I kindly got his fantastic chapter "Frame preparation" from Robb Nortier, in which he wrote he measured 8 3/4" between the centres of the seat spring mounting holes.
So if your rear frame is broken, these should be the right dimensions for making a jig plate.
I concur with Ali. The seat lug centres are 8 3/4" (I just measured mine). With the seat lugs jigged as in Marks photos, the cross tube distance can be determined. Ron
Thanks to your helpful information I've now established the cross tube is close to 5.1/2" long depending how you measure it as it has to be scalloped around the shape of the adjacent sub frame tubes. initially I assumed the cross tube was the same diameter as the rest of the upper sub-frame i.e. 3/4" but I can see from the remnants of what I have that it is a smaller diameter. Please can someone confirm the correct diameter?
