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  1. #1
    Professional Fuss-Budget Bacciagalupe's Avatar
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    Gearing Geekiness for Folding (20") Bikes

    So, I'm thinking about a Xootr Swift as an upgrade from my Dahon Mariner D7, and checking out the gearing. I'm not a "gear nerd" and am trying to figure out if I understand the differences, which seem to go a little something like this:

    Mariner D7
    50T x 11/30, 33" - 90"

    Xootr Swift - Stock
    52T x 11/28, 36" - 92"

    Xootr Swift - Different Cassette
    52T x 11/32, 32.5" x 92"

    Bike Friday NWT 24-speed
    52/42/30 x 11/32, 18.75" x 94"

    700c Road Bike w/Triple
    52/42/30 x 12/26, 33" x 125"

    700c Touring Bike w/Triple
    52/40/30 x 11/32, 27" x 137"

    I assume the stock Xootr will be a little slower up hills than the Mariner, with a little higher top speed. The NWT's range seems to go very low (which makes sense for that bike). But it seems odd that some of the folding bikes with a single will have almost as low a gear as a 700c road bike.

    So is it that the single crank loses a lot of efficiency due to the indirect chain in the low gears? Or that road bike designers are intentionally picking that gear range? And do a few inches on the low end really make a huge difference?

    Last but not least.... Will moving from an 11/28 to an 11/32 on the Xootr (as recommended by flyhi46c) make for a more troublesome drive train -- i.e. more chain stretch, rougher gear shifting, higher chance of chain jumps etc?

    Thanks!
    B

  2. #2
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    On paper this is a simple math equation but in reality the bike goes as fast as the engine(you).
    This all depends on riding conditions(flat,hilly,mountains) and your riding style.
    Do you spin at 90-100 rpm or do you mash at 70-80rpm.
    For example I have a road bike that is a double 50-39 with a 12-27. I rarely get to the 50-12 combination unless I am going downhill very fast. I just cannot turn the 12 or 13 for that matter for any length of time.
    Other riders might spend most of their time on those gears.
    I would not buy a bike simply by the gear calcs. There are too many other factors involved.
    Yes your calculations do look correct.
    Kenal0

  3. #3
    Cyclin' twosome
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    Nope, the efficiency loss due to normal derailleur chainline variations is minimal (& probably not noticeable).
    Yep, the mfg build lots in that range 'cause it suits most people's needs.
    Yep, a few inches at the low end can make a big difference. You'll also probably find that, all else being equal, you can turn a taller gear climbing the same hill with a 20"-wheeled bike (accelerates easier w/less effort due to less mass/inertia).

  4. #4
    Member, Schmember DaFriMon's Avatar
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    With most of the 8 speed models, I think that folder makers go for a happy medium. They don't expect people to race these, anyway.

    With the specific Bike Friday NWT setup mentioned, remember that this bike is set up for loaded touring, where low gears may be wanted more often, and the highest gears can be sacrificed. Some other BF setups will use enormous chainrings, up to 60t, to get higher gears. My Crusoe has a big ring of 58, which gives me 98 gear inches at the top, allowing for actual diameter of the tire.


    Other solutions to getting higher gears on folders include Capreo components, SRAM dual-drive systems, Rohloff hubs, and Schlumpf bottom brackets. All these have their plusses and minuses.

    Many road bikes are designed for people who either race, or want to think that they could. No particular reason to copy this for most folder riders.

    A Xootr will have a lighter, and (I'm told) stiffer frame than the Mariner. Dial in your riding position, make sure you have a decent pair of tires, and I'd expect you to be a lot faster on the Xootr, independent of the slight difference in gearing range.

    By the way, for accurate gear inches calculations, don't forget to use the actual diameter of the tire. 406 "20 inch" tires will be closer to 19 inches than 20. The ones I use on my own bikes range from 18.7 to 19.3.
    Last edited by DaFriMon; 06-09-06 at 01:44 PM.
    You're right, I do have more bikes than I need.

  5. #5
    All ur bike r belong Enki james_swift's Avatar
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    Yeah, tires definitely need to be taken into consideration. For instance, my single-speed 52x14 produces 69 gear inches with Primo Comet 20x1.35 tires (18.75" dia). The same drivetrain with Kenda Kwest 20x1.50 tires produces 72 gear inches (19.5" dia).

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    Quote Originally Posted by Bacciagalupe
    So, I'm thinking about a Xootr Swift as an upgrade from my Dahon Mariner D7, and checking out the gearing. I'm not a "gear nerd" and am trying to figure out if I understand the differences, which seem to go a little something like this:

    Mariner D7
    50T x 11/30, 33" - 90"

    Xootr Swift - Stock
    52T x 11/28, 36" - 92"

    Xootr Swift - Different Cassette
    52T x 11/32, 32.5" x 92"

    Bike Friday NWT 24-speed
    52/42/30 x 11/32, 18.75" x 94"

    700c Road Bike w/Triple
    52/42/30 x 12/26, 33" x 125"

    700c Touring Bike w/Triple
    52/40/30 x 11/32, 27" x 137"

    I assume the stock Xootr will be a little slower up hills than the Mariner, with a little higher top speed. The NWT's range seems to go very low (which makes sense for that bike). But it seems odd that some of the folding bikes with a single will have almost as low a gear as a 700c road bike.

    So is it that the single crank loses a lot of efficiency due to the indirect chain in the low gears? Or that road bike designers are intentionally picking that gear range? And do a few inches on the low end really make a huge difference?

    Last but not least.... Will moving from an 11/28 to an 11/32 on the Xootr (as recommended by flyhi46c) make for a more troublesome drive train -- i.e. more chain stretch, rougher gear shifting, higher chance of chain jumps etc?

    Thanks!
    B
    To answer you about upgrading the Xootr 11/28 to 11/32...no problems at all...once I understood how to adjust indexed gears. This was my first foray into bike 'upgrades' and it was simply a matter of reading the Park tools website, SRAM website, and understanding the tools needed and the potential problems. I bought another chain just in case I might have needed more length for the 11/32, but it was not required. Actually the gears shift better, more cleanly than before....I think the stock chain was too long for the 28 tooth cog. There is a huge difference for me (bad right knee) with the 32 cog on hills. You could go to a 34cog with the SRAM derailler provided, but then I think you would need to go to a 9 speed shifter. flyhi46c

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    Smaller tires require less torque. Look at the crank set of a strida.com. It is gigantic because it has tiny wheels. Basically as the wheels get smaller, the crank set gets larger. You can play with a 'moment diagram' if you did well in HS physics.

    I personally doubt that gearing will be a problem. The issue on bikes with smaller wheels is shocks and vibrations (which may not bother you). Going off a curb on a 16" Strida is like getting kicked in the ass, barely feel it on my 26" Monty.
    2000 Montague CX, I do not recommend it, but still ride it.
    Strida 3, I recommend it for rides < 10mi wo steep hills.
    2006 Rowbike 720 Sport, I recommend it as an exercise bike.
    1996 Birdy, Recommend.
    Wieleder CARiBIKE (folding), decent frame.

  8. #8
    Professional Fuss-Budget Bacciagalupe's Avatar
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    OK, allow me to specify my query a bit, in the light of the above comments...

    The thing that confuses me the most is why you'd make a road bike with a triple, when it winds up with almost the same gearing range as a single. A triple makes lots sense for a touring bike where you may have to lug 50 lbs of gear up hills all day. But it seems like it'd be easy to have a double with fairly smooth shifting and the same range as the triple, no?

    The other thing I'm trying to figure out is whether the stock Xootr will have the right gearing for the type of riding I do, so I'm trying to figure out if the 3" in the low end is critical. Part of it is I have a hybrid with a very low gear (23"), but going into the granny gears on a typical hill around here only feels like it's "one gear" (maybe 1.5) lower than what the Mariner can do.

    I'm also a bit stuck on the idea that frame rigidity will make a big difference in terms of performance/speed. A little bit counter-intuitive for me, I guess.

  9. #9
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    Quote Originally Posted by Bacciagalupe
    So, I'm thinking about a Xootr Swift as an upgrade from my Dahon Mariner D7, and checking out the gearing.

    I assume the stock Xootr will be a little slower up hills than the Mariner, with a little higher top speed. The NWT's range seems to go very low (which makes sense for that bike).
    The Xootr/Swift would be a logical upgrade to the Mariner D7 if you are looking for a stiffer, higher quality, performance oriented bike... The Xootr with the stock gearing (even with a higher low gear) would probably be as fast up your hills because you would be able to get more of 'your' energy into the rear wheel due to the lack of steering post flex with the Xootr over the Mariner (with it's long steering post).. you would also be more comfortable pedalling out of saddle with the Xootr beause of it's geometry, which would also make you faster up your hill...


    Quote Originally Posted by Bacciagalupe
    But it seems odd that some of the folding bikes with a single will have almost as low a gear as a 700c road bike.

    Road bikes usually have tightly clustered rear cassettes to keep the gear jumps close.. much like driving a close-ratio 6spd car over a 3spd..

    Quote Originally Posted by Bacciagalupe
    So is it that the single crank loses a lot of efficiency due to the indirect chain in the low gears? Or that road bike designers are intentionally picking that gear range? And do a few inches on the low end really make a huge difference?
    Depending on how steep your hills are that you need to climb and your personal horsepower, a few inches can make a lot of difference... when you get down in the low 20's however, you are almost at walking speed and some prefer to walk..

    Quote Originally Posted by Bacciagalupe
    Last but not least.... Will moving from an 11/28 to an 11/32 on the Xootr (as recommended by flyhi46c) make for a more troublesome drive train -- i.e. more chain stretch, rougher gear shifting, higher chance of chain jumps etc?

    Thanks!
    B
    I installed a 9spd 11/34 on my Xootr/Swift and am running a 58t chainwheel with no issues.. I am also running an inexpensive 'roller kit' that Gaerlan sells to keep the chain from jumping off of the chainwheel..

    Bruce

  10. #10
    Senior Member Speedo's Avatar
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    Quote Originally Posted by Bacciagalupe
    OK, allow me to specify my query a bit, in the light of the above comments...

    The thing that confuses me the most is why you'd make a road bike with a triple, when it winds up with almost the same gearing range as a single. A triple makes lots sense for a touring bike where you may have to lug 50 lbs of gear up hills all day. But it seems like it'd be easy to have a double with fairly smooth shifting and the same range as the triple, no?
    No. As a practical matter, most common road bike (vice MTB) rear derailleurs can only take freehub cogs of 27 or 28 teeth. Current Ultegras are 27 teeth max. Most common road bike (vice folding bike) minimum sprockets are 11 or 12 teeth. To get the full range out of a double that you get out of a triple (given the restrictions on the freehub cogs) you'd have to have a large spread on your chainring sizes. But the front derailleur can only handle jumps between chainrings of say 12 teeth. So, to get that big range, you need that extra chainring.

    Oh, and I think you may be confused about the "single". Some of those bikes have planetary gears in the hub that increase the range of available gear ratios. They are really the same as a "single".

  11. #11
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    Permit me to re-start this thread with a variation on Bacciagalupe's original question.

    Let's suppose my typical cruising gear on a Swift (or any equivalently spec'd 406-sized folding bike) with a 9-speed cassette is 6th, which translates into a 52x17 gearing. Using Sheldon Brown's gear calculator to calculate gain ratios, I find that pedaling in 6th gear yields a ratio of 4.3x, i.e. for every inch that the pedal travels, the bike moves 4.3 inches.

    Now, if I plug in specs for a typical road bike, say with 700x28 wheels and the same size chainring, I find that the 52x17 combination yields a gain ratio of 6.1x, which is over 40% greater than the Swift. Thus, it appears that for the same amount of effort, the road bike travels 40% further than the bike with the smaller wheels.

    (While the example above is for the 52x17 gear, it is, mathematically speaking, true that for any 2 bikes with identical gearing, the bike with the larger tires will have a higher gain ratio than the bike with the smaller tires.)

    So here's my question: is 52x17 on the 406 size tire in fact the same amount of work as 52x17 on the 700 size tire? Put another way, if I could spin 100 RPMs on the 406 size tire, does that translate into spinning 100 RPMs on the 700 size tire as well, or would I only be able to do 60 or 80 RPMs (for example), largely canceling out the greater efficiency connoted by the gain ratio?

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    2000 Montague CX, I do not recommend it, but still ride it.
    Strida 3, I recommend it for rides < 10mi wo steep hills.
    2006 Rowbike 720 Sport, I recommend it as an exercise bike.
    1996 Birdy, Recommend.
    Wieleder CARiBIKE (folding), decent frame.

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    geo8rge, yes, that's exactly the gear calculator that I'm using. Let me pose the question differently.

    Suppose two bikes have identical drivetrains--for simplicity, let's say they're both singlespeed 52x17--but one bike has 700x28 tires and the other 20"x1.50" tires. Using the MPH @ 100 RPMs setting of Sheldon's gear calculator, the bike with the 700 size tires would be moving at about 24 mph while the bike with 20" tires would be moving at about 17 mph. That's a major speed penalty for what (on paper, at least) is the same amount of pedaling effort.

    The reason for my question is this: my father-in-law has a road bike, and I have a Swift, and if we go riding together (all else being equal), based on the gear calculator I'm not at all convinced that I'd be able to keep up with him if I have to exert 40% more effort to achieve the same speed.

    Thoughts?

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    Senior Member caotropheus's Avatar
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    Quote Originally Posted by dubes
    geo8rge, yes, that's exactly the gear calculator that I'm using. Let me pose the question differently.

    Suppose two bikes have identical drivetrains--for simplicity, let's say they're both singlespeed 52x17--but one bike has 700x28 tires and the other 20"x1.50" tires. Using the MPH @ 100 RPMs setting of Sheldon's gear calculator, the bike with the 700 size tires would be moving at about 24 mph while the bike with 20" tires would be moving at about 17 mph. That's a major speed penalty for what (on paper, at least) is the same amount of pedaling effort.

    The reason for my question is this: my father-in-law has a road bike, and I have a Swift, and if we go riding together (all else being equal), based on the gear calculator I'm not at all convinced that I'd be able to keep up with him if I have to exert 40% more effort to achieve the same speed.

    Thoughts?
    My thoughts go to your phisiology and the amount of watts you can spill on the pedals. For smaller gain ratio your legs spin faster. That's the bottom line. If you make a test like setting the same gear combination of 52x17 on both the 20 inch wheeler and the road bike for 2 km on a flat road, you may be quite surprised how close the timing will be to preform those 2 km in such different bicycles. I suggest you make this test several times and by the end calculate the avarage time for each bicycle. But for this test there is one condition, you have to use similar tires with the same pressure and similar drive trains.
    Last edited by caotropheus; 08-31-06 at 06:43 AM.

  15. #15
    Neat - w/ ice on the side dalmore's Avatar
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    Quote Originally Posted by dubes
    geo8rge, yes, that's exactly the gear calculator that I'm using. Let me pose the question differently.

    Suppose two bikes have identical drivetrains--for simplicity, let's say they're both singlespeed 52x17--but one bike has 700x28 tires and the other 20"x1.50" tires. Using the MPH @ 100 RPMs setting of Sheldon's gear calculator, the bike with the 700 size tires would be moving at about 24 mph while the bike with 20" tires would be moving at about 17 mph. That's a major speed penalty for what (on paper, at least) is the same amount of pedaling effort.

    The reason for my question is this: my father-in-law has a road bike, and I have a Swift, and if we go riding together (all else being equal), based on the gear calculator I'm not at all convinced that I'd be able to keep up with him if I have to exert 40% more effort to achieve the same speed.

    Thoughts?
    Two points that you seem to be omitting from your calculations. First, the wheel and tire is part of the drivetrain. So 52/17 mated to a 700x28 is not equivalent to a 52/17 mated to a 20x1.50. Second Sheldon's gain ratio is a movement multipler, not a measure of work. Work is force times movement and his ratio only deals with movement. It's an accurate movement multiplier but without a force component you can not use it to measure work. The amount of work done and the amount of energy used to do that work in your example is greater on the 700 with a 52/17 than on the 20x1.50 with a 52/17.

    Getting to the point of your question - if you on your bike and your father on his are roughly the same weight and have roughly the same aerodynamic profile - then you will be doing roughly the same amount of work to maintain the same speed. I have no trouble keeping up with big wheeled bikes on my folder until they get into gear ranges that I don't have. ie above 90-95 gear inches. Once your father gets into his higher gears, you will have no choice but to raise your cadence to keep up. If you can pedal at a cadence of 100 and he's at a cadence of 80, then you will keep up when he's running a gear roughly 20 percent higher than yours. Hope that helps.
    Current favorite bumper sticker: Wag more. Bark less.

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    Quote Originally Posted by caotropheus
    If you make a test like setting the same gear combination of 52x17 on both the 20 inch wheeler and the road bike for 2 km on a flat road, you may be quite surprised how close the timing will be to preform those 2 km in such different bicycles. I suggest you make this test several times and by the end calculate the avarage time for each bicycle. But for this test there is one condition, you have to use similar tires with the same pressure and similar drive trains.
    caotropheus, that's a good suggestion but the only bikes I have are a Swift (my distance weekend rider) and a Downtube (my commuter)--both 20" wheels! I can't try my father-in-law's bike because it's tool tall for me (he's about 4 inches taller than I am), plus he uses clipless pedals (I haven't taken that plunge yet; I'm still experimenting with the more cost-effective Power Grips ). And he can't try the Swift because the seat post is too short for him.


    Quote Originally Posted by dalmore
    Two points that you seem to be omitting from your calculations. First, the wheel and tire is part of the drivetrain. So 52/17 mated to a 700x28 is not equivalent to a 52/17 mated to a 20x1.50. Second Sheldon's gain ratio is a movement multipler, not a measure of work. Work is force times movement and his ratio only deals with movement. It's an accurate movement multiplier but without a force component you can not use it to measure work. The amount of work done and the amount of energy used to do that work in your example is greater on the 700 with a 52/17 than on the 20x1.50 with a 52/17.
    Dalmore, your comment cuts directly to the heart of my question, i.e. whether the driving effort the same for the two bikes.


    Quote Originally Posted by dalmore
    Getting to the point of your question - if you on your bike and your father on his are roughly the same weight and have roughly the same aerodynamic profile - then you will be doing roughly the same amount of work to maintain the same speed. I have no trouble keeping up with big wheeled bikes on my folder until they get into gear ranges that I don't have. ie above 90-95 gear inches. Once your father gets into his higher gears, you will have no choice but to raise your cadence to keep up. If you can pedal at a cadence of 100 and he's at a cadence of 80, then you will keep up when he's running a gear roughly 20 percent higher than yours. Hope that helps.
    Indeed it does, thanks!

  17. #17
    Senior Member Speedo's Avatar
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    Really I'm just +1 on what Dalmore said.

    Quote Originally Posted by dubes
    The reason for my question is this: my father-in-law has a road bike, and I have a Swift, and if we go riding together (all else being equal), based on the gear calculator I'm not at all convinced that I'd be able to keep up with him if I have to exert 40% more effort to achieve the same speed.
    You won't have to exert 40% more effort. The effort you expend is in overcoming friction in the drive train, rolling resistance, aerodynamic drag (the dominant effect as you go faster) and climbing hills. For the most part what you will really notice is the aero drag and climbing. At the same speed that effort will be approximately the same for you and your father-in-law. There might be some small differences due to specifics of the bikes, but I would come down on the side of a shiny, new, clean Swift vs your father-in-law's old, rust encrusted touring bike there.

    The whole point behind the gear inches, development, gain ratios and what have you, is to describe the fundamental mechanics of your drive train without regard to the specifics of the wheel diameter and gear ratios. Here's a useful equation.

    RPM=336.14*MPH/G

    MPH=speed in miles per hour
    G=gear inches of the gear you are in
    RPM=pedal revs per minute to achieve that speed

    Suppose you and your father in law are cruising along at 18 MPH. You will probably be in your (19.5*52/14) 72.43 inch gear. You will be pedaling at 83.54 RPM. Your father-in-law might be in a gear like (26.5*42/15) 74.20 inches. (note: my 700x28 tires have a 26.5 inch diameter) He will be pedaling with a cadence of 81.54 RPM. Your perceived effort and your father-in-law's perceived effort will be the same.

    As Dalmore notes, suppose you get to a downhill, and your father-in-law starts cranking that big 115 inch gear at 100 RPM, he'll still be putting effort into overcoming aero drag at 34 MPH. You have a top gear of around 92 inches, and you can only move your legs so fast. You will "spin-out" at say 110 RPM when you reach 30 MPH. You won't be able to put any more effort into overcoming air resistance, and your father-in-law will pull away.

    You, as an engine, have some range of pedal RPM that you will be most efficient in. For most people it's in the range of 80-90 RPM. You may have a personal preference that makes you a fast or a slow spinner. Riding with another person you select a gear that puts you in that range of RPM for the speed you are riding. In the road bikes with multiple chainrings the big gear range can be achieved by big differences in the chainrings, and the cassette cogs can be tightly spaced. That way, for any given desired speed you can find a gear that puts you close to your RPM sweet spot. On a stock Swift the cassette cogs provide all of the gear range. So, the gears are not as closely spaced as on the road bike. You might find that your father-in-law is sligtly more efficient because he can get closer to his RPM sweet spot. It's a small effect, but you might notice it. I would expect that youth and strength would prevail in that case, and you still would have no problem keeping up.

    Speedo

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    Can you keep up with your father in law on a road bike now if you are on a road bike? If the answer is yes then you will be close on the swift. I ride my Bike Friday and go the same speed and cadence as my full size roadie. Roadie has a 50 with a 12-27. I cruise in the 19 and 17 on the full size. Bike Friday has a 53 with a 12-26, I cruise in the 14 and 15 on that bike. Both running in the high 90's cadence and both go the same speed.
    My guess is you could keep up with him if your engine is good.
    If not then grab his rear wheel and have him tow you around for the day!
    Kenal0

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    Speedo and Kenal0,

    Thanks for the additional comments/insights. I've never ridden with him (except in the car ), so I don't know what he's capable of. Unfortunately, I wouldn't be chasing down a rusted out touring bike but a sleek titanium racer. (Fortunately, the "engine" is a pair of 60+ year old legs--though he does keep in good shape for his age.)

    That said, I've also been wondering about group rides and things--I don't want to be a drag on anyone. It sounds like if I am, though, I can't blame the Swift!

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    Wheel size is absolutely unimportant for the purposes of this discussion. The 20" wheels being discussed have all been geared by the various manufacturer's mentioned to feel as much like full size 700C wheels as possible and therefore will need corresponding crank lengths! My Giant Halfway is equipped with a 48T chainwheel and a 13-28 7sp cassette and standard length cranks. Using Sheldon Brown's calculator and the 20" nominal tire size (a 406 is not available) yields a 34" - 74" gear spread. Using the BMX tire size it is 32" - 70". I can tell anyone considering a new bike to think more about the low end than the high end. I am glad I did not second guess Giant and have the front ring changed to a 50 or 52 before riding it. I use that 28T lots with the 48T. I use the 13T lots too. About the only improvement to this setup that I would make if I could would be to have a 9sp so as to add an 11 tooth on the top and a 32 tooth low. I think the 9sp Downtube is geared pretty much this way. My next bike may be the Downtube 9sp. Give conservatively geared bikes a chance, I think you'll like it.

    H

  21. #21
    Senior Member Speedo's Avatar
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    Quote Originally Posted by dubes
    Speedo and Kenal0,

    Thanks for the additional comments/insights. I've never ridden with him (except in the car ), so I don't know what he's capable of. Unfortunately, I wouldn't be chasing down a rusted out touring bike but a sleek titanium racer. (Fortunately, the "engine" is a pair of 60+ year old legs--though he does keep in good shape for his age.)
    The Swift will be working in your favor. A 60+ year old with a titanium racing bike is probably gear head enough to be fascinated by your folder. He may even want to switch bikes to give it at try! Either way you'll have a great ride.

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    Quote Originally Posted by Speedo
    The Swift will be working in your favor. A 60+ year old with a titanium racing bike is probably gear head enough to be fascinated by your folder. He may even want to switch bikes to give it at try! Either way you'll have a great ride.
    LOL! While he acknowledges the Swift has a "cool" look to it, he doesn't (yet) consider it to be a real bike--no matter how much I ride it. But if I can keep up with him, he just might have to take a test drive!

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    Professional Fuss-Budget Bacciagalupe's Avatar
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    Update

    OK, so I swapped out the 11-28T for an 11-32T on the Swift. Riding on the flats seems fairly normal (more on this in a bit). I haven't hit any big hills on it yet, but even on an easy hill I felt a major difference between a low end of 32" vs 36." And yet, questions remain...

    I've done a few more calculations to try and figure out how the cassette switch will impact my riding. I noticed that about half of the rings have the same teeth, it's gears 1, 2, 5 and 6 that change.

    On average, changing from one gear to the next on the Swift with an 11-28T, at a cadence of 80 (just picked as a sample) is 1.95mph. With the 11-32T, the average is 2.11mph. On a road bike with a compact double, it's closer to 1.6mph.

    So just out of curiosity, how is this going to affect my "cruising speed," if at all?

  24. #24
    Senior Member Speedo's Avatar
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    Quote Originally Posted by Bacciagalupe
    Update

    OK, so I swapped out the 11-28T for an 11-32T on the Swift. Riding on the flats seems fairly normal (more on this in a bit). I haven't hit any big hills on it yet, but even on an easy hill I felt a major difference between a low end of 32" vs 36." And yet, questions remain...

    I've done a few more calculations to try and figure out how the cassette switch will impact my riding. I noticed that about half of the rings have the same teeth, it's gears 1, 2, 5 and 6 that change.

    On average, changing from one gear to the next on the Swift with an 11-28T, at a cadence of 80 (just picked as a sample) is 1.95mph. With the 11-32T, the average is 2.11mph. On a road bike with a compact double, it's closer to 1.6mph.

    So just out of curiosity, how is this going to affect my "cruising speed," if at all?
    The granularity is an issue. You, Mr. Bacciagalupe, have a cadence/power sweet spot. It's the point where at a reasonable level of torque you will spin at a cadence that is comfortable, and that you can sustain for long periods of time. For most people it falls into the 80-90 RPM range. Fortunately the sweet spot is somewhat broad, but if you are forced to spin much higher, or much lower than you are comfortable, you will tire more quickly than you would in your sweet spot. In a world with a perfect continuum of gears, given a speed you were trying to maintain, you would dial in the gear that put you in your sweet spot. By going to an 11-32, some of the gears you now have available are more widely spaced. So, you are less likely to be able to hit your sweet spot. If you are riding with a others then this will be more noticable. The group settles into a speed, and you try to find the gear that will be comfortable at that speed. With a coarser granularity, you might not be able to find a gear that is just right. If you are riding by yourself you will probably just settle into speeds at which your gears put you in your sweet spot.

    If it really begins to bug you, you might try going to a nine speed cassette and deraillleur. the granularity for an 11-32 nine speed is about the same as an 11-28 eight speed.

    Good luck

  25. #25
    Professional Fuss-Budget Bacciagalupe's Avatar
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    Quote Originally Posted by Speedo
    The granularity is an issue. You, Mr. Bacciagalupe, have a cadence/power sweet spot.... By going to an 11-32, some of the gears you now have available are more widely spaced. So, you are less likely to be able to hit your sweet spot....
    Curiouser and curiouser. I guess that due to changing conditions during any ride -- wind, incline etc. there won't be the One True Gear that hits my output.

    Yet another reason why it looks like the stock Xootr Swift is less than optimal for fast group rides. But having the lower gear is worth it, it makes a huge difference on the hills.

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