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Formula for actual # of usable gears
Due to cross-chaining issues, I came up w/ a formula for the actual #
of usable gears on a bike, which is less than the stated number by the manufacturer. For instance, on my bike, which supposedly has 24 gears (3 in front, 8 in back), I only actually have 16 usable gears, and not 24. The formula can be expressed in this form: (# of speeds by manf) - (# of rear sprockets) = actual # of usable gears ex. 24 - 8 = 16 usable Note that this formula only works if you have 3 sprockets in the front, and any number in the back. |
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#2
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Formula for actual # of usable gears
On Jun 19, 12:18*am, Ablang wrote:
Due to cross-chaining issues, I came up w/ a formula for the actual # of usable gears on a bike, which is less than the stated number by the manufacturer. For instance, on my bike, which supposedly has 24 gears (3 in front, 8 in back), I only actually have 16 usable gears, and not 24. The formula can be expressed in this form: (# of speeds by manf) - (# of rear sprockets) = actual # of usable gears ex. 24 - 8 = 16 usable Note that this formula only works if you have 3 sprockets in the front, and any number in the back. I think it's a great idea to come up with a formula but I think that, with all due respect, what you have come up with might be too easy. Kind of like " if it sounds too good to be true, it probably isn't ". Lewis. ***** |
#3
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Formula for actual # of usable gears
"Ablang" wrote: (clip) The formula can be expressed in this form: (# of speeds by manf) - (# of rear sprockets) = actual # of usable gears ex. 24 - 8 = 16 usable Note that this formula only works if you have 3 sprockets in the front, and any number in the back. ^^^^^^^^^^^^^^^^^^ With the limitation to bikes with front triples, the formula reduces to Useful speeds = 3N - N = 2N. Would you explain by what reasoning you arrived at this? Obviously, you eliminated the two cross-chain positions, which would give you 3N - 2. It seems to me that from that point on, you would have to consider the individual ratios obtainable, and look for duplications. Your formula doesn't consider the actual ratios, so it couldn't possibly do that. |
#4
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Formula for actual # of usable gears
"emanon" wrote in message . .. "Ablang" wrote in message ... Due to cross-chaining issues, I came up w/ a formula for the actual # of usable gears on a bike, which is less than the stated number by the manufacturer. For instance, on my bike, which supposedly has 24 gears (3 in front, 8 in back), I only actually have 16 usable gears, and not 24. The formula can be expressed in this form: (# of speeds by manf) - (# of rear sprockets) = actual # of usable gears ex. 24 - 8 = 16 usable Note that this formula only works if you have 3 sprockets in the front, and any number in the back. If it works for you, great, but I'd like to know your definition of "usable". I have 9 freewheel cogs and 3 chainrings. I can physically actually use, without undue chain angle problems, any of the 9 freewheel cogs with any of the three chainrings. Therefore, I do have 27 "usable" gear combinations. I have yet to count the free wheel teeth for the cogs, but I have no doubt I have duplication in gear ratio (gear inches). In fact, I'll even allow I have more than three probably very close (2 inches or less) gear combinations. What this means to me, though, is that I do not have to keep changing my front derailleur to find my desired gearing. I use this to my advantage, by making most of my changes only on the rear. If I'm on the road, I use mostly the large chainring; mild off road / not too hilly a course, the middle and when it gets really tough, I do hit the granny gear and bounce back to the middle when the hills flatten out. Thank you for taking the time to point this out. I always wonder why people go through the exericse of trying to minimize the value of duplicate gears. It's silly and indicates how poor of an understanding some people have about gears. As long as you aren't be weighted down by excessive gear duplication, this is a good thing. Of course, I've always read that the big-big and small-small combinations should be avoided due to the cross chain issues. Indeed, it does seem that one could easily avoid these combinations for the most part to avoid a possible breakdown on the road. |
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Formula for actual # of usable gears
On Jun 19, 6:28 pm, "Roger Zoul" wrote:
"emanon" wrote in message . .. Of course, I've always read that the big-big and small-small combinations should be avoided due to the cross chain issues. Indeed, it does seem that one could easily avoid these combinations for the most part to avoid a possible breakdown on the road. I sometimes notice issues as I am downshift the cassette, I then downshift the chainring. I don't notice any issues upshifting to the highest cassette gear, then I shift the chain ring. And in actuality, I like to figure, for my Sun Bicycles EZ-1 with a triple chainring and 3*7 SRAM rear wheel, that I don't actually have 63 gears. I start by considering the internal hub and chainring are in the middle. I can change the cassette up and down over 7 gears, about 10% difference each. If I hit the limits, I can change the chain ring, for a 20% change or 2 gears on the cassette. If I am at top speed, using the hub overdrive adds more resistance and ends up slowing me down. If I am climbing, I can use the underdrive for about a 25% drop in effort, about 2 more gears. If I rush to stop without downshift, I will use the under drive to get started and downshift the derailers and go back to hub direct drive. So even though I have a hugh number of gears, the hub just gives me a 25% lower range in gear ratios. I think a more accurate calculation would be to count the # of cogs (7), + 4 additional gears for the two additional chainrings, + 2 for the hub underdrive. |
#6
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Formula for actual # of usable gears
"Ablang" wrote in message ... Due to cross-chaining issues, I came up w/ a formula for the actual # of usable gears on a bike, which is less than the stated number by the manufacturer. For instance, on my bike, which supposedly has 24 gears (3 in front, 8 in back), I only actually have 16 usable gears, and not 24. The formula can be expressed in this form: (# of speeds by manf) - (# of rear sprockets) = actual # of usable gears ex. 24 - 8 = 16 usable Note that this formula only works if you have 3 sprockets in the front, and any number in the back. If it works for you, great, but I'd like to know your definition of "usable". I have 9 freewheel cogs and 3 chainrings. I can physically actually use, without undue chain angle problems, any of the 9 freewheel cogs with any of the three chainrings. Therefore, I do have 27 "usable" gear combinations. I have yet to count the free wheel teeth for the cogs, but I have no doubt I have duplication in gear ratio (gear inches). In fact, I'll even allow I have more than three probably very close (2 inches or less) gear combinations. What this means to me, though, is that I do not have to keep changing my front derailleur to find my desired gearing. I use this to my advantage, by making most of my changes only on the rear. If I'm on the road, I use mostly the large chainring; mild off road / not too hilly a course, the middle and when it gets really tough, I do hit the granny gear and bounce back to the middle when the hills flatten out. |
#7
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Formula for actual # of usable gears
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#8
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Formula for actual # of usable gears
In article ,
Ablang writes: Due to cross-chaining issues, I came up w/ a formula for the actual # of usable gears on a bike, which is less than the stated number by the manufacturer. For instance, on my bike, which supposedly has 24 gears (3 in front, 8 in back), I only actually have 16 usable gears, and not 24. The formula can be expressed in this form: (# of speeds by manf) - (# of rear sprockets) = actual # of usable gears ex. 24 - 8 = 16 usable Note that this formula only works if you have 3 sprockets in the front, and any number in the back. What if the bicycle has half-step gearing? Or Alpine gearing? cheers, Tom -- Nothing is safe from me. I'm really at: tkeats curlicue vcn dot bc dot ca |
#9
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Formula for actual # of usable gears
On Jun 19, 12:18 am, Ablang wrote:
Due to cross-chaining issues, I came up w/ a formula for the actual # of usable gears on a bike, which is less than the stated number by the manufacturer. For instance, on my bike, which supposedly has 24 gears (3 in front, 8 in back), I only actually have 16 usable gears, and not 24. The formula can be expressed in this form: (# of speeds by manf) - (# of rear sprockets) = actual # of usable gears ex. 24 - 8 = 16 usable Note that this formula only works if you have 3 sprockets in the front, and any number in the back. I don't know how many usable gears I have nor do I care. I'm only concerned with which ones I use, which on my road bike is probably about 6 and on my mtb about 10. |
#10
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Formula for actual # of usable gears
On Sat, 21 Jun 2008 12:41:24 -0700 (PDT), bluezfolk
wrote: I don't know how many usable gears I have nor do I care. I'm only concerned with which ones I use, which on my road bike is probably about 6 and on my mtb about 10. I use all 20 gears on my latest road bike. Yes, some are redundant. This is a good thing, means I don't have to change rings. If I had a 53-11, that would be unusable, I'm not strong enough. My tourer's big-big 48-32 used to just lock the chain if I was exhausted enough to try it, that was unusable. |
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