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gearing advice? building custom 7 speed cassette

Old 03-03-15, 03:15 PM
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Randybb
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gearing advice? building custom 7 speed cassette

I have an old steel bike with a 7 speed 12-21 cassette and 53/42 chainings. I want to build a new 7 speed cassette with some lower gear ratios for climbing. I plan on doing some long distance ultralight touring in addition to fun short sprints through the park, or group rides on weekends.

Right now, I'm thinking about doing 12-15-17-19-21-23-26.

The 15-26 gives me a really good range on both chainrings, I can hit 32-33mph on the 53/15, and the 26t should give me the lower gear ratio I need for steep climbs. Looking at a speed/cadence table I can accelerate through the gears smoothly going from 90-100rpm, which is great.

The 12t would be reserved for fast descents where I'm hitting 40+mph.

What do you think? Makes sense?
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Old 03-04-15, 02:05 AM
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escii_35
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53/42 makes my knees sad pandas. You may want to ask this same question over in the c&v or rando section.
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Old 03-04-15, 02:22 AM
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I have a 13-15-17-19-22-26 freewheel on my double, which works pretty well. Its a wussy 52/39 double but I'm old and weak, so ride my bike with the triple if hitting the hills.

I don't ever wish I had a 12t cog with the 52.
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Old 03-04-15, 06:14 AM
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I hope you're fit and under 30

I have 40mph+ descents without pedaling at all. I try and setup my lower gearing (around 20 gear inches) for ascents.
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Old 03-04-15, 06:39 AM
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You can use this for calculating different ratios compared with the one you have now
Sheldon Brown's Bicycle Gear Calculator
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Old 03-04-15, 08:42 AM
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Originally Posted by BigAura View Post
I hope you're fit and under 30

I have 40mph+ descents without pedaling at all. I try and setup my lower gearing (around 20 gear inches) for ascents.
Ha yup I'm 25 and getting fitter every day.

Only thing is, it's depressingly flat where I live, so I've never really dealt with a legitimate climb. Is 42/26 going to completely wear me down on a day going through the Appalachians? I guess only experience will tell...

Also, if you can go faster on a descent, why not peddle?
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Old 03-04-15, 10:35 AM
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Originally Posted by Randybb View Post
Ha yup I'm 25 and getting fitter every day.

Only thing is, it's depressingly flat where I live, so I've never really dealt with a legitimate climb. Is 42/26 going to completely wear me down on a day going through the Appalachians? I guess only experience will tell...

Also, if you can go faster on a descent, why not peddle?
42/26 won't work. Try 24/34 for a steep assent up an Appalachian mountain pass.

My first tour involved walking my bike 6 out of the 7 miles up a 7% grade in Colorado because I didn't have a third chain ring. Don't make my mistake.
You will be using bags and camping equipment, right?

Last edited by boomhauer; 03-04-15 at 10:55 AM.
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Old 03-04-15, 10:49 AM
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My favorite 7 speed is Rohloff.. the hub uses that 7 speeds twice, again in a low range.


For Touring, Shimano's 13-34t 7 speed K cassette combination is superb. no need for Custom bodges.

Last edited by fietsbob; 03-05-15 at 10:19 AM.
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Old 03-04-15, 11:09 AM
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Originally Posted by fietsbob View Post
My favorite 7 speed is Rohloff.. the hub uses that 7 speeds twice, again in a low range.
Me too!
Last I used a 7 speed cassette, I went with a Sram 12-32T which went 12, 14, 16, 18, 21, 26, 32
I believe it was this one:
wiggle.com.au | SRAM PG730 7 Speed Cassette | Cassettes And Freewheels

Sheldon Browns calculator reckons my low gear is 16.4 but I'd prefer to drop another gear inch.
Alas I can't and stay in warranty for my Rohloff.
Look after your knees.
Low gearing is want you want for a loaded touring bike IMHO.

Last edited by rifraf; 03-04-15 at 11:26 AM.
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Old 03-04-15, 11:14 AM
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I toured on 6 speed freewheels and a triple crank for 30 years .. 7th was added in the middle
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Old 03-04-15, 12:15 PM
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What makes sense?

With any sort of camping gear. Triples + 7 speed. Take the classic 13-28 and tighten or expand from there.

If you are a bike/math nerd and running 5/6 speed, geek out on half step granny combos.

Last edited by escii_35; 03-04-15 at 12:19 PM.
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Old 03-05-15, 12:08 AM
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thanks for the responses...

I'm trying to go as light as possible.

Bike: 21 lbs.
Gear: <15 lbs (including bags/straps).
Water: ~5 lbs
Me: 160 lbs.

Total: ~200 lbs.

How does that weight compare to your touring experiences?

Also, if I have a 42/26 ratio, with a typical 50-60rpm standing cadence, I'd be going 6-7 mph. Somehow I feel like if I can't ride 6 mph on my bike for at least a few miles, I probably have no business on the bike... famous last words?

I may not have hills here in the midwest, but sustained 25mph headwinds with 40 mph gusts are pretty standard on my 10 mile commute, which I often ride with a fixed 39/16 bike. That's no joke. Only 10 miles though. I routinely hit 35 mph on flats on my way home with those tail winds.

Last edited by Randybb; 03-05-15 at 12:39 AM.
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Old 03-05-15, 06:00 AM
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Originally Posted by Randybb View Post
Also, if I have a 42/26 ratio, with a typical 50-60rpm standing cadence, I'd be going 6-7 mph. Somehow I feel like if I can't ride 6 mph on my bike for at least a few miles, I probably have no business on the bike... famous last words?
I'm not quite sure what this says.
Are you saying you ride at 50-60rpm cadence?
I aim for around 92-94rpm.
I think 50-60 would chew out my already worn knees pretty quickly.
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Old 03-05-15, 09:19 AM
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Originally Posted by rifraf View Post
I'm not quite sure what this says.
Are you saying you ride at 50-60rpm cadence?
I aim for around 92-94rpm.
I think 50-60 would chew out my already worn knees pretty quickly.
50-60rpm while standing. I usually ride close to 100rpm seated.
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Old 03-05-15, 01:06 PM
  #15  
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Originally Posted by Randybb View Post
Also, if I have a 42/26 ratio, with a typical 50-60rpm standing cadence, I'd be going 6-7 mph. Somehow I feel like if I can't ride 6 mph on my bike for at least a few miles, I probably have no business on the bike... famous last words?
When touring with a load and hills, 4-5 mph may feel pretty good at times, and I wouldn't want to climb hills assuming that I was going to be standing up them.

And gearing for pedaling fast downhill would be very low in my priority list.

I use custom cassettes on most of our bikes that work very well regardless of what Shimano might say. You might look at setting one up so that the middle cogs that you'll use on flat roads are closely spaced for your likely touring speed and seated cadence, with wider steps at the ends.

Last edited by Dfrost; 03-05-15 at 01:11 PM.
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Old 03-05-15, 02:43 PM
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I'm sure when rested and well motivated you won't have a problem with most hills if you have a bit of fitness, the real test will be how many sustained days you can chug away climbing with that setup. Piggy back multiple days and long hours in the saddle, I think your legs are going to suffer. Factor in heat, maybe a restless night or two, maybe a long ways between snacks...it can be nice to have some bail out gears and or prevent yourself from digging to deep.
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Old 03-05-15, 06:25 PM
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Originally Posted by Randybb View Post
Also, if I have a 42/26 ratio, with a typical 50-60rpm standing cadence, I'd be going 6-7 mph. Somehow I feel like if I can't ride 6 mph on my bike for at least a few miles, I probably have no business on the bike... famous last words?
I'm sure you have one steep hill where you live..
Put 20 lbs of weight on your bike and go try it.

I think you are living in a dream world. You will be walking up hills a lot.
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Old 03-05-15, 06:31 PM
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If you can get out there and tour with 15 pounds of pack weight, the added weight will barely make a difference to your bike and gearing. I recently reduced my pack weight to that range and it's amazing the difference it makes on tour. I just don't use those low gears any more.

I'm an old fart with a 7-speed I bought new, and I swapped the 13 for a 12 to give me a bit more pedaling downhill and downwind and I'm glad I did.
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Old 03-05-15, 09:16 PM
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Originally Posted by Randybb View Post
50-60rpm while standing. I usually ride close to 100rpm seated.
Ahhh
Thanks for that.
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Old 03-05-15, 09:26 PM
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Originally Posted by andrewclaus View Post
If you can get out there and tour with 15 pounds of pack weight, the added weight will barely make a difference to your bike and gearing. I recently reduced my pack weight to that range and it's amazing the difference it makes on tour. I just don't use those low gears any more.

I'm an old fart with a 7-speed I bought new, and I swapped the 13 for a 12 to give me a bit more pedaling downhill and downwind and I'm glad I did.
What's the lowest gear you use now? Do you spend much time in the mountains?

I don't think my rear derailleur will take a cog bigger than 26t. My crankset has a 130mm BCD, so maybe I could go down to a 39t? Not a big difference though. Also my front derailleur will not work with a triple ring.

So, going much lower than 42/26, about 40 gear inches, is going to be a much bigger investment.
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Old 03-05-15, 10:02 PM
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Don't listen to those weenies who say you can't tour on high gears: <-- Bicycling Magazine 04-1972 --> Raleigh International / Professional
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Old 03-05-15, 10:28 PM
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Originally Posted by Randybb View Post
What's the lowest gear you use now? Do you spend much time in the mountains?

I don't think my rear derailleur will take a cog bigger than 26t. My crankset has a 130mm BCD, so maybe I could go down to a 39t? Not a big difference though. Also my front derailleur will not work with a triple ring.

So, going much lower than 42/26, about 40 gear inches, is going to be a much bigger investment.
You can do pretty well for not too much dough.

38T is the smallest chainring you can do.

These aren't too pricey, you can file down the teeth that coincide with short teeth on your current ring if it has any.
https://www.danscomp.com/products/45...Chainring.html

Most rear derailleurs will handle 28T. I've had a few Shimano road derailleurs that were rated at 26 or 27 max cog tooth count and handled 28T no problemo.
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Old 03-05-15, 10:50 PM
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Originally Posted by ThermionicScott View Post
Don't listen to those weenies who say you can't tour on high gears: <-- Bicycling Magazine 04-1972 --> Raleigh International / Professional
Ha! That's awesome. Maybe I should just stick with my 12-21 cassette. And upgrade to a 55t chainring while I'm at it! The heavier the bike, the higher the gears??

I mean on flat ground, 42/21 is only usable in the strongest of headwinds. I just wonder about hills...
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Old 03-05-15, 11:26 PM
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I'd suggest a 15-17-19-21-24-29-34. made up from a Shimano 13-34, a Shimano 13-23 and a Miche 15T first position cog.

Shimano HG50 7-Speed 13-23 Cassette
Shimano HG50 7-Speed Cassette - 13-34T, Silver
Miche Shimano 15t First Position Cog, 8/9-Speed

The spacing of the inner and outer cogs is not super critical because the RD position on them is controlled by the limit screws, not the indexing in the shifter.

And RD: Shimano RD-M410 Alivio Rear Derailleur 7/8-Speed, SGS Silver

You'll be using the 42/34 on the hills, and wishing for lower.

If you have friction rear shifting, I suggest an 8 of 9 with 13-34:
13,15,17,20,23,26,30,34

Regarding your 12-26 idea; Shimano's 13-26 is
13,15,17,19,21,23,26; you purchase it, and just use your current 12T 1st position cog and lock ring.
http://www.niagaracycle.com/categories/shimano-hg50-7-speed-cassette-13-26t-silver


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Old 03-06-15, 07:14 AM
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Originally Posted by Randybb View Post
What's the lowest gear you use now? Do you spend much time in the mountains?

I don't think my rear derailleur will take a cog bigger than 26t. My crankset has a 130mm BCD, so maybe I could go down to a 39t? Not a big difference though. Also my front derailleur will not work with a triple ring.

So, going much lower than 42/26, about 40 gear inches, is going to be a much bigger investment.
I do a lot of climbing where I live in the Front Range in Colorado, but on fairly easy grades. My normal climbing gear on 6-7% grades is 36/21. My recent XC tour went through Mississippi River bluff country and the Northern Appalachians (short steep grades), as well as the North Cascades and Rockies (looong grades). On that tour, I packed less than 15 pounds and the granny gear on my touring bike was just along for the ride--never used it on pavement, just a few times climbing out of campgrounds on gravel when I felt fatigued. My typical low gear on that ride was 36/23, and I bailed out to 36/26 a few times. Keep in mind I'm fairly old (almost finished with my sixth decade), but blessed with strong knees and half a lifetime of cycling in mountains.

Plenty of touring cyclists don't mind walking a grade or two on tour, in fact even sort of welcome it as a change (cross training?). I don't like it so I still tour on a bike with a triple so I never, ever have to walk. But when it comes time to replace that bike, I'll consider getting one with a double if it's an otherwise perfect bike. Then I might have to walk out of those campgrounds or creek fords on gravel roads when I'm carrying a full load of food and water.

Gearing on a touring bike is quite a personal decision and it needs to match the rider, the load, and the road. The good news is it's fairly inexpensive to make minor changes, especially when you routinely wear out cogs, and occasionally chain rings anyway. Last time I replaced a worn cassette and chain ring they were less than $20 each.
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