Gear ratios and climbing

[Saratoga Dave]

Hey, perhaps one of you math/numbers whiz folks can help a brother out here… two bikes, 1X setups, 1 to 1 ratios on each, one is 42:42, the other 36:36. Everything else being equal, which has more oomph for climbing, and how come?

And since nothing else is ever equal, if the 36:36 bike has about ten less alleged Newton meters, what does that do to the picture?

 

[Jeremy McCreary]

For climbing purposes, all that matters is the chainring/cog ratio and the wheel diameter. All other things being equal, if the ratio and diameter are equal, the climbing experience will be the same. Might not wear the same, though.

 

[PedalUma]

To figure it all out use a gear calculator. It accounts for stuff like wheel size and crank length. As @Jeremy McCreary notes bigger to bigger gives longer service life. There are 10-tooth rear cogs out there and even nine-t. But only four or five teeth are taking all that force at any given time. They self destruct quickly. It is better to up the chainring. But that can throw off the shifting to the lowest gears by cross chaining leading to dropping the chain off the chainring.

Sheldon Brown's Bicycle Gear Calculator

A JavaScript calculator for analyzing bicycle gearing

sheldonbrown.com

 

[Stefan Mikes]

Hey, perhaps one of you math/numbers whiz folks can help a brother out here… two bikes, 1X setups, 1 to 1 ratios on each, one is 42:42, the other 36:36. Everything else being equal, which has more oomph for climbing, and how come?

And since nothing else is ever equal, if the 36:36 bike has about ten less alleged Newton meters, what does that do to the picture?

Dave: Only the gear ratio counts here. The 36-36T or 42-42T gearing is 1:1 and both work identically.
Now, 10 Nm less is by standard 62.8 W less. How to determine the performance?

For climbing, you need to dececide on the minimum rideable speed uphill, let it be 5 mph.

Use Speed at Cadence Calculator first. Enter all necessary data, of which the cadence the rider can maintain is vital. An example:

This is for my Vado, the granny gear (44-46T). My requirement is riding at 10 km/h (6 mph). As you can see, the gearing I have will allow me maintainong 6 mph at the cadence between 70 and 80, which is doable for me. Now, will I climb my hill?!

The Bike Calculator is your friend here. An example:

Red are the input fields, Green is the calculated speed. Having all parameters fixed, only manipulate the Power to get at the desired Speed.

In my case, I need 625 W on the chainring to get me at 6 mph. My motor can provide up to 520 W mechanical. I need to pedal at least at 105 W. (In reality, it is not that simple, and you have to pedal harder to force the motor to max out).

I did that climb. I travelled at 6 mph indeed there
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The last thing: If you trust the torque for your motor as given by the marketing department just multiply it by 6.28 and you will get the max mechanical power of your motor.

 

[Saratoga Dave]

Thanks, guys. All this just to ride up a stinking hill!

 

[Nomad]

To figure it all out use a gear calculator. It accounts for stuff like wheel size and crank length. As @Jeremy McCreary notes bigger to bigger gives longer service life. There are 10-tooth rear cogs out there and even nine-t. But only four or five teeth are taking all that force at any given time. They self destruct quickly. It is better to up the chainring. But that can throw off the shifting to the lowest gears by cross chaining leading to dropping the chain off the chainring.

Sheldon Brown's Bicycle Gear Calculator

A JavaScript calculator for analyzing bicycle gearing

sheldonbrown.com

View attachment 175999

Actual that 10 tooth will last you if it setup right and only use it when you should and shift right if it's a good one. It's mostly for pedaling down hill and occasionally on the flats. you will chew up quick if don't use it right. It does tend to wear a little faster but set it up right and learn to use it correctly and it will reward you under the right conditions. I don't want to mislead anybody it not for everyone but it's a little like lockers on a 4x4 use it wrong and well..... For a lot people a bigger front chainring will be a better choice depend on application.

 

[Nvreloader]

Here is some more information that may be helpful,
all kinds of info to be found here.

Tables | BikeCalc

www.bikecalc.com

ymmv

 

[BikerG]

For a non-assisted bike I like my low gear inch in the 17“ range, as I do a lot of hilly fire road rides, often carrying bikepacking gear, so having that low gear is critical.
But on my hardtail e-bike running a similarly low gear inch is not that important with the obvious pedal assist, and especially when running a 1x setup not having to run a dinner plate sized rear cassette.