[SeptimusFry]

I am newly returned to bikes after umpteen years of another sport entirely. I have bought a bike, basically on price, which has 30 gears. I have no local friends who ride bikes. I am, by most standards, old, but not yet dead.

I realise that all 30 ratios are not practical, for example the smallest front gear driving the smallest rear gear is quite horrible to consider.

So, being mathematically minded, I have done a little spreadsheet which gives me all the ratios, for all the combinations (1.15 to 6.91).

I hope I will be corrected now in the following mathematical thinking...

I think of the front sprockets as selecting LOW, MEDIUM or HIGH gear regimes.

Logically, I would progress through the LOW gears, until I get to a ratio which is duplilcated in the MEDIUM gears. So, then I change up the front sprocket - and logically change back the rear gears as well, to get the next ratio up from where I was... NOT well explained, but I am sure you will understand. This seems to me to be the only way to progress through ratios??

Alternative thinking: start with the lowest gear on the second front gear, and only change the rear gears??

 

[manabiker]

Your middle ring on the front is your primary gear, on a up hill you will go to the small ring in the front, if you want to go fast you'll use the big ring in the front/small in the rear, you may have 30 gears, but you'll only need 15 or so of them.
Zinn & the art of Mountain Bike Maintenance has a chapter on gears that will discribe it much better then I can, and there is a chart in there that will tell you the gears of any bike and how they relate to the other gears, the book is under $20 from Amazon, Borders has it too, there is plenty of useful info in that book.
By the way I'm 64 yrs old, and going strong on the bike, there are guys much older then me that I can't keep in sight. I'm having fun with it, being an exmotocrosser there are simularities, like pain, when I ride over my head..LOL!! Happy Trails

 

[jeffscott]

Pretty much you start somewhere....then shift the rear to get the right ratio for the terrain...

If you are cross chained Ie the chain is going from big to big or little to little...you change the FD...

Course you shift the FD before you get to big big or little little...

The high end shifters don't have indicators so you just get used to the feel after a while.

 

[vic06]

I usually start in the middle and change cogs until I start crossing the chain, then I change rings and go back one or two cogs to smooth the transition and keep the cadence. After a while you'll develop a feeling for the right ratios to keep the chain more less parallel to the bike and rarely look at the shifters.

 

[xenon]

I always prefer to get same or nearly same ratio with large chainring and a bigger cog in the rear rather than with middle chainring and a smaller cog - as long, as it doesn't cause cross-chaining. The more teeth carry the load, the less they wear out. Besides, in this large ring/bigger cog combination the chain is less bent in the rear derailleur, hence less resistance and smoother pedaling. Not sure, if it is scientific, just applying common sense.

 

[AndrwSwitch]

I think of them in terms of the chain rings for what I'm doing (climbing, flats or rolling, descending, road) and the rear cogs for fine-tuning the ratio. I typically use the small ring to climb, the middle ring almost exclusively on flat or rolling off-road terrain, and either the middle or big for descending and road.

As long as you avoid cross-chaining, though, it's a matter of figuring out what works best for you.

 

[JCullen]

I tried the same thing when I started out - gave up when I realized I was spending more time thinking about shifts than enjoying the ride. With 9 on the rear, I try and avoid the smallest three on the cassette in the granny ring and the biggest three on the cassette in the big ring. I'll run them all in the middle. I usually just listen and my front derailleur lets me know if I've gone a shift too far.