Which sprocket for highest top speed?

Discussion in 'Motorized Bicycle General Discussion' started by MitchP, Aug 24, 2013.

  1. MitchP

    MitchP New Member

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    I'm running a 66cc/44 tooth set-up on 26" wheels. I weigh 180 and there are no hills to speak of. Which sprocket size will give me the highest top speed? I think I'm pushing 20mph right now drn2.
     
  2. biknut

    biknut Active Member

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    36 tooth would get you to about 35-40 mph.
     
  3. MitchP

    MitchP New Member

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    What if I wanted to go about 30 mph, top speed? My bike isn't ready for that kind of you're talking about (wheels out-of-true, coaster brakes). 20 mph is my top-ish speed currently.
     
  4. biknut

    biknut Active Member

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    40T would be good for you.
     
  5. stinky

    stinky New Member

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    most people say 36 tooth is best compromise. I have a 32 tooth sprocket.

    I can get it to go from a slow 5th gear pedaling start, without pedaling. I mean after i am moving like 3mph, dump the clutch and she will get going without pedaling.
    But i have found that pedaling until the engine hits its first smooth power band its best thing to do. 32 runs ragged at low speed, it makes me go faster than I want to on the sidewalks as there is little low end smoothness.

    Dude!!! if you wheels are all ossilating, then I would not be concerned with top speed at all LOL! Don't even try to go full speed until you have your rims trued!!! Then as I found out here, go fast you'll need better brakes!!! I have a 90mm Sturmey Archer on the way. There are sooo many stop and go street crossings where I live, that I doubt the stock brakes would last a month!!

    I learned after riding around for awhile, to let off the gas farther out from where I was going to stop, letting the gears slow me down, then hit brakes.

    Going fast is not the problem. It's stopping after gettin goin fast that's a hassle. If you have a big rural area you can haul ass on then don't worry so much about the brakes.
    Inner city, get good brakes!!
     
  6. stinky

    stinky New Member

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    Oh I wanted to have my bike run in the mid speeds like 20 to 30, without having to flog it to death to 8000 rpm. So lower RPM cruise speed, with higher top speed if I want to use it.

    Do a search for 32 tooth sprocket. 32 vs 44 or something like that is good read.

    Oh, and I do get some exercise, more than I thought having to pedal assist start it in 5th and 6th gears. Almost ate the bars starting it in 2nd gear lol!!
     
    #6 stinky, Aug 24, 2013
    Last edited: Aug 24, 2013
  7. biknut

    biknut Active Member

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    This is the calculated speed for a 40T sprocket

    20....crank gear
    82....clutch gear

    10....counter shaft sprocket
    40T.... rear wheel sprocket

    The Atomic BB
    26x2.125 tire 81.8" circumference


    RPM MPH

    1000 4.7
    1200 5.7
    1400 6.6
    1600 7.6
    1800 8.5
    2000 9.4
    2200 10.4
    2400 11.3
    2600 12.3
    2800 13.2
    3000 14.2
    3200 15.1
    3400 16.1
    3600 17.0
    3800 17.9
    4000 18.9
    4200 19.8
    4400 20.8
    4600 21.7
    4800 22.7
    5000 23.6
    5200 24.6
    5400 25.5
    5600 26.5
    5800 27.4
    6000 28.3
    6200 29.3
    6400 30.2
    6600 31.2
    6800 32.1
    7000 33.1
     
  8. biknut

    biknut Active Member

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    This is with a 36t sprocket.

    Cadillac AV Sport
    36T sprocket
    26x1.95 tire 80.25" circumference


    RPM MPH
    1000 5.2
    1200 6.2
    1400 7.2
    1600 8.3
    1800 9.3
    2000 10.3
    2200 11.4
    2400 12.4
    2600 13.4
    2800 14.5
    3000 15.5
    3200 16.5
    3400 17.6
    3600 18.6
    3800 19.6
    4000 20.7
    4200 21.7
    4400 22.7
    4600 23.8
    4800 24.8
    5000 25.8
    5200 26.9
    5400 27.9
    5600 28.9
    5800 30.0
    6000 31.0
    6200 32.0
    6400 33.1
    6600 34.1
    6800 35.1
    7000 36.2
     
  9. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I'm 210 lbs & I use 40T sprockets on all of my personal bikes... It adds a little more top speed without losing too much bottom end power.

    There are many skinny guys who use 36T (or smaller) sprockets who go real fast without losing too much bottom end... (But they couldn't pull it off it if they weighed more). :rolleyes:

    The ability to quickly build up speed & safely merge (& deal) with traffic is a very important thing to consider before installing a real small rear sprocket because you're only thinking of top speed! ;)
     
  10. MitchP

    MitchP New Member

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    I can get my wheels trued, but buying brakes and a dual pull lever would cost more than the sprocket itself. I want those parts eventually but I don't have $$ to throw at this bike for every project. 40 tooth is probably what I'll go with. I've seen and used the gear calculators but they're only accurate to a degree.
     
  11. oldsurfer

    oldsurfer New Member

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    what would you recommend for a 220lb guy on a 4stroke grubee as far as sprocket size?.xx.
     
  12. Huffydavidson

    Huffydavidson STREETRACER/MANUFACTURER

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    or you could buy a shift kit by the way they're on sale right now and you can have the best of both lowend & highend. laff
     
  13. mapbike

    mapbike Active Member

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    Wish I could help ya here, dont run the little 4 strokes but I have seen them normally with 50+ tooth sprockets just not sure what is the most common.
     
  14. mrfubs

    mrfubs New Member

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    i have a built 66cc balanced the crank my self runs around 7000 rpm no vibes and will run all day long at 45 mph with the 36T sprocket
     

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