# Prewar frame question



## digger (Aug 24, 2018)

Could someone please clarify something for me? I notice while looking at Schwinn catalogs the straight bar, curved down tube frames were offered in 16'', 18'', and 20''. My question is, are all these frames the same size other than the length the seat tube protrudes above the top tube?     Thanks


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## REC (Aug 25, 2018)

16 and 18 are the same other than the seat post - the 20" one has different geometry from the headtube to the seatpost tube as well as the seatpost tube and rear stays being different.
REC


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## digger (Aug 25, 2018)

Thanks


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## fattyre (Aug 25, 2018)

My two 20 inch frames do have the seat tube extending farther past the top tube than a 16 or an 18.  20 inch frames have taller head tubes as well. So not only do they have that seat tube that extends a bit farther the frames also stretch out vertically between the down tube & top tube, witch also changes the seat stay angle and why the rear fenders are slightly different.

  I've never seen longer chainstays on 20 inch frames.  Hub axle to crank axle are all around 18 1/2 inches on my pre war bikes regardless of frame size.  All boys bike I've had have used the same length chain given the cog & sprocket are the same sizes throughout.


Top tubes are all over the place on my bikes, but all within an inch or so.  Seems top tube is dependent on frame style, not size?    A 16 inch frame I have measures at 23 along with one of my 20 inch frames and the other 20 inch is right around 22 inches??

I really don't think any of these bikes were made with exact uniform geometry.   As long as the rake of the fork, head tube angle & wheelbase are similar, the rest just follows.

I by no means am an expert.  Just differences I've personally seen on the pre war frames I've owned.


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## bobcycles (Aug 25, 2018)

18" are sexiest!


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## digger (Aug 25, 2018)

Thanks fattyre, that's the answer I was lookin' for. So is this space larger on a 20'' frame? Since the head tube is longer (by how much?) does it take a different fork? Thanks again.


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## digger (Aug 25, 2018)

bobcycles said:


> 18" are sexiest!



I agree!


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## 2jakes (Aug 26, 2018)

fattyre said:


> I really don't think any of these bikes were made with exact uniform geometry.   As long as the rake of the fork, head tube angle & wheelbase are similar, the rest just follows.




This is also true with the pin-striping on the frames which were done by hand by different people at Chicago factory
 over the years.
I own several Schwinn phantoms from different years and each one is slightly different.
There have been many heated adult discussions as to what is the correct application or location.
But for the kids back then...it really was no big deal. I know for myself I was just happy to receive 
a bike for Christmas. (X-53 Western Flyer Super Deluxe in the carton for around $59.99 plus tax.)


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## fattyre (Aug 26, 2018)

digger said:


> Thanks fattyre, that's the answer I was lookin' for. So is this space larger on a 20'' frame? Since the head tube is longer (by how much?) does it take a different fork? Thanks again./QUOTE]
> 
> 
> Head tubes are 6 inch and steerer tubes are 7 1/8 on 20 inch frames.  Truss rods are longer too.  And even longer truss rods for locking forks.
> ...


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## fattyre (Aug 26, 2018)

Head tubes are 6 inch and steerer tubes are 7 1/8 on 20 inch frames. Truss rods are longer too. And even longer truss rods for locking forks.
Also note on 20 inch frames where the lower tube intersects near the head tube.

From the top of the BB shell to the bottom of the straight bar is about 14 inches measured along the seat post on this bike:

1941 whatever model it is. Similar frame to the one you pictured with the curved down tube.


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## digger (Aug 26, 2018)

Thanks fattyre, that info helps. I appreciate it.


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