Originally Posted by
ultraman6970
If i understand right.... U mean that some gear ratios are repeated??? yes. Some combinations are almost the same but the feel of the gears are different. For example (just putting numbers in my head ok? i might be off because im not looking at any tables right now ok?) 52x19 is around the same than 42x16 but they feel completely different.
Now with a triple geared bike is even worse because there u have stuff repeated like like 3 times with some gears, u get the same development using 2 or 3 different combinations of gears, non efficient if you ask me, but for people that really can't climb at all it works. Now u know why compact cranksets are sold
How the gear will feel is given by the cog, as smaller the cog less torque has, as bigger the cog more torque it has. So even thought u have 2 gears that are almost the same they will feel different.
Have no idea what u mean with decending from 18 to 1 ??
On my bike (mountain bike) the chainrings at the front are 44-32-22 and the sprockets at the back are 11-13-15-17-20-23-26-30-34
So based on the chainring I'm using the gearing, calculated as the ratio between the front and rear cogs, is (to three decimal places):
44:- 1.294 1.467 1.692 1.913 2.200 2.588 2.933 3.385 4.000
32:- 0.941 1.067 1.231 1.391 1.600 1.882 2.133 2.462 2.909
22:- 0.647 0.733 0.846 0.957 1.100 1.294 1.467 1.692 2.000
As you can see there are lots of similar gears. Referring to gear combinations as chainring/sprocket where small numbers indicate large cogs we can see that, for example, 1/5 is very similar to 2/7 which is similar to 3/9. 1/1 is similar to 2/3 and identical to 3/6. 1/2 is identical to 3/7, and 1/3 is identical to 3/8.
Which gear to choose would depend on what type of flexibility you want. If in any given situation you're comfortable with a gearing of about 1.6-1.7 but expect to want to go lower rather than higher then 2/5 makes more sense than 1/3. From 1/3 the only way you can go down is to 1/2 (which gets into chain-crossing territory) or to 2/3 which represents quite a substantial drop in gearing. From 2/5 you can drop to 2/4 which isn't such a drop, but you can still drop to 3/5 if you need a big drop.
If you're looking for gearing around 2 but expect to want to change up then 3/9 makes little sense because you've got nowhere to go and you've got chain-crossing issues. 2/7 makes more sense, but 1/5 probably makes more sense still because it gives you more scope to change up if you need it.