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 Cog

Caution: I'm not a mechanic or any kind of bike expert. I hardly know anything at all. But I will try to share what little I do know. What you read here is just based on my own personal experience and the research I've done. It might not be adequate or even accurate.


So don't blame me if you ruin your bike, get hurt, maimed, or die after following my instructions. If you have any corrections or thoughts please let me know - anything to make these instructions clearer or more accurate for others.


Besides the number of teeth (that's a much bigger discussion here's one of my posts on choosing a ratio) you need to look at the following:

1. Width of the base
2. Chain size
3. Material

There are a few other things to consider, like color, one piece or two, brand, and uh, yeah, price. But those are more subjective and I'll leave them up to you to decide!

I'm assuming you know to buy one that fits your hub, and that your hub isn't a fixie or BMX one that would require a threaded cog. The cogs here are not threaded and will not work on a singlespeed bike.

Width
If you buy a cheap singlespeed conversion kit, it may come with an equally-cheap stamped stainless steel cog. This should be a one-piece skinny one as seen here.

Look how skinny this cheap cog is

So what's wrong with cog with a thin base? It will dig into the freehub body of your hub, especially if your freehub body is of the more common, and softer, aluminum variant (as opposed to stainless steel or titanium).

When a cog (or even cassette) digs into your hub like this it can be difficult to remove, and it destroys part of your hub. You may have to file it down to remove the ridges in the freehub body if this happens.

A higher-quality cog, like a Surly or a Chris King, will be a machined piece with a fatter base. Check it:

See how thick the base is: 4.35mm. By the way, the wear you see is from 428 km of off-road use.

Chain Size
There are two main chain sizes you should know about: 3/32 and 1/8. The first is the standard that you will probably be familiar with if you ride a geared mountain or road bike. The latter is a BMX standard. Either can be used on singlespeeds, but your cogs will have to be compatible.

There are plenty of arguments for both sides, but that is another discussion. If you are converting from geared to singlespeed, it'll be simpler to opt for the more conventional 3/32.

Just ensure that your chainring and your cog match your chain. Notice on the Surly image above it says "3/32"".

Material
Cogs are made from stainless steel, aluminum, titanium, or in the case of the Surly SCM415 ChroMoly. (Turns out motorcycle cogs are made of the same material as Surly's cogs). And in some cases, they're a combination of titanium and stainless steel, as in the case of one example from Homebrewed Components. See image below.

The black center is stainless steel, the teeth titanium

So which material should you choose? Stainless steel is the strongest, but also the heaviest. According to the Homebrewed site, it's two times the weight of titanium, and more than two times the weight of aluminum.

Aluminum is the lightest, but naturally the weakest. It's best for racing and those that don't mind changing their parts more often.

Aluminum can break easily

While not a cog, you can see that aluminum can break easily. This happened under normal conditions, just climbing over a log. It's unlikely that a cog, with a much smaller diameter, would fail so catastrophically, but after having witnessed this absurd breakage, I won't be buying aluminum cogs.

Titanium is by many considered the best of both: It's almost as strong as steel and almost as light as aluminum. But it's expensive.