Has anybody tried a 4-chainring crankset?

Discussion in 'Recumbent bicycles' started by Hugh Johnson, Feb 28, 2003.

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  1. Hugh Johnson

    Hugh Johnson Guest

    Last week I graduated from a Rocket to a V-Rex, because, I guess, I'm just hungry for speed. So I've
    been sprinting around on the V-rex ever since (still too wintery for a serious ride), and I've been
    feeling a little let-down by the small chainrings. I thought I'd have to get some bigger rings at
    high cost, but then I saw a closeout deal on complete Rocket cranksets, so I bought one, just for
    the rings.

    Haven't installed the rings yet. It's not a simple swap, after all; there are complications. I'll
    need to replace my front derailleur with a "bottom-swing" type, to move the cage higher than the
    top of the mounting tube (the mock seat tube), and I'll have to add a few links to my chain, and
    maybe a new shift cable, and who knows what other problems will crop up. But, I've been eyeballing
    it, and imagining my granny with 9 more teeth, and thinking it over, and there's something I'm
    wondering about...

    What if I could keep my current granny ring, or better yet, keep all my current rings, but move them
    inward with spacers -- and then just put the big Rocket 62t ring in the outtermost position? I would
    have four chainrings, not three. If I can find a bottom-swing derailleur with a sufficiently wide
    range of movement, and either a very long cage or a cage that I can lengthen (maybe add a steel
    stiffener if necessary), this should be doable, should it not?

    Obviously there will be lots of chain slack when I'm using the granny, but the V-rex rides high
    enough to keep it way off the ground, and I won't use the granny very often anyway. The granny,
    being spaced inward close to the bike tube, might cause the chain to chaff a bit in the front idler
    pully, but again, it's not going to happen very often, and the granny puts the least strain on
    things anyway. My front shifter is indexed for a nine-speed cassette (SRAM does that so they're
    interchangable for southpaws, I think), so there should be plenty of ways I can adjust it to a
    4-ring crankset...

    Well, I guess that's one of the big questions I have. Will I be able to tweak my shifter for these
    four chainring positions?

    And where can I find the sort of derailleur I need? Do they exist? What do I ask for?

    And the biggest question: has anybody done this before? Is it doable? Are there any big drawbacks?
    Or just tell me what you think.

    Thanks in advance.
     
    Tags:


  2. Pete Huber

    Pete Huber Guest

    Hugh,

    I have used four chainrings on my Speed Ross for several years using a now discontinued Avid
    adapter. As a result I have 20-30-42-60 chainrings and use an 11-21 rear cassette. This combination
    allows for maximum range with minimum change between gears. I use a second chain tentioner and a
    fair amount of modification to the front derailler (removing the stop screws, filing down stop
    points, etc). In spite of these modifications, shifting is not ideal but the gearing works well.

    Hope this is helpful.

    Pete Huber Speed Ross Pulaski, VA

    "Hugh Johnson" <[email protected]> wrote in message
    news:[email protected]...
    > Last week I graduated from a Rocket to a V-Rex, because, I guess, I'm just hungry for speed. So
    > I've been sprinting around on the V-rex ever since (still too wintery for a serious ride), and
    > I've been feeling a little let-down by the small chainrings. I thought I'd have to get some bigger
    > rings at high cost, but then I saw a closeout deal on complete Rocket cranksets, so I bought one,
    > just for the rings.
    >
    > Haven't installed the rings yet. It's not a simple swap, after all; there are complications. I'll
    > need to replace my front derailleur with a "bottom-swing" type, to move the cage higher than the
    > top of the mounting tube (the mock seat tube), and I'll have to add a few links to my chain,
    and
    > maybe a new shift cable, and who knows what other problems will crop up. But, I've been eyeballing
    > it, and imagining my granny with 9 more teeth,
    and
    > thinking it over, and there's something I'm wondering about...
    >
    > What if I could keep my current granny ring, or better yet, keep all my current rings, but move
    > them inward with spacers -- and then just put the big Rocket 62t ring in the outtermost position?
    > I would have four chainrings, not three. If I can find a bottom-swing derailleur with a
    > sufficiently wide range of movement, and either a very long cage or a cage that I can lengthen
    > (maybe add a steel stiffener if necessary), this
    should
    > be doable, should it not?
    >
    > Obviously there will be lots of chain slack when I'm using the granny, but the V-rex rides high
    > enough to keep it way off the ground, and I won't use the granny very often anyway. The granny,
    > being spaced inward close to the bike tube, might cause the chain to chaff a bit in the front
    > idler pully, but again, it's not going to happen very often, and the granny puts the least strain
    > on things anyway. My front shifter is indexed for a
    nine-speed
    > cassette (SRAM does that so they're interchangable for southpaws, I
    think),
    > so there should be plenty of ways I can adjust it to a 4-ring crankset...
    >
    > Well, I guess that's one of the big questions I have. Will I be able to tweak my shifter for these
    > four chainring positions?
    >
    > And where can I find the sort of derailleur I need? Do they exist? What do
    I
    > ask for?
    >
    > And the biggest question: has anybody done this before? Is it doable? Are there any big drawbacks?
    > Or just tell me what you think.
    >
    > Thanks in advance.
    >
     
  3. Try Mountaintamer. I have installed a fourth ring on P-38s and GRR. End result 22-32-42-52, with up
    to 11-32 cogs. Shifts well, though tighter cogset is better. "Hugh Johnson" <[email protected]>
    wrote in message news:[email protected]...
    > Last week I graduated from a Rocket to a V-Rex, because, I guess, I'm just hungry for speed. So
    > I've been sprinting around on the V-rex ever since (still too wintery for a serious ride), and
    > I've been feeling a little let-down by the small chainrings. I thought I'd have to get some bigger
    > rings at high cost, but then I saw a closeout deal on complete Rocket cranksets, so I bought one,
    > just for the rings.
    >
    > Haven't installed the rings yet. It's not a simple swap, after all; there are complications. I'll
    > need to replace my front derailleur with a "bottom-swing" type, to move the cage higher than the
    > top of the mounting tube (the mock seat tube), and I'll have to add a few links to my chain,
    and
    > maybe a new shift cable, and who knows what other problems will crop up. But, I've been eyeballing
    > it, and imagining my granny with 9 more teeth,
    and
    > thinking it over, and there's something I'm wondering about...
    >
    > What if I could keep my current granny ring, or better yet, keep all my current rings, but move
    > them inward with spacers -- and then just put the big Rocket 62t ring in the outtermost position?
    > I would have four chainrings, not three. If I can find a bottom-swing derailleur with a
    > sufficiently wide range of movement, and either a very long cage or a cage that I can lengthen
    > (maybe add a steel stiffener if necessary), this
    should
    > be doable, should it not?
    >
    > Obviously there will be lots of chain slack when I'm using the granny, but the V-rex rides high
    > enough to keep it way off the ground, and I won't use the granny very often anyway. The granny,
    > being spaced inward close to the bike tube, might cause the chain to chaff a bit in the front
    > idler pully, but again, it's not going to happen very often, and the granny puts the least strain
    > on things anyway. My front shifter is indexed for a
    nine-speed
    > cassette (SRAM does that so they're interchangable for southpaws, I
    think),
    > so there should be plenty of ways I can adjust it to a 4-ring crankset...
    >
    > Well, I guess that's one of the big questions I have. Will I be able to tweak my shifter for these
    > four chainring positions?
    >
    > And where can I find the sort of derailleur I need? Do they exist? What do
    I
    > ask for?
    >
    > And the biggest question: has anybody done this before? Is it doable? Are there any big drawbacks?
    > Or just tell me what you think.
    >
    > Thanks in advance.
    >
    >
     
  4. Dave Is Here

    Dave Is Here Guest

    Hugh My take is that if you need a real low gear for the uphills you probably don't need such a high
    gear for the downs. Probably by the time that you have 3000 miles in the summer, you won't need the
    granny ring at all. Dave Balfour

    "Hugh Johnson" <[email protected]> wrote in message
    news:<[email protected]>...
    > Last week I graduated from a Rocket to a V-Rex, because, I guess, I'm just hungry for speed. So
    > I've been sprinting around on the V-rex ever since (still too wintery for a serious ride), and
    > I've been feeling a little let-down by the small chainrings. I thought I'd have to get some bigger
    > rings at high cost, but then I saw a closeout deal on complete Rocket cranksets, so I bought one,
    > just for the rings.
    >
    > Haven't installed the rings yet. It's not a simple swap, after all; there are complications. I'll
    > need to replace my front derailleur with a "bottom-swing" type, to move the cage higher than the
    > top of the mounting tube (the mock seat tube), and I'll have to add a few links to my chain, and
    > maybe a new shift cable, and who knows what other problems will crop up. But, I've been eyeballing
    > it, and imagining my granny with 9 more teeth, and thinking it over, and there's something I'm
    > wondering about...
    >
    > What if I could keep my current granny ring, or better yet, keep all my current rings, but move
    > them inward with spacers -- and then just put the big Rocket 62t ring in the outtermost position?
    > I would have four chainrings, not three. If I can find a bottom-swing derailleur with a
    > sufficiently wide range of movement, and either a very long cage or a cage that I can lengthen
    > (maybe add a steel stiffener if necessary), this should be doable, should it not?
    >
    > Obviously there will be lots of chain slack when I'm using the granny, but the V-rex rides high
    > enough to keep it way off the ground, and I won't use the granny very often anyway. The granny,
    > being spaced inward close to the bike tube, might cause the chain to chaff a bit in the front
    > idler pully, but again, it's not going to happen very often, and the granny puts the least strain
    > on things anyway. My front shifter is indexed for a nine-speed cassette (SRAM does that so they're
    > interchangable for southpaws, I think), so there should be plenty of ways I can adjust it to a
    > 4-ring crankset...
    >
    > Well, I guess that's one of the big questions I have. Will I be able to tweak my shifter for these
    > four chainring positions?
    >
    > And where can I find the sort of derailleur I need? Do they exist? What do I ask for?
    >
    > And the biggest question: has anybody done this before? Is it doable? Are there any big drawbacks?
    > Or just tell me what you think.
    >
    > Thanks in advance.
     
  5. Phil Wolfe

    Phil Wolfe Guest

    Where did you see the deal on complete Rocket cranksets if you don't mind me asking? Thanks,
    Phil Wolfe

    dave is here wrote:

    > Hugh My take is that if you need a real low gear for the uphills you probably don't need such a
    > high gear for the downs. Probably by the time that you have 3000 miles in the summer, you won't
    > need the granny ring at all. Dave Balfour
    >
    > "Hugh Johnson" <[email protected]> wrote in message
    > news:<[email protected]>...
    > > Last week I graduated from a Rocket to a V-Rex, because, I guess, I'm just hungry for speed. So
    > > I've been sprinting around on the V-rex ever since (still too wintery for a serious ride), and
    > > I've been feeling a little let-down by the small chainrings. I thought I'd have to get some
    > > bigger rings at high cost, but then I saw a closeout deal on complete Rocket cranksets, so I
    > > bought one, just for the rings.
    > >
    > > Haven't installed the rings yet. It's not a simple swap, after all; there are complications.
    > > I'll need to replace my front derailleur with a "bottom-swing" type, to move the cage higher
    > > than the top of the mounting tube (the mock seat tube), and I'll have to add a few links to my
    > > chain, and maybe a new shift cable, and who knows what other problems will crop up. But, I've
    > > been eyeballing it, and imagining my granny with 9 more teeth, and thinking it over, and there's
    > > something I'm wondering about...
    > >
    > > What if I could keep my current granny ring, or better yet, keep all my current rings, but move
    > > them inward with spacers -- and then just put the big Rocket 62t ring in the outtermost
    > > position? I would have four chainrings, not three. If I can find a bottom-swing derailleur with
    > > a sufficiently wide range of movement, and either a very long cage or a cage that I can lengthen
    > > (maybe add a steel stiffener if necessary), this should be doable, should it not?
    > >
    > > Obviously there will be lots of chain slack when I'm using the granny, but the V-rex rides high
    > > enough to keep it way off the ground, and I won't use the granny very often anyway. The granny,
    > > being spaced inward close to the bike tube, might cause the chain to chaff a bit in the front
    > > idler pully, but again, it's not going to happen very often, and the granny puts the least
    > > strain on things anyway. My front shifter is indexed for a nine-speed cassette (SRAM does that
    > > so they're interchangable for southpaws, I think), so there should be plenty of ways I can
    > > adjust it to a 4-ring crankset...
    > >
    > > Well, I guess that's one of the big questions I have. Will I be able to tweak my shifter for
    > > these four chainring positions?
    > >
    > > And where can I find the sort of derailleur I need? Do they exist? What do I ask for?
    > >
    > > And the biggest question: has anybody done this before? Is it doable? Are there any big
    > > drawbacks? Or just tell me what you think.
    > >
    > > Thanks in advance.
     
  6. Mark Stonich

    Mark Stonich Guest

    > Where did you see the deal on complete Rocket cranksets if you don't mind me asking? Thanks,
    > Phil Wolfe

    Among people who actually know how to pedal a bicycle, replacing the stock Rocket cranks with
    165mm Tiagras (30-42-52) is fairly common. I'll be changing out a set for a friend soon. Want the
    old cranks
    (w/about 500 miles)?

    The original poster wanted to know about a Quad, I've been running one for 15 years.
    > > > And the biggest question: has anybody done this before? Is it doable? Are there any big
    > > > drawbacks? Or just tell me what you think. Thanks in advance.

    It's easy to add a quad to a Rocket crankset, make a ring of 1/8" aluminum plate with 10mm holes in
    both 130mm and 74mm BCD and use it to replace the spacers between the 1st and 2nd rings.

    Bottom swing deraillers won't work well with the giant chainring, extend your der. tube. (If I
    started making aluminum derailleur tube extenders, would they sell?)

    You will need to extend your cage and do something about wrapping up extra chain. See
    http://bikesmithdesign.com/temp/Der2Small.jpg and http://bikesmithdesign.com/temp/WrapUp.JPG

    You will need to have exactly the right BB spindle length. I had to modify an old Suntour BarCon to
    pull enough cable. Your 1-2 and 2-1 shifts will never be reliable with such a large #4 ring.
     
  7. Hugh Johnson

    Hugh Johnson Guest

    Oh no, I don't want a lower low, I want a higher high. I think the Mountain Tamer and other things
    like that are only for lower lows.

    "Alma Williams" <[email protected]> wrote in message
    news:[email protected]...
    > Try Mountaintamer. I have installed a fourth ring on P-38s and GRR. End result 22-32-42-52, with
    > up to 11-32 cogs. Shifts well, though tighter cogset is better.
     
  8. Hugh Johnson

    Hugh Johnson Guest

    When I carry a load, I need the granny on uphills.

    "dave is here" <[email protected]> wrote in message
    news:[email protected]...
    > Hugh My take is that if you need a real low gear for the uphills you probably don't need such a
    > high gear for the downs. Probably by the time that you have 3000 miles in the summer, you won't
    > need the granny ring at all. Dave Balfour
     
  9. Hugh Johnson

    Hugh Johnson Guest

    My lbs, Calhoun Cycle.

    "Phil Wolfe" <[email protected]> wrote in message news:[email protected]...
    > Where did you see the deal on complete Rocket cranksets if you don't mind
    me asking?
    > Thanks, Phil Wolfe
     
  10. Hugh Johnson

    Hugh Johnson Guest

    "Mark Stonich" <[email protected]> wrote in message
    news:[email protected]...
    >
    > It's easy to add a quad to a Rocket crankset, make a ring of 1/8" aluminum plate with 10mm holes
    > in both 130mm and 74mm BCD and use it to replace the spacers between the 1st and 2nd rings.

    Hi Mark, I'm not talking about the Rocket crankset. I only bought that for the rings, to use the
    rings on my new V-Rex crankset. But I'd rather keep all 3 V-Rex rings and just add the Rocket 62t to
    the outside.

    BTW, my Rocket (purchased almost a year ago) came with an unusual crankset, both 130 & 74 bcd. When
    I mentioned this to Luke last week he mumbled something about it being a mid-season change, but I
    didn't correct him about my purchase date (the first 2002 Rocket they sold that season). I think
    maybe I got a prototype production unit, or whatever you would call it. The hubs were different from
    the listed specs, too.

    When I sell my Rocket, I think I'll keep the old 74/130 cranks. I'll install my new closeout cranks
    instead. The oddball originals might come in handy someday.

    >
    > Bottom swing deraillers won't work well with the giant chainring, extend your der. tube. (If I
    > started making aluminum derailleur tube extenders, would they sell?)

    I meant top swing. I'm easily confused. I've considered a tube extension but that might get in the
    way of my plans for a homemade faring.

    >
    > You will need to extend your cage and do something about wrapping up extra chain. See
    > http://bikesmithdesign.com/temp/Der2Small.jpg and http://bikesmithdesign.com/temp/WrapUp.JPG

    Thanks! I actually found those pictures yesterday after snooping around the ihpv archives. I found a
    message you'd written with these same links.

    >
    > You will need to have exactly the right BB spindle length. I had to modify an old Suntour BarCon
    > to pull enough cable. Your 1-2 and 2-1 shifts will never be reliable with such a large #4 ring.

    Yes, I was afraid I might need a longer spindle. I know nothing about these HollowTech BB's. I
    suppose this will be more costly than swapping out a normal BB, but will it be more difficult to
    find exactly what I need?

    Thanks.
     
  11. Paul Worden

    Paul Worden Guest

    >Oh no, I don't want a lower low, I want a higher high. I think the
    Mountain
    >Tamer and other things like that are only for lower lows.

    I find this the frustrating problem. With a head wind and a steep hill I need a 28 or 30 granny. But
    on flat undulating ground with a tail wind, my 60 isn't big enough (20 inch wheels) (I run 36 43 60)

    I have tried an internal rear hub, but I don't like the slight drag and extra kilo. I also found
    that effectively you just got two more gears and they might as well have been added to the rear
    sprocket...if it could handle the shifting.

    The 24 tooth limit just isn't enough for maximising effort when touring/commuting. It shouldn't be
    beyond the bounds of engineering to devise a front shifter with a much larger range, coupled with a
    rear arm that will handle the slack.

    Paul Worden - MR Swift Trike
     
  12. Hugh Johnson

    Hugh Johnson Guest

    "Paul Worden" <[email protected]> wrote in message
    news:[email protected]...
    >
    > It shouldn't be beyond the bounds of engineering to devise a front shifter with a much larger
    > range, coupled with a rear arm that will handle the slack.
    >

    I was just thinking, imagine a front derailleur cage that pitches nose-up and nose-down, in
    addition to moving inboard and outboard. Actually, since the heel of the cage sticks out farther
    than the nose, maybe I should use "heel up" and "heel down" imagery to better convey what I mean.
    When it shifts inboard to the smaller cogs, the heel of the cage drops down to stay closer to the
    inboard teeth.

    This could be accomplished with a simple pivot joint and tiny rack-and-pinion sort of linkage,
    driven by the changing angle of the parallelogram arms (or whatever the heck you call those little
    arms). Or, alternately, you might use two sets of parallelogram arms, fore and aft, with different
    geometries, but then I suppose it would get overly complicated with a need for a ball-and-socket or
    something and, well, it needs more brainstorming.

    As for the chain tensioner, I'm not sure I need to worry about that on the V-Rex. My seat is high,
    my cranks are high, and the chain is high, and I think I'll only need to add 6 more links, right? I
    mean, my high gear is going from 52t to 62t, a difference of 10 teeth, and the chain only wraps
    around half of the chainring, so that brings it down to a difference of 5, and you add one to get an
    even number -- six! It's not going to kill me if my chain is 6 links longer, is it? I'll only be in
    the granny when I'm going slow uphill.
     
  13. Mark Stonich

    Mark Stonich Guest

    "Hugh Johnson" <[email protected]> wrote in message

    > I meant top swing. I'm easily confused.

    So did I, the confusion is contageous.

    > I've considered a tube extension but that might get in the way of my plans for a homemade faring.

    A tube extension could be integrated into your fairing mount. It could be offset to allow the cage
    to better follow the contour of the larger ring, or to allow micro-adjustment of distance from
    chainrings.

    > > You will need to have exactly the right BB spindle length.

    > Yes, I was afraid I might need a longer spindle. I know nothing about these HollowTech BB's. I
    > suppose this will be more costly than swapping out a normal BB, but will it be more difficult to
    > find exactly what I need? Thanks.

    The reason I suggested using the Rocket crank is that square spindles are available in a near
    infinite variety of lengths. With the 105s there are only two lengths available, 109.5 for doubles,
    and 118.5 for triples. Nothing else fits.
     
  14. Freewheeling

    Freewheeling Guest

    GOD, you must be fast! Or should I say: You must be fast, GOD!

    --
    --Scott [email protected] Cut the "tail" to send email.

    "Hugh Johnson" <[email protected]> wrote in message
    news:[email protected]...
    > Last week I graduated from a Rocket to a V-Rex, because, I guess, I'm just hungry for speed. So
    > I've been sprinting around on the V-rex ever since (still too wintery for a serious ride), and
    > I've been feeling a little let-down by the small chainrings. I thought I'd have to get some bigger
    > rings at high cost, but then I saw a closeout deal on complete Rocket cranksets, so I bought one,
    > just for the rings.
    >
    > Haven't installed the rings yet. It's not a simple swap, after all; there are complications. I'll
    > need to replace my front derailleur with a "bottom-swing" type, to move the cage higher than the
    > top of the mounting tube (the mock seat tube), and I'll have to add a few links to my chain,
    and
    > maybe a new shift cable, and who knows what other problems will crop up. But, I've been eyeballing
    > it, and imagining my granny with 9 more teeth,
    and
    > thinking it over, and there's something I'm wondering about...
    >
    > What if I could keep my current granny ring, or better yet, keep all my current rings, but move
    > them inward with spacers -- and then just put the big Rocket 62t ring in the outtermost position?
    > I would have four chainrings, not three. If I can find a bottom-swing derailleur with a
    > sufficiently wide range of movement, and either a very long cage or a cage that I can lengthen
    > (maybe add a steel stiffener if necessary), this
    should
    > be doable, should it not?
    >
    > Obviously there will be lots of chain slack when I'm using the granny, but the V-rex rides high
    > enough to keep it way off the ground, and I won't use the granny very often anyway. The granny,
    > being spaced inward close to the bike tube, might cause the chain to chaff a bit in the front
    > idler pully, but again, it's not going to happen very often, and the granny puts the least strain
    > on things anyway. My front shifter is indexed for a
    nine-speed
    > cassette (SRAM does that so they're interchangable for southpaws, I
    think),
    > so there should be plenty of ways I can adjust it to a 4-ring crankset...
    >
    > Well, I guess that's one of the big questions I have. Will I be able to tweak my shifter for these
    > four chainring positions?
    >
    > And where can I find the sort of derailleur I need? Do they exist? What do
    I
    > ask for?
    >
    > And the biggest question: has anybody done this before? Is it doable? Are there any big drawbacks?
    > Or just tell me what you think.
    >
    > Thanks in advance.
    >
     
  15. Freewheeling

    Freewheeling Guest

    Pete:

    You were the first person I thought of when I saw the question. Good luck on the MoM this year. I
    may not make it if my foot hasn't healed up well. Broke it about six weeks ago. I don't think that
    62T ring would help me much, though I'd be a demon with it on the rollers. At a cadence of 142 with
    an 11T sprocket I'd be doing 60 mph!

    --
    --Scott [email protected] Cut the "tail" to send email.

    "Pete Huber" <[email protected]> wrote in message
    news:[email protected]...
    > Hugh,
    >
    > I have used four chainrings on my Speed Ross for several years using a now discontinued Avid
    > adapter. As a result I have 20-30-42-60 chainrings and use an 11-21 rear cassette. This
    > combination allows for maximum range
    with
    > minimum change between gears. I use a second chain tentioner and a fair amount of modification to
    > the front derailler (removing the stop screws, filing down stop points, etc). In spite of these
    > modifications, shifting
    is
    > not ideal but the gearing works well.
    >
    > Hope this is helpful.
    >
    > Pete Huber Speed Ross Pulaski, VA
    >
    >
    > "Hugh Johnson" <[email protected]> wrote in message
    > news:[email protected]...
    > > Last week I graduated from a Rocket to a V-Rex, because, I guess, I'm
    just
    > > hungry for speed. So I've been sprinting around on the V-rex ever since (still too wintery for a
    > > serious ride), and I've been feeling a little let-down by the small chainrings. I thought I'd
    > > have to get some bigger rings at high cost, but then I saw a closeout deal on complete Rocket
    > > cranksets, so I bought one, just for the rings.
    > >
    > > Haven't installed the rings yet. It's not a simple swap, after all;
    there
    > > are complications. I'll need to replace my front derailleur with a "bottom-swing" type, to move
    > > the cage higher than the top of the
    mounting
    > > tube (the mock seat tube), and I'll have to add a few links to my chain,
    > and
    > > maybe a new shift cable, and who knows what other problems will crop up. But, I've been
    > > eyeballing it, and imagining my granny with 9 more teeth,
    > and
    > > thinking it over, and there's something I'm wondering about...
    > >
    > > What if I could keep my current granny ring, or better yet, keep all my current rings, but move
    > > them inward with spacers -- and then just put
    the
    > > big Rocket 62t ring in the outtermost position? I would have four chainrings, not three. If I
    > > can find a bottom-swing derailleur with a sufficiently wide range of movement, and either a very
    > > long cage or a
    cage
    > > that I can lengthen (maybe add a steel stiffener if necessary), this
    > should
    > > be doable, should it not?
    > >
    > > Obviously there will be lots of chain slack when I'm using the granny,
    but
    > > the V-rex rides high enough to keep it way off the ground, and I won't
    use
    > > the granny very often anyway. The granny, being spaced inward close to
    the
    > > bike tube, might cause the chain to chaff a bit in the front idler
    pully,
    > > but again, it's not going to happen very often, and the granny puts the least strain on things
    > > anyway. My front shifter is indexed for a
    > nine-speed
    > > cassette (SRAM does that so they're interchangable for southpaws, I
    > think),
    > > so there should be plenty of ways I can adjust it to a 4-ring
    crankset...
    > >
    > > Well, I guess that's one of the big questions I have. Will I be able to tweak my shifter for
    > > these four chainring positions?
    > >
    > > And where can I find the sort of derailleur I need? Do they exist? What
    do
    > I
    > > ask for?
    > >
    > > And the biggest question: has anybody done this before? Is it doable?
    Are
    > > there any big drawbacks? Or just tell me what you think.
    > >
    > > Thanks in advance.
    > >
    > >
    > >
    >
     
  16. Freewheeling

    Freewheeling Guest

    Paul:

    Let's see, if you got a Rohloff and used two rings with a front derailleur (and rear singulator)
    you'd have a range of 16.6 to 166.8 gear inches. Would that be enough?

    --
    --Scott [email protected] Cut the "tail" to send email.

    "Paul Worden" <[email protected]> wrote in message
    news:[email protected]...
    > >Oh no, I don't want a lower low, I want a higher high. I think the
    > Mountain
    > >Tamer and other things like that are only for lower lows.
    >
    > I find this the frustrating problem. With a head wind and a steep hill I need a 28 or 30 granny.
    > But on flat undulating ground with a tail wind, my 60 isn't big enough (20 inch wheels) (I run
    > 36 43 60)
    >
    > I have tried an internal rear hub, but I don't like the slight drag and extra kilo. I also found
    > that effectively you just got two more gears and they might as well have been added to the rear
    > sprocket...if it could
    handle
    > the shifting.
    >
    > The 24 tooth limit just isn't enough for maximising effort when touring/commuting. It shouldn't be
    > beyond the bounds of engineering to devise a front shifter with a much larger range, coupled with
    > a rear arm that will handle the slack.
    >
    > Paul Worden - MR Swift Trike
     
  17. Freewheeling

    Freewheeling Guest

    Oops, never mind. Plugged the numbers in the wrong cell of my spreadsheet. If you used a 38T and a
    52T the range would be 16.6 to 119.2. Not bad, but not quite as awesome as I thought. Oh well.

    You could put a 62T on the front, but the result would be inelegant and the singulator would be hard
    pressed to take up the slack.

    --
    --Scott [email protected] Cut the "tail" to send email.

    "Freewheeling" <[email protected]> wrote in message
    news:[email protected]...
    > Paul:
    >
    > Let's see, if you got a Rohloff and used two rings with a front derailleur (and rear singulator)
    > you'd have a range of 16.6 to 166.8 gear inches. Would that be enough?
    >
    > --
    > --Scott [email protected] Cut the "tail" to send email.
    >
    >
    > "Paul Worden" <[email protected]> wrote in message
    > news:[email protected]...
    > > >Oh no, I don't want a lower low, I want a higher high. I think the
    > > Mountain
    > > >Tamer and other things like that are only for lower lows.
    > >
    > > I find this the frustrating problem. With a head wind and a steep hill I need a 28 or 30 granny.
    > > But on flat undulating ground with a tail wind, my 60 isn't big enough
    (20
    > > inch wheels) (I run 36 43 60)
    > >
    > > I have tried an internal rear hub, but I don't like the slight drag and extra kilo. I also found
    > > that effectively you just got two more gears
    and
    > > they might as well have been added to the rear sprocket...if it could
    > handle
    > > the shifting.
    > >
    > > The 24 tooth limit just isn't enough for maximising effort when touring/commuting. It shouldn't
    > > be beyond the bounds of engineering to devise a front
    shifter
    > > with a much larger range, coupled with a rear arm that will handle the slack.
    > >
    > > Paul Worden - MR Swift Trike
    > >
    >
     
  18. I have a TE with a 3 speed hub and a triple crank. If you can't find some gear that is perfect for
    what you are doing in the 63 offered (sorry, no reverse), you need to give up biking. I believe the
    hub offers a (more or less) 1/3 reduction in 1st, direct in 2nd, 1/3 increase in 3rd. The "drag"
    issue mentioned below ia a concern in 1st and 3rd, but 2nd is a direct drive, and there isn't any
    additional drag from the internal gears, which are actually locked up in 2nd. I can't argue that
    the wheel bearing may not be as high a quality as a highe end road hub - I just don't know. I
    understand that the additional drag in 1st and 3rd may be as high as 3-5%. I have never felt it to
    be a problem.

    Without doing all the math I can't tell you about the lowest low and the highest high, except to
    tell you that an old guy like me needs to get up to 40 mph downhill to even engage high-high-high
    gear, and when using low-low-low, the biggest issue is not how steep the hill is, but how fast you
    can spin to keep up enough speed so that you don't just fall over sidewways like the "Laugh-in" TV
    show tricycle.

    The biggest issue with adding more chainrings is the rear changers ability to "absorb" more slack in
    the chain which is measured as the "tooth capacity" of the changer. Mountain bike changers (AKA long
    cage) have a bigger tooth capacity. In addition, I don't think I've ever seen a 4 ring front
    changer. The width of the crank assembly might get ungainly wide with 4 rings.

    The TE uses an intermediate tensioned (like the changer tensioning mechanism) half way back due to
    the long chain, but such an arrangement could supplement the rear changers capacity. It's ability to
    shift would then depend on the number of teeth on the rear cluster only, not on the length of the
    entire chain.

    In addition, there are bikes (Trek bent??) that use two rear changer clusters in series to create
    wider gearing.

    Paul Worden" <[email protected]> wrote in message
    news:[email protected]...
    > >Oh no, I don't want a lower low, I want a higher high. I think the
    > Mountain
    > >Tamer and other things like that are only for lower lows.
    >
    > I find this the frustrating problem. With a head wind and a steep hill I need a 28 or 30 granny.
    > But on flat undulating ground with a tail wind, my 60 isn't big enough (20 inch wheels) (I run
    > 36 43 60)
    >
    > I have tried an internal rear hub, but I don't like the slight drag and extra kilo. I also found
    > that effectively you just got two more gears and they might as well have been added to the rear
    > sprocket...if it could
    handle
    > the shifting.
    >
    > The 24 tooth limit just isn't enough for maximising effort when touring/commuting. It shouldn't be
    > beyond the bounds of engineering to devise a front shifter with a much larger range, coupled with
    > a rear arm that will handle the slack.
    >
    > Paul Worden - MR Swift Trike
     
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