16 Tooth Sprocket

Discussion in 'Motorized Bicycle General Discussion' started by Road82, Jul 17, 2009.

  1. Road82

    Road82 New Member

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    Lets say you you can get your bike up to 20mph pedaling on a long straight road. Who many teeth would it take to... I should say, what would be the minimum amount of teeth would it take to start the motor. And then, how fast might the bike go? Assuming the bike could handle going 90mph.

    I know of the 36 tooth sprocket but what about a 26 tooth sprocket? Or a 16 tooth sprocket. I know at some point it would be like shifting into 5th gear while starting out in first (in a car).

    Smart people tell me! What would be the minimum? This is all hypothetical, Im just curious and wondering what it would be like to go that fast.

    ~Aaron
     
  2. Finfan

    Finfan New Member

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    There is a certain minimum diameter you can have before the sprocket becomes too small to attach to the wheel. It has to be larger in diameter than your attachment points. This will be the lower limit to the number of teeth it can have since the teeth must maintain the proper spacing for the chain. Unfortunately I do not know what that number is but I bet somebody here will.
     
  3. matt167

    matt167 New Member

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    there is a point, the engine just won't pull any faster.. consider accelerating with a car in 5th. very slow, and some can't even accelerate in 5th
     
  4. Road82

    Road82 New Member

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    I think i got a 5mph trade from switching from the old 44 tooth to a 40 tooth. The bike can do 30mph now without screaming.
    36 tooth = 35mph
    32 tooth = 40mph
    28 tooth = 45mph
    24 tooth = 50mph
    20 tooth = 55mph
    16 tooth = 60mph
    12 tooth = 65mph
    8 tooth = 70mph
    4 tooth = 75mph
    0 teeth = 80mph

    Ya i know.. if you have zero teeth, you're only going to be able to eat soup. It would be cool to see how fast you could go by changing modifying gears and teeth though.

    You're right though Matt, at some point the motor would only be adding a small percentage of power to your pedaling, if you had the gears to pedal that fast.
     
    #4 Road82, Jul 18, 2009
    Last edited: Jul 18, 2009
  5. Cabinfever1977

    Cabinfever1977 New Member

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    i can do 35mph with my 44t, i believe its around 1mph gained per tooth lost on the sprocket.
     
    #5 Cabinfever1977, Jul 18, 2009
    Last edited: Jul 18, 2009
  6. Junster

    Junster New Member

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    It's a matter of torque and horsepower. Ya theoretically you can gear up for say 60mph but the motor would never pull it. If you ever buy a shift kit you'll really see what your motor can do. I use to run a 44 and with the motor screaming I could just hit 35 mph. I have a shift kit now and I can hit an honest 40 mph. SBP is offering a extra sprocket with the kit and I got a 11 tooth to go with the stock 10. I wish I'd gotten the 9 tooth. I have a 8 speed rear and on a level road with little wind I can run in the 7th gear at 40 mph with the 10 tooth, motor purring nicely. With the 11 tooth it's 6th gear same speed but the motor's running faster and it won't pull the 7th gear. Downhill I can kick it up to the 8th gear and really get moving but I haven't had anyone clock me at that speed. When I figure out how to mount my GPS I'll post my max speed. Alot of the HP is used up spinning the spokes thru the air. I'm on the lookout for a deal on a set of those 3 spoke wheels. I have a expansion chamber, slanthead, custom intake, accel super stock wire to get it to do a honest 40 mph.
     
  7. Road82

    Road82 New Member

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    I just pulled out the tape measure. Looks like a sprocket with about a 13 inch circumference would work. And it looks like there is a 1/2 inch gap between every tooth so that's 6-7 teeth?

    Hmm, 60-70mph range?
     
  8. RedB66

    RedB66 New Member

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    I've used a 25T sprocket and had to trim the rubber to clear the chain. I don't think you could go much smaller without a hub clamshell set-up. The bike had no low end at all but would cruise along at 37-40MPH.
     
  9. matt167

    matt167 New Member

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    the engine sprocket is 11 teeth. so anything less than 11 teeth as a drive sprocket, will be overdriven ( 11 tooth to 11 tooth would be a 1:1 ratio, normally a final drive ratio ) .. I don't have any calculators for sprocket gear ratio's but they are around..... if you were to try to go 60+ with a 1:1 final drive or even an overdrive.. you would have to start off down a hill or start by getting pulled up to 60 MPH by a tow vehicle.. the motor will not have enough to pull itself to speed at those gear ratios but would probably hold those speeds once there.
     
  10. kicok

    kicok New Member

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    i search everywhere a 25T sprocket for my bicycle. could You tell me where could i find it ? I am from Poland and that engine and parts aren't so popular here. Maby in USA that 25T sprocket is possible to buy it... I would be very happy if You helped me :) please.
     
  11. bairdco

    bairdco a guy who makes cool bikes

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    i've run a 28 tooth on my bike with 24" wheels. unofficial school speed trap reading 48mph. unfortunately, when my chain broke, it ripped the teeth off the sprocket, so now i'm back to a 30 tooth.

    i've got heavy duty worksman wheels with Jim's sprocket adapter, and with the 28 my chain was really close to my spokes. might be able to squeeze a 27, maybe even a 26 on there, but that's about the clearance limit for me.

    if you're looking for a 25tooth, try modifying a BMX sprocket.
     
  12. shiloh0

    shiloh0 New Member

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    i ran two bikes with 27 tooth sprockets so i could get to and from work at a reasonable speed without all the vibrations from the bigger sprockets. never had any problems. this yr im building a 29er with a 26 tooth since they have them available now. will also use an expansion pipe and bottle to give some torque back
     

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