In the past few days I have been going through a dilemma on the size of my Crank and Cassette. What is the best ratio for hills, for flats, for a long distance, for ….
Today I am getting installed a compact Shimano FC-R700 (ultegra) 50/34 with a 170mm crank. I originally had an SL-K FSA 50/34 with a 172.5 crank and been told that I need to go to a 170mm. The big question is if I should go with a 11-25, a 12-25, or a 12-27 cassette. It seems that every other person I talk to has a different opinion so I turned to the net and explored my geeky side. Here are my findings:
Ultegra has the following available ratios:
• 11-23: 11-12-13-14-15-16-17-19-21-23
• 11-25: 11-12-13-14-15-17-19-21-23-25
• 11-28: 11-12-13-14-15-17-19-21-24-28
• 12-23: 12-13-14-15-16-17-18-19-21-23
• 12-25: 12-13-14-15-16-17-19-21-23-25
Hey, where is my 12-27?
Oh there it is…
Shimano 105 ratios are:
• 11-23 – 11, 12, 13, 14, 15, 16, 17, 19, 21, 23
• 11-25 – 11, 12, 13, 14, 15, 17, 19, 21, 23, 25
• 12-25 – 12, 13, 14, 15, 16, 17, 19, 21, 23, 25
• 12-27 – 12, 13, 14, 15, 16, 17, 19, 21, 24, 27
Amit Levinson (AKA Amit Loser-son) screwed me when he sold me what was supposed to be an ultegra cassette:
So far it looks like the 12-27 provides me with 24 and 27 teeth while the 12-25 provides me with 23 and 25 teeth on the cassette cogs.
Now to make it more confusing I found this web site: http://www.jbarrm.com/cycal/cycal.html
Using their calculator these are the results:
This is obviously the better choice.
The conclusion:
1. Amit Loser-son is only good for ordering a brand new Cervelo in Israel. Other than that they suck as they also screwed up the tune up and maint. on the used bike which I purchased from them.
2. I am keeping the 50/34 with the 12-27 for the Israman.
3. On the next trip to the USA I will be getting an 11-25 ultegra cassette.
Questions?
Yea, but lets talk practical. How much time will it take us , on a cadence of 85 , to complete 180km??
SP CRxFW PRPK CADENCE min / km 180 Time
— ——- ———-
1> 34×27 360.59 85 4.2 763.6023529 12:43
2> 34×24 320.53 85 3.8 678.7694118 11:18
3> 34×21 280.46 85 3.3 593.9152941 9:53
4> 34×19 253.75 85 3.0 537.3529412 8:57
5> 50×27 245.2 85 2.9 519.2470588 8:39
6> 34×17 227.04 85 2.7 480.7905882 8:00
7> 50×24 217.96 85 2.6 461.5623529 7:41
8> 34×15 200.33 85 2.4 424.2282353 7:04
9> 50×21 190.71 85 2.2 403.8564706 6:43
10> 34×13 173.62 85 2.0 367.6658824 6:07
11> 50×19 172.55 85 2.0 365.4 6:05
12> 34×12 160.26 85 1.9 339.3741176 5:39
13> 50×17 154.39 85 1.8 326.9435294 5:26
14> 50×15 136.22 85 1.6 288.4658824 4:48
15> 50×13 118.06 85 1.4 250.0094118 4:10
16> 50×12 108.98 85 1.3 230.7811765 3:50
In other words ,you can ride a sub 6 ride without even moving to the big ring…