Brad's Kona Unit: A Single Speed in Three Evenings

Manufacturer

Kona

Model

Unit

Wheel size

29

Gear ratio

32:20

Fork

RockShox Reba, replacing the original rigid fork

Brakes

Shimano M400, pulled off my Mukluk, replacing the stock set

Tires

Maxxis Ardent, tan wall

Crankset

FSA

Chainring

32t

Cog

20t Wolf Tooth

Saddle

Charge

Owner

Brad

Build purpose

Brad's first single speed

Brad actually liked it.

If you've read the Genesee Mountain Loop write-up, you know Brad is my neighbor, and that I lent him a Karate Monkey so he could try one gear without committing to it. I assumed that would be the end of it. People ride a single speed once, say something polite about simplicity, and go back to their 12 gears. It's the same pitch as One Gear Is Enough, and it usually gets a nod and no follow-up.

Brad thought it was cool. Then he went and bought his own.

An Entire Bike, In Pieces

The bike is a used Kona Unit, bought off eBay from the Goodwill in Minneapolis. I didn't know Goodwill sold bikes on eBay, and I'm not sure why I'm surprised.

It showed up totally disassembled. Not a frame with a few parts missing. Every piece, every component, individually accounted for, in the order a bike is not built. So Brad brought it to Blake's Machine Shop, which is what I call my garage because we do shit there, and we put it together over the course of three evenings.

Why three evenings, and why the Machine Shop? Because sometimes things don't work the way you think they will. Brad would've been fine with that answer. I'm just saying it out loud so it's on the record before the rest of this article.

The FSA Crank

The first thing to slow us down was the crank. It's an FSA, and neither of us could figure out how it came apart or went back together.

We had to read the docs. Turns out FSA does things its own way, differently from Shimano, which I know well, and SRAM, which I know less well. I'd like to say I picked it up in a minute. I did not, and neither did Brad, so at least it was a fair fight.

The Cog

Then there was the cog, which is where the build really got interesting.

The bike came with a 16-tooth cog. It was small and very thin, and it came with just two single speed spacers for the hub. A 16t is a joke in Colorado. Anyone who has seen a Colorado hill knows that, and Brad was about to meet a lot of them.

So Brad bought a nice thick 20-tooth Wolf Tooth cog, which was the right call for the terrain. With the 32-tooth chainring on the FSA crank, that makes it a 32:20 gear ratio. Then we chucked the wheel up on the bike with the thick cog and the same two spacers, and the wheel wouldn't turn.

There was too much space. The two spacers that suited a thin cog weren't enough to fill the hub around a thick one, and the wheel was not interested in rotating.

So Brad had to go back and buy a proper single speed spacer kit. If you want the reason a spacer kit exists, I wrote about how cog position and chainline work in So You Want to Build a Single Speed. The short version is that the spacers decide where the cog sits, and the cog has to sit in a place where the wheel can turn. I wrote that article, and Brad still had to make a second trip to the shop. Knowing a thing and having the part are different problems.

If you want to do the math on 16 versus 20, there's also the gear ratio calculator.

Everything Else

We did what we could. New tires, a new saddle, and the rest of the small stuff that makes a used bike feel like Brad's.

The biggest change is up front. The Unit came with a rigid fork, and it now has a RockShox Reba instead. The Reba's axle-to-crown length is a little longer than the frame's spec, which slackens things out a bit. We're calling that a geometry upgrade.

When Brad came back the next week, we set up the drivetrain again, now with the right spacers, and he rode off. It's not a dramatic ending, which is probably the best kind.

The Brakes

Brad did a couple of rides on the Unit and came back with a review of the original brakes. It was short. They weren't good enough, and I'll leave it there, because it's a used bike and I don't want to be the guy who kicks it.

Luckily, I'd just bought the Mukluk, and its brakes were already on their way out. Bryan Gillespie had found me a set of Hope E4 Tech 3s on Facebook Marketplace in Salt Lake City, Utah, which I planned to swap onto the Mukluk, and did. That left the Shimano M400s that came off it sitting on my bench. They're not great brakes either, but they were better than what Brad had. So we put them on the Unit.

That brings us to the hoses. They're ridiculously long. This is what happens when brakes from one bike go onto another, and I didn't have time to fix it, because I was leaving for Single Speed Worlds the same weekend. So the hoses are still as long as they were when we bolted the brakes on, and the loops are exactly as charming as they look.

We'll get to that eventually.

• colorado
• single-speed
• conversion
• kona
• build