↑This is the SRAM Force 12-speed 10–33T cassette
that was on the Lovall's rear wheel
when I was reassembling it the other day.
SRAM's XDR-standard 12-speed cassettes come in four options for Red and Force:
10–28T, 10–30T, 10–33T, and 10–36T.
Rival has the same tooth counts
but only two options: 10–30T and 10–36T.
Among these four tooth configurations,
if you ask which represents the most close-ratio
and which represents the widest ratio,
most people would say that based on the top-to-low tooth difference,
the 10–28T is close-ratio
and the 10–36T is wide-ratio.
But if you think about it differently,
you could argue that the 10–30T is close-ratio
and the 10–33T is wide-ratio.
That's what I'm writing about today.
I've written out a summary of the tooth configurations.
In the range under 17T,
only the 10–28T has a 16T cog,
and only the 10–36T is missing a 14T cog.
The 17–19–21–24T section
is common across all configurations,
and after that, the number of cogs differs:
the 10–28T has one fewer cog because it includes the 16T,
while the 10–36T has one more cog because it's missing the 14T.
Let me focus on the low-gear section.
I've added the tooth differences between each sprocket in red.
Writing out the tooth differences of the four lowest cogs
for each configuration:
10–28T: 2–3–4
10–30T: 3–3–3
10–33T: 3–4–5
10–36T: 4–4–4
SRAM's front double chainrings all have a 13T difference,
with 50–37T and then progressively smaller by 2T:
48–35T and 46–33T for three total options.
Unless you absolutely need a 36T cassette cog
with a 33T inner chainring,
if you choose a lowest gear ratio heavier than 33×36,
you'll find that you have more room to make effective use
of the cassette's tooth range.
The reason I said the 10–30T is the most close-ratio
is because it's the only one where the shift to low gear
is a uniform 3T difference.
Similarly, I said the 10–33T is the most wide-ratio
because it's the only configuration that includes a 5T shift.
Imagine you're climbing a hill at 14 km/h
on the second-lowest cog,
and you want to either shift up one cog to pedal harder
or shift down to low gear to spin easier
while maintaining that speed—let me check
the cadence change in each case.
Using 2136mm for the wheel circumference of 700×28C
(both CatEye and Garmin list it the same),
The 27T of the 10–30T and the 28T of the 10–33T.
I've added the cogs on both sides of these as well.
Naturally, the cadence at 24T is the same for both.
Also, for example, the cadence difference between 28T and 33T
calculates to 14.7 from the table numbers,
but shows 14.8—this is just due to how Excel rounds
when displaying one decimal place, so ignore it.
The numbers between the cadence figures
represent the cadence difference when shifting
while maintaining the speed of 14 km/h.
I've set the front inner chainring to 37T for both,
but if I made the 10–30T version 35T instead,
at 35×27T the 14 km/h speed would be 84.3 cadence,
which would match the previous table's cadence more closely.
But I unified them at 37T so as not to seem
like I'm inserting bias into my argument.
The odd blank space in the table above is because
I'm adding the cases for 35T and 33T.
The pattern that emerges is this:
when you reduce the inner chainring teeth,
the cadence difference per cog increases
when maintaining speed (14 km/h) after shifting.
Regarding how much harder or easier things get
when shifting up or down one cog from the second-lowest gear,
you can't say from looking at this
that the 10–33T is easier than the 10–30T.
What I'm saying is that the configuration
that minimizes cadence differences in this gear range
is what truly qualifies as close-ratio.
In my opinion, with SRAM's 12-speed cassettes,
given the 13T front difference (Shimano goes up to 16T),
if you give careful thought to what outer chainring teeth
feel right for flat riding and what inner teeth
let you handle your normal riding range with a 30T low cog
(and preferably lean toward 37T),
the 10–30T is the better choice.
The 10–28T and 10–33T
are essentially 11-speed cassettes
—11–12–13–14–15–17–19–21–24–28T—
with either a 16T or a 33T added.
I'm not denying that some people think
having a 4T jump to low is more important than having a 16T,
or that some prefer the 28T-plus-emergency-low configuration of 33T
(like the 10T jump from 42–52T on MTB cassettes).
Or there are those who simply buy
whichever has the largest low cog
the manufacturer offers within derailleur capacity limits
(the 10–36T).
What I wanted to convey this time is that with SRAM 12-speed,
if you want to minimize fatigue when rapidly shifting
near low gear while climbing,
if a certain inner chainring or front single
×30T low cog would suffice,
then the 10–30T—which stays within 3T jumps—
is my recommendation.
For what it's worth, I'm using
the old 12-speed Force with a front single crankset
(with a power meter built in, by the way)
that came stock with a 40T,
which I've wanted to change to 42T but haven't,
and I've paired it with a 10–30T cassette.
Bonus
Shimano has an entry-level groupset called CUES (キューズ),
and its younger sibling is ESSA (エッサ)—a 1×8-speed component group.
The flat-bar version uses hydraulic disc brakes,
while the drop-bar version uses road-style STI levers
with cable-actuated mechanical disc brakes.
The front single chainring comes in 32T and 40T.
The cassette is either CS-HG400-8 (higher-end)
in 11–40T or 11–45T, or CS-HG-300-8 (simpler finish)
in only 11–45T,
so they seem to be pushing the 11–45T.
11–45T on 8-speed!
SRAM has the XPLR (Explorer)—a specialized rear derailleur
paired with an ultra-wide-ratio front-single
cassette. The latest Red, Force, and Rival become 1×13
in front-single mode with a 10–46T cassette.
In the old 12-speed it was 10–44T.
Apex had mechanical options for both double and single front,
but once it went to wireless e-tap AXS,
the manufacturer imposed its philosophy—
Apex is now front-single XPLR only.
Since Apex uses HG freebody, not XDR,
its 12-speed cassette is 11–44T with an 11T top.
Shimano's ESSA does the same thing as XPLR on 8-speed,
so the jumps in the low-gear section are pretty wild.
To spell it out, the configuration is
11–13–15–18–22–27–35–45T,
with tooth jumps of 2–2–3–4–5–8–10.
For the five lowest cogs, I made the same table
as before for a 40T front chainring—
and here it is.
The middle of the five cogs: 27T.
Nothing particularly odd about it.
I've filled in the rest.
That's wild.