Saturday 21 May 2016

SRAM PG850 gears

My SRAM PG-850 11-32 cassette (newly cleaned up) weighs in at 274g, including lockring
Today I stripped the gears off the wheel I was using on Mermaid.

I had the 11-32 set, which gave me ratios of 11, 12, 14, 16, 18, 21, 26, and 32.
The 11 and 12 are separate gears, each made with a built-in spacer to spread the (high) loading, in order to stop them cutting a notch in the freehub.
The rest of the gears came assembled as a group.
The 11 is a "top" gear, so the grooves for the splines don't go all the way through, while the 12 has fully-cut grooves.

Today, I discovered that the "group" of six gears are actually held together with a very long thin bolt, and a rather small Allen key will unscrew them.
Separating the "group" of six gears has two advantages:
1) I can clean them all properly!
2) I can monkey about with the ratios.
If I was to purchase another set of PG850 gears with a different ratio spread, then I could make up some useful extra combinations.

Say, for example, I bought a 12-26 set.
Well, that contains 12 (presumably a "top" gear), 13 (presumably a "stand alone" gear, like the 12 I already have), 15, 17, 19, 21, 23, 26 (presumably with a bolted-together group of 6).
So I could make a couple of new (unavailable) combinations, including two "time trial" "corn cob" sets:
a) 11(top), 12 (single), 13 (single), 14, 15, 16, 17, 18
b) 12 (top), 13 (single), 14, 15, 16, 17, 18, 19
Plus I would have enough parts to build the "official" 12-23 ,"road" set :
12 (top), 13 (single), 14, 15, 17, 19, 21, 23

Then, of course, there are the "road + granny" sets, where the cassette is build up as a "road" 7-speed, with the addition of a large sprocket in the inside position.
E.g. 11(top), 12 (single), 14, 16, 18, 21, 23, 32
Or 11 (top), 12 (single), 13 (single), 15, 17, 19, 23, 32

There is, of course, a variant of the 11-32 wide ratio set I started with, substituting a few to give:
11, 12, 14, 16, 19, 23, 26, 32

There is, of course, one more set of ratios available from SRAM, and this includes 2 more sizes of sprockets. Whether it is worth buying a cassette just for two new sprocket sizes depends how much the cassette costs (!)
Any way, that cassette comes as an 11-28, and the two new sizes are a 24 and a 28, giving 11, 12, 14, 16, 18, 21, 24, 28.

Taking the 11-32 I already have, and buying both the 12-26 and the 11-28 allows a very nice, well-balanced, wide-range cassette to be built:
12 (top), 14, 16, 18, 21, 24, 28, 32. Indeed, this is the same set of ratios as the 9-speed 11-32 offered by SRAM without the 11-tooth sprocket.
 
So there we are.
If I buy another couple of SRAM PG850 cassettes, I can customise my ratios to my little heart's content, as well as having a couple of spare sizes in case some start to show a lot of wear and tear:
11 (top x2), 12 (top and single x2), 13 (single), 14 (x2), 15, 16 (x2), 17, 18 (x2), 19, 21 (x3), 23, 24, 26 (x2), 28, and 32.
Let's see how much (or, more importantly, how little!) I can get that extra pair of PG850 cassettes for!

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