Gears.

[PpPete]

The OP has worked it out for himself, but one way I use to explain gears to those confused by seeing
1-2-3 on one shifter and 1-2-3-4-5-6-7 etc on t'other is to forget the numbers on the front (left changer)
Shimano really ought to label them H-M-L (High Range, Medium Range, Low Range) ... and then the numbers are within those ranges.
The idea of overlap is more easily grasped then.

 

[jonny jeez]

Thanks all - there's some really helpful advice here. I would never have considered the additional strain on the chain in the "forbidden combinations", for example. It makes a lot of sense too. Makes me even more glad I asked the question!

I guess I'm actually getting the hang of it by instinct. For the first couple of weeks I didn't really come out of the middle chainring. I still don't, much, but I have found myself dropping into the smaller chainring when I see the road rising up in front of me - I know there's a good chance I'll need it. Same with a good downhill section - I know I'll run out of gears in the middle ring so change up to the big one.

I think it's the same with cadence. I know when I'm grinding to a halt, and I know when I can't pedal fast enough to keep up. So I change gear. I've absolutely no idea how many I'm doing per minute. Probably about 12.

Thats it, you've got it.

Perhaps think of the the big spikey things at the front (chainrings) as a gear all of its own and the small rear spikey things (cassette and sprockets) as ratios/degrees of that gear.

So you work through the degrees of gear whilst on a large chainring till you reach the top ratio/degree.

then if you change chainrings, you also need to flick back to the lowest ratio/degree or you'll be in a new chainring but at the highest ration.

So in summary, if you swap rings, you'll need to shift the sprockets as well to find the lowest/higest ratio and thus move through the gears sequentially

 

[mrbadexample]

No. It's the big spiky thing at the front .

Nah, surely not! That'd be impossible!

 

[Jimmy Doug]

FTFY

Thanks 2Loose! Sorry about that mrbadexample! Hope I didn't confuse you! It's quite logical when you think about it, though.

 

[mrbadexample]

Thanks 2Loose! Sorry about that mrbadexample! Hope I didn't confuse you! It's quite logical when you think about it, though.

I spotted it because everyone else had it right. Not a bother.