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Bicycle Gearing


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#1 Darth Lefty

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Posted 13 February 2013 - 05:15 PM

Warning, this goes deep into nerd territory. I won't be dismayed if no one replies.

I have an old Specialized Hardrock with 1.5" tires to serve as my commuter. I'm due to replace the chain pretty soon and I thought I'd bin the crankset along with it. Despite my health problems the gearing is still too low. I'd like to switch from a "mountain" crankset (22-32-42) to a "hybrid" crankset (26-36-46). The 46 with the 11 in the rear would give me 105 gear inches, which about like a 1970's 10-speed in top gear. I'm not likely to spend a lot of time off the middle ring and I've even considered going to a 1x8 setup where I take off the upper and lower rings and the front derailleur.

At the same time, I've been bike shopping. The idea of 75 inches for cruise and 100 inches for downhill seems like a pretty good rule. So why do so many bikes have insane gear ranges? I looked at a Cannondale CAADX. It has a "compact" crank (36&46) and a well matched cassette (12-28). The gearing seems entirely rational, with a 46 in the front and a 12 in the back, which works fine with the larger wheel. The granny gear (36/28) is not low as a mountain bike but probably low enough. You could maybe swap for a slightly lower granny. But on a Giant TCX, an otherwise similar bike, the jump between the chainrings is huge and the top gear is 122 inches. Who could possibly make use of this? I did the math just for fun, and at your supposed ricky-racer 90 cadence that makes the speed 33 mph. Where could you make safe use of this gear?

It seems like there are well matched sets of hardware, and bike manufacturers aren't using them. A 46/12 top gear and a 700c road wheel go well together. A 42/11 top gear and a 26" MTB tire go well together. But a 50/11 is silly, isn't it? At the other end, I've never used the full granny gear on my MTB except for doing wheelies, and it's not especially low, I can do wheelies with the next gear and my fiancee's bike has a "Megarange" cassette that's even lower. What's the point?
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#2 chris v

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Posted 13 February 2013 - 10:01 PM

Steep climbs. I've used and still use every gear on my MTB. Climbing off road can be way steeper than anything you will find on road. Hence the granny gear.

#3 andy

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Posted 14 February 2013 - 06:02 AM

Most bikes are spec'd to product cost and marketing - it's about profit and MSRP, not customized gearing. Over the years, I've adjusted the size of cassettes and chain rings many times to suit my mood, level of fitness, ride locations, etc. But I can't expect a mass market product to anticipate my individualized needs.

if you want custom, you can swap stuff out and sell your unused parts on eBay to defray the cost.

#4 Logan

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Posted 14 February 2013 - 08:39 AM

I have an old mountain bike with "biopace" front gears, and the granny gear is really really low and I use it on hills on city streets. I can climb the steepest hill in town without standing on the pedals. I'm not in great physical shape, and rarely use the top gears as I have no desire to work that hard or go that fast when riding. I ride for casual pleasure and to get my low level of physical exercise. What you may think are ridiculous low gears, aren't necessarily ridiculous to others. And while I don't use my top gears, I'm sure there are speed-demons that do.

Do what you want with your bike, but don't assume that gears you find useless are useless for everyone.

#5 Darth Lefty

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Posted 14 February 2013 - 08:55 AM

Steep climbs. I've used and still use every gear on my MTB. Climbing off road can be way steeper than anything you will find on road. Hence the granny gear.

At some point it has to make more sense to get off the bike. And I think that point is probably somewhere before you get to the 22 cog in the front and the 34 in the rear.

But this is still not nearly as sily as the top gear you get from 52-11 and a 700c wheel.

I have an old mountain bike with "biopace" front gears, and the granny gear is really really low and I use it on hills on city streets. I can climb the steepest hill in town without standing on the pedals. I'm not in great physical shape, and rarely use the top gears as I have no desire to work that hard or go that fast when riding. I ride for casual pleasure and to get my low level of physical exercise. What you may think are ridiculous low gears, aren't necessarily ridiculous to others. And while I don't use my top gears, I'm sure there are speed-demons that do.

Do what you want with your bike, but don't assume that gears you find useless are useless for everyone.

Biopace gears were cool. I don't know why they stopped making them. I had them on my college bike. They worked great.
"I enjoy a bit of cooking, and this has always worried me. But it's OK. I only like it because it allows me to play with knives." - James May

Genesis 49:16-17
http://www.active2030folsom.org

#6 chris v

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Posted 14 February 2013 - 09:32 AM

At some point it has to make more sense to get off the bike. And I think that point is probably somewhere before you get to the 22 cog in the front and the 34 in the rear.


I 100% disagree. The whole point to me is not to get off the bike. I know certain sections of trail I used to have to walk and being able to ride something so steep now is a really great feeling.

#7 folsombound

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Posted 14 February 2013 - 10:56 AM

The whole point to me is not to get off the bike.

Exactly! I refuse to get off and walk. If I can't climb it today and I want to, I just keep working on it until I can. I WILL NOT walk my bike up a hill.

#8 The Average Joe

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Posted 14 February 2013 - 12:21 PM

Alpine touring is where you use those ratios. When I rode across Colorado on a mtb, I used a HUGE variety of gearing. Where do you use a 50t gear? Going downhill, or on the shoulder of the highway with a tailwind (or an absolute stud pushing wind for you on the flat).

"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive" -- C.S. Lewis

 

If the only way to combat "global warming" was to lower taxes, we would never hear of the issue again. - Anonymous

 

"Society in every state is a blessing, but Government, even in its best state, is but a necessary evil; in its worst state an intolerable one" — Thomas Paine, 𝘊𝘰𝘮𝘮𝘰𝘯 𝘚𝘦𝘯𝘴𝘦 (1776)

 


#9 Darth Lefty

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Posted 20 February 2013 - 02:02 PM

Anyone have a bike with a gear hub, and thoughts on same? It seems like the 3-speeds don't have the total gear range I'd want for my commute on the AR trail. 26-inch, 3-speed wheels are available cheap for cruisers. I thought of getting one for my commuter MTB, but it has vertical dropouts. It would be possible but I'd need to keep the rear derailleur as a chain tensioner, and the front derailleur to get the range needed. The higher-speed hubs have wider ranges but get progressively more expensive.
"I enjoy a bit of cooking, and this has always worried me. But it's OK. I only like it because it allows me to play with knives." - James May

Genesis 49:16-17
http://www.active2030folsom.org

#10 MSgt

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Posted 29 May 2013 - 12:08 PM

I have the 50/34 crank and the 11/32 chain rings on my Felt Z4 road bike for help in the hills. I have had the bike a year now.  I bought it at Folsom Bike and they changed the gearing for me.  It was a great help on Mormon Emigrant trail,

http://app.strava.co...vities/51444952


 

 

and I am climbing Beaty Hill in Folsom w/o stopping now.

http://app.strava.com/segments/1425516

 

I love my granny gear.



#11 benning

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Posted 31 May 2013 - 08:47 AM

That is awesome, MSgt!  I told people I refuse to do double digit grade but this is just under that so I guess I will need to try it with my granny gear.


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#12 chris v

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Posted 31 May 2013 - 03:49 PM

Isn't Beatty Dr like 18%?

#13 The Average Joe

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Posted 31 May 2013 - 07:23 PM

Sometimes, even granny fear won't work... above tree line before dropping into Aspen (it's actually steeper than it looks!).

https://fbcdn-sphoto...2_2375755_n.jpg


"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive" -- C.S. Lewis

 

If the only way to combat "global warming" was to lower taxes, we would never hear of the issue again. - Anonymous

 

"Society in every state is a blessing, but Government, even in its best state, is but a necessary evil; in its worst state an intolerable one" — Thomas Paine, 𝘊𝘰𝘮𝘮𝘰𝘯 𝘚𝘦𝘯𝘴𝘦 (1776)

 


#14 MSgt

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Posted 01 June 2013 - 10:23 PM

Isn't Beatty Dr like 18%?

9.5 for the first part.  The second part is easier.  






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