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Going below 1:1 ratio

Old 09-22-20, 05:09 PM
  #1  
adlai
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Going below 1:1 ratio

I'm contemplating an advent build. They have really wide cassettes that go down to 42t.

On a double, you could have a front crank that is smaller in diameter than the rear. Like 30-42 ratio.

Is that useful? Or below a certain point is it pointless to have?
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Old 09-22-20, 05:23 PM
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The only limitations for what you can build are the capacities of the derailleurs involved. If you have 46-30t chaingrings in the front, and 11-42t x 10 speed cassette in the rear, you would need a derailleur system with 47 tooth capacity. My touring bike has a rear derailleur that can handle this, but 47 tooth capacity is the largest I have seen for sale. Of course, there will also be a limit to what size large cog a derailleur can handle, as going too big will cause interference with the derailleur pulley wheel.

For the front gears, you need to make sure the derailleur can reliably handle whatever jump is between the chainrings. Usually the manufacturer will tell you the limits, but I've never seen one that can reliably handle more than a 16t change. Here's a calculator where you can play with your planned setup:

Bicycle Gear Calculator

One more item: your low gear (30x42) would give you about 20 gear-inches, which is very useful for exceptionally steep climbs and/or climbing with a load.
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Old 09-22-20, 08:55 PM
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Advent has just 1 fd option, i think. So that better fit whatever your setup is.

As for the general question, yes a sub 1:1 ratio can be useful. Its standard on mountain bikes and standard on almost all gravel bikes.
My gravel bike is 48/32 mated to 11-36 and while I don't spend much time in the 32/36 combo, it does get used on some of the punchy 12-16% grade climbs I ride.
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Old 09-22-20, 11:14 PM
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I have an old Cannondale touring bike with a 48-38-28 triple and a 14-34 cassette. When the load is large, the day is long, and the hills are seemingly endless, all that matters is not falling over as you creep along.

If I were doing serious mountain touring fully loaded, I'd consider a 42-32-22 triple.
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Old 09-23-20, 12:52 AM
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Originally Posted by adlai View Post
Is that useful? Or below a certain point is it pointless to have?
Depends on your legs and the hills you're riding.

I have sub-1:1 gears on my gravel bike and my touring bike, and they definitely get used.
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Old 09-23-20, 01:04 AM
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I use 30/36 often on my mtn/pasture bike. Often difficult to avoid "organic bumps" on pasture paths, need low ratio to not spin on them.
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Old 09-23-20, 09:43 AM
  #7  
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Never had a gear too low to use at some point. 700c tire bike below 0.8 gear ratio might be too slow to stay upright without spinning mightily... 3mph gets a little shaky.
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Old 09-23-20, 11:16 AM
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Definitely useful to have options
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Old 09-23-20, 11:26 AM
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Extremely useful, if you need it. I have a triple and the lowest I have is 24 to 34. Of course mine is a touring bike, and is often loaded, and I live in a very hilly area with hills near my house with 20% or greater grades.

When I commuted in the Ozarks, I would go downhill at 40-45mph, and up at around 3-4mph. I was happy to have the 24-34.
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Old 09-23-20, 12:05 PM
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Originally Posted by Chuckles1 View Post
Never had a gear too low to use at some point. 700c tire bike below 0.8 gear ratio might be too slow to stay upright without spinning mightily... 3mph gets a little shaky.
A 25mm 700c tire on a .8 gear ratio is about 4.5mph even when you're down around 70rpm. You wouldn't drop below 3mph until your cadence drops below 50rpm, which is low enough that most people would be wanting an even lower gear.
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Old 09-23-20, 12:16 PM
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I admit to using a 24-34 combo riding up to the Ski Lifts on Mt Baldy Rd on my MTB. So yes, 15% grades makes a triple come in handy.
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Old 09-23-20, 12:20 PM
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Somewhere below 20 gear inches it's better to walk -- easier than trying to stay balanced, and uses different muscles.

Less that 1:1? Oh heck yeah. What you don't have in your legs you need to have in your gears.
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Old 09-23-20, 01:04 PM
  #13  
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Touring.
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Old 09-24-20, 11:42 AM
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Originally Posted by Chuckles1 View Post
Never had a gear too low to use at some point. 700c tire bike below 0.8 gear ratio might be too slow to stay upright without spinning mightily... 3mph gets a little shaky.
I have a 0.56 (20/36) on my touring bike (15.1”) and on a couple of mountain bikes (14.6”). Riding at 3 mph isn’t that difficult. If you know how to track stand, it’s easier but it’s still not that hard to ride very slow.
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Old 09-24-20, 12:24 PM
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Originally Posted by adlai View Post
I'm contemplating an advent build. They have really wide cassettes that go down to 42t.

On a double, you could have a front crank that is smaller in diameter than the rear. Like 30-42 ratio.

Is that useful? Or below a certain point is it pointless to have?
This question depends on your riding. Are you really fit? Do you live in a hilly location? Do you prefer to spin higher cadence? If you're regularly on really steep terrain, then going lower than 1:1 on a road bike is definitely in order.

I'm just about to modify my road gearing. When I was racing, going from a 42T small ring to 39T was such a luxury. I did fine in the hilly east bay area with a 39-23. Well, let's just say things have changed! My current 39-25 is fine for the flats and mellow climbs, but not what I need to get over the real hills encountered regularly. Plus, spending so much time on 3 X 8 or 9 means my cadence has increased since the 39-23 days. So I'm hoping the spare parts I have can accommodate my needs of getting my old 8-speed setup more ideal. Hoping a 39-32 will be enough. (It won't for the really steep stuff, but I'm not planning on climbing walls on this bike a the moment. That's what the bikes with triples are for!)

But switching the rear 8-spd to a 12-32 will mean fewer ideal gear ratios when I'm on the flats. I know I'll miss some of the gears I currently appreciate now. But if I want to climb more comfortably on my old road bike, this is the compromise I'll have to accept. I am NOT going to 10 or 11 speed. Nope, my '89 SLX road bike is a treasure and I'm not "Frankenbiking" it. Just a little optimization, gearing-wise.
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Old 09-24-20, 03:48 PM
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Originally Posted by pdlamb View Post
Somewhere below 20 gear inches it's better to walk -- easier than trying to stay balanced, and uses different muscles.

Less that 1:1? Oh heck yeah. What you don't have in your legs you need to have in your gears.
Not a problem on a trike.

Really low gears on a loaded touring trike ensure that you will never have to get off and walk. Walking a trike sucks, or a bike for that matter.

Last edited by rydabent; 09-29-20 at 09:14 AM.
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Old 09-24-20, 03:50 PM
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What you lowest gear inches are is pretty much dictated by your terrain. While my riding is pretty much not very hilly, my lowest is a 28 front 34 rear. As the Boy Scouts say----------be prepared.

Last edited by rydabent; 09-29-20 at 09:12 AM.
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Old 09-24-20, 04:41 PM
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I use my gravel bike for touring. It doesn't go below 1:1 so I am seriously considering dropping $150 or so on a new crank to make it do that.

Have to agree with the others below a certain range you are better off walking.
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Old 09-24-20, 08:47 PM
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Better off walking BAH!!!!! Maybe it is because I'm mostly a mountain biker but the whole point is making up the hill on the bike.
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Old 09-24-20, 09:53 PM
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Originally Posted by pdlamb View Post
Somewhere below 20 gear inches it's better to walk -- easier than trying to stay balanced, and uses different muscles.

Less that 1:1? Oh heck yeah. What you don't have in your legs you need to have in your gears.
LOL.

It's more fun to ride, than to walk. It sounds like you need to work on your low speed balancing/climbing skills.

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Old 09-24-20, 11:08 PM
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On walking---trying to balance a heavily laden touring bike while pushing it up a steep slope is a Very annoying exercise. Balance is automatic while riding---and the faster one goes the more centripetal acceleration and/or gyroscopic effect help keep it upright.

Standing beside it, trying to to get hit by the pedal or the pannier while pushing a big load up a steep hill .... the slightest deviatio0n from pure vertical demands attention, and the slightest overcorrection leads to an oscillating feedback situation which forces the pusher to grab the brakes to catch the bike.

Better to ride up at 4 mph than to push up at a quarter that speed.
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Old 09-25-20, 06:53 AM
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Originally Posted by HD3andMe View Post
It's more fun to ride, than to walk. It sounds like you need to work on your low speed balancing/climbing skills.
Oookay. Did I mention I know from experience the speed at which my cyclometer stops registering movement while slowly climbing? When I'm going that slow, getting off and walking a few hundred yards lets me use different muscles, and I'm not losing any speed by doing so. I've still got another 50 to 150 miles that day to enjoy riding.
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Old 09-25-20, 10:46 AM
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Originally Posted by pdlamb View Post
Oookay. Did I mention I know from experience the speed at which my cyclometer stops registering movement while slowly climbing? When I'm going that slow, getting off and walking a few hundred yards lets me use different muscles, and I'm not losing any speed by doing so. I've still got another 50 to 150 miles that day to enjoy riding.
The "speed at which my cyclometer stops registering movement has nothing to do with your hilarious "Somewhere below 20 gear inches it's better to walk -- easier than trying to stay balanced" claim.

There are thousands and thousands of cyclists who don't struggle with gearing below 20 gear inches, who don't have balance issues and who ride rather than walk.

That's why I suggested that you work on your low speed riding/balancing skills.
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Old 09-25-20, 11:20 AM
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Originally Posted by pdlamb View Post
Somewhere below 20 gear inches it's better to walk -- easier than trying to stay balanced, and uses different muscles.

Less that 1:1? Oh heck yeah. What you don't have in your legs you need to have in your gears.
No it isn't. Many of us use a combination that results in sub 20 gear inches very successfully. I am much happier climbing a hill at 3.5 mph than I am trying to push a loaded bike uphill. My lowest gives me 17.6 gear inches, and I have used it a lot, and wouldn't even want to go back to the 26 I swapped for the 24.

Trust me, it is easier to stay balanced on the bike while riding it, than it is to balance the fully loaded bike pushing it uphill.
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Old 09-25-20, 12:15 PM
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Originally Posted by HD3andMe View Post
There are thousands and thousands of cyclists who don't struggle with gearing below 20 gear inches, who don't have balance issues and who ride rather than walk.
Maybe a few dozen can ride more than a quarter mile at less than 2.5 mph. Or can you name even 100?
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