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Gearing

Old 03-21-20, 04:03 AM
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Adrian99
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Gearing

Hi, I have an old adventure/gravel touring bike where the mechanicals are well past their use-by-date and I'm thinking of replacing them and correcting a couple of issues at the same time. I am looking for as wide a range of gearing as I can get - so looking at my needs I considered
  1. what top speed do I need - using my road, MTB and gravel bikes as examples I plonked for a minimum of 110 gear inches
  2. what bottom speed - after experiencing many hills with loaded panniers I decided a maximum of 20 gear inches
How can I do this with commonly available components and my 700x38 wheels? Trying to use 2x11 gearset to give as many intermediate gears as possible. Well the smallest sprocket is 11T then my large chainwheel would need to be 46T giving a top speed gear of 114.2 gear inches. That is available in the GRX component range with a 46/30 chainset. I would need a GRX front derailleur and 105 hydraulic STI shifters would allow me to upgrade to hydraulic disk brakes. One of the issues (extra stopping power) solved.

Now with a 30T small front chainwheel I need a 42T rear cog to get the 20 gear inches lowest speed. In fact it would be 19.5 gear inches. A 11/42 cassette is readily available. Is there a rear derailleur that will handle this? A search gives me the Shimano XT RD-M8000 Shadow+ 11Sp long cage rear derailleur. According to the specs this has a low sprocket_Max.42T(2x11-speed)[TICK], max. front difference 18T[TICK], Total capacity 47T[TICK]. So this looks like a goer.

So to summarise:-
  • GRX FD-RX810 11 Speed Front Derailleur
  • GRX FC-RX600-11 46-30T 2x11 Speed CrankSet
  • XT RD-M8000 11Sp Long Cage Rear Derailleur
  • SLX CS-M7000 11-Speed 11-42 MTB Cassette
  • Jtek Shiftmate to adapt MTB derailleur to Road shifters
  • 105 RS-505/BR-RS785 Road 2x11 Lever/Caliper Set
Comments welcome - I hope it all works.

Last edited by Adrian99; 03-21-20 at 04:08 AM.
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Old 03-21-20, 06:37 AM
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I have a 700c touring bike with a road triple crankset where I swapped out the 30T granny gear for a 24t. 11/32 cassette. My lowest gear (24/32) is 20.7 gear inches. I also swapped out the 52T big chainring for a 46T, that has a highest gear (46/11) of 115.5 gear inches.

A lot of people use triples that have stock gearing that is lower than what I used that might meet your criteria even better.

Any reason you are not considering a triple? They are getting a bit harder to find but they are still readily available if you look for them.

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Old 03-21-20, 11:04 AM
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check out pathlesspedaled for the fellows vids on mixing and matching stuff that goes to 42t that works but officially shouldnt.

a 20-100+ gear inch range is smart, although I wouldnt go past 110. One of my bikes has a 104 top gear and while I spin out at about 50-55kph, I prefer to have the lower low gear for the weight I carry on that bike, and its very rare that I need to pedal past that 50k 30mph speed , but am fine going along at 40-45kph the few times I have long downhills.
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Old 03-21-20, 11:43 AM
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I run a couple of 46x30 cranks with 11-34 cassettes but I personally don't care for those large last few steps at the low end of that 11-42. An 11-40 gets you down to 20" with smaller steps. Let us know how it works out as I would be very interested.

Last edited by robow; 03-21-20 at 11:51 AM.
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Old 03-22-20, 03:16 PM
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For my first 10 or 15 years of touring, my bikes always had doubles, and although I didn't realize it at the time, the gearing was never low enough for significant hills.

When I finally upgraded to a triple, I couldn't believe the difference those extra low-end gears made. During the following twenty years, I have replaced drive trains three or four times as they wore out, and I each time, I reduced the low gears a bit more, even when it meant sacrificing the top-end gears.

I would rather spin-out at the high-end once in a while rather than struggle while climbing for even a minute. I figure I spend much more time climbing hills than bombing down them, so I choose my gearing with that in mind.

Last edited by acantor; 03-24-20 at 09:43 AM.
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Old 03-22-20, 03:47 PM
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Low Gear Range: Road Shifters & Gears For Easier Hill Climbing - CyclingAbout.com

Thought this was interesting take on multiple options. Might be something there you have not thought of.
Seems like your on the right track.

I'm going from 11-32 to 12-36 on my old 9 speed triple, 48-36-26 because it's easy and cheap.
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Old 03-22-20, 04:34 PM
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I have recently renewed the drive train on my gravel/touring bike. I use a Sora triple in front, but only use the small and middle chain ring. Previous to the recent change, I had a 26/38 tooth combo in front, and a SRAM 10-42 cassette. I only used the 26 tooth in Alaska on some very steep climbs, with luggage. Skip ahead a few years, I have worn out the 38T chainring, using it like it was a 1x11 drive. I really enjoyed the 38T, it was everything I needed, anywhere, on training rides. But it wore down to shark's teeth. Having recently discovered the Path Less Pedaled channel and researched gravel bike gearing, I went with a 30/46 front and kept (replaced with identical) the 10-42. Practically speaking, it's all I should need, if I pack light enough. Oh yeah, I run 700x40c tires. I can always put a bigger chain ring on the outside spot of the crank, but I have never felt the need, even when I ran the 38. With the 46, I'm sure that I have plenty of top end.
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Old 03-22-20, 05:54 PM
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Originally Posted by robow View Post
I run a couple of 46x30 cranks with 11-34 cassettes but I personally don't care for those large last few steps at the low end of that 11-42. An 11-40 gets you down to 20" with smaller steps. Let us know how it works out as I would be very interested.
I agree with Robow's statement... I would rather give up some top speed for better stepped gearing.
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Old 03-24-20, 08:27 AM
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Originally Posted by acantor View Post
...I would rather spin-out at the high-end once in a while rather than struggle while climbing for even a minute...
+1 on that. I've never once minded coasting down a hill. When compared to pushing a bike up one, there's no question which I prefer.
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Old 03-25-20, 07:44 PM
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Originally Posted by Tourist in MSN View Post
I have a 700c touring bike with a road triple crankset where I swapped out the 30T granny gear for a 24t. 11/32 cassette. My lowest gear (24/32) is 20.7 gear inches. I also swapped out the 52T big chainring for a 46T, that has a highest gear (46/11) of 115.5 gear inches.

A lot of people use triples that have stock gearing that is lower than what I used that might meet your criteria even better.

Any reason you are not considering a triple? They are getting a bit harder to find but they are still readily available if you look for them.

I'm reading this post and it is almost precisely what I did. But my tourer is a bit older and has a 6 speed freewheel. 13,15,17,20,26,30. I swapped to a 46/36/24 and pushed my derailleur's chain wrap to it's limit.
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Old 03-25-20, 07:46 PM
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Originally Posted by timdow View Post
I agree with Robow's statement... I would rather give up some top speed for better stepped gearing.
Totally agree. Speed isn't the game, it's the ride....
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Old 03-30-20, 04:31 AM
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20 gear inches?

The hell with that.

Quite happy with my 15.3 GI for my aged worn knees and Ogres 700x 2.3' tires.

YMMV
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Old 03-30-20, 06:59 AM
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The other day with my bike that has a 16.7 gear inch low, I rode it up a short steep section unloaded beside my wife pushing her bike up the hill, so that we could talk and I hate pushing bikes.

3.5kph and easy to ride, this was the slowest I've ridden this bike, but waa able to hold this speed because it was so light. I've been riding all winter on snow so my balance is pretty good, so I'm sure this helped.

but all that to say that lower than 20 g.i. is always a plus on a touring bike.
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Old 03-30-20, 08:28 AM
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Originally Posted by djb View Post
The other day with my bike that has a 16.7 gear inch low, I rode it up a short steep section unloaded beside my wife pushing her bike up the hill, so that we could talk and I hate pushing bikes.

3.5kph and easy to ride, this was the slowest I've ridden this bike, but waa able to hold this speed because it was so light. I've been riding all winter on snow so my balance is pretty good, so I'm sure this helped.

but all that to say that lower than 20 g.i. is always a plus on a touring bike.
I find that 3.5 mph (5.6 km/hr) is my minimum speed to maintain vertical and directional stability. If you can balance at 3.5 km/hr, I am impressed.

I sized the chainring that I use for touring on my Rohloff bike to give me 3.5 mph at a cadence of 72. That is a low gear of 16.2 gear inches. Sometimes if the wind is not blowing and the conditions are good, I might find myself pedaling up a hill in a cadence in the 60s, but I am not much below that 3.5 mph that I consider a minimuim.

That said, my derailleur touring bikes have a lowest gear of 19.3 or 20.7 gear inches and I manage to live with those bikes too.
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Old 03-30-20, 08:43 AM
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Thanks, it was actually fun, we were chatting and I looked down at computer and saw the 3.4,5,6 just as muy wife said, yup we're going 3.5....
I had hundreds of snowy slippy front wheel understeer moments this winter, and like I wrote in my thread about winter riding, it became a game for me to not put a foot down, so keeping the power on and using body language to push through the understeer, so going up this hill with one light pannier on pavement was easy more or less.

but as for the lowest gear inch, like you say, the old adage of 20 to 100 is still pretty valid, although for unloaded riding I do prefer a taller high gear. I like the 112 g.i. on my lighter bike to be able to spin up to close to 70kph.45mph, so if this fellow rides a lot unloaded and is comfortable going fast, he very well may like a taller top gear.
I have a friend who never goes past 40kph and she really doesn't need a 50t , especially given that her knees and low gearing that isn't low enough kill her on climbs.... but she has been ignoring my loud comments for years and won't change her bike....
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