chain rubbing...

Discussion in 'Cycling Equipment' started by Joel Rose, Jan 22, 2003.

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  1. Joel Rose

    Joel Rose Guest

    Hello,

    On my new bike while on a trainer I noticed that while in the smaller front ring ( Ultegra double )
    the chain rubs against the "inside" of the larger ring while shifting into #8 and 9 gears. I have
    never experienced this before with my old bike, but then again it only had a 6 gear rear cog.

    If this makes any sense, can anyone give me any advice as to what is the problem and if there is a
    fix for it? Thanks in advance.

    Joel in KW
     
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  2. "Joel Rose" <[email protected]> writes:
    > On my new bike while on a trainer I noticed that while in the smaller front ring ( Ultegra double
    > ) the chain rubs against the "inside" of the larger ring while shifting into #8 and 9 gears. I
    > have never experienced this before with my old bike, but then again it only had a 6 gear rear cog.

    Am I right in assuming that the "#8 and 9 gears" are counted from the spokes outward, i.e. the
    smallest cogs?

    If so: Don't do that. It's called "cross-chaining" and it's bad for your chain, and it will cause
    your chain to jump when riding outside, which could be dangerous. It's a no-no for modern
    drivetrains with more than seven cogs across the back. What might look like sixteen available gears
    is really about twelve, where you avoid the combinations of small chainring plus two smallest cogs
    and large chainring plus two largest cogs.

    Your chain "wants" to stay in a plane and resists running at an angle.

    Morgan
     
  3. Joel Rose

    Joel Rose Guest

    Yes, it happens when the gearing is in the smallest 2 cogs at the rear. That's unfortunate that you
    can't really use your entire gearing system because of the cross-chaining.

    Thanks for the tip.

    Joel

    "Joel Rose" <[email protected]> wrote in message news:[email protected]...
    > Hello,
    >
    > On my new bike while on a trainer I noticed that while in the smaller
    front
    > ring ( Ultegra double ) the chain rubs against the "inside" of the larger ring while shifting into
    > #8 and 9 gears. I have never experienced this before with my old bike, but then again it only had
    > a 6 gear rear cog.
    >
    > If this makes any sense, can anyone give me any advice as to what is the problem and if there is a
    > fix for it? Thanks in advance.
    >
    > Joel in KW
     
  4. bobqzzi

    bobqzzi Guest

    On Mon, 20 Jan 2003 16:31:15 -0500, "Joel Rose" <[email protected]> wrote:

    >Hello,
    >
    >On my new bike while on a trainer I noticed that while in the smaller front ring ( Ultegra double )
    >the chain rubs against the "inside" of the larger ring while shifting into #8 and 9 gears. I have
    >never experienced this before with my old bike, but then again it only had a 6 gear rear cog.
    >
    >If this makes any sense, can anyone give me any advice as to what is the problem and if there is a
    >fix for it? Thanks in advance.
    >
    >Joel in KW
    >

    It's a design "problem". Quite common on 9speed shimano stuff. It is exacerbated by shorter
    chainstays. There really is no cure or adjustment. The easiest thing to do is simply shift to the
    big ring and use a bigger cog. You get a better chainline and larger cogs are more efficient and
    wear more slowly. No doubt the is a combo that will give you the same ratio as a 39/ 12or 13 (you're
    not using an 11 with a 39/52 are you?But that's another story.)

    Bob Quindazzi
     
  5. Ed Ness

    Ed Ness Guest

    "Joel Rose" <[email protected]> wrote:
    > "On my new bike while on a trainer I noticed that while in the smaller front ring ( Ultegra double
    > ) the chain rubs against the "inside" of the larger ring while shifting into #8 and 9 gears."

    This is a common problem on Shimano 9 speed drivetrain systems. It can be improved by shimming the
    bottom bracket over to the right slightly or by spacing the chainrings slightly farther apart -
    similar distance apart to that of 8 speed. Most LBS's should have bottom bracket shims and I read
    somewhere that Shimano has a spacer kit should you want to try this way. I have no actual experience
    with the chainring spacers so maybe their availability is just an urban legend? At any rate, good
    luck and don't give up yet!

    Ed
     
  6. jro-<< On my new bike while on a trainer I noticed that while in the smaller front ring ( Ultegra
    double ) the chain rubs against the "inside" of the larger ring while shifting into #8 and 9 gears.

    Common, normal, a result of lots o' cogs that have only one place to go-outward, with the increased
    chain angle and the propensity of 39t small rings.

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
    (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"
     
  7. jro-<< That's unfortunate that you can't really use your entire gearing system because of the
    cross-chaining

    Small ring and smallest two cogs is thew same ratio as big ring and middleish/up a few cogs ....

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
    (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"
     
  8. Mark Lee

    Mark Lee Guest

    "Joel Rose" <[email protected]> wrote in message

    >>SNIP<<
    > while in the smaller front ring ... the chain rubs against the "inside" of the larger ring while
    > shifting into #8 and 9 gears. ... ... any advice as to what is the problem ...

    Joel, The problem is: you are using extreme crossover. Don't do it.
    1. Why? D A N G E R An inexperienced but strong young rider (Under 19 - 6'2") in the 60-strong
    training bunch last Saturday DID and when he sprinted up a hill, the chain sucked and jumped off
    - pulling his left foot and throwing him over the bars to the left at 35kph. He sustained a big
    chainring bite on the ankle and lost a bit of skin and claret from various parts of his body -
    his back (& a leg) is still stiff as of last night out at the Velodrome racing - and his mobile
    phone looked like something found under the wreckage of the twin towers. The guy on his wheel
    wasn't so lucky - dislocated shoulder - and another came down too. My 12 yr old son just managed
    to squeeze around. They were chasing me and I could hear what sounded like an avalanche of light
    metal rolling and building speed behind me. I stayed out of the saddle, sprinting, until the
    noise no longer threatened to engulf me.
    2. Why? W E A R & T E A R Small cogs, lots of chain flex/angle and higher chain tension.
    3. Why? Evidence of inexperience. It's just not the way things are done by cyclists who want the
    most out of their sport. That crossover is what is known in Australia as a "gumby" gear.

    You've done the right thing asking about it. Mark Lee
     
  9. edwardness-<< This is a common problem on Shimano 9 speed drivetrain systems. It can be improved by
    shimming the bottom bracket over to the right slightly or by spacing the chainrings slightly farther
    apart - similar

    And by doing this you will have an adverse affect on fder operation. It isn't a design flaw that
    needs to be fixed. The gent just needs to stop riding in small/small combos. It's kinda like
    starting you car from a stop light in second gear, just use first.

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
    (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"
     
  10. "Joel Rose" <[email protected]> writes:
    > Yes, it happens when the gearing is in the smallest 2 cogs at the rear. That's unfortunate that
    > you can't really use your entire gearing system because of the cross-chaining.

    It might seem like a loss, but if you figure out the gear ratios afforded by those sixteen gear
    combinations there is redundancy. In other words, the gears you "miss" are probably already
    represented somewhere in the other chainring's range.

    Morgan
     
  11. Robin Hubert

    Robin Hubert Guest

    "Joel Rose" <[email protected]> wrote in message news:pn%[email protected]...
    > Yes, it happens when the gearing is in the smallest 2 cogs at the rear. That's unfortunate that
    > you can't really use your entire gearing system because of the cross-chaining.

    Joel, Were you to examine a gearing chart for your (now standard) "crossover" gearing setup, you'll
    see that you're lucky to have 13 distinct gear combinations. It just so happens that, by the time
    you're down to the two (three, or four) smallest cogs, you might as well be in the big ring. You'll
    find those gears there as well.

    Robin Hubert
     
  12. Joel Rose

    Joel Rose Guest

    Thanks for the real life examples. I will not be adding a shim to the rear cog or front rings as
    suggested; this is beyond my scope of knowledge at this time. I have really appreciated all of the
    advice on this topic and I have changed my gear selection accordingly. I'm glad I asked as I have
    learned something new!

    Joel R "Mark Lee" <[email protected]> wrote in message
    news:[email protected]...
    >
    > "Joel Rose" <[email protected]> wrote in message
    >
    > >>SNIP<<
    > > while in the smaller front ring ... the chain rubs against the "inside" of the larger ring while
    > > shifting into #8 and 9 gears. ... ... any advice as to what is the problem ...
    >
    > Joel, The problem is: you are using extreme crossover. Don't do it.
    > 1. Why? D A N G E R An inexperienced but strong young rider (Under 19 - 6'2") in the 60-strong
    > training bunch last Saturday DID and when he sprinted up a hill, the chain sucked and jumped
    > off - pulling his left foot and throwing him over the
    bars
    > to the left at 35kph. He sustained a big chainring bite on the ankle and lost a bit of skin and
    > claret from various parts of his body - his back (&
    a
    > leg) is still stiff as of last night out at the Velodrome racing - and his mobile phone looked
    > like something found under the wreckage of the twin towers. The guy on his wheel wasn't so lucky -
    > dislocated shoulder - and another came down too. My 12 yr old son just managed to squeeze around.
    > They were chasing me and I could hear what sounded like an avalanche of light metal rolling and
    > building speed behind me. I stayed out of the saddle, sprinting, until the noise no longer
    > threatened to engulf me.
    > 2. Why? W E A R & T E A R Small cogs, lots of chain flex/angle and higher chain tension.
    > 3. Why? Evidence of inexperience. It's just not the way things are done by
    cyclists
    > who want the most out of their sport. That crossover is what is known in Australia as a
    > "gumby" gear.
    >
    > You've done the right thing asking about it. Mark Lee
     
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