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Old 04-20-07, 06:51 PM   #1
Motorad
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Custom 10-Speed Cassettes?

Is this done often, when putting a bike together? The reason I ask is that if you know what range of speed you will do most of your riding, you could select cogs to minimize the amount of shifting from small to big chainring.

I do notice that most 10-speed cassettes come set up where the six smallest cogs are only one tooth apart, I'm guessing because bike makers guess that's where you're doing the most riding, and it makes sense to have the gears close together in the riding range.

Where cassettes deviate the most are with the number of teeth on the four biggest cogs. One question I'm wondering, is there a rule on how many teeth apart that the four biggest cogs should not exceed (example, going from 21 cog to 24 cog is three apart, 24 to 28 cog is four apart)?

The main question is whether any of you had custom cassettes built and what were you trying to achieve with the custom cassette? It would be interesting to hear the cog-selection you chose, and how it turned out.
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Old 04-20-07, 07:56 PM   #2
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Since you asked you should take the time to calculate the gear inches for every potential gear combination on your bike.

What you'll find is that small cassette cogs, even with single tooth differences, will be fairly widely spaced gear-inch wise. Larger cogs, even with 3 tooth differences, might be comparatively more closely spaced. I assume that the cog sizes on most standard cassettes are chosen to keep the gear-inch differences as nearly constant as possible throughout the entire cassette.

While not a cassette, I once built up a bike that had a 48/38/28 triple crankset and a 14/18 5-speed freewheel. My idea was to eliminate all overlap between the chainrings. You'd shift the back until you ran out of gears and then double shift and start over again.

It was a PITA to ride. The problem was where you happened to be when you were forced to make the big double shift. If you happened to be going uphill, for example, the double shift would take so much time that you'd lose all of your momentum.

I suppose that somebody will dream up some special use that would make a non-standard cassette beneficial but with 10 cogs on the back I'm having a hard time thinking of how much you could improve the spacing.

Last edited by Retro Grouch; 04-20-07 at 08:06 PM.
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Old 04-20-07, 08:18 PM   #3
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You can get just about any range of gears made at..................

http://www.sheldonbrown.com/harris/index.html
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Old 04-21-07, 05:40 AM   #4
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You can get just about any range of gears made at..................

http://www.sheldonbrown.com/harris/index.html

+1 and a pretty detailed explanation of gearing in general.
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Old 04-21-07, 09:12 AM   #5
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Quote:
Originally Posted by Retro Grouch
What you'll find is that small cassette cogs, even with single tooth differences, will be fairly widely spaced gear-inch wise. Larger cogs, even with 3 tooth differences, might be comparatively more closely spaced. I assume that the cog sizes on most standard cassettes are chosen to keep the gear-inch differences as nearly constant as possible throughout the entire cassette.
I'd say the same thing in a slightly different way. A three tooth change
in a 30 tooth sprocket is a 10% change. A one tooth change in a 10
tooth sprocket is also a 10% change.
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Old 04-21-07, 02:40 PM   #6
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I run 8 speed on the road bike and this has a 12/28 cassette. That gives me a 2t change between gears. May seem odd for a road bike but I am used to it. On the MTB I use 11/32 and on some gears I have a 4t difference. (32 down to 28.) I don't normally use the 32 so most of my hill work is in the 28. When I have to go to the survival gear (32) all that happens is I slow down a lot. However on one set of wheels I have a 12/34 The 34 is never used as the change from 28 to 34 stops me in my tracks. That is too large a gap and if I am struggling in the 28- when I go to the 34 I will not have enough speed to keep mobile.

There are so many different cassettes made- that I cannot see the point in going to a custom cassette. Not certain what is available but there must be a cassette that will fit almost every gearing concievable- Off the shelf.
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Old 04-21-07, 04:08 PM   #7
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Just my opinion, but if you can't find what you want in a standard 10 speed double, look at 8-9 speed triples.
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Old 04-21-07, 06:17 PM   #8
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Quote:
Originally Posted by Retro Grouch
... While not a cassette, I once built up a bike that had a 48/38/28 triple crankset and a 14/18 5-speed freewheel. My idea was to eliminate all overlap between the chainrings. You'd shift the back until you ran out of gears and then double shift and start over again.

It was a PITA to ride. The problem was where you happened to be when you were forced to make the big double shift. If you happened to be going uphill, for example, the double shift would take so much time that you'd lose all of your momentum. ...
I did it the other way around, with "third-step" gearing, such that each step in back was 3x the ratiometric step in front, viz: 49-46-43 / 13-16-19-23-26, which gave me 14 very nicely-spaced gears without resorting to the 49/26 cross-chain. I generally rode in the 46 and shifted the rear cogset, using the fronts for fine-tuning, as desired. I actually found it quite satisfactory, although I later made a half-step-plus-grannie combination I liked even better: 48-45-34 / 13-15-17-19-21-24.
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Old 04-21-07, 06:25 PM   #9
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Quote:
Originally Posted by John E
I did it the other way around, with "third-step" gearing, such that each step in back was 3x the ratiometric step in front, viz: 49-46-43 / 13-16-19-23-26, which gave me 14 very nicely-spaced gears without resorting to the 49/26 cross-chain. I generally rode in the 46 and shifted the rear cogset, using the fronts for fine-tuning, as desired. I actually found it quite satisfactory, although I later made a half-step-plus-grannie combination I liked even better: 48-45-34 / 13-15-17-19-21-24.
With only 5 cogs in the back it sometimes made sense to do some creative things to make use of every gear ratio that was available. With 9 or 10 cogs on the back who cares?
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Old 04-21-07, 06:52 PM   #10
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As a "what if" how about 1/2 stepping a Rohloff? 28 gears about 6.6% apart. So what if you don't need 2/3 of them!
It's certainly not in my budget, but one can wonder.....
Use the big rings for "trimming" your cadence.
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Old 04-21-07, 10:54 PM   #11
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Great idea Bill. I like playing with gear ratios and have calculated:
1) A nearly perfect half step is 46-49,
2) A nearly perfect 1.5 step is 38-46, and
3) If you could get a 15-16 double cog on a Rohloff, that is also an almost perfect half step (if that is what you would call it).
I can just imagine 28 gears with an even 6.6% step between each gear. This change is equivalent to the 15-16 change on your rear cog. You could find the perfect gear for almost any condition and no crazy shift patterns either.
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Old 04-22-07, 01:58 AM   #12
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"Great idea Bill. I like playing with gear ratios and have calculated:
1) A nearly perfect half step is 46-49"

Me too, but I chose 45-48 on my "what if", since I figured one was more likely to have an old 48 laying around. After buying a Rohloff, who can afford any other parts
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Old 04-22-07, 05:47 AM   #13
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Thanks everyone for input. Just when I thought I would be happy with a 50-34 compact crank ...

BikeForum has a ton of discussion about chainring-cassette setups, cross chaining, and advice on how to avoid cross chaining. One point, although I have no experience with, seems to make sense: With a compact, the circumference of the big chainring far outshadows the circumference of the small chainring ... the point being that when using the small chainring, there would be a good potential of the chain to rub on the inside of the large chainring if cross-chaining on the small rear cogs.

To defend discussion of chainrub in the 50+ forum: to find a good double crank that would be good on 50+ club rides. With that in mind, I offer more discussion about cross-chaining:
< cross chaining? >.

A lot of people make reference to the "Rule of Three", as far as cross-chaining with triple cranks. This triple crank Rule of Three means you should not use the 3 smallest cogs when using the small inner chainring ... and should not use the 3 biggest cogs when using the big outer chainring.

What is not clear is whether there is a "rule", as far as cross-chaining with double cranks. One discussion that a gentleman provided, is that both chainrings of a double crank are closer to the center of the cassette ... than would be the inner & outer chainrings of a triple crank. He and others indicate that it would be okay to adopt a "Rule of Two", as far as avoiding cross-chaining with a double crank. In the BikeForum thread that I pasted above, someone is quoting a Shimano representative about considering a "Rule of Three" for triple cranks ... and considering a "Rule of Two" for double cranks.

Any thoughts about following a "Rule of Three" for triple cranks ... and a "Rule of Two" for double cranks and 10-speed cassettes?
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Old 04-22-07, 04:08 PM   #14
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With either a double or a triple, I default to a "rule of one," i.e., no large-to-large ever, and sometimes no small-to-small, depending on the bike's chainline. If the next-to-cross combinations also run roughly, then I eschew them, as well.
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Old 04-22-07, 04:15 PM   #15
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Quote:
Originally Posted by Bill Kapaun
As a "what if" how about 1/2 stepping a Rohloff? 28 gears about 6.6% apart. So what if you don't need 2/3 of them! ...
I always try for about a 6 or 7 percent ratiometric progression when I gear my bikes, because a 10% or greater jump feels too large and a 3% change seems hardly worthwhile. 49/46 was extremely popular in years past because it yields a good top gear (49/13 = 102 for racing or 49/14 = 94 for touring) and a nice half-step against a 2-tooth rear progression, such as 13-15-17-19-22-25 or 14-16-18-20-23-26.
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Old 04-22-07, 06:21 PM   #16
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Rule of one works very well for me as well on a compact. Use any combination other than large chainring to easiest cog and smallest chainring to hardest cog. Keep things simple......

BTW, I ride a 53/39 on one bike and a 50/34 on another. I typically use the 53/39 as my training/everyday bike and use it around the house in most rides. I intentionally use the stronger gears as training for strengthen the legs. After two consecutive days I realize I really like the Compact Crank more and more. That little sucker is a great combination for all terrain, for what it's worth.
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Old 04-23-07, 03:55 AM   #17
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Quote:
Originally Posted by jppe
Rule of one works very well for me as well on a compact. Use any combination other than large chainring to easiest cog and smallest chainring to hardest cog. Keep things simple......

BTW, I ride a 53/39 on one bike and a 50/34 on another. I typically use the 53/39 as my training/everyday bike and use it around the house in most rides. I intentionally use the stronger gears as training for strengthen the legs. After two consecutive days I realize I really like the Compact Crank more and more. That little sucker is a great combination for all terrain, for what it's worth.
Thanks jppe. Are your rides always on hilly terrain, with signficant incline? Also, what is the gearing of your cassettes, on your 50/34 bike and your 53/39 bike?
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