Fixed gear ratios

[OneEighth]

Usually 48×16. Sometimes 48×15 on the lighter bike. Currently 48×17 on the steel frame because I’m still nowhere near full strength.

[DismalScientist]

44×16, but my quad size would suggest that 53×11 would be more appropriate.:rolleyes:

[ShawnoftheDread]

46/18, but I’m probably going to switch to 17 or 16.

[dkel]

I haven’t gotten this far on my FG project yet, but in looking around, I was interested in 46×17. Seems like there’s a lot of 46×16 around, as well as some 48×18. I was also interested in running fixed/fixed, so I could have a taller and a shorter gear, without all that freewheel nonsense. :p

[dkel]

@DismalScientist 97758 wrote:

44×16, but my quad size would suggest that 53×11 would be more appropriate.:rolleyes:

The only reason you don’t run 53×11 is because they don’t make bike chains strong enough for someone like you at that gearing, right? The lower gearing is a concession to the unavailability of suitably robust components.

[dcv]

Switching to gear inches: 71gi and 74gi for my fixed bikes, 61gi for SSCX

[TwoWheelsDC]

48×17 (74gi) on the Cinelli, 46×18 (67gi) on my State for riding back and forth to class. I consider 48×17 a decently big gear for living in north Arlington, but apparently that’s a recovery gear for 1/8, so now I feel weak

Check out http://www.bikecalc.com if you want to compare different ratios and figure out speed and cadence for whatever ratio you’re interested in.

Also, I may still have the 16t cog that came with my State laying around the shop. It’s a cheap-o part, but it’s yours free if I can find it…

[vvill]

Between 65 and 79 GI. I can spin 120rpm fine and 140+ for short bursts so usually now I’m on 42/16 fixed on 28mm.
I ran 48/16 SS for quite some time on 23mm, I would be happy with that on a stiff, light bike and no significant cargo but I think for fixed 47/16 would be about my max. Tough if you need to start on a hill with traffic behind you.

My SSCX runs 39/18 on 30-32mm for racing but I have 41/17 fixed right now for the C&O commute tomorrow.

I also keep a bike gear calculator app handy on my phone, you can save configs which makes it really helpful.

[jrenaut]

@dcv 97767 wrote:

Switching to gear inches: 71gi and 74gi for my fixed bikes, 61gi for SSCX

If the gear inches are the same, that means the speed at a given cadence is the same? Is that correct? So, for example, 46/16 and 43/15 are both about 77 gear inches, so they’re equivalent gearings?

[jabberwocky]

My OG fixie was 44/16. The two current ones are 48/18 and 46/17.

[DismalScientist]

Sorta. But you want to run 46/16 and 43/15 at different tire pressures, which does affect the effective diameter of the rear wheel.

[jrenaut]

@DismalScientist 97809 wrote:

Sorta. But you want to run 46/16 and 43/15 at different tire pressures, which does affect the effective diameter of the rear wheel.

I had no idea tire pressure even entered into the equation.

[TwoWheelsDC]

@jrenaut 97801 wrote:

If the gear inches are the same, that means the speed at a given cadence is the same? Is that correct? So, for example, 46/16 and 43/15 are both about 77 gear inches, so they’re equivalent gearings?

Yes. There are some theoretical differences in efficiency and chainring wear (larger is better), but for all intents and purposes they are the same. Per bikecalc.com, below is speed (top row) and cadence (second and third rows) for your given ratios:

Speed 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0
43×15 53 58 62 67 71 76 80 85 89 43×15
46×16 53 58 62 67 71 75 80 84 89 46×16

[DismalScientist]

Sorry, I was BSing you. Tire pressure potentially matters a trivial amount, but there is no reason to run different tire pressures. The real answer is that 46/16 is 0.29% higher than 43/15 because the world does not operate in whole numbers.

[jrenaut]

@DismalScientist 97814 wrote:

Sorry, I was BSing you. Tire pressure potentially matters a trivial amount, but there is no reason to run different tire pressures. The real answer is that 46/16 is 0.29% higher than 43/15 because the world does not operate in whole numbers.

I thought you might be. I’m good with whole numbers in this case as I can’t imagine ever noticing a difference of .29%.

So I think this all means I want to try to go down to a 16 in back. There’s some special tool I need to get the old one off, right? And I’ll have to take a link or two out of my chain?

[Author]

Posts