Roaduno gearing question

[Edwin W]

I am running my Roaduno with 49/19, 40mm (or so) tires, 165mm crank, which works out to 70.5 (fixed) gear inches. 

I was thinking of making it a slightly easier gear. For those that have experience in small changes in fixed gear gearing:

I would love to hear about your experiences in changing gearing. How "big" is a jump from 70.5 to 69 (48 tooth)? to 67.6 (47 tooth)?

Or to 66.9 (20 tooth rear cog) or 63.7 (21 tooth cog)?

I know these are subjective differences,. I was trying to think about how to better quantify it but I was not sure how to. I would like it a little easier but don't want to be spinning too hard!

Let me know what you think,

Edwin

[CMR]

Do you have a multi-geared bike you can compare to? Even if you have a different chainring size you can often find something comparable.

[Gregger]

As someone who is always messing about with SS gearing, I can't really notice a 2 gear inch change, but can begin to feel 3 inches;  and definitely will notice with a 4 inch change.  For what it's worth.

I like to have two single speed bikes available in my garage - a taller gear when I've limited time (or it's really cold) and I want to put in a good work out quickly.  And then another bike geared 4 or 5 gear inches lower for those beautiful sunny days when I want to be out sputtering along all afternoon.

[Rick Harries]

Like Greg said, I notice the one tooth cog changes immediately. They are in the 6% per tooth range with the cogs I use. The one tooth chain ring changes are in the 2% range which is subtler, kind of like a slight headwind vs slight tailwind. I find my sweet spot with chain ring changes. There is an eBay seller who has unpolished 110 chainrings for $15 a piece. Not necessarily pretty to look at but an inexpensive way to dial in the gear you like. 

Rick Harries, feeling strong until he turns around in breezy Easton, MD. 

[Bill Lindsay]

"I was trying to think about how to better quantify it but I was not sure how to. I would like it a little easier but don't want to be spinning too hard!"

The way I do exactly this is I decide what my comfort-range is for pedal RPM.  I've ridden enough miles with a cadence RPM cyclometer that I know this range pretty well.  I have a MAX and MIN comfortable RPM in my pocket.  So, for a particular gear, I calculate how fast I'm going at my MIN and at my MAX RPM and if that range of speed makes sense, that's a decent gear.  For some environments, maybe 8-14 MPH would be a decent range.  For other environments, maybe 13-22 MPH might be a more appropriate target.  

Let's say for example you decided your comfortable RPM range was 60-120RPM.  At 60RPM in a 70.5 inch gear, you would be traveling 13,300 inches per minute or about 12.5MPH.  That means you NEVER plan to ride comfortably below 12.5MPH.  At 120RPM you are going 25MPH.  That means you expect to spend a significant amount of time cruising along at 25MPH.  If those were my numbers for my RoadUno, I'd want to shift them way down.  I'm never comfortably cruising at 25MPH on my RoadUno.  I go 25MPH on my fixed gear in Michigan but only on the downhill side of an undulation, and that's just for a moment at WAY over my max comfortable RPM.  For something like a city-bike application I may shoot for 9-18MPH which is a gear in the low 50s.  A gear around 60 inches would be more like that 11MPH to 22MPH range.  

FWIW, my RoadUno is a two-speed drivetrain with a 38/26 in front and a 16T freewheel, giving me a "high" gear of 66 inches and a "low" of 45.  

Your comfortable RPM range depends entirely on you.  I know some mashers that are perfectly content at 30RPM for long periods.  Some spinners can easily spin up to 140RPM and maintain it.  

Bill Lindsay

El Cerrito, CA

On Wednesday, December 18, 2024 at 3:16:05 PM UTC-8 Edwin W wrote:

[tio ryan]

In mostly flat NYC, I found the stock 38/16 ratio at 62" way too spinny. I’ve settled on a 42/16 setup at 69", which feels just right. I also tried a 49/18 combo at 72", but it was a noticeable jump that made the bike less enjoyable for stop-and-go commuting.

-tio "you only need one" ryan 

[Bill Lindsay]

"the stock 38/16 ratio at 62" way too spinny"

That must be on a 650B RoadUno.  That same gear is 66 inches on a 700c RoadUno.  

BL in EC

[tio ryan]

That's right, Bill! I should have clarified in my post. I've got one of the rare 47.5 silver roaduno completes. 

[John Williams]

Hi Edwin, You pose a great question...and you deserve respectful answers. You didn't mention your bike frame size, the terrain (hilly, steep or flat-ish) and the comfortable (OR NOT) speed you like to ride. Us SS'ers tend to be more of a solitary sort, or ride with others similarly "geared". If you are riding solo, your knees will be your guide. On my fixed or SS bikes on pavement and only moderate grades, I feel low 70's in gear inches is the sweet spot.....again, that's on pavement. I also may be longer legged than you and ride with longer length cranks. Asking some of this advice is like asking how much salt or pepper to sprinkle on your food....we do not know. Your comfort and pace is paramount. Changing the front ring is not the way to go....you won't feel or detect the differences. Keep your 49 up front and try a 20 in the back. We don't know how fatigued you were with the 19...only you know that. Once you get to mid 60 inch gearing, you'll feel like you are spinning too many revs to get to where you want to go.(unless you are climbing, climbing, climbing) Happy trails! ~JRW

On Wednesday, December 18, 2024 at 7:48:11 PM UTC-5 Gregger wrote:

[Edwin W]

Thanks to all of you - 

Gregger - good to know about 2 in vs 3 in vs 4 in changes.

Bill - as usual, very helpful to actually measure what cadence I like! I know I am more of a masher than a spinner, but 70.5 is just a wee bit too much mashing for me right now.

John - v helpful - I think to go to 20 in the back or 47 up front will be a good first step.

I will update you all with what I do.

Edwin