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Schwinn Lightweight Frame Geometry
- Thread starter momo608
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Eric Amlie
Wore out three sets of tires already!
I'm going to go get some popcorn, sit back, and enjoy this! 
Metacortex
Wore out three sets of tires already!
1963 and later electro-forged lightweight frames such as the Varsity, Suburban, and Continental had very "layed-back" 70 degree head and seat tube angles, a 2" fork rake and a relatively long wheelbase. The '60-'62 models had even more layed-back 69 degree HT/ST angles.
Fillet-brazed lightweights (e.g. Superior, Super Sport, S/S Tourer and Sports Tourer) and Paramounts had more upright 73 degree HT/ST angles and a shorter wheelbase than the EF models. The fork rake was 2" (same as the EF bikes) on all except the '72 and later P13, where the rake was reduced to 1-3/4".
Paramount P14 track frames had even more upright 74 degree HT/ST angles, a fork rake of only 1-3/8", and an even shorter wheelbase than the other Paramounts.
More "layed-back" HT/ST angles and longer wheelbases contribute to stability (for example making it very easy to ride no-handed) but also make a bike slower to respond and corner. As the angles increase and the wheelbase shortens the bike becomes more nimble and quicker handling.
All of the above had parallel head and seat tubes, meaning they were both at the same angle. There were exceptions to this. One very notable exception was the '74-'77 Sprint, which had the same 70 degree layed-back head tube as other EF bikes, however this was combined with a more upright 73 degree seat tube that was also bent or curved to significantly shorten the wheelbase. This would create a bike much more responsive and quicker handling as compared to the other EF frame lightweights.
There are other items contributing to a given frame geometry such as top tube length, bottom bracket height and of course the overall size (seat tube height) of the frame, but the above points out the basic differences in geometry between the EF, FB, and Paramount models.
Fillet-brazed lightweights (e.g. Superior, Super Sport, S/S Tourer and Sports Tourer) and Paramounts had more upright 73 degree HT/ST angles and a shorter wheelbase than the EF models. The fork rake was 2" (same as the EF bikes) on all except the '72 and later P13, where the rake was reduced to 1-3/4".
Paramount P14 track frames had even more upright 74 degree HT/ST angles, a fork rake of only 1-3/8", and an even shorter wheelbase than the other Paramounts.
More "layed-back" HT/ST angles and longer wheelbases contribute to stability (for example making it very easy to ride no-handed) but also make a bike slower to respond and corner. As the angles increase and the wheelbase shortens the bike becomes more nimble and quicker handling.
All of the above had parallel head and seat tubes, meaning they were both at the same angle. There were exceptions to this. One very notable exception was the '74-'77 Sprint, which had the same 70 degree layed-back head tube as other EF bikes, however this was combined with a more upright 73 degree seat tube that was also bent or curved to significantly shorten the wheelbase. This would create a bike much more responsive and quicker handling as compared to the other EF frame lightweights.
There are other items contributing to a given frame geometry such as top tube length, bottom bracket height and of course the overall size (seat tube height) of the frame, but the above points out the basic differences in geometry between the EF, FB, and Paramount models.
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Eric Amlie
Wore out three sets of tires already!
Something that was started long ago either on the original Schwinn Forums, or perhaps the later SchwinnBikeForums was a discussion of the frame sizes. Early on(mid sixties or so and back), Schwinn called two of the frame sizes 21" & 23" on the electroforged lightweights. At some point these changed to 22" & 24". The question was, did the actual frames change, or just method of measuring? I don't think the question ever was completely answered. I started measuring frames on my many fifties & sixties lightweights and found so many differences(like how far the seat tube extends above the top tube) that I gave up, hoping to get back to it sometime when I had more time(that hasn't happened yet).
Does anyone have any thoughts on this?
Does anyone have any thoughts on this?
Well I can say this. I just now measured again my 1960 Continental 23" and my 1982 Continental 28", the only two bikes I keep in the house. They were both advertised in these frame sizes and they both measure that way from the center of the bottom bracket to the top of the seat tube.
I measured quite a few bikes and I have never seen a deviation from the advertised frame size and the actual frame size, Schwinn lightweights anyway.
I measured quite a few bikes and I have never seen a deviation from the advertised frame size and the actual frame size, Schwinn lightweights anyway.
Eric Amlie
Wore out three sets of tires already!
I remember the advertising(for the '63 Superior I think) talking about the new more upright geometry. I only have '62 Superiors, so am not able to confirm any difference between the '62 & '63, but years ago I bought a '62 Varsity frameset and built it up with 27" wheels. Last summer I brought home both that bike and a '64 Varsity(my last recently completed project) and had them parked next to each other. I figured that with the 27" wheels on both bikes that they would stand the same. Not so. I didn't do any measuring, but the '64 model has a higher bottom bracket and sits noticeably higher, presumably from the steeper geometry that Metacortex mentioned. Both frames are 21".
That makes sense. We can assume by that that Schwinn and I suspect the industry norm, was to cite frame sizes measured from the center of the bottom bracket to the top of the seat tube. Obviously there is a disconnect when considering geometrical differences and advertised frame sizes. I always thought the stand over height should have been the one advertised. At least you would know if you could ride the damn thing by measuring your inseam.
Eric Amlie
Wore out three sets of tires already!
Yes, agree with both of you on the standover height. When I buy bikes on ebay I always ask about that. Unfortunately, often, the sellers don't know what it means and I have to explain it to them. Even then some of them get it wrong. I've bought at least two bikes that are too big for me after the sellers assured me that the standover was no more than 32"(my preferred max.).
