Why are the sprockets on the crank inverse from the sprockets on the cassette?
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Why are the sprockets on the crank inverse from the sprockets on the cassette?
If you start from the frame and count outwards, the cassette goes large gear, smaller gear, smaller gear, etc. On the crank, assuming you have a double or a triple, they go smaller, larger, larger.
I know there is a good and probably obvious reason, but I am not mechanical enough to figure it out by intuition. Could someone please tell me?
Thanks.
I know there is a good and probably obvious reason, but I am not mechanical enough to figure it out by intuition. Could someone please tell me?
Thanks.
#2
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So it looks better.
So you don't have to crossover to get max high and low gears.
So there are fewer rings that can come in contact with your calf.
Howzat?
So you don't have to crossover to get max high and low gears.
So there are fewer rings that can come in contact with your calf.
Howzat?
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look at how the derailleur functions. it would be much more complicated to try to shift gears if you had to navigate between the crank arm and the big chain ring.
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I've got another:
So the right side chainstay has got more clearance from the rings.
This is fun!
So the right side chainstay has got more clearance from the rings.
This is fun!
#6
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If you start from the frame and count outwards, the cassette goes large gear, smaller gear, smaller gear, etc. On the crank, assuming you have a double or a triple, they go smaller, larger, larger.
I know there is a good and probably obvious reason, but I am not mechanical enough to figure it out by intuition. Could someone please tell me?
Thanks.
I know there is a good and probably obvious reason, but I am not mechanical enough to figure it out by intuition. Could someone please tell me?
Thanks.
#7
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also try sticking a 34T where the 11T would usually go, you'll find that the cog will be grinding away at your stays.
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https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
#8
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The opposite arrangement would create poor chainlines and the big ring would hit the chainstay.
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Envision the chain as it comes off a small outer chainring bumping into the bigger inner ring as you shift to a large inner sprocket on the rear.
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There are some exceptions to the rule
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See here: https://www.bikexprt.com/bicycle/tancrank.htm
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The chainline argument never quite made sense to me since to get to the middle of the total gear range, where presumably you're spending most of your time, you're going to be somewhat cross-chained. Of course, the tradeoff of the reversed setup is that your lowest and highest gears might be unusable, but you can likely work around that.
Seat/chainstay clearance is of course the big problem, and you can't easily do anything about that.
Seat/chainstay clearance is of course the big problem, and you can't easily do anything about that.
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Same-side sync drives are used for a number of reasons:
- They're economical in that they use two standard cranksets instead of a more expensive tandem cross-over crankset.
- They put less wear and tear on the rear bottom bracket, not that that's a big issue as bottom brackets are pretty beefy.
- They move all the chains to one side of the bike.
- Etc...
As to why the timing ring was put outboard instead of inboard for a same-side drive, there are some plusses and minuses on putting them inboard vs. outboard and it ultimately comes down to chain stay clearance, chain lines and things that are gemane to each tandem.
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...might get a little crowded around the f. derailleur, though.
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Single-side drive doesn't require expensive tandem-specific cranksets, is a pretty good reason.
See here: https://www.bikexprt.com/bicycle/tancrank.htm
See here: https://www.bikexprt.com/bicycle/tancrank.htm
#17
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The chainline argument never quite made sense to me since to get to the middle of the total gear range, where presumably you're spending most of your time, you're going to be somewhat cross-chained. Of course, the tradeoff of the reversed setup is that your lowest and highest gears might be unusable, but you can likely work around that.
Seat/chainstay clearance is of course the big problem, and you can't easily do anything about that.
Seat/chainstay clearance is of course the big problem, and you can't easily do anything about that.
I am having a hard time imagining a rear cassette with big cog on the outside, even absent chainline and seatstay issues. Logically it just makes sense to me to move chain in same direction both front and rear to move to higher gears (i.e. to the right). Also, when shifting from small ring/cog to larger, because I am in essence lifting the chain up to get from smaller to larger, pushing the lever on my shifters in the same direction the chain is moving (i.e. to the left for right shifter/rear cogs and to the right for left shifter/front rings) also makes logical sense to my brain. Could be, however, I am just used to what I am used to and could get used to doing things backwards.
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you can get a high rise RD which would reverse the low normal and high normal thing.
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Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
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Also, when shifting from small ring/cog to larger, because I am in essence lifting the chain up to get from smaller to larger, pushing the lever on my shifters in the same direction the chain is moving (i.e. to the left for right shifter/rear cogs and to the right for left shifter/front rings) also makes logical sense to my brain. Could be, however, I am just used to what I am used to and could get used to doing things backwards.
In any case, I don't deny that there are other, probably more important, reasons to do things the way we do now. I just don't think that improved chainline is one of them in most situations.
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The Q-factor for the stoker is exactly the same as if it were a standard triple - less than it would be for a triple with a synch chainring on the left side too.
I'm not sure how they got the synch chain line right though - maybe the BB shell is not symetrical, or maybe the synch chain is so long the chain line isn't that critical.
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IIRC, Sun Tour made a front derailleur that was in effect "Rapid Rise", that is the spring tension moved the cage toward the big chainring and the cable tension pulled it toward the smaller rings. The reasoning here was to have both shifters do the same thing (upshift or downshift) while moving in the same direction. It never really caught on.
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The ability to accomodate the height difference without any modifications was the reason I went with this Bike Friday tandem instead of something more conventional.
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Not germane to chain line but many old tandems from the 1890s or so did have the lady up front as the old rules of courtesy included "ladies first". Most such setups included remote steering so that the stoker could steer the bike. Many had both capable of steering so that the strongest presumably won! Usually set up so the stoker had a higher saddle to look over the head of the captain. Added complication to meet the requirements of Victorian etiquette.
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