Bike gear calculator
 

Is bikecalc.com accurate? Not an app, not sure if they have one, it’s just a website. Site looks so simple, but what i like abt it is aside from gearing ratios, they also calculate the cadence u need to achieve or maintain a certain speed per gearing combination, plus some more.

My favorite so far is Bicycle Gear Calculator -- I could play with those sliders all day. :)

I’ll try it out. Thanks.

Edit: Just tried playing with it now. It’s great. I like how those triangle marks are lined up for each chainring, you can easily see where it’s best to shift down from big to small ring, compared to using the bikecalc chart. This will be very useful for me. Instead of just trying to grind it out on the big ring on not so steep hills, i now know which small ring and cog combo to switch to to climb faster and easier. Thanks for sharing!

These two gear calculators have been around for years. I never read a complaint about inaccurate results.
Mike Sherman's Bicycle Gear Calculator
https://www.sheldonbrown.com/gear-calc.html

The speed calculations for any gear calculator are going to depend on several factors that probably aren’t...and can’t be... considered in the calculations. Wind resistance will change the value. Headwinds will have an effect as well. They shouldn’t be looked on as “absolute” but only as estimates. They are probably good estimates but just estimates.

umm, no.

Umm, yes. No bicycle gearing calculator can take into account the size of the rider, the rolling resistance of the tires, the wind and weather conditions, etc. All of those are going to have a small impact on the speed. That’s the real world vs the model.

The bikecalc.com calculator is probably worse than others I’ve seen. It gives the speed to the nearest 100th of a mile per hour. That’s a ridiculous number to report. Someone doesn’t understand significant figures. Giving the calculation to the nearest mile per hour is likely inaccurate.

I Ihave done the math using Excel and compared my results with two web based calculators and got so close with both I have no reason to believe any of them are inaccurate.

If you remember you grade 9 math, you can set up a custom chart showing speeds in gears at different cadences, gear inches and ratios in Excel too, like I have. It's not rocket science.

Keep in mind these are theoretical speeds in gears assuming we can generate enough power to overcome weight, Wind resistance, rolling resistance, ect.

:thumb:
Nor does hills.

Wind and road conditions DO affect the power required to maintain cadence in a specific gear, but it doesn't affect the gear calculation one bit.

None of the wind or rolling resistance or weight or weather matters. The gear calculators provide speed based on gear AND cadence -- if I weigh 500 lbs, and pedal a 50/16 gear at a 90 cadence into a headwind, I will be going just as fast as a 100lb rider pedaling at a 90 cadence in a 50/16 gear riding with a tailwind.

Wow, that one is pretty great - it's helpful to see all the information at once. The only thing missing is meters of development (which is likely only of interest for OCD riders such as myself.) Thank you for sharing.

I've used - and been happy with - various gear calculators for working out basic information on speed, cadence, development, etc., and found the information helpful for gearing choices on geared but especially single speed bicycles. Accurate enough for an average user/rider; for purposes of engineering, etc. there are probably more variables that need to be considered.

Meters/development is the option right above gear inches in the "Display" drop-down menu. :thumb:

it's just a math equation, it works fine.

Mine, too! I have the others saved as well, but I love the instant display of any gearing changes I'm considering.

What? Some explanation of how these things might affect the cadence vs speed relationship, please. How small is "small"?

A very large rider will push the tires down, in effect making a smaller wheel diameter, throwing off the speed calculation.

These calculators only cater for one crank. I have two. I don't use my CS-RK3 hub on the single-pedal tandem, but if i did, i'd have...

3-speeds front crank
2-speeds mid crank
10-speeds cassette
3-speeds hub

I know this'd be 180 gears but i don't know their actual ratios, and it could take some time to work out. I use an e-hub instead of the CS-RK3 but it'd still be nice to calculate the effect of experimenting with the front two cranks, which turn at different speeds.

I think the part a lot of people have trouble understanding is how rider strength and power enter into the equation.

I don't know how many times I've seen somebody post you'll go faster with a 26" wheel than with a 20" wheel. While it's true that, at the same cadence, you'll definitely go faster with the 26" wheel it's equally true that it will be harder to pedal the 26" wheel at that cadence. Think about it this way. If you could somehow fit a Ferrari transmission into a Yugo, do you think it would go 200 MPH? No because the Yugo simply doesn't have enough power to go 200 MPH.

They don't figure in at all. The calculation is for a specific cadence. If you can achieve that cadence (say 90), then you will go that speed. Now, it is possible that you may not be ABLE to achieve that cadence in a specific gear combination because you aren't strong enough. Maybe you can only do 70 RPM in that gear up the hill. Yes, you will be slower than the person who can spin 90 rpm in the same gear. It doesn't mean the equation is wrong.

Actually the calculation is not based on diameter, It is based on circumference. Which does not change with weight when properly inflated.

If the correct formula is used (grade 9 math at best) these calculators are probably 99.9% accurate.

I get almost identical results as the online calculators when I set up an Excel chart for the same gear ratio to speed calculations. The tiny differences are probably due to rounding.

Isn't that what I said? I think that's the point cyccommute was trying to say too. There's more to speed it than just final gear ratio.

You can say that "there's more to the maximum speed that you can achieve than just final gear ratio" -- that would be correct. But it's also really obvious that TDF riders go faster than all of us and it's not because of gear ratios they have on their bikes that none of us have thought to install.

Nobody's talking about that though, the discussion was specifically about gear calculators which do one simple thing -- show you the speed you would go for a given cadence and gear combination for a given bike/wheel size.

Clearly, you have not actually tried this.

What?!


Yeah, he's talking out of his backside. Of course it does. One revolution of a wheel with a fully inflated tyre will travel further than the same wheel if the tyre is half flat.

+1. It's a work of art.