Monday, April 11, 2016

Regearing my SARS roadbike

Wheels of Happiness

Rizal Philippines
April 11, 2016

                                         FSA carbon fiber chainwheel crank 53 - 39

I regeared my SARS road bike, inspired by the Mt. Province, Banawe Sagada ride last June to lower gears. I had 3 x 10 set up, with Deore triplet 44 32, 22 set up with 11 to 36 rear cogs, medium cage rear derailleur.  It had so many issues though. When at 44 x 32 the chain jumps to 32 without provocation resulting in loss of timing or failed climb.  It wont go down to 22 when asked for.  So it was better to use a mt. bike.

But you have issues with MTB:  it is heavy (none can match the lightness yet of road bike even the wt of iron bikes.  And the friction with wide tires easily tires you out.  So the ideal is the road bike that has low gears when elevation gets high.

The solution according to experts and mechanics is to go to 2 x10 or 2 x 11.  But such are expensive proposition even for a MTB. Your 2 x  10 crank, xt will set you back by 7t.  And you are not even sure.

So I experimented with putting back the original chainwheel/cranks set of FSA 53 39. I hope it will fit the chain.  Fortunately I had to buy a new chain for `10 speed. The mechanic said that the chain was pretty worn out (I could see the clearance of the chain in some section of the chain wheel to be from 0.5 to 1.5 mm.) That was after 4 years of use and long distance riding to Laguna loop, Real, Atimonan,

                                        No issue with 53 x 36

For the 2 x 10, the combinations are 40 x 28, 34 x 24

I computed for the gears inches:

                                                  53                               39

         11                                   130                              95.7

         13                                   110                              81

         15                                     95.39                         70.2

         17                                     84,17                         61,94

         19                                     75,31                         55,42

         21                                     68.14                         50.14

         24                                     59.,62                        43.87

        28                                      55,93                         36,66

        32                                      44.7                            32.90

        36                                      39.74                          29.24

Thus certain conclusions can be made:

1.  With this set up, you have all the gear inches of all the gears of 53 39    x   12 to 25.  The gear inches of 53 x 25 is 39.  See how one chain ring can have it all. If you are strong rider, all you need is to run on a big chain rings in flats or in hills.    

2. If you are one chain ring advocate for MTB, you can have speed and very low gear with 39 x 11 to 36.  29.24 gear inches is low low all ready .  The only lower gear from a 34 x 36 is 25.99;  for 24 chain ring by 28 it is 24.92.   You are behind the 24 chain ring for only 2 chain ring.

I tried riding this bike this morning with this set up and I could speed up from 11 to 15 x 53 with great speed.   Time to practice speed at flats.    

                                       At 39 x 36

                                    At 53 x 32;

                                                 At 53 x 36;  no sound no jumping of gears

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