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I'm riding the 172km Paris Roubaix Sportive in April and was looking to use SRAM 1x with 40T x 11x32 cassette. Do you think a 44T chainring would be better, as there's still over 120km of road to ride? Just didn't want to spin out. Would like to know your thoughts?  

22 comments

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fukawitribe [2803 posts] 2 months ago
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40, 42 or 44 should be fine - depending on your strengths you might spin a bit with the 40 if you're in a big-ish group on the flat, but 40 x 11 @ 90 rpm is ~42km/h already. I guess a 44 might make the chain-line a bit better, getting a narrow-wide is probably more important though, dunno - love to, but not done PR (yet). Here's a quick couple of figures.

 

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BehindTheBikesheds [3069 posts] 2 months ago
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You might want to fathom out what you feel comfortable with cadence wise, I'm a biggish chap and I don't find any problem at all doing 100+rpm, you might well find you can do 120rpm before truly 'spinning out'.

I know that 39x11 will do me for 30mph, that's only 107rpm on 28mm tyres/172.5mm crank length, I probably will have shifted onto the biggest ring beforehand but if only having one ring then I could cope with a 39, even the 12T sprocket would give you 27.6mph @107rpm, a 40/11 is 31mph at the same rpm.

At 120rpm 40/11 is 34.7mph, unless you have some lngish and fairly steep downslopes then you won't need bigger than a 40 IMHO and a 44 is simply unecessary, IF you can pedal at anything around the 110 rpm mark.

Don't worry about a 'wide-narrow' ring, waste of time and money, not seeing any evidence that a std ring will ship the chain. 

Have a great ride.

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fukawitribe [2803 posts] 2 months ago
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BehindTheBikesheds wrote:

Don't worry about a 'wide-narrow' ring, waste of time and money, not seeing any evidence that a std ring will ship the chain. 

No, not vital but...

(a) He's going on the PR cobbles, not your average British road, plenty of folk have recommended chain catchers, clutch mechs or NW rings for it in the past.

(b) They work

(c) They're cheap and sounded like he's getting a new ring anyway

 

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cmcg867 [28 posts] 2 months ago
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BehindTheBikesheds wrote:

Don't worry about a 'wide-narrow' ring, waste of time and money, not seeing any evidence that a std ring will ship the chain. 

Well, yes. But also no.

Double ring yeah no issues.

Single ring? Narrow-wide is essential IMO. I've tested every combination of narrow-wide or standard chainring with standard and clutch mech and the single most important part is the narrow-wide ring for chain retention.

Source: too many dropped chains.

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Jimthebikeguy.com [252 posts] 2 months ago
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Narrow wide not even open to debate in this case, and usually either included with a sram chainset anyway, or real cheap from somewhere like super star components. Must have.

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Welsh boy [630 posts] 2 months ago
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BehindTheBikesheds wrote:

I know that 39x11 will do me for 30mph, that's only 107rpm on 28mm tyres/172.5mm crank length

Why do you mention crank length, it has no bearing whatsoever on gear size. 

 

In in response to the original question, why do you want such a low bottom  gear for what is basically a flat ride?  I would have thought that a narrower range cassette giving you smaller jumps between gears would be a good idea. 

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Chris Hayes [415 posts] 2 months ago
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Paris-Roubaix is pan flat.  If it's any help, I'll be riding 53/39-25/11.  You might want to try riding in a high gear over the 'cobbles' (which is a ridiculously quaint word for what you're going to encounter) - but this is difficult to maintain for mere mortals. You certainly won't need your lower gears.  

I'd worry more about spoke-count; tyres (25mm+ and tough - Conti 4 Seasons); bar tape (or gel inserts); adjusting your chain so it doesn't come off (more likely with a 1x group set?); taking spare spokes; old fashioned bottle cages you can bend in; and whether your gloves are comfortable (i.e. no pressure points).  Enjoy. I cried when I finished it first time. It was 212km. I used Bernard Hinault's shower cubicle. 

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BehindTheBikesheds [3069 posts] 2 months ago
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Welsh boy wrote:
BehindTheBikesheds wrote:

I know that 39x11 will do me for 30mph, that's only 107rpm on 28mm tyres/172.5mm crank length

Why do you mention crank length, it has no bearing whatsoever on gear size. 

 

In in response to the original question, why do you want such a low bottom  gear for what is basically a flat ride?  I would have thought that a narrower range cassette giving you smaller jumps between gears would be a good idea. 

Crank length DOES have an impact, 175 to 170 on for instance a 50x14 means the 175s give you an effective 3% lower ratio. 

it's not rocket science and the explanation is simple to understand, go look it up, when at the bottom or top end and nowhere else to go (and not just change through a multi gear system to effect ratio change) that extra difference can make matters harder or easier due to crank length, it might not be much but it's there.

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Chris Hayes [415 posts] 2 months ago
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I guess the other point to raise here is that it is traditional to do the ride on a road bike; not a tourer; not a gravel bike; and definitely not a mountain-bike - all of which would defintely make it a more comfortable experience.  

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Welsh boy [630 posts] 2 months ago
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[/quote]

Crank length DOES have an impact, 175 to 170 on for instance a 50x14 means the 175s give you an effective 3% lower ratio. 

 

[/quote]

Rubbish.  Crank length does not make a difference.  Gear ratio is the ratio of the size of the chainring compared with the size of the sprocket.  For example, if your chainging is 4 times the size of your sprocket, for one rotation of the chainring your sprocket will go around 4 times.  Your sprocket is attached to your wheel so your wheel will go around 4 times too.  This ratio does not vary with the length of lever (crank) you use to turn that chainring.

If you still think that crank length changes the gear ratio think about having two different length cranks (yes, I have do it, I have considerably different length legs so thought I would experiment).  Are you telling me that one leg is riding a different size gear from the other leg?  If so, they must be going around at different speeds so one leg would eventually catch the other up and overtake it.  Stupid thought isn't it, stupid to think that crank length affects gear ratio.

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hawkinspeter [3502 posts] 2 months ago
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Welsh boy wrote:
BTBS wrote:

Crank length DOES have an impact, 175 to 170 on for instance a 50x14 means the 175s give you an effective 3% lower ratio. 

Rubbish.  Crank length does not make a difference.  Gear ratio is the ratio of the size of the chainring compared with the size of the sprocket.  For example, if your chainging is 4 times the size of your sprocket, for one rotation of the chainring your sprocket will go around 4 times.  Your sprocket is attached to your wheel so your wheel will go around 4 times too.  This ratio does not vary with the length of lever (crank) you use to turn that chainring.

If you still think that crank length changes the gear ratio think about having two different length cranks (yes, I have do it, I have considerably different length legs so thought I would experiment).  Are you telling me that one leg is riding a different size gear from the other leg?  If so, they must be going around at different speeds so one leg would eventually catch the other up and overtake it.  Stupid thought isn't it, stupid to think that crank length affects gear ratio.

However, the "effective" gear ratio is the ratio between force applied at the pedal and force applied by the back wheel and that can indeed be changed by different wheel sizes or crank lengths.

With your different length cranks, one foot will be applying more force (but over a shorter distance) than the other foot, but just measuring the gear ratios will miss out that aspect (admittedly, crank lengths don't make a huge difference to cyclists). Similarly, changing your rear wheel for a different size (if it's possible on your bike) will also change the "effective" gear ratio.

The effective gear ratio goes back to the old penny farthings where the pedals were directly connected to the wheel, so the "actual" gear ratio was 1:1 (i.e. the wheel went round once as your foot went round once). Obviously, different wheel sizes would change the rider's top speed and ability to go up hills - hence the "effective" gear ratio would be the ratio between crank length and wheel circumference (easy to measure) or the ratio between force applied at the pedal and force applied by the wheel on the ground.

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fukawitribe [2803 posts] 2 months ago
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Yeah, they're talking about two different things - WelshBoy specifically said gear size, Mr Sheds is talking about torque, as it were..

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Canyon48 [1136 posts] 2 months ago
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I have a 40t Narrow Wide on my CX bike with an 11-36 cassette.

With road tyres on, I find the gearing is great for more or less every type of road riding and I have no issues keeping up 18/19mph averages on a typical ride.

The only issue is I spin out of gears much above 25mph.

I'd rather lose the tough gears and keep the easy gears though!

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Welsh boy [630 posts] 2 months ago
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HawkinsPeter wrote:

The effective gear ratio goes back to the old penny farthings where the pedals were directly connected to the wheel, so the "actual" gear ratio was 1:1 (i.e. the wheel went round once as your foot went round once). Obviously, different wheel sizes would change the rider's top speed and ability to go up hills - hence the "effective" gear ratio would be the ratio between crank length and wheel circumference (easy to measure) or the ratio between force applied at the pedal and force applied by the wheel on the ground.

 

More rubbish,  if your crank goes around once and your wheel goes around once, you have a gear ratio of 1:1.  It is not difficult to understand is it.

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hawkinspeter [3502 posts] 2 months ago
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Welsh boy wrote:
HawkinsPeter wrote:

The effective gear ratio goes back to the old penny farthings where the pedals were directly connected to the wheel, so the "actual" gear ratio was 1:1 (i.e. the wheel went round once as your foot went round once). Obviously, different wheel sizes would change the rider's top speed and ability to go up hills - hence the "effective" gear ratio would be the ratio between crank length and wheel circumference (easy to measure) or the ratio between force applied at the pedal and force applied by the wheel on the ground.

 

More rubbish,  if your crank goes around once and your wheel goes around once, you have a gear ratio of 1:1.  It is not difficult to understand is it.

I fail to see which part of my argument is classified as "rubbish" - could you provide more details please so that I can further improve my understanding?

In case it is your understanding that is lacking, here's a helpful little breakdown: https://prevelobikes.com/blogs/news/bicycle-gear-ratio-gear-inches-and-g...

To fit in with that terminology, you are talking exclusively about "gear ratios" and I am talking about "gain ratios" (which I prefer to call "effective gear ratio").

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Welsh boy [630 posts] 2 months ago
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HawkinsPeter wrote:

I fail to see which part of my argument is classified as "rubbish" - could you provide more details please so that I can further improve my understanding?

In case it is your understanding that is lacking, here's a helpful little breakdown: https://prevelobikes.com/blogs/news/bicycle-gear-ratio-gear-inches-and-g...

To fit in with that terminology, you are talking exclusively about "gear ratios" and I am talking about "gain ratios" (which I prefer to call "effective gear ratio").

I will quote directly from the article you reference: “Gear ratio is simply the ratio of the chain ring size to the rear sprocket size.”

Since you have pointed us to that article I assume that you have read it. 

With refence to other arguments about “effective” gearing being affected by crank length, if increasing crank length increases your “effective” gearing then riding longer cranks would make climbing hills harder wouldn’t it, try riding up a hill in a higher gear, it is harder than riding up the same hill in a lower gear isn’t it. A lot of you are confusing leverage or torque with gear ratio, it is not my understanding that is lacking. 

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hawkinspeter [3502 posts] 2 months ago
2 likes
Welsh boy wrote:
HawkinsPeter wrote:

I fail to see which part of my argument is classified as "rubbish" - could you provide more details please so that I can further improve my understanding?

In case it is your understanding that is lacking, here's a helpful little breakdown: https://prevelobikes.com/blogs/news/bicycle-gear-ratio-gear-inches-and-g...

To fit in with that terminology, you are talking exclusively about "gear ratios" and I am talking about "gain ratios" (which I prefer to call "effective gear ratio").

I will quote directly from the article you reference: “Gear ratio is simply the ratio of the chain ring size to the rear sprocket size.”

Since you have pointed us to that article I assume that you have read it. 

With refence to other arguments about “effective” gearing being affected by crank length, if increasing crank length increases your “effective” gearing then riding longer cranks would make climbing hills harder wouldn’t it, try riding up a hill in a higher gear, it is harder than riding up the same hill in a lower gear isn’t it. A lot of you are confusing leverage or torque with gear ratio, it is not my understanding that is lacking. 

No, longer cranks would make it easier to go up a hill as your foot travels a longer distance and thus can apply less force to produce the same force at the rear wheel.

Similarly, swapping in a smaller rear wheel/tyre would also make it easier to go uphill.

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Welsh boy [630 posts] 1 month ago
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HawkinsPeter wrote:
Welsh boy wrote:
HawkinsPeter wrote:

I fail to see which part of my argument is classified as "rubbish" - could you provide more details please so that I can further improve my understanding?

In case it is your understanding that is lacking, here's a helpful little breakdown: https://prevelobikes.com/blogs/news/bicycle-gear-ratio-gear-inches-and-g...

To fit in with that terminology, you are talking exclusively about "gear ratios" and I am talking about "gain ratios" (which I prefer to call "effective gear ratio").

I will quote directly from the article you reference: “Gear ratio is simply the ratio of the chain ring size to the rear sprocket size.”

Since you have pointed us to that article I assume that you have read it. 

With refence to other arguments about “effective” gearing being affected by crank length, if increasing crank length increases your “effective” gearing then riding longer cranks would make climbing hills harder wouldn’t it, try riding up a hill in a higher gear, it is harder than riding up the same hill in a lower gear isn’t it. A lot of you are confusing leverage or torque with gear ratio, it is not my understanding that is lacking. 

No, longer cranks would make it easier to go up a hill as your foot travels a longer distance and thus can apply less force to produce the same force at the rear wheel.

Similarly, swapping in a smaller rear wheel/tyre would also make it easier to go uphill.

So these magical cranks increase your gearing AND make it easier to ride up hills too! 

Can I interest you in some L shaped cranks or a handful of magic beans?

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BehindTheBikesheds [3069 posts] 1 month ago
1 like
Welsh boy wrote:
HawkinsPeter wrote:
Welsh boy wrote:
HawkinsPeter wrote:

I fail to see which part of my argument is classified as "rubbish" - could you provide more details please so that I can further improve my understanding?

In case it is your understanding that is lacking, here's a helpful little breakdown: https://prevelobikes.com/blogs/news/bicycle-gear-ratio-gear-inches-and-g...

To fit in with that terminology, you are talking exclusively about "gear ratios" and I am talking about "gain ratios" (which I prefer to call "effective gear ratio").

I will quote directly from the article you reference: “Gear ratio is simply the ratio of the chain ring size to the rear sprocket size.”

Since you have pointed us to that article I assume that you have read it. 

With refence to other arguments about “effective” gearing being affected by crank length, if increasing crank length increases your “effective” gearing then riding longer cranks would make climbing hills harder wouldn’t it, try riding up a hill in a higher gear, it is harder than riding up the same hill in a lower gear isn’t it. A lot of you are confusing leverage or torque with gear ratio, it is not my understanding that is lacking. 

No, longer cranks would make it easier to go up a hill as your foot travels a longer distance and thus can apply less force to produce the same force at the rear wheel.

Similarly, swapping in a smaller rear wheel/tyre would also make it easier to go uphill.

So these magical cranks increase your gearing AND make it easier to ride up hills too! 

Can I interest you in some L shaped cranks or a handful of magic beans?

EFFECTIVE, read what I said, it will FEEL like a lower gear because of the crank length between 170-175, trouble yourself to understand the science ffs and what people have actually said. Crank length does make a difference when considering gear ratios. subtle but it's there, too subtle for people like you and others obviously!

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fukawitribe [2803 posts] 1 month ago
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Welsh boy wrote:

So these magical cranks increase your gearing AND make it easier to ride up hills too! 

Can I interest you in some L shaped cranks or a handful of magic beans?

Still think we're talking cross purposes here - have a butchers at the link below, play with the crank length and have a look at the Average Pedal Force and Effective Pedal Force as you do.

https://analyticcycling.com/GearSelectionTouring_Page.html

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ktache [1507 posts] 1 month ago
1 like

Archimedes and levers anyone?

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hawkinspeter [3502 posts] 1 month ago
3 likes
ktache wrote:

Archimedes and levers anyone?

.