Tooth sprocket question...

Discussion in 'Motorized Bicycle General Discussion' started by ueyteuor, Jul 23, 2010.

  1. ueyteuor

    ueyteuor New Member

    Joined:
    May 28, 2010
    Messages:
    37
    Likes Received:
    0
    Hi there, I need some advice... I just purchased a grubee 66/80cc starfire kit... though i do not know how many teeth the sprocket it includes has...

    Anyhow, what I am wondering is what type of sprocket tooth count would be right for my bicycle? Bicycle wheel is 20"!! So this is why I am wondering, since I don't see many motorized bicycle with only 20" wheels...

    Another concern is that where I live there are many hills... which sprocket would be best for pedal-helped hills, and with the fastest speed, on 20" wheels...

    Thank you!
     
  2. corgi1

    corgi1 New Member

    Joined:
    Aug 13, 2009
    Messages:
    2,282
    Likes Received:
    2
    Probebly a 40 to 44 tooth came with it,,,,that on a 20 inch wheel would possibly be able to climb trees,I don't know if they make a gear ,for 20 inch wheels,that would need pedaling help on hills,I'm thinking the smallest is 36 teeth.someone may know of others
     
  3. bairdco

    bairdco a guy who makes cool bikes

    Joined:
    Aug 18, 2009
    Messages:
    6,403
    Likes Received:
    50
    the smaller the wheel, the quicker the acceleration. you can get away with a smaller gear than the average 26" bike has. in theory, you'll need a smaller sprocket to get up to top speed, compared to a bigger wheel.

    like, if a 26" had a 46 tooth, you'd need a 36 to keep up (i'm just guessing, i'm sure there's an equation somewhere that'll tell you actual wheel diameter + sprocket size = speed..)

    there's people that claim a smaller bike won't be able to keep up with a larger wheeled bike at top speed, but in the real world, they're wrong.

    with a 20", you could run a 30, or even a 28 and still climb hills, as long as your engine is tuned right.

    i have a 24" with a 30 tooth, and i've run 30mph+ up 6% grades.
     
  4. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

    Joined:
    Jan 8, 2008
    Messages:
    11,529
    Likes Received:
    4
    A 20" bike? I thought that's what those 27T sprockets were made for?
     
  5. xzackx

    xzackx New Member

    Joined:
    Jun 30, 2010
    Messages:
    44
    Likes Received:
    0
    i have a question my scwhinn has a 24'' front and a 20'' back tire i have a stock gear on mine should i upgrade to a lower tooth gear?
     
  6. corgi1

    corgi1 New Member

    Joined:
    Aug 13, 2009
    Messages:
    2,282
    Likes Received:
    2
    62.83 inches per turn on a 20 inch wheel/
    81.68 inches per turn on a 26 inch wheel/
    about 25% less travel
    40 tooth divided by 4 =10, x 3 =30 tooth ?
     
  7. corgi1

    corgi1 New Member

    Joined:
    Aug 13, 2009
    Messages:
    2,282
    Likes Received:
    2
    75.4 inches travel on a 24 inch tire
    12.96% shorter than 26 inch wh.travel
    about 1/8 difference
    40 tooth divide by 8 = 5,x 7 =35 tooth ?
     
  8. ueyteuor

    ueyteuor New Member

    Joined:
    May 28, 2010
    Messages:
    37
    Likes Received:
    0
    Very nice equation!

    Thank you all for your help... i'll be looking for either a 27T or 30T sprocket...
     
  9. corgi1

    corgi1 New Member

    Joined:
    Aug 13, 2009
    Messages:
    2,282
    Likes Received:
    2
    27 would be for more speed on the flat lands ,and less power on the hills,your weight will play a part,100-145 pounds 27 tooth,above that I would do the 30 tooth(or more w/cargo being carried),,,,,simi trucks dont hold 65 mph on hills and gear down (same as putting a larger gear on their rear axle) to climb the hills and use the power their engine has w/out boging down, slower speed "but works",,,,,,,,,,,,,
     
  10. ueyteuor

    ueyteuor New Member

    Joined:
    May 28, 2010
    Messages:
    37
    Likes Received:
    0
    Thanks! So I guess I should settle for 27t, I am a light person...

    Do you know where I can get a 27t that's a direct fit? If not I would probably just have to find a 27t and have the mounting holes made custom...
     

Share This Page