gear ratio questions
hey all. i'm going to be picking up a singlespeed in two weeks and i noticed the gearing on the one i want is really low and i want to change it. i almost exclusively do city riding and commuting and don't really have many crazy hills anywhere in my city. what ratio is best for this kind of riding? i also want to get pretty good speed while riding the flats. will i have to compromise for this and be forced to grind up even the tiniest hill? all your help is appreciated.
On my 26" wheeled townie/grocery getter I've played around and run the following gears: 44x16, 44x18, 42x16, 42x18. The 42x18 was way too low for the flats. I liked 44x16 a lot for making time. 44x18 is on there now and works good for the times I have the bike loaded down with groceries and have to climb the steep hill back to my house. I don't notice much of a loss of the top end (compared to 44x16) when cruising. FWIW, the bike is a pig too, even unloaded.
On my 700c fixed gear I run 44x17 or 42x17 and it works pretty good. Lots of hills around my way.
all hail der Fuhrer Bush
how to compare
use the gear inch formula to compare and contrast gear combos and wheel diameters, then you can arrive at your own conclusions.
#chainring teeth divided by #cog teeth multiplied by wheel diameter = gear inches.
for 26" knobbies use 26 for the diameter
26 inch" slicks probably 25 is more accurate.
For road tires, 27"
for 700C fatties, probably 28, or 29 for true 29er knobbies
just carefully measure the actual rolling diameter of the wheel in question for a real accurate number for the above calculation.
For road use with some ups and downs but no real climbing, something in the 65" to 70" range should be perfect. The classic gear for fixed gear training is 65" give or take.
The lighter the wheels the higher the gear you'll want other things being equal.
Short,like 170mm cranks let you spin quicker but with less leverage, so a slightly lower gear could work
Long, like 180mm crank arms give you leverage but hinder quick spinning so muscling a slightly higher gear could work.
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