Debbie wrote:
> Please can someone tell me either (a) how to work out whether I have suitable gears, or (b) do the
> arithmetic for me and tell me - preferably (a) as I really ought to get the hang of this stuff.
(a) is tricky because different people need/like different gears, and for different places/uses.
Maths (or anyone else's advice) can't provide the all answers to this one. Really, you have to
use either previous experience of different gears or experiment. I've seen some ludicrous plans
from people who are clearly mathematical geniuses but obviously have no clue about cycling.
rec.bicycles.tech is a great place for that
(b) is easy: Front chainring divided by rear sprocket times tyre diameter. But what to do with the
numbers?... Compare to other bikes or other gears you could bung on the bike........
> 3 front chainwheels at the front - 48,38 and 28 6 sprockets on the back, the smallest has 14 teeth
> and the biggest has
> 28.
>
> The wheels are 26 inches.
Not a bad selection, more sensible than a lot of bikes have I think, but they could be changed if
you like. The easiest and probably cheapest way is to change the freewheel (rear sprockets).
Do you feel you need a lower bottom gear, higher top gear, closer gears, or different middle gears
or what? Then we could make suggestions. Bear in mind that, unless upgrading to a larger number of
gears (expensive), something would have to be compromised in the process: usually bigger jumps
between gears and/or: lower top gear or higher bottom gear, or less reliable or difficult gear
changes (in the case sometimes of changing front chainrings too much).
For comparisions: modern mountain bikes have a wider range, typically
22/32/42 with 11-30 (8/9-speed); hybrids can have all sorts. Your top gear is unusually low but then
a lot of bikes have unnecessarily high top gears - I think it's more important to optimise for
middle and low gears. Try simply pedalling faster if the high gears feel too low. I'm happy
enough with a 50x14 top gear on my tourer (with near-27" wheel). It may be well worth having
lower bottom gears if you have trouble climbing steep hills (and would be able to balance at
lower speeds).
Don't rush into it, though, if you are newly returning to cycling or riding any new bike, because it
takes a fair while to get used to the bike and gears, and in particular, to pedalling at a good
cadence. Also of course, you'll get fitter and stronger so will be able to power the gears better.
With 6-speed freewheel*, you probably won't be able to have one with a top sprocket smaller than 13
teeth; 34T probably the largest (although not all rear derailleurs can cope with 34T). Note that it
takes more of a difference in number of teeth at the large end to make a difference than to the
small. Front chainring possibilities depend on make & model of cranks (please state).
info: www.sheldonbrown.com/gears.html
calculator: www.sheldonbrown.com/gears ("gear inches" are best units for making comparisons)
* as opposed to "cassette". See: www.sheldonbrown.com/free-k7.html . If you do have a cassette (prob
not), you'll be able to use 12 and 11T.
~PB