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@Yawn
Hi, would anyone know why this might be….
I’m spec’ing the parts for a new fixed and am trying to work out a good gear, something similar to my geared road bike. Unfortunately the figures I get from my Sigma computer (which has the correct wheel circumference entered) are very different from http://software.bareknucklebrigade.com/rabbit.applet.html or Sheldon Brown’s site.
53 x 19, 700 x 23, 175mm cranks = 73.3 gear inches. @ 90rpm = 19.6mph
My Sigma tells me I’m doing 89rpm and 22 mph.
Also, my geared bike is quite light with fairly good wheels (Mavic Kysrium SSCs), if I do choose a similar gear ratio for the fixed will heavier wheels (probably Open Pros) have much of an impact on the gear I’ll be pushing? Are fixed’s, because of the fact you’ve got momentum from the wheels carrying your legs around, slightly easier to push a larger gear or is this wishful thinking? I’ve been doing my daily commute in all weathers at 73.3 and except for a full on 20 mph headwind I’m usually OK.
Getting a close match to my current 73.3 gear inches would be a 46x17 = 71.1.
Many thanks if anyone has any thoughts.