Mountain Bike Reviews Forum banner

1 - 20 of 24 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter · #1 ·
Hello, I need some help understanding gear ratios. Currently I have a 2x XTR rig with 28 & 40 chainrings and a 11-36 cassette. On the granny side it gives me a ratio of 0.8.

The new rig will have 1x XX0 with 30 chainring and 10-42 cassette. This gives me a gear ratio of 0.7.

Does this mean in theory it should be slightly EASIER to pedal up these French mountains? This is counter to everything I have heard about one-by drivetrains, but maybe it is just a particularity of my setup.

Thanks for any clarification,
Chris
 

·
Formerly of Kent
Joined
·
12,352 Posts
Yes. The lower gain ratio means it will be easier to get up the mountain.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
97 Posts
Yes, your calculations and conclusion are correct, 30-42 is a lower (easier) gear ratio than 28-36.

It's counter to everything you've heard about 1x drive trains because you probably have read or been told a lot of BS implying that they are reserved for pros and elite riders. I'm below average fitness. I went straight from 3x9 to 1x11. I did a full gear ratio calculation and a graphical plot for 3x, 2x and 1x set ups and saw that XX1 could give me almost the same coverage as all the other set ups. A graphical plot will also show you how much redundancy there is in the 3x and 2x drive trains, and will make you question why they exist in the first place. I just had to accept a slight sacrifice in the highest gear ratio, which wasn't an issue as I don't race or ride my bike on bitumen or fire roads at high speeds.

One thing to consider though is that if you plan to spend a LOT of time in the "granny" gear then you will experience more wear and tear with your 1x11 set up because of the more extreme chain angle when you're in the 42t cog.
 

·
Registered
Joined
·
4,198 Posts
Yes, your calculations and conclusion are correct, 30-42 is a lower (easier) gear ratio than 28-36.

It's counter to everything you've heard about 1x drive trains because you probably have read or been told a lot of BS implying that they are reserved for pros and elite riders. I'm below average fitness. I went straight from 3x9 to 1x11. I did a full gear ratio calculation and a graphical plot for 3x, 2x and 1x set ups and saw that XX1 could give me almost the same coverage as all the other set ups. A graphical plot will also show you how much redundancy there is in the 3x and 2x drive trains, and will make you question why they exist in the first place. I just had to accept a slight sacrifice in the highest gear ratio, which wasn't an issue as I don't race or ride my bike on bitumen or fire roads at high speeds.

One thing to consider though is that if you plan to spend a LOT of time in the "granny" gear then you will experience more wear and tear with your 1x11 set up because of the more extreme chain angle when you're in the 42t cog.
Well obviously! A 28T small ring is not exactly very low gearing.

XX1 have a 28T single ring to go with their 42T cassette cog and that ratio is not as low as my current 22/34 (0.65 ratio) so for me there is no point other than perhaps a few grams, which I don't care about. You may be able to manage in your local terrain with one chain ring but it doesn't work for everyone and everywhere.
 

·
NedwannaB
Joined
·
12,765 Posts
ReallyReally....

Yes. The lower gain ratio means it will be easier to get up the mountain.


Sent from my iPhone using Tapatalk
I support and follow most all of these new drivetrain component threads but find it hard to believe you'd really notice/benefit from a .01% change in gear ratio.
 

·
Formerly of Kent
Joined
·
12,352 Posts
I support and follow most all of these new drivetrain component threads but find it hard to believe you'd really notice/benefit from a .01% change in gear ratio.
22.5 gear inches using 28x36. 20.7 gear inches using 30x42.

Assuming 29x2.3" tires.

8.6% difference. You can feel that.


Sent from my iPhone using Tapatalk
 

·
The joy of ski is Yours
Joined
·
1,367 Posts
The .1% - not .O1% - change remember is one complete rotation of the wheel. If you factor in a quick burst of say 20 revolutions that is as you can see about a few feet of what can be described a 'swept area' since there is power being applied upon a definite surface-plane.
 

·
NedwannaB
Joined
·
12,765 Posts
Right. Typo. Ment .1%. If that's the same as the 8.6% Le Duke is quoting then I can agree with noticing that.
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #12 ·
I support and follow most all of these new drivetrain component threads but find it hard to believe you'd really notice/benefit from a .01% change in gear ratio.
I was just glad to find out it wasn't going to be harder like everything I had read. The point is, I'm hoping I DON'T notice much difference...other than the high end that is, and I don't do a ton of fire roads.

Chris
 

·
Registered
Joined
·
2,431 Posts
I think what you'll notice the most is the very simple way you can get from your lowest gears to your highest.
 

·
Registered
Joined
·
2,431 Posts
Right. Typo. Ment .1%. If that's the same as the 8.6% Le Duke is quoting then I can agree with noticing that.
Its not percentage. The 0.8 vs 0.7 is a ratio of crank to wheel revolutions. If that does come to 8.6% then you are indeed right in your 'noticeability' reckoning.
 

·
Registered
Joined
·
5,308 Posts
Well obviously! A 28T small ring is not exactly very low gearing.

XX1 have a 28T single ring to go with their 42T cassette cog and that ratio is not as low as my current 22/34 (0.65 ratio) so for me there is no point other than perhaps a few grams, which I don't care about. You may be able to manage in your local terrain with one chain ring but it doesn't work for everyone and everywhere.
I went from 3x10 to 1x11 for the simplicity. Between the brake lever, shifter and dropper post remote, it was getting pretty crowded. Taking off the front D, shifter and cable dropped 300+ grams. New Next SL crank, another 200 + grams. I did, however lose some high end gearing. 28/42 same as 24/36 low end ( you're right, not as low as 22/34 ), as there is a stupid amount of steep climbing in the Wasatch range. 28/10 is my high end, now.
 

·
Registered
Joined
·
8,626 Posts
Well obviously! A 28T small ring is not exactly very low gearing.

XX1 have a 28T single ring to go with their 42T cassette cog and that ratio is not as low as my current 22/34 (0.65 ratio) so for me there is no point other than perhaps a few grams, which I don't care about. You may be able to manage in your local terrain with one chain ring but it doesn't work for everyone and everywhere.
22/34 = .647
28/42 = .667

Not as low but pretty close. I'm switching to X01, and I love my granny gear. I'm hoping I will just lose some body fat and get in better shape and be satisfied with the 28x42.
The other option is to get a 26T direct mount chainring from Wolftooth. :)
 

·
NedwannaB
Joined
·
12,765 Posts
Its not percentage. The 0.8 vs 0.7 is a ratio of crank to wheel revolutions. If that does come to 8.6% then you are indeed right in your 'noticeability' reckoning.
Alas, the "ratios and percentages" of my math is lacking lately. But I digress....:)
 

·
Registered
Joined
·
4,198 Posts
22/34 = .647
28/42 = .667

Not as low but pretty close. I'm switching to X01, and I love my granny gear. I'm hoping I will just lose some body fat and get in better shape and be satisfied with the 28x42.
The other option is to get a 26T direct mount chainring from Wolftooth. :)
The smallest ring available for a XO1 crank is 30T.

I find the 34T cog to be a bit too high as it's on a 29" bike. I live in Northern California and there are extended climbs of thousands of feet around here. I could change to a 36T cassette for under $60 and that would give me a lower ratio of 0.61. There is just no point for me to spend over $1000 on a XX1 drive train.
 

·
Registered
Joined
·
2,431 Posts
^ the direct mount from Wolftooth solves this though. Its a spider inclusive ring. You're bolting it to the cranks.
 

·
transmitter~receiver
Joined
·
9,311 Posts
I support and follow most all of these new drivetrain component threads but find it hard to believe you'd really notice/benefit from a .01% change in gear ratio.
28/36=0.78
30/42=0.71
0.78-0.71=0.06
0.06/0.78=0.08

0.08=8.0% and yes, that is noticeable (if you can notice shifting one gear on the cassette... I can)
 
1 - 20 of 24 Posts
Top