1952-56 rear shock absorber length?

The later Nomad and Model 77 used swinging arm frames very similar to the first Model 7 with a Factory swinginging arm fitted.

From 1952 up to 1957 Armstrong units, were fitted to the Model 7 and some Wideline Frames. The first of these units had no means of adjustment to cope with a passenger load but later versions came with an adjustment ring to alter the spring preload. Then Girling oil damped 3-position units arrived to become the standard fitment. Eventually, as with many other motorcycle component suppliers, the demise of most British manufacturers led to Girlings association with Norton motorcycles ending. However, a number of specialist companies now produce variations of the Girling type and some specialise in refurbishing the older suspension units. This service does tend to cost much more than purchasing new reproduction parts. 

I do not have any numbers for the Armstrong units but the The Girling units had an extended length of 12.9“ and came with 80 lb springs, plus an option of 110 lbs springs and  145 lb for a sidecar. Perhaps somebody else can fill in the gaps.

Just measured the original Armstrong units from my '56 19S - 12.75" eye to eye. Currently have Hagon units fitted at 13".  I think that would be the maximum acceptable due to the limited clearance between the chain and the swing arm pivot.

Cheers, Ian McD

NJB do adjustable length shocks if you want to play! 

Dan

... a copy of the Girling fitment catalogue and it says 12.6" length. Other possibly useful info: spring ID SA286/54, 120 lb/in rate.

To maximise the chain clearance use reduced head (both AF & height) bolts, without washers, to secure the cross brace to the swing arm pivots. When I first aquired the 19S a slack chain had completely worn away those bolt heads. With the brace unable to do it's job the handling was interesting. Not knowing any better back then, and with the bolts not being visible, it took me quite a while to spot the problem.