Tuesday 8 January 2019

Two speed + larger chainring


The two speed is an obvious choice to save weight, but with the limited gears you need to pick you options well or be left churning a massive gear or spinning out too quickly! 


The stock ratio / MPH for RPM/cadence of 90 is - 3.38-4.5 / 15.1-20.1 mph.

It is very common to increase the chainring size, 60t seems to be the biggest option without too many issues. Larger hits the front fork hook / the chainstay. On my personal bike I now use a 122mm BB to stop the chainring contacting the chainstay when folded. 


The following ratios and MPH90C are per increased ring sizes;

56t - 3.5-4.67 / 15.6-20.8mph 
58t - 3.63-4.83 / 16.2-21.6mph 
60t - 3.75-5.00 / 16.7-22.3mph

The BWR with 50t has a gear range of 302%, ratio of 1.99-6.03 with MPH per 90 RPM (cadence) at 8.9-26.9mph.

So with a 60t x 12/16 you would need to pedal at 108.5 RPM to equal a BWR hub using 50t 13/16 at 90 RPM.  


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