" for the process...

the difference mentioned above wrt drive-side vs non-drive side is due to the double dimpling of the drive side chainstay; unless of course chainstays are rapier pattern (conical without dimples) or round-oval-round pattern

the best procedure is to have the empty bottom bracket shell clamped solidly in a beefy bench vise

this leaves both hands free for the setting and measuring

other techniques come with complications...

never attempt cold setting in the repair stand


-----

 

[GTs58]

Is cold setting a Paramount rear fork end spacing 5/16" wider, 5/32" per stay, more involved than doing a gas pipe model?

 

[juvela]

-----

quality tubesets have a different "feel" than hi-tensile

it generally takes more pressure to get the same amount of movement

quality tubesets have a "lively" feel while hi-tensile sets feel more "dead"

also, Columbus for example tends to have a stiffer feel than Reynolds

Columbus SL/SP has a nominal tensile strength of 120,00PSI while Reynolds 531c is rated at 100,000PSI

these values are pre-brazing and there is typically some loss in tensile strength due to the heat of brazing

some framebuilders assert their tensile strength is about the same post brazing

hope this gives the sort of information you seek...

---

disclaimer:

have no metallurgical knowledge and only a very little bit regarding cycle frame tubing

---

tip for John G. -

in case it is your wish to be able to run a 6V gear block on the Paramount i would like to let you know that there are such animals as 6V gear blocks in the lateral space of 5V

one such recalled is MAEDA's (Suntour) Ultra 6

these are likely covered at velobase and are also included in the Sutherland manuals in case you might wish to investigate them


-----