Originally Posted by
branko_76
I have two 23-1/2" 1978 Super Grand Prix frames (Made In England). Both have 71mm BB shells and are tapped for 26TPI and built with 20-30 seamed tubing.
I also have two 23-1/2" 1972 Super Course frames.Both have 68mm BB shells tapped for 24TPI and built with Reynolds 531 Plain Gauge tubing.
SGP frames weigh more than SC frames.
I currently have both 25.5" frames apart for overhaul, the clean, bare SC frame (no fork, no bb or hs, not even a headbadge), weighs 5lb 7oz.
The SC fork weighs 1lb 15.6oz
The SGP frame, which still has its headbadge but is otherwise bare, stripped of all parts and cleaned, weighs 5lb 2.8oz
The SGP fork weighs 1lb 15.8oz.
I did weight the 23.5" frames when they were apart, both of them were 4lb 9oz each. I didn't write down the weight of the forks on those two bikes for some reason.
Sitting side by side, both triangles are the same on these frames.
The BB on the SC measures 68.29mm, the BB on the SGP measures 68.53mm.checked with a digital caliper.
(Without removing the BBs on the two 23.5" bikes I can see those are also between 68 and 69mm.)
Both are standard BSC threaded, 24tpi. (I just put the SGP all back to original, for a while I had it outfitted with full Shimano 600, including the Shimano BB and cups.
I moved the whole 600 group directly over to a 1980 Panasonic frame, cups and all.
Back in 1978 when I bought my 25.5" SGP, a buddy of mine bought a red one a few weeks later, (Both of mine are blue), his had the 72mm BB shell and 26tpi threading, but his frame was a 21.5" model. Fully assembled, with all factory components the SGP and SC are nearly identical in weight, within a few grams with the same tires and tubes.