David Damerell wrote:
>
> Greg <
[email protected]> wrote:
> >My gear ratio's are 53/39 on the front and 21-19-17-16-15-14-13-12 - is this normal?
>
> Is it normal? Yes. Is it good? No. What are you (or any normal non-racer) going to do with a
> 53/12, eh?
>
> I have a 52/39 on the front (why a 39? They don't come any smaller in 130mm BCD), but a 13-34 on
> the rear - much more useful.
As others have pointed out, a 38t ring is available. Some 130 cranks might need a bit of "dremeling"
to take the 38t. My DA 7402 cranks take the 38t without modification.
> I don't have the teeny jumps you do, but they are not really useful for normal riding.
By definition, they are useful if they are used and I would hardly call it *not* normal -- a lot of
people use it and enjoy it. I used a 12-21 8sp almost exclusively for the 6 or so years I owned it
before 9sp's came out. If riders didn't perceive and advantage to "small" step sizes, they wouldn't
bother with tight cassettes. They recognize the tradeoffs. Once one is wont to "close spacing," it
is hard to give up. I've done a lot of experimenting with step sizes. I find I like resolution at or
below 9%. For example, the 19 to 21 difference is a teensy bit high for my taste, but in the end,
the 18t isn't quite worth the sacrifice of a low for a 17-18 sequence. On the low end, I find a step
of 4% to be the bottom end of what can be distinctly sensed as a "different gear." But I never
design to go below 6%, and it is really the integer based teeth constraint that causes the 6% step
(16 <=> 17), not the actual desire for that step size.
For causal riding, it is much easier to tolerate, and even "not notice" larger step sizes. I've
found I'm most sensitive to step sizes for "max effort" (Time Trial) style riding. For me, this
amounts to max effort intervals of 15 to 60 min. I don't like steps above 9% for TT style efforts
and I've come to this through experimentation. "Max effort" is roughly defined by me as delivering
the maximum joules for the time interval of concern. A power meter is not necessarily required
because a speedometer and the body's sensations provide feedback in the short term. A stopwatch and
a "same course" are sufficient as a relative power meter in the longer term for hill climbs. I
think even casual riders might want to occasionally see "how hard they can go." In this case, I
believe they will appreciate tight gear spacing from time to time, although the cost might not be
worth it to them.
So my philosophy is:
1. Try to get spacing under 10%
2. For the high, shoot for an rpm under 120
3. For the low, shoot for an rpm above 80
4. Simple crossover, double-shift pattern (crossover available in at least two "spots")
Naturally these goals are difficult to simultaneously satisfy if one pedals over varied terrain --
as ususal. A set of compromises will take place. Each of the goals will need to give some. How the
constraints are balanced depends upon the riding style of the particular individual. One of my
favorite tradoffs is to "stretch the lows" a bit. This also has the "unintended" benefit of delaying
the need to shift down to the little ring for knolls. Sometimes a delay means the double shift never
needs to be made at all -- that's nice for those of us who don't have indexed front shifting.
The nice thing about 10 cogs and indexed triple fronts is that the compromises begin to vaporize.
Shall we feast on cake?
> However, if your machine came with a 'road' derailleur it probably will not accommodate a rear
> sprocket larger than _about_ 28t. That would still effect an improvement.
