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Old 03-14-13, 02:44 AM
  #48  
Turbotandem
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Join Date: Nov 2011
Location: Boulder, CO
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Bikes: Paketa V2r di2, C-Dale MT 3000, Teesdale, 1963 Huffy Daisey

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Originally Posted by waynesulak View Post
See graphic below for internet gear calculator:

At 20mph with a 13 tooth cog and a 36 tooth chain ring the cadence in shown as 92. Moving from the 13 tooth cog to the 15 tooth cog we get a cadence of 107. Diff in cadence is 15 or increase of 16.3% (15/92).

At 20mph with a 13 tooth cog and a 36 tooth chain ring the cadence in shown as 92. Moving from the 13 tooth cog to the 14 tooth cog we get a cadence of 99. Diff in cadence is 7 or increase of 7.6% (7/92).
I see that; when in the small 36t ring and high in the cogset going fast in small cogs the difference in cadence is highlighted. I was evaluating what I see as our normal riding gears, not the extremes. I wish I knew how to post a web image. Since I can, I can only implore readers to consider this cadence site, http://www.machars.net/bikecalc.htm and enter my gearing; what I see is that at speeds in the teens while riding in the 36t my shifts are a change in cadence btwn 10 and 12 rpm. However, I would suggest that we are more often in the 36t when climbing and therefore run at cadences of 75-85 so the steps again come down to 10rpm. And when riding at speeds in the 20's while in the 52t ring, the shifts are a change in cadence of consistently 10 rpm. All well within a ridable range, for us.

When confronted with the unlikely avaialbility of a triple di2, it seems worth evaluating if a cadence range of 10 is worth the gains of Di2 in a deep 2x10 configuration. It was a no brainer for me. And I am not saying it is for everyone, but the positions on the forum suggest the configuration should not even be on the table for consideration. Since the recent advent of the 11-36 light weight casette, it has opened up the potential for tandem di2 for a wide swath of riders. Ritterview's comparison of pro bikes might be more accurate to compare to pro mountain bikes where the range of speeds, including climbing, more closeley resemble tandeming range of speeds. On those pro mtn bikes wide range casettes are well suited as I suggest they are for tandeming.

I acknowledge that if you need more than 24" of gear for your climbs, triples are the only way to go. We sure don't grind to death at 24" of develpment until we get over 15% grades which is not often. Or if you need steps of 5 or 6 rpm.
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