Chain length...how long?

Discussion in 'The Garage' started by craigincali, Jan 12, 2018.

  1. craigincali

    craigincali Just hanging around

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    I have a new chain on a bike that I am converting from dirt to Supermoto. How do I know how long to make the chain? I am not sure of my gearing yet because I am going to use the bike on different tracks.

    Do I put axle in the middle of the swing arm and guess at a good gearing?
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  2. Tim McKittrick

    Tim McKittrick Long timer

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    Start with stock length and reduce in links to match the sprockets selected for the given track. Since the supermoto wheels will be smaller in diameter than stock all the gearing will be taller so the sprockets will be smaller- and the chain shorter.
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  3. craigincali

    craigincali Just hanging around

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    Right now my dirt set up is 12/47. I'm going to go with a 13/44 set up for now. I might be able to use same chain huh?
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  4. cagiva549

    cagiva549 whats a cagiva

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    Put the bike together , wrap the chain around the sprockets and cut it where it needs to be . An inch or more of slack with axle all the way forward . I had a 950 SE with motard wheels and I used the same chain , I don't remember what the gearing was but the motard sprocket was several teeth smaller and I went up one on the primary .
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  5. Boatman

    Boatman Membership has it's privileges ;-)

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  6. JensEskildsen

    JensEskildsen Long timer

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    Yeah, play around on gearingcommander.
    You should be able to vary your gearing quite a bit, with the same chain, with a good combination of swapping both sprockets if needed.

    I can run from 16/45 down to 13/47 on my xt600 with the same chain.
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  7. Boatman

    Boatman Membership has it's privileges ;-)

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    Gearing commander will also give you the length of chain you need.
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  8. lnewqban

    lnewqban Ninjetter

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    I would calculate the length of the chain for the combination of the bigest sprockets you believe you would use:
    http://www.rebelgears.com/chainlengthcalculator.html

    The front sprocket cannot be reduced or incresed by much, due to geometry limitations.
    As the rear wheel gets a smaller exterior diameter, the rear sprocket should get a smaller diameter in a proportional way, in order to keep the same reduction ratio.
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  9. kenny robert

    kenny robert Long timer

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    slide axle all the way back wrap the chain slide forward the wheel until you have a linkable chain length with zero or minimal slack
    this method will keep you from cutting it too short before you even realize it
    y ou can always cut it a link shorter if needed but it saves you that feeling of fail and running 2 master links
    which is perfectly fine
    if you find one chain length wont suit all your gearing options
    its ok to cut it a few links too short and use 2 differemnt make-up short sections and 2 masterlinks
    just dont mix brands of chain and dont put a fresh new makeup section on a 10,000 mile chain
    a little used speed secret make sure the rear sprocket has as close to zero radial runout as possible
    and always with a new chain and or new to you motorcycle,create your own correct full droop chain slack benchmark by adjusting the chain to have minimal slack at the 3 axis point
    then when at full droop observe and write in your notes the actual slack for future reference
    and it will always be a specific slack no matter what sprocket combos you run as long as the top run is not being kept from a straight line from swingarm buffer pitching it up at the pivot,by a certain sprocket combination but not with all of them
    this creating your own correct full droop slack benchmark is a must with rear ride height changes such as shorter or longer shock/shocks
    because the factory oem chain slack is no longer relevent
    and even more so with vintage bikes that have a larger amount of chain slack variation due to the c/s being further from swinger pivot than on modern long travel bikes
    thats all just some simple details
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  10. craigincali

    craigincali Just hanging around

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    Thanks guys !!
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  11. kenny robert

    kenny robert Long timer

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    i stressed all of that stuff without saying that the main thing above all else is to not have too little slack in the chain when rear suspension is at full extension ie on a centerstand
    because if you do not have any slack at the 3 axis point it can be big trouble ,say if you run out of slack with still an inch or more of wheel travel before you cross over the 3 axis point
    c/s swinger pivot rear axle all lined up is where the chain is going to need enough slack as this is the tightest
    it is here the rear axle is furthest from the c/s
    an analogy and it has chain in it a chain binder an over center multiplier of force that gives a human about 10 times leverage lashing that clapped out tractor onto a flatbed
    the swingarm allows this same exact type of mechanical force multiplication on the chain and drive system if not enough slack is provided
    bottom line it could kill you
    and i am convinced over the last 75 years of swingarms that a very sad number of riders have been killed or were lucky to only be near killed
    think about it
    who is doing accident forensics to identify why a rider lost control other than "they let the chain get rusty and it snapped"
    HORSESHIT
    thing is this thing i am explaining in my opinion IS THE ONLY THING THAT CAN SNAP EVEN A BADLY RUSTED CHAIN as long as the rider is not dropping the clutch hard at every stoplight
    but that is not so dangerous cause speed is low
    even a severly rusty chain can go on and on a lot more durable than most think
    eventually locking up tight or making so much noise the drone minded rider gets fed up and buys a 23 doller chain but soon looses interest when winter comes
    but combine that pretty badly rusted chain,can be from a battery hose routed wrong,with extreme mechanical force of too little slack because the rider thought the noise was from a loose chain and catastrophic failure absolutely isca very real deal
    i have seen it this guy asked me why his chain was so noisy and jumpy
    one of the new bread of calf racer buildders straight pipers on his cm400 struts for shocks,his dumb luck saved his hide with that mod
    he would not have the issue of extreme forces but this is to ilistrate how ignorant a human can be
    its a new chain he cried the point being is this ,im sorry,moron,had bought the 23 doller dime city chain open chain not sealed
    and it was obvious it had never seen anything slick ever applied to it but the water from an hb pressure washer
    8,000 miles never ever a drop of oil horrible chain with tiny red rust dust clouds of rust dust at each pin puffing out as he showed me how crappy it was pos chain he cried
    i was speachless no booshit
    lube never crossed this motorcyclists thoughts
    well shit a person like that does not deserve to be killed in a chain of events of the own making
    he had a family wife and lil girl
    so is it rare to snap a chain ?rare yes but it takes a rusty chain and a well meaning wrench weilder to overtight the noisy pos chain before it happens ....
    on the street at 75mph snapping a chain on the freeway with a pack of throbbing cages surrounding you cause you ignored the uneven pavement signs
    and it wads up rear wheel sending machine and hapless rider into a lurid slide
    ....wel... buying the farm is not out of reality
    we need education on this one little detail and by god lives and flesh will be saved
    #11
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