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please suggest gear ratio choice

Old 07-13-12, 07:44 AM
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please suggest gear ratio choice

I need advice on gearing. Iím installing a compact crank with 50/34 chainrings. My current cassette is 11-28. My goal with the compact crank is to give me some relief on big hills. I really donít find myself in situations where I need a really high gear, but I often find myself in situations where I would like some lower gear choices on the hills Ė hence the change to the compact crankset. When I order the compact crankset, I might also order a new cassette to give me lower gear choices on the cassette. Some have suggested a 14-34. Iíll order the proper rear derailer to handle the cassette size.

I used Sheldon Brownís gear calculator and determined that the compact crank combined with my existing 11-28 cassette would yield gear ratios of 6.2 to 2.5. If I change to a 14-34 cassette, combined with the compact crankset, I would get ratios from 5.3 to 2.0.

So, advice please. For a 50-year-old guy who isnít racing but who rides hilly terrain and will be doing some light touring, whatís the better ratio, 6.2 to 2.5 or 5.3 to 2.0?
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Old 07-13-12, 08:33 AM
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Originally Posted by motorapido
whatís the better ratio, 6.2 to 2.5 or 5.3 to 2.0?
It's a personal decision.
When you're climbing, do you wish you had 1 lower gear ? 2 lower gears ?
Try the compact with your current cassette, then decide.
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Old 07-13-12, 08:41 AM
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"I’ll order the proper rear derailer to handle the cassette size."

If you get a derailleur which can handle the larger cassette you are contemplating, it will also work fine with smaller ones. The reverse is not necessarily true. The downside will be slightly more weight and slightly less ground clearance with the longer cage. Shifting might be slightly compromised with smaller cassettes than the derailleur is intended for but it might not even be noticeable.
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Old 07-13-12, 08:47 AM
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6.2 is a screwy number -- are you talking about gain ratios? Nobody really uses that.

My advice would be to try out the compact crank with the 11-28 cassette before spending more money on the back end. That may be all you need to do.
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Old 07-13-12, 09:00 AM
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There's no way anyone here can predict what you'll need for gearing in the Harrisburg area. I know it can be very hilly, but I can't know your physical condition or riding style.

Certainly a 14-34 cassette will give you a lower gear range on any crank than an 11-28. Moving to a compact crank is already giving you improvement at the low end, but we can't know if that'll be enough. At the high end, there shouldn't be any issue. I toured for decades with a 51/15 high gear. There were some times I wanted a higher gear, but at those times I'd be moving along pretty well, or coasting down hills, so it wasn't a big deal.

I suggest you take this in two steps. Since you've decided to go with a compact crank anyway, start with that and see how it goes. Then you can decide if you need a still lower gear, and how much lower, and replace the cassette accordingly. I don't believe it makes sense to try to guess gearing needs, unless you have the experience and self knowledge to do so meaningfully. Instead, think of it as an evolutionary process, making changes and adjusting as you go.

BTW- I'm not a fan of doubles with a wide cassette as the solution for touring bikes. Wide cassettes come at the expense coarser mid-range gearing. I give very high priority to mid range gearing since that's what you use 90% of the time. My advice is to consider buying a mid-priced mtb crankset, like a 26-26-46, or 28-38-48 and keep your current, or maybe even a tighter cassette like a 12-26 (if they still exist) which will give you both the gear range you need, and nice tight steps in the mid range.
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Old 07-13-12, 09:02 AM
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You've already said you need some relief and that the high gears aren't that useful to you (who really needs a 50/11?). But we don't know if your previous crankset was different, how many speeds your cassette is, or even if you've actually purchased the 50/34. If the 34/28 is lower than previously then maybe try out the 28, but in my opinion 11/28 gives you 1-4 almost useless gears. There's a middle ground of a 32 low also, which would allow better gear selection in the middle range.

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Old 07-13-12, 11:24 AM
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what 14-34 cassette? 7 speed shimano K is a 13-34..

A single ratio or a range of ratios?
count teeth do the calculation, what ratio do you use the most ,
where you live?

I tried a 2:1 in a 26" wheel bike, it worked OK, but I prefer
more choices, wider range..

(95 inch) 50/14, 700c wheel, got me and my touring load down the road satisfactory
for decades. gear sufficiently high.. It was a 6~7 speed freewheel.

with a 34t inside ring a 1:1 is what you can do MTB cassette to a 34t cog.

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Old 07-13-12, 11:40 AM
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Originally Posted by FBinNY
BTW- I'm not a fan of doubles with a wide cassette as the solution for touring bikes. Wide cassettes come at the expense coarser mid-range gearing. I give very high priority to mid range gearing since that's what you use 90% of the time.
In hilly terrain, you're in your lowest or highest gears 90% of the time - even moreso if you're touring and triple moreso for mountain pass riding. Mid range is for flat riding. Wide cassettes are right for a lot of people.
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Old 07-13-12, 01:07 PM
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I have used this webpage https://www.analyticcycling.com/ForcesSpeed_Page.html to calculate speed given grade and power output, and then used my desired lowest cadence (usually ~60 rpm) to calculate my low gear requirement. It helped me nail the gearing for the Mt Evans Hillclimb and Boulder Peak Triathlon races in Colorado even though I live ~1000 miles away. The key is that you need to know the grade of your climb and your desired sustained power output. To estimate your power, you can time your ride up a known grade at your desired effort and use this web page https://www.analyticcycling.com/ForcesPower_Page.html
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Old 07-13-12, 01:42 PM
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Originally Posted by DiabloScott
In hilly terrain, you're in your lowest or highest gears 90% of the time - even moreso if you're touring and triple moreso for mountain pass riding. Mid range is for flat riding. Wide cassettes are right for a lot of people.
It isn't about the overall range of gearing, but about how best to achieve it. A well configured triple will always offer closer steps for the same range than a double with a wide cassette. And closely spaced gearing is always valuable in any terrain.

If we accept your premise of continual climbing, a triple still wins out. Compare the spacing of the three lowest gears on a 13-34 cassette with those of a granny and 12-24 or 12-26 combination with the identical low gear.

The only disadvantage of triples is that folks who think they're cool consider them dorky, or un-macho.
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Old 07-13-12, 01:55 PM
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Old 07-13-12, 02:13 PM
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Originally Posted by FBinNY
My advice is to consider buying a mid-priced mtb crankset, like a 26-26-46, or 28-38-48 and keep your current, or maybe even a tighter cassette like a 12-26 (if they still exist) which will give you both the gear range you need, and nice tight steps in the mid range.
This sounds good but may not work well if the bike is equipped with a braze-on type front derailleur because it may not be possible to lower the front derailleur low enough for chainrings this small. Braze-on FD's are very common on carbon fiber bikes, especially those with aerodynamically shaped down tubes. I put 49-39-29 chainrings on my wife's 5200 Trek and had to deepen the slot in the derailleur hanger to get the derailleur low enough. There was no way to get it any lower for smaller rings. With a 14-28 9-speed cassette she can climb a 15% grade or even steeper. (And she's way past 50.)
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Old 07-13-12, 02:50 PM
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Originally Posted by FBinNY
The only disadvantage of triples is that folks who think they're cool consider them dorky, or un-macho.
For a new bike that's true - for a retrofit it's a lot cheaper to go MTB RD plus new cassette and chain, than new triple crank plus bottom bracket, RD, FD, brifters, chain, and probably cassette too; it'd almost be cheaper to get a whole new bike than all that swapping.

This topic comes up probably twice a week - it's always about retrofits for lower gears and cost is almost always the motivator and almost everyone agrees. If you need really low gears and you're shopping for a new bike or building up a bare frame - triple is a good idea. If you want low gears for low cost on an existing build - MTB/Alpine.



Originally Posted by FBinNY
Compare the spacing of the three lowest gears on a 13-34 cassette with those of a granny and 12-24 or 12-26 combination with the identical low gear.

If the cassette mfr's would get wise we could have some better combo's.
ie: 12-13-15-17-21-24-26-29-32
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