dirt jump ratio
- Thread starter kuip
- Start date
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Pebble
Likes Bikes and Dirt
There are two ways to look at ratios, you can calculate it using gear inches or just the plain ratio.
Gear Inches:
It takes into account wheel size . Supposedly the ideal gear inch ratio is around 55 obviously depending on individual preference how far you deviate from that.
As an example if you're running a 32T chain ring and 16T cog with 26 inch wheels
the calculation is 32/16*26 = 52 (32 divided by 16 times 26).
And on a BMX running a 25/9 combo (20" wheels) comes to 25/9*20= 55.56
So as you can see running the 25/9 ratio on a MTB would make it 72.22 gear inches which would be pretty hard to pedal I imagine.
Running a 25/11 on a MTB is 59, so not too far off 55 so it might be a bit hard for some riding I guess.
The above is a useful way of calculating it if you're familiar with BMX and want to translate that to MTB or vice versa.
But for MTB you can do it with just plain Gear Ratios not taking into account wheels....
Using just the ratio calculation alone is just the two numbers divided (ie 25 divided by 9 for example equals 2.8)
For BMX the ideal is supposed to be around 2.8 (ie 25/9 combo or 28/10 etc).
And for MTB you're looking at a ratio closer to 2 (ie 25/11 is a ratio of 2.27, the 32/16 combo gives you a ratio of 2)
Basically knowing the calculations just helps you figure out what might work with the parts you might already have around or getting the same result using different chainring / cog combos.
The higher the number the harder to pedal basically.
Hope I've helped rather than confused. On my STP I had 32/16 for a bit and it seemed like a good all round ratio, if you wanted that same ratio in the micro gearing trend you would run 22/11
So hopefully armed with that info if you currently have a normal geared set up you can try out a few different gears to see what you like and then from that calculate what ratio you're looking at running and figure out what chainring / cog combo you need to buy!
Gear Inches:
It takes into account wheel size . Supposedly the ideal gear inch ratio is around 55 obviously depending on individual preference how far you deviate from that.
As an example if you're running a 32T chain ring and 16T cog with 26 inch wheels
the calculation is 32/16*26 = 52 (32 divided by 16 times 26).
And on a BMX running a 25/9 combo (20" wheels) comes to 25/9*20= 55.56
So as you can see running the 25/9 ratio on a MTB would make it 72.22 gear inches which would be pretty hard to pedal I imagine.
Running a 25/11 on a MTB is 59, so not too far off 55 so it might be a bit hard for some riding I guess.
The above is a useful way of calculating it if you're familiar with BMX and want to translate that to MTB or vice versa.
But for MTB you can do it with just plain Gear Ratios not taking into account wheels....
Using just the ratio calculation alone is just the two numbers divided (ie 25 divided by 9 for example equals 2.8)
For BMX the ideal is supposed to be around 2.8 (ie 25/9 combo or 28/10 etc).
And for MTB you're looking at a ratio closer to 2 (ie 25/11 is a ratio of 2.27, the 32/16 combo gives you a ratio of 2)
Basically knowing the calculations just helps you figure out what might work with the parts you might already have around or getting the same result using different chainring / cog combos.
The higher the number the harder to pedal basically.
Hope I've helped rather than confused. On my STP I had 32/16 for a bit and it seemed like a good all round ratio, if you wanted that same ratio in the micro gearing trend you would run 22/11
So hopefully armed with that info if you currently have a normal geared set up you can try out a few different gears to see what you like and then from that calculate what ratio you're looking at running and figure out what chainring / cog combo you need to buy!
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