Brian Ratliff

You know how most gear charts are kind of confusing and hard to read, especially if your brain is fried from too much sprinting...

Check this out:


(PS: I was really bored at work today...)

carleton

Nice and Simple!

Stickied!

David Broon 

That's awesome!

carleton

Brian,

One small request: Is there any way that you can add 45/13 and 52/15 to the chart? Those are sort of common ratios by advanced racers. They make almost the exact same gear ratio, but the feel different. The 45/13 is used by sprinters and 52/15 by enduros. 45/13 feels "snappy" and 52/15 is good for cruising at speed. I can't really explain why, but they do feel different.

Brian Ratliff

Yea, no problem. The gear range was originally related to what I had in my gear bag.


You can see the "one chainring tooth equals two inches" rule of thumb (this is what I used for the "nominal gearing") breaks down a bit across the full range... I hadn't thought of a 45/13 before; right between a 49/14 and a 48/14 which are common gears for me. Might have to experiment with that a bit.

carleton

Thanks!

It was random (and cool) meeting you today at the track! I'll see you Thursday or Friday for racing.

carleton

Unsticking this and adding a link to if from the Tips thread.

myth001

Sorry to bring out another relic thread, but am new to track , and am trying to figure out some basics here.

According to your chart, and (Track Racing) the gearing in inches come out to the following:

46 x 15 = 82.8
48 x 14 = 92.6
49 x 14 = 94.5
50 x 15 = 90.0
50 x 14 = 96.4

But according to some other sites such as (BikeCalc.com - Bicycle Gear Inches Chart)
the numbers differ quite a bit:

46 x 15 = 80.7
48 x 14 = 90.2
49 x 14 = 92.1
50 x 15 = 87.6
50 x 14 = 93.9

Is this due to various tire sizes kept in mind, or something else? I tried a few tire sizes, but that didn't make for the difference.

I just got a new bike with a 46 x 15, and am spinning it out on the track. I just ordered a 48 and 49 chainring, along with 14, 15, 16 cogs. Looking at gear charts, perhaps a 50 will also be a good one to keep and that can give me a wider range of gears to start with.

PS: not looking at TT or Pursuits, possible scratch and point races for now.

queerpunk

It all depends on the constant you use. The formula for gear inches is: (Chainring/cog)*wheel diameter.

A 700c wheel with a 23mm tire has a wheel diameter of something like 26.3 inches. However, on the track, most people use the nominal 27" constant. Why? Who cares. a 50/15 is a 90" gear.

carleton

queerpunk is right.


myth, basically you hit on a minor inconsistency in the track cycling world: Actual vs Nominal Gear Inches

"Nominal" means: Existing in name only.

Actual: The actual distance that your wheel travels per complete pedal revolution based on your actual tire circumference (which obviously will vary).
Nominal: The distance that our wheel travels based on a commonly adopted "close enough" standard wheel diameter. 27 inch diameter for Imperial and 2.1 meter circumference for metric.

So, some general (and more technical) bike calculators will ask for your tire size and calculate your actual gear inches. Usually track-specific calculators will use a 27" track standard as the factor when calculating.

So, when trackies are talking to each other they use 27" in their calculations to figure out relative gearing. "I was on a 90-inch gear. I made it using 50t/15t x 27 inches" They don't take the time to figure in the actual diameter of their tires because they will vary between 19-23c tires.

So, stick with the track standard chaining/cog X 27 to calculate your gear inches and when you are discussing gear inches with your fellow trackies.

carleton

myth, I created an app in the Apple app store that might help you. It's free: https://itunes.apple.com/us/app/trac...925659197?mt=8

myth001

Thanks guys for nice explanations.
And Carlton, yes I did get that app already, I just got lazy to manually calculate and saw the charts as a direct simpler comparison tool. Guess I'll be back to your app for these gear calculations from now on.

dunderhi

How is that this is the first I've ever heard of trackies using a generic nominal gear terminology? Here, I thought I was a trackie, but I also thought that if I switched to 19c tires for a pursuit that I would need to a add a tooth to chainwheel to maintain my gearing.

When asked about my gearing, I've always stated 47x14 or 48x14. If they asked about the number of inches, I would just refer to my track bag. I guess it's good to learn something new everyday. Unfortunately for the "trackies", I don't plan to change the way I talk about gearing. As an engineer, I just can just round pi to 3 and feel good about it.



P.S. If I switch out my tires, I just insert a new table.


P.P.S Based on iPhone App example above is 51x14 a nominal 98.4 or rounded to 98?

carleton

When we (Americans) ask about gear inches, what we really want to know is a relative measure of chainring/cog ratio instead of chainring/cog * 27". Because all of the tires are more similar than different.

I think if we started using ratio of chainring/cog like the Japanese do when they speak of gearing, we'd be better off.

Basically:

46/14 would be "3.3"
50/15 would be "3.3"
51/15 would be "3.4"
47/14 would be "3.5"
45/13 would be "3.5"
52/15 would be "3.5"

That's why I included ratios in my app.

Next I'm gonna try to get the USA on the Metric system...

Dan Burkhart 

Here is my go to gear inch calculator.
HTML5 Gear Calculator
It lets you chose between single speed, cassette or popular IGHs. In KPH, it will show meters development, for gear inches, switch to mph.
It also allows you to chose your tire size for greater accuracy.

dunderhi

That's pretty nice. After playing with it a bit, I see I can enter the rollout distance rather than use the tire size drop down, which would help account for my 23mm road tubulars having a different diameter than my 23mm track tubulars.

Dan Burkhart 

Yes, I should have been clearer about that, but it does give you that option.

carleton

You can do all of that with my other app.