Installed SickBikeParts 30 tooth freewheel chainring and custom 9 speed cassette

Discussion in 'General Questions' started by Fabian, Feb 1, 2010.

  1. Fabian

    Fabian Well-Known Member

    G'day all

    I've finished replacing the serviceable drive train components on my SickBikeParts Shift Kit and installed a few useful optional additions.

    Firstly the standard 36 tooth chainring has been coupled with the optional 30 tooth chainring and i can report excellent results - it's a "must have" item.

    Secondly, the standard Shimano 11-32T 9 speed Hyperglide cassette has been replaced with a custom 9 speed cassette made up out of two cassettes (11-34T + 12-36T) and an individually purchased 19 tooth hyperglide sprocket, giving a combination as follows:

    11 - 12 - 13 - 14 - 16 - 19 - 23 - 28 - 36.

    I spent a full day swapping and testing sprocket combinations to finally end up with a nicely balanced cassette perfect for serious hill climbs and squeezing the last bit of speed out of the system with a heavy trailer attached.

    Amazing how much torque must be transmitted through the ratchet pawls when in super low gear (30T chainring driving a 36T cassette sprocket).

    It's with enthusiasm that i can recommend the SickBikeParts optional 30 tooth axillary chainring sprocket.
    Although a bit of a wild thought, i may even have enough room to attach the SBP 24 tooth sprocket onto the 30T with a 4mm spacer, enabling a triple chainring setup.

    Cheers Fabian

    ps i'll get some pics tomorrow.
    Last edited: Feb 1, 2010

  2. Ghost0

    Ghost0 Guest

    We have another customer looking to do a similar thing. There reason is to assist in starting. Do you find that it is a little easier starting the engine with the 30-36 combo than the 36-44 combo?
  3. Fabian

    Fabian Well-Known Member

    Yes, i can say that starting the engine is easier insomuch as the rolling speed of the bike is significantly reduced.

    For a heavier person, it would be a major advantage.
    As for myself, i never found "starting it to be a problem with the issue related to rolling speed.
    The issue was always overcoming engine compression when pedal starting - the reason why i pondered the concept of installing a chainsaw decompression button in the cylinder head.

    What's really impressive is the low speed pulling power - just awesome; like selecting low range gear in a four wheel drive.
    Using the optional 11T jackshaft sprocket the bike speed at idle (1850rpm) is 6.5 kilometers per hour (4mp/h) and bike with trailer attached will idle up a slight incline.

    I set a test to see if the engine could pull the bike and trailer through rain soaked, spongy grass, at a local park.
    I've tried this before with standard gearing: 36T chainring driving a 32T cassette sprocket - as soon as the wheels started to sink, bike and trailer came to a stop, even with me busting my guts trying to push the whole kit and caboodle forward.
    In very similar conditions the 30T chainring powering the 36T cassette sprocket still has the engine loading up quite heavily but it just keeps pushing forward.

    Am i happy - tickled pink would be one way to describe it! - should have installed the 30T from the start.

    Last edited: Feb 1, 2010
  4. Skyliner70cc

    Skyliner70cc Active Member

    Several months ago when it was warm, I did some offroad Mbiking in the mountains. Even with a 36 megagear and a 9 tooth sprocket on the jackshaft, I encounted hills that the motor couldn't tackle...even with a SBP tuned pipe!

    I just ordered a 30T chainring and am excited to think it will solve my problem. Thanks for the info, Fabian! It'll be several months before it is warm enough for me to tackle the same trails but I'm sure it'll be a breeze.
  5. Fabian

    Fabian Well-Known Member

    Hi Skyliner

    Yes, you'll be over the moon when you install the 30T.

    Just to give some background to the described situation below: i've raced motorbikes in the past and still participate in recreational racetrack days. Typically when exiting a corner hard on the gas, you cover the rear brake with your foot, to prevent the bike lifting the front wheel, should it occur in an unexpected manner.
    I'm used to covering the rear brake as the front wheel comes off the ground - it's instinctive.

    Yesterday, i was mucking about in the back yard after installing the 30T and doing the clutch camshaft modification.
    To my great surprise, the bike would aggressively lift the front wheel with a decent slip of the clutch at 4,000 rpm.

    A funny situation arose when getting adventurous.
    I decided to give her some berries and try for a decent wheelie down the garden path.
    You can guess what happed next!
    The front end came up with savage command and i knew the bike was going over.
    Instinctively i went to feed in some rear brake but it wasn't there - it didn't happen and it got to the point where i knew it was going to get messy.
    Needless to say the bike flew out from underneath me and i was desperately trying to hang onto the thing and looking like a right royal idiot dancing down the path with an out of control pushbike.

    One thing is for sure - the bike never lifted the front wheel with standard shift kit gearing and my engine is stock standard except for carby jetting changes and a modified intake tube.

    Ok, big thumbs up emoticon for the 30T chainwheel sprocket and the 36T cassette sprocket.

    In my opinion, SickBikeParts should allow for optional inclusion of the dished 30T and also design a dished 26T to be offered in the Deluxe Shift Kit package.
    People who order the Deluxe Kit are not going to cry over an extra $15.
    A dished 26T would allow heavier riders to get up the steepest hills without pedaling, whilst using the optional 11T Jackshaft sprocket to give good road going speed on flat ground.

    Cheers Fabian
    Last edited: Feb 2, 2010