MTB gearing

Discussion in 'Road Cycling' started by Dave Moak, Jun 9, 2003.

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  1. Dave Moak

    Dave Moak Guest

    I have a mountain bike that I ride primarily on the road. The gearing that came with the bike is too
    low for road riding. What's the easiest way to increase the gearing? Is it possible to swap
    chainrings? Or do I need a whole new crank/bottom bracket?

    Thanks!

    Dave
     
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  2. Archer

    Archer Guest

    In article <[email protected]>, [email protected] says...
    > I have a mountain bike that I ride primarily on the road. The gearing that came with the bike is
    > too low for road riding. What's the easiest way to increase the gearing? Is it possible to swap
    > chainrings? Or do I need a whole new crank/bottom bracket?

    It's probably just as easy to swap the cluster than the chainrings.

    --
    David Kerber An optimist says "Good morning, Lord." While a pessimist says "Good Lord,
    it's morning".

    Remove the ns_ from the address before e-mailing.
     
  3. David

    David Guest

    "Dave Moak" <[email protected]> wrote in message
    news:[email protected]...
    > I have a mountain bike that I ride primarily on the road. The gearing that came with the bike is
    > too low for road riding.

    It's never been a problem for me except downhill, where it really is a problem! If you have a
    problem on the flats, you might spin faster. Or ride slower ;)

    > What's the easiest way to increase the gearing? Is it possible to swap chainrings?

    On most cranks, yes. On really cheap ones, no. It should be obvious by inspection. If there is a
    circle of 4 or 5 bolts hoding the big ring on, it should be easy to replace. Check the # of teeth
    (marked on the ring, or count them). If it's 42 or 44 (and you have an 11t cog in back), probably
    going to 48 will solve your problems. Do an internet search or LBS query to see if you can find a
    ring with enough teeth with the right bolt-circle.

    You will need to move/adjust the front derr. You will likely need to add a couple of links to
    your chain. Possibly you could have issues with the rear derr too, but you can deal with that if
    it arises.

    >Or do I need a whole new crank/bottom bracket?

    It may be better to buy a new crank/rings. Unless the new crank wants a different spindle length (or
    type), no need to change the BB.
     
  4. On Mon, 09 Jun 2003 13:51:31 +0000, David wrote:

    >
    > "Dave Moak" <[email protected]> wrote in message
    > news:[email protected]...
    >> I have a mountain bike that I ride primarily on the road. The gearing that came with the bike is
    >> too low for road riding.
    >
    >> What's the easiest way to increase the gearing? Is it possible to swap chainrings?
    >
    > On most cranks, yes. On really cheap ones, no. It should be obvious by inspection. If there is a
    > circle of 4 or 5 bolts hoding the big ring on, it should be easy to replace. Check the # of teeth
    > (marked on the ring, or count them). If it's 42 or 44 (and you have an 11t cog in back), probably
    > going to 48 will solve your problems.

    The problem is going to be availability and cost. The 4-bolt Shimano chainrings (104mm) will be hard
    to find in more than 44 teeth. 5-bolt 94mm rings are pretty easily found in sizes up to 46; 48 takes
    a bit more looking. There are some really large rings for downhills, but they are probably more than
    you need. 110mm 5-bolt patterns apparently have a wider range of available sizes, but you may have
    to look longer.

    > You will need to move/adjust the front derr. You will likely need to add a couple of links to
    > your chain.

    Don't do that. The pin you remove to add links will, with modern chains, cause a weak link. Better
    to just replace the chain.

    >>Or do I need a whole new crank/bottom bracket?
    >
    > It may be better to buy a new crank/rings. Unless the new crank wants a different spindle length
    > (or type), no need to change the BB.

    Well, it does depend on what you have now, which can vary from standard sizes with easily-replaced
    rings to non-replacable rings on cheap cranks.

    Of course, the real solution to improving your riding on the road is, surprisingly enough, to get a
    road bike.

    --

    David L. Johnson

    __o | Accept risk. Accept responsibility. Put a lawyer out of _`\(,_ | business. (_)/ (_) |
     
  5. Matt O'Toole

    Matt O'Toole Guest

    "David L. Johnson" <[email protected]> wrote in message
    news:[email protected]...

    > The problem is going to be availability and cost. The 4-bolt Shimano chainrings (104mm) will be
    > hard to find in more than 44 teeth. 5-bolt 94mm rings are pretty easily found in sizes up to 46;
    > 48 takes a bit more looking. There are some really large rings for downhills, but they are
    > probably more than you need. 110mm 5-bolt patterns apparently have a wider range of available
    > sizes, but you may have to look longer.

    48T is pretty big, and not very available. However, 46T is pretty common from aftermarket suppliers.
    With an 11t rear cog, a 46T will give you a 110 inch or so gear. This is a good top road gear, on
    par with what most road bikes have.

    My ultimate all-around MTB setup would have an 11-32 9 speed cassette with a 24-34-46 crank (like
    XTR). With the jump from 8 to 9 speed cassettes, most bikes gained a gear at the low end. For me the
    lows were low enough, but having a higher gear for road riding would be helpful.

    Matt O.
     
  6. David

    David Guest

    "David L. Johnson" <[email protected]> wrote in message
    news:[email protected]...
    > On Mon, 09 Jun 2003 13:51:31 +0000, David wrote:
    >
    >
    > Don't do that. The pin you remove to add links will, with modern chains, cause a weak link. Better
    > to just replace the chain.

    By "modern" do you mean Shimano? I use Sram: no special pins. When I've increased chainring size, or
    broken links or whatever, I add links that I had removed when I first installed the chain.
     
  7. troyq

    troyq New Member

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    Agreed. I cannot recall ever using the lowest gear with the granny ring - unless you need to go up something at an angle of 90 deg. I liked 8 speed better as it seemed more robust. Perhaps to counter the increase in lower gears, Shimano should have increased the count on the front big chainring?
     
  8. Matt O'Toole

    Matt O'Toole Guest

    "troyq" <[email protected]> wrote in message news:[email protected]...

    I wrote:

    > > My ultimate all-around MTB setup would have an 11-32 9 speed cassette with a 24-34-46 crank
    > > (like XTR). With the jump from 8 to 9 speed cassettes, most bikes gained a gear at the low
    > > end. For me the lows were low enough, but having a higher gear for road riding would be
    > > helpful.

    > Agreed. I cannot recall ever using the lowest gear with the granny ring
    > - unless you need to go up something at an angle of 90 deg. I liked 8 speed better as it seemed
    > more robust. Perhaps to counter the increase in lower gears, Shimano should have increased the
    > count on the front big chainring?

    Perhaps, but that would make for a big jump between chainrings. I've ridden with a 34-48 jump, and
    while it works, it's non-optimal. Shimano has had all kinds of combos since the beginning, and I've
    tried most variations at one time or another. The XTR-like setup seems to work best all around.

    Matt O.
     
  9. Jim Edgar

    Jim Edgar Guest

    >> "David L. Johnson" <[email protected]> wrote in message news:bc3-
    >> [email protected]:[email protected] 48T is pretty big, and not
    >> very available. However, 46T is pretty common from aftermarket suppliers. With an 11t rear cog, a
    >> 46T will give you a 110 inch or so gear. This is a good top road gear, on par with what most road
    >> bikes have.

    46T w/ 11 cog on a 26.2125 tires is ~108 inches. 46T w/ 12 cog on a 26.2125 tires is ~99 inches.

    (Road bikes with the all-too-common 39/53T would be about 127 w/ 11 and 116
    w/ 12 with a 700x23 tire)

    Or, if you were pedaling at 100 rpms,

    46T/11 = ~32 mph
    46U/12 = ~29 mph

    Which is chugging along pretty good on the flats.

    You can play this game yourself at:

    http://www.sheldonbrown.com/gears/
     
  10. Chalo

    Chalo Guest

    "David" <[email protected]> wrote:

    > "David L. Johnson" <[email protected]> wrote:
    > >
    > > The pin you remove to add links will, with modern chains, cause a weak link. Better to just
    > > replace the chain.
    >
    > By "modern" do you mean Shimano? I use Sram: no special pins. When I've increased chainring size,
    > or broken links or whatever, I add links that I had removed when I first installed the chain.

    SRAM chains are weakened by opening them too; the issue is that "modern" chains are riveted,
    causing the ends of the pins to be a bit fatter than the pin itself. Pushing the fattened end
    through the sideplates can promote cracking at the hole with subsequent failure of the chain.
    That's why SRAM chains come with a connector link-- to replace the sideplates which were damaged by
    pushing the pins through.

    I sometimes push the pins back in the old-fashioned way, but the risk is something to be aware of,
    especially with the high chain tensions implicated by "compact" triple drivetrains. I will only
    re-press a pin when the chain is to be used on a single ring or full-sized double.

    Chalo Colina
     
  11. >That's why SRAM chains come with a connector link-- to replace the sideplates which were damaged by
    >pushing the pins through.

    Actually, once you've cut it to size you only break the SRAM chain at the power link. They're
    reusable and the system totally blows Shimano's approach away.

    --

    _______________________ALL AMIGA IN MY MIND_______________________ ------------------"Buddy Holly,
    the Texas Elvis"------------------
    __________306.350.357.38>>[email protected]__________
     
  12. Chalo

    Chalo Guest

    "Eric S. Sande" <[email protected]> wrote

    (I wrote)
    > >That's why SRAM chains come with a connector link-- to replace the sideplates which were damaged
    > >by pushing the pins through.
    >
    > Actually, once you've cut it to size you only break the SRAM chain at the power link. They're
    > reusable and the system totally blows Shimano's approach away.

    Right, when you shorten the chain you have to push pins, and thereby deform the sideplates. The
    "power link" replaces the damaged plates regardless how much chain was removed.

    The reusability of the power link is a worthy bonus for the end user, but probably secondary in
    importance to the replacement of rivet-damaged sideplates. KMC for instance use a similar link that
    allows tool-free chain closure, but they recommend that their link not be reused.

    Chalo Colina
     
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