That is an app for the iPhone.
Chainring: Bicycle Gear Calculator
PS. I made it, so you're welcome to DM any feedback. Thanks
Nicely presented app.
The first thing that hits me is that making “Gear Ratio” the default display is a strange choice. I’d have thought most people would be interested in gear inches and/or skid patches so I’d have put gear inches as the default/first option with the other stuff later.
Next is a less obvious but probably more serious flaw and that is that you’ve made assumptions about wheel and tyre size for the gear inches and development calculations and chainstay length for the chain length calculations.
I’m not really sure why you would ever need to calculate chain length but doing so based on an unknown assumption about chainstay length renders the information provided completely useless anyway.
Similarly, because you have not specified what wheel and tyre size you used to calculate the development, the information is useless.
I figure you’re probably aiming this at fixed gear street riders rather than trackies but gear checks for youth racing are based upon development so you could have a potential market for your app there, if the parameters for the calculation were known, or even better, adjustable.
I have to have a few gear calculator apps on my phone as I haven’t found one that provides all the info I look for.
My wish list would be:
Ability to set wheel and tyre size with a good range of size options. Personally I’d use down to 20” wheel but giving a 16” option would appeal to Brompton owners. 29+ at the top end. I have an app that allows setting crank length but I don’t think it actually figures in any of the calculations.
Speed based cadence calculator. I have an app that provides a cadence calculation but in a clunky way. You have to dial in a cadence and it gives you the speed this would generate for the specified gear along with times for certain distances. I’d like to be able to take my max speed from Strava and calculate what cadence I got up to.
Development can be useful if comparing gearings for say a 20” wheel with a 700c wheel but it’s not something I look at often so this doesn’t need to be front and centre.
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