So I got the Homebrewed cogs in the mail awhile back - and they are every bit as beautiful as people say they are.

15, 16, 33

Nice and thick to prevent damaging your  cassette body

On the bike

Homebrewed Components - Choosing a Chainring and Cog Combo

For my post on choosing a rear cog go here: choosing a cog

I'm in the market for a new cog and chainring for my singlespeed. Homebrewed Components seems to be a preferred designer and manufacturer of cogs and rings by many singlespeeders, and is mentioned quite a bit in the mtbr.com forums.

Dan Wilcox is the man behind Homebrewed. He explains how the business started:

After being a Machinist/Engineer for my whole working life, i decided to start up my own machine shop. Granted, doing it in the height of the economic recession was probably not the best of ideas, but i figured what does not kill me will only make me stronger. Also, i figured it would keep me from making a bunch of useless crap that has flooded the markets partially causing this predicament we’re in.

At first, i started making parts for other companies and building tooling for people i had worked for in the past. That was going OK, but it wasn't really what i wanted to do with my capabilities. Also, i take pride in what i do, and if I’m going to make something, i want my name on it, not someone else’s. 

Now here’s where i started thinking… what do i like to do the most? Well, that would be creating things and mountain biking. How can i put those 2 together? Well duh, make bike parts! At first it was just going to be a hobby to cure some boredom in between the normal work. I started making chain tensioners using part of a design that i had made a few years ago. The only modifications i did to it were basically a little material removal to lighten them up. I posted them up on a web forum and got some decent feedback along with a few orders.

Read the full post at the Homebrewed Components blog.

I'm currently running a 2:1 ratio, and feel I could do better with a fraction more, maybe 2.1:1 or 2.2:1. This will make my flats a bit faster and the hills harder. Coming from a 32 - 18, I was on a 1.78:1 ratio. So a jump up to 2:1 was 22 tenths.

Using this 22 tenths figure as a benchmark, I don't think I could handle another jump of 22 tenths considering the terrain where I live (it's not very hilly but the few hills we have would be very hard for me at 2.22:1 I think.

Let's take a look at the combinations Dan from Homebrewed offers. This is a grid between the aluminum chainrings he has which are compatible with 104 BCD (for Shimano) and his aluminum standard cogs.

Ratios between Homebrewed Al chainrings and Al cogs

The red cells are ratios I don't think I can handle. The greens are even less viable as they're even easier than what I'm running now. And the orange cells are what I'm on now.

So my best options are those in the white, above 2.0 and below 2.22. I think 2.21, 2.20, and 2.19 are probably just about the same or indistinguishable from 2.22, so I'll avoid those. I think 2.12 or 2.13 would be best.

Starting from the bottom of the chart, 2.12 at 36-17 is good, as it affords more chainwrap than the other options, but it doesn't leave me with many options if 2.12 is too hard or too easy - the neighboring cells are 2.0 and 2.25.

The next choice is 35-17 producing a ratio of 2.06, which probably isn't quite aggressive enough. 35-16 sounds just right, and if it is too hard, I can keep the 35 and easily move to a 17 cog.

The problem with 34-16, is I can only move down to a 2.0 if the 2.13 is too hard.

A 33 chainring give me almost exactly the same ratios as a 35, but being smaller would be a hair lighter - but I'd lose some chainwrap.

32-15 is the same as 34-16, including the neighboring options.

A 31 ring looks good, as I can get 2.21 with a 14 or if that's too hard, 2.07 with a 15.

I wonder just how critical chainwrap is. I suppose there's only one way to find out, and that's test it myself by buying a 31-14 and 15.

Last, I wonder why Homebrewed has so many other ratios that very few singlespeeders would ever want. I'd imagine the 31-24 combo would be far too slow to ride on the road and not practical unless you lived in a super hilly area.

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Update, 11 Oct, 11

As I was about to place my order, I noticed a note regarding the 31T chainring. It says:

This is enough for me to not order the 31, not knowing the extent to the modifications or why it may not fit.

Thus, I'll go with a 33 and a 15 and 16 for almost identical ratios to the 31 with a 14 and 15.

Choosing a Singlespeed Ratio

All first-time singlespeeders wonder what gear ratio to start out with. How big or small should the chainring and rear cog be? Can existing chainrings or gears be reused? What's best for a beginner?

It's often said that for mountainbikers, 2:1 is the best to start. This means that if your front chainring is 32 your rear should be 16. So for every revolution of your pedals, the rear wheel makes two. By the way, a 34:17 ratio is still 2:1.

For road riding the ratio needs to be much more aggressive - a bigger chainring and a smaller cog for faster road speeds.

Back to mountianbiking - while 2:1 may be a good rule of thumb, there are a number of factors you need to consider:

How strong are you?
If you're the fastest and fittest rider around, you may do well with something more challenging than 32:16 - you may try 32:15*...but that's highly dependent on the next point.

How hilly or flat are your trails?
If you live in the Himalayas or Tetons 32:16 may be crazy hard, meaning you won't be able to climb many hills no matter how fit you are. But if you live in Kansas you may want to look up some roadie ratios!

How much road riding will you do?
I have to do a few kilometers of riding to get to my trails, and anything beyond 32:18 makes me spin out really fast on the road - pedaling like crazy but getting nowhere fast.

How much pain are you willing to endure?
If you think you can train up fast, 32:15* could be good - but be ready to suffer. I started on 32:18 but then moved to 32:16 and never looked back.

What components are you using?
Are you on a 26" bike or 29er? This changes the ratio. How long are your cranks? 175 or other? This will affect your ratio too. Check out Sheldon Brown's online gear calculator to get into the dirty math.

Also, if you can manage to find the 'magic gear' or the ratio that gives you a tight chain based on your chainstay length, meaning you won't need a tensioner, you may be inclined to go with that. But will that ratio be ideal for you? This could dictate your ratio. See the Fixed Innovations magic gear calculator.

If you opt for a cog less than 16T, you will have fewer teeth interacting with the chain (less chainwrap) which can lead to chain skipping. Even with a 16, you only have 8 teeth biting into the chain, and on a tough climb you could blast your chain over the cog.

In short, the more teeth on your cog (for mountainbiking) the better. But your 30 speed bike has an 11T cog you say? That's because gearies will only use the 11T on the fast flats or downhills - when they hit a hill they always shift to an easier gear!! ALWAYS!

Plus, because you are never shifting gears, that rear cog is constantly subjected to wear, and the smaller it is, the fewer teeth there are to absorb all this brutal chain pulling. Smaller cogs wear out faster.

The workaround, if you need a 15 or smaller in back, is simply to get a larger front chainring. 32:16 is the same as 38:19, for example, except with the 38:19 you have a lot more chainwrap. Less skipping, less wear.

A new Surly 16T cog

Once you have considered these factors and understand the variables, simply ask other singlespeeders in your area. Another approach is to ride a multi-geared bike in a certain gear for a while and don't shift. It will be hard to resist the urge to shift but this is a good way to find out what you are capable of.

You will be surprised.

*The 15T idea is just for illustration purposes - it's not recommended to use such a small cog - see the last section on components