Thanks for all that information
I feel a bit dense now - I hadn't thought of counting the teeth to see if the chain would fit! Is that a standard procedure?
Don't know about Standard: it just occurred to me.
So, if I've got this right, the necessary changes for me would seem to be...
1) change rear cassette for e.g. 11-30/32/34
Yes.
2) for rear 30T or more change mech for acera/alivio etc.
Yes. I am not confident about using existing Sora rear mech with 30T. The Alivio works like a charm. The purpose of the slant parallelogram changer is to keep the guide pulley close to the sprocket one wishes to engage - not actually mesh with it.
3) Either get a new chainwheel such that total teeth ~77 or less & adjust chain accordingly e.g. 46T + 30T = 76T so remove a link, or just keep 52T front & find a long enough new chain of same spec.
Yes if you don't want to buy a new chain for the extra links you'll need.
It seems chains are not too costly, but to me it looks a fiddly job to replace, maybe requiring expertise &/or special tools?
A little practice on chains might not go amiss considering the excrutiating chain line on the Torq - at its worst in the lowest gear when you are intent on giving the bike some real welly.
I would not say "expertise" just a little know-how. Yes, you will need a Chain Tool. Not dear £ 5 -£7 cheapest "Buy it now" on E Bay.
Its not too fiddly to fit/shorten/lengthen a chain (a bit mucky maybe)
A TIP! Do NOT. whatever you do, push the pin right thru' the link behind. You'll curse the day you sold the Hobby-Horse. Just leave enough (trial and error) of the link proud on the inside to be able to "catch" the hole in the link when you offer the join up again. On the subject of re-joining: turn the chain over so that the pin that is protruding is on the outside facing you: then you won't have to operate the rejoining with the chain tool thru' a mass of machinery.
Oh on the subject of chains: make sure its a 3/32nd and the same for the chain ring - there are some BMX stuffs on the market and they do not carry a SIZE warning - they are 1/8th.
But then you knew all this already.
I suspected the Sora may not make 30T, even though I've heard its possible in some cases, which is a shame because I could accept 52T + 30T as a cheapish upgrade (given the chain can be changed cheaply/easily).
Don't know about the price of chains (or two for that matter). Are you a 'spinner' or a 'pusher'? (If you like fast revs when climbing I would go for the 44/46 - a decent reduction, then go off to Wales for the w/end and convince yourself how astute you are) If the gear seems a bit too low on that grade you've got a higher gear or two. If it's too high you can always walk.
Still, this way I can choose a lower bottom gear i.e. 32/34T rear, though without changing the front 52T as you say Pete, I may need a longer than standard chain.....
Yes the Torq is a long bike and I think a standard chain has fewer links - the Torq needs.....where did I put that note? ....67 links for a 25 x 52 set up and the same for a 32 x 44 set up. I took one link out but put it back because the chain was a bit taught in the lowest gear.
Hmmm... I guess its still worth it for ease of pedalling off from a standstill: I did wonder if doing so would save much battery power & extend the range any, or if the Torq's standard gearing was designed for "motor-assisted" starts i.e. pedal + motor for getaway & that the motor & controller were designed to do this with minimal power drain usually associated with using the motor at starts, especially I'd have thought in a high geared motor such as the Torq?
I am less concerned with losing battery power than leg power. If your anticipation is good you can get bottom gear before coming to rest. A higher gear than the lowest will get you started easily enough - but if you come to a standstill on a hill the lowest gear will be a blessing. There is quite a bit of power in my Torq from standstill, even on a hill, but at what cost in battery power/life I can't guess.
P.S. Those Sugino chainrings are cheap Pete! I must look out for one of those... is 46T a standard size, as that might work well for me?