Thread: OCR 2 shifting
View Single Post
Old 04-21-05 | 05:33 AM
  #3  
khuon's Avatar
khuon
DEADBEEF
20 Anniversary
 
Joined: Aug 2002
Posts: 12,234
Likes: 10
From: Catching his breath alongside a road near Seattle, WA USA

Bikes: 1999 K2 OzM, 2001 Aegis Aro Svelte

The Giant OCR3 has a 30/42/52 front triple chainring setup (I'm going to assume a 170mm crank) and a SRAM PG-950 12-26 cassette with a gear breakdown of 12-13-14-15-17-19-21-23-26. Based on that data and assuming a nominal 27" wheel diameter, I plugged everything into the gear calculator at this website and got the following shifting pattern.

Code:
Gear-Inch Chart
         (9)   (8)   (7)   (6)   (5)   (4)   (3)   (2)   (1)
    |    12    13    14    15    17    19    21    23    26
----+------------------------------------------------------
 52 | 114.3 105.5  98.0  91.4  80.7  72.2  65.3  59.6  52.8
 42 |  92.3  85.2  79.1  73.9  65.2  58.3  52.8  48.2  42.6
 30 |  65.9  60.9  56.5  52.8  46.5  41.6  37.7  34.4  30.4

Semi-Log Graph
  2                 3           4         5      6      7     8    9   1   1   2  3
 ----------------------------------------------------------------------------------
I                   1   2     3   4    5    6  7  8  9                             
M                                  1  2     3   4    5    6  7  8   9              
O                                           1  2     3   4    5    6  7   8  9     

Sheldon Brown's Gain Ratio Chart
    |    12    13    14    15    17    19    21    23    26
----+------------------------------------------------------
 52 |  8.54  7.88  7.32  6.83  6.03  5.39  4.88  4.46  3.94
 42 |  6.90  6.37  5.91  5.52  4.87  4.36  3.94  3.60  3.18
 30 |  4.93  4.55  4.22  3.94  3.48  3.11  2.82  2.57  2.27

Rollout Table in Inches
    |     12     13     14     15     17     19     21     23     26
----+---------------------------------------------------------------
 52 |  359.1  331.5  307.8  287.3  253.5  226.8  205.2  187.4  165.7
 42 |  290.0  267.7  248.6  232.0  204.7  183.2  165.7  151.3  133.9
 30 |  207.2  191.2  177.6  165.7  146.2  130.8  118.4  108.1   95.6
The semi-log chart is probably what you're looking for. This chart shows gear position as overlayed onto a development table. Across the top are gear-inches. The letters on the side denote (I)nner, (M)iddle and (O)utter chainrings and the numbers in each row indicate cog position with 1=26T and 9=12T.
__________________
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
khuon is offline  
Reply