Subtlety of gearing
24 Aug 2022
For some time now I have been running an 11-36T rear cassette on my road bike. That’s right 36T, not that common. Specific if you are interested it’s this Zitto cassete
Reason being I was after a little additional help on the hills. I’m a big bloke as a Doctor once told me I’m not built for running marathons. I’m more the front row of you local Rugby team
I run a pretty standard 34/50 compact crank This gives me a gear ratios in the table below with a handy 1:1 ratio at the bottom.
11-34 Cassette
| Cog / Chainring | 11 | 13 | 15 | 17 | 19 | 21 | 23 | 25 | 27 | 30 | 34 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 34 | 3.0909 | 2.6154 | 2.2667 | 2.0000 | 1.7895 | 1.6190 | 1.4783 | 1.3600 | 1.2593 | 1.1333 | 1.0000 |
| 50 | 4.5455 | 3.8462 | 3.3333 | 2.9412 | 2.6316 | 2.3810 | 2.1739 | 2.0000 | 1.8519 | 1.6667 | 1.4706 |
A change to 11-36 resulted in a different set of ratios.
11-36 Cassette
| Cog / Chainring | 11 | 13 | 15 | 17 | 19 | 21 | 23 | 25 | 28 | 32 | 36 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 34 | 3.0909 | 2.6154 | 2.2667 | 2.0000 | 1.7895 | 1.6190 | 1.4783 | 1.3600 | 1.2143 | 1.0625 | 0.9444 |
| 50 | 4.5455 | 3.8462 | 3.3333 | 2.9412 | 2.6316 | 2.3810 | 2.1739 | 2.0000 | 1.7857 | 1.5625 | 1.3889 |
I have been running this for some time (~8000kms). My only query was I felt I was in 36 Cog earlier than I should be on the steep climbs and until I looked hard at the numbers in the table. I would have told you the second last cog was the issue. However looking at the numbers I’m not sure it was.
Enter the Sub Compact crank. I’m now running a Praxis Alba 32/48 crank, second hand on Ebay for a little over $100. At the same time I have change back to the the 11-34T cassette that has had very little wear (~1000km)
11-34 Cassette
| Cog/ Chainring | 11 | 13 | 15 | 17 | 19 | 21 | 23 | 25 | 27 | 30 | 34 |
| 32 | 2.9091 | 2.4615 | 2.1333 | 1.8824 | 1.6842 | 1.5238 | 1.3913 | 1.2800 | 1.1852 | 1.0667 | 0.9412 |
| 48 | 4.3636 | 3.6923 | 3.2000 | 2.8235 | 2.5263 | 2.2857 | 2.0870 | 1.9200 | 1.7778 | 1.6000 | 1.4118 |
Now the feel on the bike is like I am not going into the 34 Cog as often as the I was the 36 Cog in fact the 34 is typical now only for the extra pinches >9%. What the maths shows is that in the <1.2 ratio I have 4 gears in that range to play whereas both the 34T and 36T on the compact chainring I only have 3 gears.
The difference is very subtle and honestly on paper it really does not look a whole lot different. On the bike however I now feel I have better options at the lower end of the gear selection.
Now the obvious thing is I have lost some top end speed. I’m topping out at around 53Km/hr as opposed to what would maybe have been 54-55Km/hr. Now if I was doing fast bunch rides mostly on the flat this may be an issue. But I’m no. A flat ride for me has at least 300meters of climbing in it and I’m riding solo, not in any condition to be doing sustained 55Km/hr on my own.
So give it try don;t be afraid to look outside the standard setups There is a pretty good article on Cycling tips from 2016 that talks about this.
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