Gear Inches and Granny Gears

On some recent climby training rides, especially when feeling effects of accumulated fatigue, I found myself wishing for a lower granny gear.  I’ve been riding a 28/42 crankset + 11-36 cassette.  With a 2.2×29″ tire, that’s roughly 22.5 gear inch granny gear (and 110.3 gear inches on the high end).  I’ve been riding this for a while now and it’s been fine for normal, unloaded riding.  Throw in back-to-back long/climby days and 20+ lbs of gear, water, food, and trying to ride at a more sustainable “all day” pace – a lower granny gear would be nice.

Back in 2015 when I trained for the TD I was running a 1×11 with a 30-42 granny – 20.6 gear inches.  I never considered that granny gear to be inadequate, but I didn’t like how I spun out almost any gradual descent.  The high-end was a meager 86.7 gear inches.

So I figure I have two options:

  1. Replace the 28/42 chainrings with 26/39.  That would change the gear inch range to 20.9 – 102.5.  A granny gear 7% lower than previously.
  2. Keep the 28/42 chainrings and add a 42T Wolftooth cog to the cassette. Gear inch range:  19.3 – 110.3.  A granny gear 14% lower than previously.

I opted for #2 and installed it last night.  It offers a lower granny gear without sacrificing the upper range.

Because we’re adding a new granny gear, a different cog must be removed – typically the 15T or 17T.  The downside is that it introduces a larger jump between gears: 11-13-17-19-22 or 11-13-15-19-22.  Of course, Wolftooth thought of a solution for this: replace the 15T and 17T with a 16T cog.  So the stack looks like 11-13-16-19-22.  Two 3T jumps jumps instead of a 2T and 4T jump.

And here it is, in red of course.  Very nice looking!

In the work stand everything sounds and works fine.  For the first time ever, I actually had to add links (just one) to a new chain for it to be the proper size.  We’ll see how it works in the field soon enough.  Mental notes to myself: how noticeable the lower granny gear is?  Has shifting crispness has changed at all? Are the jumps between the 13-16-19 cogs more jarring?

 

While on the topic of gear inches, I just had to figure out my granny gear of the commuter bike I rode on the Great Divide in 2010.  28/38/48 crankset + 11-32 cassette with 2.2×26″ tires: 23.1 gear inch granny gear.  So slightly harder than the cutthroat’s 28/36 granny.  Considering I had never ridden in mountains, inefficient bike position, a heavy bike, and a far more/heavier gear I don’t know how my knees didn’t explode.  On the high end, the 48/11 combo gave 115.2 gear inches.  Even with such a tall gear, I remember spinning out on various descents, wishing to be able to pedal to generate some warmth.

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