Single Speed Conversion

so my current project is converting one of my bikes that I don’t use much to a single speed. it’s sort of a cross between a road bike and an all road. I ride on the road at all times.

I know there will be experimentation to be had with picking cogs and chainrings…but can someone help with a starting point?

is there a preference for having a certain chainring in the front? then change up the rear one? (or vice versa?). which would give me the most versatility as I dial in what I need? not sure if there is a strategy on this.

the options I see that will fit my bike / powermeter are:

Front Chainring, 30T, 32T, 34T, 36T, 38T
Rear Cog: 16T, 17T, 18T, 19T, 20T

I am ~ 195 lbs…bike is ~20 lbs. it will be used on 30-40 km ride to work (and back) - rolling terrain…two “steep” hills in each direction (8 degrees) but it’s short. I’m prepared to walk if needed or just hit it hard…would rather be geared properly for the rest of the ride.

Thank you!!

A couple things to consider.

  • what are you doing for chain tension? If using a tensioner, pick the front chainring you think you want and the rear, and the tensioner will give enough adjustment to go up or down a bit with cogs.
  • if you’re not using a tensioner, it can be a tedious to get everything to work. But usually with SS, once it works it’s all good. I had better luck with a White Ind ENO hub conversion than I did with a Wheels Mfg eccentric BB.

Personally I would pick a gear that would just let you get up the hills, so that it’s all rideable and not too spun out on the flat. FWIW I have 40/18 right now.

SS feels magical when you are on the right terrain for your gearing, and hellish when not.

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yeah I am going to get a chain tensioner…have a few different models i’m looking at. would love a recommendation.

looking forward to the magic and the hell :slight_smile:

so why would you do that vs say 38 / 16? that’s what I don’t get. which do I chose first? the front or the rear?

I started at 40/19, and just recently switched to 40/18. And honestly don’t remember why I started where I did. Probably looked at what others were doing. Generally bigger chainrings and cogs last longer and have less energy loss than smaller gears at the same ratio. So there’s that.

I ended up with a Paul Melvin. That is after starting with a Wheels Mfg eccentric in PF30 frame. The WM was forever creaking and a hassle to adjust, and also has limited adjustment range. I tried a Surly singleator, which didn’t work for me and then the Paul.

ok awesome!! the Melvin was on my list to check out.

thank you for taking the time to write me.

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42x15 is my preferred, suitable for rolling gravel - I race this gearing on gravel also. I think your gearing is light. For reference, I race CX w 38x17 which is suitable for sand/mud and undulating course, it also happens to be a “magic gear”, meaning no tensioner needed. As mentioned, if you can find an aluminium frame w a PF30, wheelsmfg make a great BB tensioner.

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What bottom bracket is on the frame?

Most of the time I’ve seen this done, people start with what they already have lying around, and then adjust from there.

If you already have a geared bike, I might try this:
Ride the geared bike on the commute a few times without shifting, and try out different gear ratios. Is there one that seems to work better?

Note that gears (front and rear), wheel/tire diameter and crank arm length all factor into how the gear ratio feels. So if you’re going to larger tires on your SS than your geared bike, you’ll probably want an easier (shorter) gear. There’s a calculation called “gear inches” that accounts for all this, but I don’t have an explanation handy. Maybe the site might?

The only “rule of thumb” that I’m aware of is to try to stay with at least 16 teeth in the cog - the chain wrap tends to be more difficult if you have fewer than 16 teeth in the rear.

I have an aluminum frame with PF30 and tried the Wheels Mfg BB. Couldn’t get it to stop squeaking. Happy to pass it on if someone else would like to try it.

Also chain tensioners frequently have a max/min cog they work with. And some, I am thinking the Paul Melvin, specifically call out cogs that don’t work well with it (I think it was Surly they don’t recommend),

it’s a chris king 30mm. I don’t want to mess with that much because i am happy with my cranks and powermeter.

so I bought a Melvin chain tensioner and a Shimano GRX 11 speed 1x chain 40T. and some spacers for the rear wheel. I will just use a few of the cogs I have from my rear cassette as advised. that gives me 17, 19, 21, and 23 to hopefully get close.

I have read that single speeders prefer an 8 or 9 speed that is a little thicker…don’t really understand why. I’ll try to figure out a decent gear for now and if the chain stays on maybe just keep it…or upgrade to singlespeed specific stuff if that exists when I know what my gearing should be.

i’ll check with Melvin on what they recommend / don’t.